init commit

plugin/cron/README.md

@@ -0,0 +1 @@
+Fork from https://github.com/robfig/cron

plugin/cron/chain.go

@@ -0,0 +1,96 @@
+package cron
+
+import (
+	"errors"
+	"fmt"
+	"runtime"
+	"sync"
+	"time"
+)
+
+// JobWrapper decorates the given Job with some behavior.
+type JobWrapper func(Job) Job
+
+// Chain is a sequence of JobWrappers that decorates submitted jobs with
+// cross-cutting behaviors like logging or synchronization.
+type Chain struct {
+	wrappers []JobWrapper
+}
+
+// NewChain returns a Chain consisting of the given JobWrappers.
+func NewChain(c ...JobWrapper) Chain {
+	return Chain{c}
+}
+
+// Then decorates the given job with all JobWrappers in the chain.
+//
+// This:
+//
+//	NewChain(m1, m2, m3).Then(job)
+//
+// is equivalent to:
+//
+//	m1(m2(m3(job)))
+func (c Chain) Then(j Job) Job {
+	for i := range c.wrappers {
+		j = c.wrappers[len(c.wrappers)-i-1](j)
+	}
+	return j
+}
+
+// Recover panics in wrapped jobs and log them with the provided logger.
+func Recover(logger Logger) JobWrapper {
+	return func(j Job) Job {
+		return FuncJob(func() {
+			defer func() {
+				if r := recover(); r != nil {
+					const size = 64 << 10
+					buf := make([]byte, size)
+					buf = buf[:runtime.Stack(buf, false)]
+					err, ok := r.(error)
+					if !ok {
+						err = errors.New("panic: " + fmt.Sprint(r))
+					}
+					logger.Error(err, "panic", "stack", "...\n"+string(buf))
+				}
+			}()
+			j.Run()
+		})
+	}
+}
+
+// DelayIfStillRunning serializes jobs, delaying subsequent runs until the
+// previous one is complete. Jobs running after a delay of more than a minute
+// have the delay logged at Info.
+func DelayIfStillRunning(logger Logger) JobWrapper {
+	return func(j Job) Job {
+		var mu sync.Mutex
+		return FuncJob(func() {
+			start := time.Now()
+			mu.Lock()
+			defer mu.Unlock()
+			if dur := time.Since(start); dur > time.Minute {
+				logger.Info("delay", "duration", dur)
+			}
+			j.Run()
+		})
+	}
+}
+
+// SkipIfStillRunning skips an invocation of the Job if a previous invocation is
+// still running. It logs skips to the given logger at Info level.
+func SkipIfStillRunning(logger Logger) JobWrapper {
+	return func(j Job) Job {
+		var ch = make(chan struct{}, 1)
+		ch <- struct{}{}
+		return FuncJob(func() {
+			select {
+			case v := <-ch:
+				defer func() { ch <- v }()
+				j.Run()
+			default:
+				logger.Info("skip")
+			}
+		})
+	}
+}

plugin/cron/chain_test.go

@@ -0,0 +1,239 @@
+//nolint:all
+package cron
+
+import (
+	"io"
+	"log"
+	"reflect"
+	"sync"
+	"testing"
+	"time"
+)
+
+func appendingJob(slice *[]int, value int) Job {
+	var m sync.Mutex
+	return FuncJob(func() {
+		m.Lock()
+		*slice = append(*slice, value)
+		m.Unlock()
+	})
+}
+
+func appendingWrapper(slice *[]int, value int) JobWrapper {
+	return func(j Job) Job {
+		return FuncJob(func() {
+			appendingJob(slice, value).Run()
+			j.Run()
+		})
+	}
+}
+
+func TestChain(t *testing.T) {
+	var nums []int
+	var (
+		append1 = appendingWrapper(&nums, 1)
+		append2 = appendingWrapper(&nums, 2)
+		append3 = appendingWrapper(&nums, 3)
+		append4 = appendingJob(&nums, 4)
+	)
+	NewChain(append1, append2, append3).Then(append4).Run()
+	if !reflect.DeepEqual(nums, []int{1, 2, 3, 4}) {
+		t.Error("unexpected order of calls:", nums)
+	}
+}
+
+func TestChainRecover(t *testing.T) {
+	panickingJob := FuncJob(func() {
+		panic("panickingJob panics")
+	})
+
+	t.Run("panic exits job by default", func(*testing.T) {
+		defer func() {
+			if err := recover(); err == nil {
+				t.Errorf("panic expected, but none received")
+			}
+		}()
+		NewChain().Then(panickingJob).
+			Run()
+	})
+
+	t.Run("Recovering JobWrapper recovers", func(*testing.T) {
+		NewChain(Recover(PrintfLogger(log.New(io.Discard, "", 0)))).
+			Then(panickingJob).
+			Run()
+	})
+
+	t.Run("composed with the *IfStillRunning wrappers", func(*testing.T) {
+		NewChain(Recover(PrintfLogger(log.New(io.Discard, "", 0)))).
+			Then(panickingJob).
+			Run()
+	})
+}
+
+type countJob struct {
+	m       sync.Mutex
+	started int
+	done    int
+	delay   time.Duration
+}
+
+func (j *countJob) Run() {
+	j.m.Lock()
+	j.started++
+	j.m.Unlock()
+	time.Sleep(j.delay)
+	j.m.Lock()
+	j.done++
+	j.m.Unlock()
+}
+
+func (j *countJob) Started() int {
+	defer j.m.Unlock()
+	j.m.Lock()
+	return j.started
+}
+
+func (j *countJob) Done() int {
+	defer j.m.Unlock()
+	j.m.Lock()
+	return j.done
+}
+
+func TestChainDelayIfStillRunning(t *testing.T) {
+	t.Run("runs immediately", func(*testing.T) {
+		var j countJob
+		wrappedJob := NewChain(DelayIfStillRunning(DiscardLogger)).Then(&j)
+		go wrappedJob.Run()
+		time.Sleep(2 * time.Millisecond) // Give the job 2ms to complete.
+		if c := j.Done(); c != 1 {
+			t.Errorf("expected job run once, immediately, got %d", c)
+		}
+	})
+
+	t.Run("second run immediate if first done", func(*testing.T) {
+		var j countJob
+		wrappedJob := NewChain(DelayIfStillRunning(DiscardLogger)).Then(&j)
+		go func() {
+			go wrappedJob.Run()
+			time.Sleep(time.Millisecond)
+			go wrappedJob.Run()
+		}()
+		time.Sleep(3 * time.Millisecond) // Give both jobs 3ms to complete.
+		if c := j.Done(); c != 2 {
+			t.Errorf("expected job run twice, immediately, got %d", c)
+		}
+	})
+
+	t.Run("second run delayed if first not done", func(*testing.T) {
+		var j countJob
+		j.delay = 10 * time.Millisecond
+		wrappedJob := NewChain(DelayIfStillRunning(DiscardLogger)).Then(&j)
+		go func() {
+			go wrappedJob.Run()
+			time.Sleep(time.Millisecond)
+			go wrappedJob.Run()
+		}()
+
+		// After 5ms, the first job is still in progress, and the second job was
+		// run but should be waiting for it to finish.
+		time.Sleep(5 * time.Millisecond)
+		started, done := j.Started(), j.Done()
+		if started != 1 || done != 0 {
+			t.Error("expected first job started, but not finished, got", started, done)
+		}
+
+		// Verify that the second job completes.
+		time.Sleep(25 * time.Millisecond)
+		started, done = j.Started(), j.Done()
+		if started != 2 || done != 2 {
+			t.Error("expected both jobs done, got", started, done)
+		}
+	})
+}
+
+func TestChainSkipIfStillRunning(t *testing.T) {
+	t.Run("runs immediately", func(*testing.T) {
+		var j countJob
+		wrappedJob := NewChain(SkipIfStillRunning(DiscardLogger)).Then(&j)
+		go wrappedJob.Run()
+		time.Sleep(2 * time.Millisecond) // Give the job 2ms to complete.
+		if c := j.Done(); c != 1 {
+			t.Errorf("expected job run once, immediately, got %d", c)
+		}
+	})
+
+	t.Run("second run immediate if first done", func(*testing.T) {
+		var j countJob
+		wrappedJob := NewChain(SkipIfStillRunning(DiscardLogger)).Then(&j)
+		go func() {
+			go wrappedJob.Run()
+			time.Sleep(time.Millisecond)
+			go wrappedJob.Run()
+		}()
+		time.Sleep(3 * time.Millisecond) // Give both jobs 3ms to complete.
+		if c := j.Done(); c != 2 {
+			t.Errorf("expected job run twice, immediately, got %d", c)
+		}
+	})
+
+	t.Run("second run skipped if first not done", func(*testing.T) {
+		var j countJob
+		j.delay = 10 * time.Millisecond
+		wrappedJob := NewChain(SkipIfStillRunning(DiscardLogger)).Then(&j)
+		go func() {
+			go wrappedJob.Run()
+			time.Sleep(time.Millisecond)
+			go wrappedJob.Run()
+		}()
+
+		// After 5ms, the first job is still in progress, and the second job was
+		// aleady skipped.
+		time.Sleep(5 * time.Millisecond)
+		started, done := j.Started(), j.Done()
+		if started != 1 || done != 0 {
+			t.Error("expected first job started, but not finished, got", started, done)
+		}
+
+		// Verify that the first job completes and second does not run.
+		time.Sleep(25 * time.Millisecond)
+		started, done = j.Started(), j.Done()
+		if started != 1 || done != 1 {
+			t.Error("expected second job skipped, got", started, done)
+		}
+	})
+
+	t.Run("skip 10 jobs on rapid fire", func(*testing.T) {
+		var j countJob
+		j.delay = 10 * time.Millisecond
+		wrappedJob := NewChain(SkipIfStillRunning(DiscardLogger)).Then(&j)
+		for i := 0; i < 11; i++ {
+			go wrappedJob.Run()
+		}
+		time.Sleep(200 * time.Millisecond)
+		done := j.Done()
+		if done != 1 {
+			t.Error("expected 1 jobs executed, 10 jobs dropped, got", done)
+		}
+	})
+
+	t.Run("different jobs independent", func(*testing.T) {
+		var j1, j2 countJob
+		j1.delay = 10 * time.Millisecond
+		j2.delay = 10 * time.Millisecond
+		chain := NewChain(SkipIfStillRunning(DiscardLogger))
+		wrappedJob1 := chain.Then(&j1)
+		wrappedJob2 := chain.Then(&j2)
+		for i := 0; i < 11; i++ {
+			go wrappedJob1.Run()
+			go wrappedJob2.Run()
+		}
+		time.Sleep(100 * time.Millisecond)
+		var (
+			done1 = j1.Done()
+			done2 = j2.Done()
+		)
+		if done1 != 1 || done2 != 1 {
+			t.Error("expected both jobs executed once, got", done1, "and", done2)
+		}
+	})
+}

plugin/cron/constantdelay.go

@@ -0,0 +1,27 @@
+package cron
+
+import "time"
+
+// ConstantDelaySchedule represents a simple recurring duty cycle, e.g. "Every 5 minutes".
+// It does not support jobs more frequent than once a second.
+type ConstantDelaySchedule struct {
+	Delay time.Duration
+}
+
+// Every returns a crontab Schedule that activates once every duration.
+// Delays of less than a second are not supported (will round up to 1 second).
+// Any fields less than a Second are truncated.
+func Every(duration time.Duration) ConstantDelaySchedule {
+	if duration < time.Second {
+		duration = time.Second
+	}
+	return ConstantDelaySchedule{
+		Delay: duration - time.Duration(duration.Nanoseconds())%time.Second,
+	}
+}
+
+// Next returns the next time this should be run.
+// This rounds so that the next activation time will be on the second.
+func (schedule ConstantDelaySchedule) Next(t time.Time) time.Time {
+	return t.Add(schedule.Delay - time.Duration(t.Nanosecond())*time.Nanosecond)
+}

plugin/cron/constantdelay_test.go

@@ -0,0 +1,55 @@
+//nolint:all
+package cron
+
+import (
+	"testing"
+	"time"
+)
+
+func TestConstantDelayNext(t *testing.T) {
+	tests := []struct {
+		time     string
+		delay    time.Duration
+		expected string
+	}{
+		// Simple cases
+		{"Mon Jul 9 14:45 2012", 15*time.Minute + 50*time.Nanosecond, "Mon Jul 9 15:00 2012"},
+		{"Mon Jul 9 14:59 2012", 15 * time.Minute, "Mon Jul 9 15:14 2012"},
+		{"Mon Jul 9 14:59:59 2012", 15 * time.Minute, "Mon Jul 9 15:14:59 2012"},
+
+		// Wrap around hours
+		{"Mon Jul 9 15:45 2012", 35 * time.Minute, "Mon Jul 9 16:20 2012"},
+
+		// Wrap around days
+		{"Mon Jul 9 23:46 2012", 14 * time.Minute, "Tue Jul 10 00:00 2012"},
+		{"Mon Jul 9 23:45 2012", 35 * time.Minute, "Tue Jul 10 00:20 2012"},
+		{"Mon Jul 9 23:35:51 2012", 44*time.Minute + 24*time.Second, "Tue Jul 10 00:20:15 2012"},
+		{"Mon Jul 9 23:35:51 2012", 25*time.Hour + 44*time.Minute + 24*time.Second, "Thu Jul 11 01:20:15 2012"},
+
+		// Wrap around months
+		{"Mon Jul 9 23:35 2012", 91*24*time.Hour + 25*time.Minute, "Thu Oct 9 00:00 2012"},
+
+		// Wrap around minute, hour, day, month, and year
+		{"Mon Dec 31 23:59:45 2012", 15 * time.Second, "Tue Jan 1 00:00:00 2013"},
+
+		// Round to nearest second on the delay
+		{"Mon Jul 9 14:45 2012", 15*time.Minute + 50*time.Nanosecond, "Mon Jul 9 15:00 2012"},
+
+		// Round up to 1 second if the duration is less.
+		{"Mon Jul 9 14:45:00 2012", 15 * time.Millisecond, "Mon Jul 9 14:45:01 2012"},
+
+		// Round to nearest second when calculating the next time.
+		{"Mon Jul 9 14:45:00.005 2012", 15 * time.Minute, "Mon Jul 9 15:00 2012"},
+
+		// Round to nearest second for both.
+		{"Mon Jul 9 14:45:00.005 2012", 15*time.Minute + 50*time.Nanosecond, "Mon Jul 9 15:00 2012"},
+	}
+
+	for _, c := range tests {
+		actual := Every(c.delay).Next(getTime(c.time))
+		expected := getTime(c.expected)
+		if actual != expected {
+			t.Errorf("%s, \"%s\": (expected) %v != %v (actual)", c.time, c.delay, expected, actual)
+		}
+	}
+}

plugin/cron/cron.go

@@ -0,0 +1,355 @@
+package cron
+
+import (
+	"context"
+	"sort"
+	"sync"
+	"time"
+)
+
+// Cron keeps track of any number of entries, invoking the associated func as
+// specified by the schedule. It may be started, stopped, and the entries may
+// be inspected while running.
+type Cron struct {
+	entries   []*Entry
+	chain     Chain
+	stop      chan struct{}
+	add       chan *Entry
+	remove    chan EntryID
+	snapshot  chan chan []Entry
+	running   bool
+	logger    Logger
+	runningMu sync.Mutex
+	location  *time.Location
+	parser    ScheduleParser
+	nextID    EntryID
+	jobWaiter sync.WaitGroup
+}
+
+// ScheduleParser is an interface for schedule spec parsers that return a Schedule.
+type ScheduleParser interface {
+	Parse(spec string) (Schedule, error)
+}
+
+// Job is an interface for submitted cron jobs.
+type Job interface {
+	Run()
+}
+
+// Schedule describes a job's duty cycle.
+type Schedule interface {
+	// Next returns the next activation time, later than the given time.
+	// Next is invoked initially, and then each time the job is run.
+	Next(time.Time) time.Time
+}
+
+// EntryID identifies an entry within a Cron instance.
+type EntryID int
+
+// Entry consists of a schedule and the func to execute on that schedule.
+type Entry struct {
+	// ID is the cron-assigned ID of this entry, which may be used to look up a
+	// snapshot or remove it.
+	ID EntryID
+
+	// Schedule on which this job should be run.
+	Schedule Schedule
+
+	// Next time the job will run, or the zero time if Cron has not been
+	// started or this entry's schedule is unsatisfiable
+	Next time.Time
+
+	// Prev is the last time this job was run, or the zero time if never.
+	Prev time.Time
+
+	// WrappedJob is the thing to run when the Schedule is activated.
+	WrappedJob Job
+
+	// Job is the thing that was submitted to cron.
+	// It is kept around so that user code that needs to get at the job later,
+	// e.g. via Entries() can do so.
+	Job Job
+}
+
+// Valid returns true if this is not the zero entry.
+func (e Entry) Valid() bool { return e.ID != 0 }
+
+// byTime is a wrapper for sorting the entry array by time
+// (with zero time at the end).
+type byTime []*Entry
+
+func (s byTime) Len() int      { return len(s) }
+func (s byTime) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+func (s byTime) Less(i, j int) bool {
+	// Two zero times should return false.
+	// Otherwise, zero is "greater" than any other time.
+	// (To sort it at the end of the list.)
+	if s[i].Next.IsZero() {
+		return false
+	}
+	if s[j].Next.IsZero() {
+		return true
+	}
+	return s[i].Next.Before(s[j].Next)
+}
+
+// New returns a new Cron job runner, modified by the given options.
+//
+// Available Settings
+//
+//	Time Zone
+//	  Description: The time zone in which schedules are interpreted
+//	  Default:     time.Local
+//
+//	Parser
+//	  Description: Parser converts cron spec strings into cron.Schedules.
+//	  Default:     Accepts this spec: https://en.wikipedia.org/wiki/Cron
+//
+//	Chain
+//	  Description: Wrap submitted jobs to customize behavior.
+//	  Default:     A chain that recovers panics and logs them to stderr.
+//
+// See "cron.With*" to modify the default behavior.
+func New(opts ...Option) *Cron {
+	c := &Cron{
+		entries:   nil,
+		chain:     NewChain(),
+		add:       make(chan *Entry),
+		stop:      make(chan struct{}),
+		snapshot:  make(chan chan []Entry),
+		remove:    make(chan EntryID),
+		running:   false,
+		runningMu: sync.Mutex{},
+		logger:    DefaultLogger,
+		location:  time.Local,
+		parser:    standardParser,
+	}
+	for _, opt := range opts {
+		opt(c)
+	}
+	return c
+}
+
+// FuncJob is a wrapper that turns a func() into a cron.Job.
+type FuncJob func()
+
+func (f FuncJob) Run() { f() }
+
+// AddFunc adds a func to the Cron to be run on the given schedule.
+// The spec is parsed using the time zone of this Cron instance as the default.
+// An opaque ID is returned that can be used to later remove it.
+func (c *Cron) AddFunc(spec string, cmd func()) (EntryID, error) {
+	return c.AddJob(spec, FuncJob(cmd))
+}
+
+// AddJob adds a Job to the Cron to be run on the given schedule.
+// The spec is parsed using the time zone of this Cron instance as the default.
+// An opaque ID is returned that can be used to later remove it.
+func (c *Cron) AddJob(spec string, cmd Job) (EntryID, error) {
+	schedule, err := c.parser.Parse(spec)
+	if err != nil {
+		return 0, err
+	}
+	return c.Schedule(schedule, cmd), nil
+}
+
+// Schedule adds a Job to the Cron to be run on the given schedule.
+// The job is wrapped with the configured Chain.
+func (c *Cron) Schedule(schedule Schedule, cmd Job) EntryID {
+	c.runningMu.Lock()
+	defer c.runningMu.Unlock()
+	c.nextID++
+	entry := &Entry{
+		ID:         c.nextID,
+		Schedule:   schedule,
+		WrappedJob: c.chain.Then(cmd),
+		Job:        cmd,
+	}
+	if !c.running {
+		c.entries = append(c.entries, entry)
+	} else {
+		c.add <- entry
+	}
+	return entry.ID
+}
+
+// Entries returns a snapshot of the cron entries.
+func (c *Cron) Entries() []Entry {
+	c.runningMu.Lock()
+	defer c.runningMu.Unlock()
+	if c.running {
+		replyChan := make(chan []Entry, 1)
+		c.snapshot <- replyChan
+		return <-replyChan
+	}
+	return c.entrySnapshot()
+}
+
+// Location gets the time zone location.
+func (c *Cron) Location() *time.Location {
+	return c.location
+}
+
+// Entry returns a snapshot of the given entry, or nil if it couldn't be found.
+func (c *Cron) Entry(id EntryID) Entry {
+	for _, entry := range c.Entries() {
+		if id == entry.ID {
+			return entry
+		}
+	}
+	return Entry{}
+}
+
+// Remove an entry from being run in the future.
+func (c *Cron) Remove(id EntryID) {
+	c.runningMu.Lock()
+	defer c.runningMu.Unlock()
+	if c.running {
+		c.remove <- id
+	} else {
+		c.removeEntry(id)
+	}
+}
+
+// Start the cron scheduler in its own goroutine, or no-op if already started.
+func (c *Cron) Start() {
+	c.runningMu.Lock()
+	defer c.runningMu.Unlock()
+	if c.running {
+		return
+	}
+	c.running = true
+	go c.runScheduler()
+}
+
+// Run the cron scheduler, or no-op if already running.
+func (c *Cron) Run() {
+	c.runningMu.Lock()
+	if c.running {
+		c.runningMu.Unlock()
+		return
+	}
+	c.running = true
+	c.runningMu.Unlock()
+	c.runScheduler()
+}
+
+// runScheduler runs the scheduler.. this is private just due to the need to synchronize
+// access to the 'running' state variable.
+func (c *Cron) runScheduler() {
+	c.logger.Info("start")
+
+	// Figure out the next activation times for each entry.
+	now := c.now()
+	for _, entry := range c.entries {
+		entry.Next = entry.Schedule.Next(now)
+		c.logger.Info("schedule", "now", now, "entry", entry.ID, "next", entry.Next)
+	}
+
+	for {
+		// Determine the next entry to run.
+		sort.Sort(byTime(c.entries))
+
+		var timer *time.Timer
+		if len(c.entries) == 0 || c.entries[0].Next.IsZero() {
+			// If there are no entries yet, just sleep - it still handles new entries
+			// and stop requests.
+			timer = time.NewTimer(100000 * time.Hour)
+		} else {
+			timer = time.NewTimer(c.entries[0].Next.Sub(now))
+		}
+
+		for {
+			select {
+			case now = <-timer.C:
+				now = now.In(c.location)
+				c.logger.Info("wake", "now", now)
+
+				// Run every entry whose next time was less than now
+				for _, e := range c.entries {
+					if e.Next.After(now) || e.Next.IsZero() {
+						break
+					}
+					c.startJob(e.WrappedJob)
+					e.Prev = e.Next
+					e.Next = e.Schedule.Next(now)
+					c.logger.Info("run", "now", now, "entry", e.ID, "next", e.Next)
+				}
+
+			case newEntry := <-c.add:
+				timer.Stop()
+				now = c.now()
+				newEntry.Next = newEntry.Schedule.Next(now)
+				c.entries = append(c.entries, newEntry)
+				c.logger.Info("added", "now", now, "entry", newEntry.ID, "next", newEntry.Next)
+
+			case replyChan := <-c.snapshot:
+				replyChan <- c.entrySnapshot()
+				continue
+
+			case <-c.stop:
+				timer.Stop()
+				c.logger.Info("stop")
+				return
+
+			case id := <-c.remove:
+				timer.Stop()
+				now = c.now()
+				c.removeEntry(id)
+				c.logger.Info("removed", "entry", id)
+			}
+
+			break
+		}
+	}
+}
+
+// startJob runs the given job in a new goroutine.
+func (c *Cron) startJob(j Job) {
+	c.jobWaiter.Add(1)
+	go func() {
+		defer c.jobWaiter.Done()
+		j.Run()
+	}()
+}
+
+// now returns current time in c location.
+func (c *Cron) now() time.Time {
+	return time.Now().In(c.location)
+}
+
+// Stop stops the cron scheduler if it is running; otherwise it does nothing.
+// A context is returned so the caller can wait for running jobs to complete.
+func (c *Cron) Stop() context.Context {
+	c.runningMu.Lock()
+	defer c.runningMu.Unlock()
+	if c.running {
+		c.stop <- struct{}{}
+		c.running = false
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		c.jobWaiter.Wait()
+		cancel()
+	}()
+	return ctx
+}
+
+// entrySnapshot returns a copy of the current cron entry list.
+func (c *Cron) entrySnapshot() []Entry {
+	var entries = make([]Entry, len(c.entries))
+	for i, e := range c.entries {
+		entries[i] = *e
+	}
+	return entries
+}
+
+func (c *Cron) removeEntry(id EntryID) {
+	var entries []*Entry
+	for _, e := range c.entries {
+		if e.ID != id {
+			entries = append(entries, e)
+		}
+	}
+	c.entries = entries
+}

plugin/cron/cron_test.go

@@ -0,0 +1,702 @@
+//nolint:all
+package cron
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+// Many tests schedule a job for every second, and then wait at most a second
+// for it to run.  This amount is just slightly larger than 1 second to
+// compensate for a few milliseconds of runtime.
+const OneSecond = 1*time.Second + 50*time.Millisecond
+
+type syncWriter struct {
+	wr bytes.Buffer
+	m  sync.Mutex
+}
+
+func (sw *syncWriter) Write(data []byte) (n int, err error) {
+	sw.m.Lock()
+	n, err = sw.wr.Write(data)
+	sw.m.Unlock()
+	return
+}
+
+func (sw *syncWriter) String() string {
+	sw.m.Lock()
+	defer sw.m.Unlock()
+	return sw.wr.String()
+}
+
+func newBufLogger(sw *syncWriter) Logger {
+	return PrintfLogger(log.New(sw, "", log.LstdFlags))
+}
+
+func TestFuncPanicRecovery(t *testing.T) {
+	var buf syncWriter
+	cron := New(WithParser(secondParser),
+		WithChain(Recover(newBufLogger(&buf))))
+	cron.Start()
+	defer cron.Stop()
+	cron.AddFunc("* * * * * ?", func() {
+		panic("YOLO")
+	})
+
+	select {
+	case <-time.After(OneSecond):
+		if !strings.Contains(buf.String(), "YOLO") {
+			t.Error("expected a panic to be logged, got none")
+		}
+		return
+	}
+}
+
+type DummyJob struct{}
+
+func (DummyJob) Run() {
+	panic("YOLO")
+}
+
+func TestJobPanicRecovery(t *testing.T) {
+	var job DummyJob
+
+	var buf syncWriter
+	cron := New(WithParser(secondParser),
+		WithChain(Recover(newBufLogger(&buf))))
+	cron.Start()
+	defer cron.Stop()
+	cron.AddJob("* * * * * ?", job)
+
+	select {
+	case <-time.After(OneSecond):
+		if !strings.Contains(buf.String(), "YOLO") {
+			t.Error("expected a panic to be logged, got none")
+		}
+		return
+	}
+}
+
+// Start and stop cron with no entries.
+func TestNoEntries(t *testing.T) {
+	cron := newWithSeconds()
+	cron.Start()
+
+	select {
+	case <-time.After(OneSecond):
+		t.Fatal("expected cron will be stopped immediately")
+	case <-stop(cron):
+	}
+}
+
+// Start, stop, then add an entry. Verify entry doesn't run.
+func TestStopCausesJobsToNotRun(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := newWithSeconds()
+	cron.Start()
+	cron.Stop()
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+
+	select {
+	case <-time.After(OneSecond):
+		// No job ran!
+	case <-wait(wg):
+		t.Fatal("expected stopped cron does not run any job")
+	}
+}
+
+// Add a job, start cron, expect it runs.
+func TestAddBeforeRunning(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := newWithSeconds()
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+	cron.Start()
+	defer cron.Stop()
+
+	// Give cron 2 seconds to run our job (which is always activated).
+	select {
+	case <-time.After(OneSecond):
+		t.Fatal("expected job runs")
+	case <-wait(wg):
+	}
+}
+
+// Start cron, add a job, expect it runs.
+func TestAddWhileRunning(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := newWithSeconds()
+	cron.Start()
+	defer cron.Stop()
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+
+	select {
+	case <-time.After(OneSecond):
+		t.Fatal("expected job runs")
+	case <-wait(wg):
+	}
+}
+
+// Test for #34. Adding a job after calling start results in multiple job invocations
+func TestAddWhileRunningWithDelay(t *testing.T) {
+	cron := newWithSeconds()
+	cron.Start()
+	defer cron.Stop()
+	time.Sleep(5 * time.Second)
+	var calls int64
+	cron.AddFunc("* * * * * *", func() { atomic.AddInt64(&calls, 1) })
+
+	<-time.After(OneSecond)
+	if atomic.LoadInt64(&calls) != 1 {
+		t.Errorf("called %d times, expected 1\n", calls)
+	}
+}
+
+// Add a job, remove a job, start cron, expect nothing runs.
+func TestRemoveBeforeRunning(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := newWithSeconds()
+	id, _ := cron.AddFunc("* * * * * ?", func() { wg.Done() })
+	cron.Remove(id)
+	cron.Start()
+	defer cron.Stop()
+
+	select {
+	case <-time.After(OneSecond):
+		// Success, shouldn't run
+	case <-wait(wg):
+		t.FailNow()
+	}
+}
+
+// Start cron, add a job, remove it, expect it doesn't run.
+func TestRemoveWhileRunning(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := newWithSeconds()
+	cron.Start()
+	defer cron.Stop()
+	id, _ := cron.AddFunc("* * * * * ?", func() { wg.Done() })
+	cron.Remove(id)
+
+	select {
+	case <-time.After(OneSecond):
+	case <-wait(wg):
+		t.FailNow()
+	}
+}
+
+// Test timing with Entries.
+func TestSnapshotEntries(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := New()
+	cron.AddFunc("@every 2s", func() { wg.Done() })
+	cron.Start()
+	defer cron.Stop()
+
+	// Cron should fire in 2 seconds. After 1 second, call Entries.
+	select {
+	case <-time.After(OneSecond):
+		cron.Entries()
+	}
+
+	// Even though Entries was called, the cron should fire at the 2 second mark.
+	select {
+	case <-time.After(OneSecond):
+		t.Error("expected job runs at 2 second mark")
+	case <-wait(wg):
+	}
+}
+
+// Test that the entries are correctly sorted.
+// Add a bunch of long-in-the-future entries, and an immediate entry, and ensure
+// that the immediate entry runs immediately.
+// Also: Test that multiple jobs run in the same instant.
+func TestMultipleEntries(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(2)
+
+	cron := newWithSeconds()
+	cron.AddFunc("0 0 0 1 1 ?", func() {})
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+	id1, _ := cron.AddFunc("* * * * * ?", func() { t.Fatal() })
+	id2, _ := cron.AddFunc("* * * * * ?", func() { t.Fatal() })
+	cron.AddFunc("0 0 0 31 12 ?", func() {})
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+
+	cron.Remove(id1)
+	cron.Start()
+	cron.Remove(id2)
+	defer cron.Stop()
+
+	select {
+	case <-time.After(OneSecond):
+		t.Error("expected job run in proper order")
+	case <-wait(wg):
+	}
+}
+
+// Test running the same job twice.
+func TestRunningJobTwice(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(2)
+
+	cron := newWithSeconds()
+	cron.AddFunc("0 0 0 1 1 ?", func() {})
+	cron.AddFunc("0 0 0 31 12 ?", func() {})
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+
+	cron.Start()
+	defer cron.Stop()
+
+	select {
+	case <-time.After(2 * OneSecond):
+		t.Error("expected job fires 2 times")
+	case <-wait(wg):
+	}
+}
+
+func TestRunningMultipleSchedules(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(2)
+
+	cron := newWithSeconds()
+	cron.AddFunc("0 0 0 1 1 ?", func() {})
+	cron.AddFunc("0 0 0 31 12 ?", func() {})
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+	cron.Schedule(Every(time.Minute), FuncJob(func() {}))
+	cron.Schedule(Every(time.Second), FuncJob(func() { wg.Done() }))
+	cron.Schedule(Every(time.Hour), FuncJob(func() {}))
+
+	cron.Start()
+	defer cron.Stop()
+
+	select {
+	case <-time.After(2 * OneSecond):
+		t.Error("expected job fires 2 times")
+	case <-wait(wg):
+	}
+}
+
+// Test that the cron is run in the local time zone (as opposed to UTC).
+func TestLocalTimezone(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(2)
+
+	now := time.Now()
+	// FIX: Issue #205
+	// This calculation doesn't work in seconds 58 or 59.
+	// Take the easy way out and sleep.
+	if now.Second() >= 58 {
+		time.Sleep(2 * time.Second)
+		now = time.Now()
+	}
+	spec := fmt.Sprintf("%d,%d %d %d %d %d ?",
+		now.Second()+1, now.Second()+2, now.Minute(), now.Hour(), now.Day(), now.Month())
+
+	cron := newWithSeconds()
+	cron.AddFunc(spec, func() { wg.Done() })
+	cron.Start()
+	defer cron.Stop()
+
+	select {
+	case <-time.After(OneSecond * 2):
+		t.Error("expected job fires 2 times")
+	case <-wait(wg):
+	}
+}
+
+// Test that the cron is run in the given time zone (as opposed to local).
+func TestNonLocalTimezone(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(2)
+
+	loc, err := time.LoadLocation("Atlantic/Cape_Verde")
+	if err != nil {
+		fmt.Printf("Failed to load time zone Atlantic/Cape_Verde: %+v", err)
+		t.Fail()
+	}
+
+	now := time.Now().In(loc)
+	// FIX: Issue #205
+	// This calculation doesn't work in seconds 58 or 59.
+	// Take the easy way out and sleep.
+	if now.Second() >= 58 {
+		time.Sleep(2 * time.Second)
+		now = time.Now().In(loc)
+	}
+	spec := fmt.Sprintf("%d,%d %d %d %d %d ?",
+		now.Second()+1, now.Second()+2, now.Minute(), now.Hour(), now.Day(), now.Month())
+
+	cron := New(WithLocation(loc), WithParser(secondParser))
+	cron.AddFunc(spec, func() { wg.Done() })
+	cron.Start()
+	defer cron.Stop()
+
+	select {
+	case <-time.After(OneSecond * 2):
+		t.Error("expected job fires 2 times")
+	case <-wait(wg):
+	}
+}
+
+// Test that calling stop before start silently returns without
+// blocking the stop channel.
+func TestStopWithoutStart(t *testing.T) {
+	cron := New()
+	cron.Stop()
+}
+
+type testJob struct {
+	wg   *sync.WaitGroup
+	name string
+}
+
+func (t testJob) Run() {
+	t.wg.Done()
+}
+
+// Test that adding an invalid job spec returns an error
+func TestInvalidJobSpec(t *testing.T) {
+	cron := New()
+	_, err := cron.AddJob("this will not parse", nil)
+	if err == nil {
+		t.Errorf("expected an error with invalid spec, got nil")
+	}
+}
+
+// Test blocking run method behaves as Start()
+func TestBlockingRun(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := newWithSeconds()
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+
+	var unblockChan = make(chan struct{})
+
+	go func() {
+		cron.Run()
+		close(unblockChan)
+	}()
+	defer cron.Stop()
+
+	select {
+	case <-time.After(OneSecond):
+		t.Error("expected job fires")
+	case <-unblockChan:
+		t.Error("expected that Run() blocks")
+	case <-wait(wg):
+	}
+}
+
+// Test that double-running is a no-op
+func TestStartNoop(t *testing.T) {
+	var tickChan = make(chan struct{}, 2)
+
+	cron := newWithSeconds()
+	cron.AddFunc("* * * * * ?", func() {
+		tickChan <- struct{}{}
+	})
+
+	cron.Start()
+	defer cron.Stop()
+
+	// Wait for the first firing to ensure the runner is going
+	<-tickChan
+
+	cron.Start()
+
+	<-tickChan
+
+	// Fail if this job fires again in a short period, indicating a double-run
+	select {
+	case <-time.After(time.Millisecond):
+	case <-tickChan:
+		t.Error("expected job fires exactly twice")
+	}
+}
+
+// Simple test using Runnables.
+func TestJob(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := newWithSeconds()
+	cron.AddJob("0 0 0 30 Feb ?", testJob{wg, "job0"})
+	cron.AddJob("0 0 0 1 1 ?", testJob{wg, "job1"})
+	job2, _ := cron.AddJob("* * * * * ?", testJob{wg, "job2"})
+	cron.AddJob("1 0 0 1 1 ?", testJob{wg, "job3"})
+	cron.Schedule(Every(5*time.Second+5*time.Nanosecond), testJob{wg, "job4"})
+	job5 := cron.Schedule(Every(5*time.Minute), testJob{wg, "job5"})
+
+	// Test getting an Entry pre-Start.
+	if actualName := cron.Entry(job2).Job.(testJob).name; actualName != "job2" {
+		t.Error("wrong job retrieved:", actualName)
+	}
+	if actualName := cron.Entry(job5).Job.(testJob).name; actualName != "job5" {
+		t.Error("wrong job retrieved:", actualName)
+	}
+
+	cron.Start()
+	defer cron.Stop()
+
+	select {
+	case <-time.After(OneSecond):
+		t.FailNow()
+	case <-wait(wg):
+	}
+
+	// Ensure the entries are in the right order.
+	expecteds := []string{"job2", "job4", "job5", "job1", "job3", "job0"}
+
+	var actuals []string
+	for _, entry := range cron.Entries() {
+		actuals = append(actuals, entry.Job.(testJob).name)
+	}
+
+	for i, expected := range expecteds {
+		if actuals[i] != expected {
+			t.Fatalf("Jobs not in the right order.  (expected) %s != %s (actual)", expecteds, actuals)
+		}
+	}
+
+	// Test getting Entries.
+	if actualName := cron.Entry(job2).Job.(testJob).name; actualName != "job2" {
+		t.Error("wrong job retrieved:", actualName)
+	}
+	if actualName := cron.Entry(job5).Job.(testJob).name; actualName != "job5" {
+		t.Error("wrong job retrieved:", actualName)
+	}
+}
+
+// Issue #206
+// Ensure that the next run of a job after removing an entry is accurate.
+func TestScheduleAfterRemoval(t *testing.T) {
+	var wg1 sync.WaitGroup
+	var wg2 sync.WaitGroup
+	wg1.Add(1)
+	wg2.Add(1)
+
+	// The first time this job is run, set a timer and remove the other job
+	// 750ms later. Correct behavior would be to still run the job again in
+	// 250ms, but the bug would cause it to run instead 1s later.
+
+	var calls int
+	var mu sync.Mutex
+
+	cron := newWithSeconds()
+	hourJob := cron.Schedule(Every(time.Hour), FuncJob(func() {}))
+	cron.Schedule(Every(time.Second), FuncJob(func() {
+		mu.Lock()
+		defer mu.Unlock()
+		switch calls {
+		case 0:
+			wg1.Done()
+			calls++
+		case 1:
+			time.Sleep(750 * time.Millisecond)
+			cron.Remove(hourJob)
+			calls++
+		case 2:
+			calls++
+			wg2.Done()
+		case 3:
+			panic("unexpected 3rd call")
+		}
+	}))
+
+	cron.Start()
+	defer cron.Stop()
+
+	// the first run might be any length of time 0 - 1s, since the schedule
+	// rounds to the second. wait for the first run to true up.
+	wg1.Wait()
+
+	select {
+	case <-time.After(2 * OneSecond):
+		t.Error("expected job fires 2 times")
+	case <-wait(&wg2):
+	}
+}
+
+type ZeroSchedule struct{}
+
+func (*ZeroSchedule) Next(time.Time) time.Time {
+	return time.Time{}
+}
+
+// Tests that job without time does not run
+func TestJobWithZeroTimeDoesNotRun(t *testing.T) {
+	cron := newWithSeconds()
+	var calls int64
+	cron.AddFunc("* * * * * *", func() { atomic.AddInt64(&calls, 1) })
+	cron.Schedule(new(ZeroSchedule), FuncJob(func() { t.Error("expected zero task will not run") }))
+	cron.Start()
+	defer cron.Stop()
+	<-time.After(OneSecond)
+	if atomic.LoadInt64(&calls) != 1 {
+		t.Errorf("called %d times, expected 1\n", calls)
+	}
+}
+
+func TestStopAndWait(t *testing.T) {
+	t.Run("nothing running, returns immediately", func(*testing.T) {
+		cron := newWithSeconds()
+		cron.Start()
+		ctx := cron.Stop()
+		select {
+		case <-ctx.Done():
+		case <-time.After(time.Millisecond):
+			t.Error("context was not done immediately")
+		}
+	})
+
+	t.Run("repeated calls to Stop", func(*testing.T) {
+		cron := newWithSeconds()
+		cron.Start()
+		_ = cron.Stop()
+		time.Sleep(time.Millisecond)
+		ctx := cron.Stop()
+		select {
+		case <-ctx.Done():
+		case <-time.After(time.Millisecond):
+			t.Error("context was not done immediately")
+		}
+	})
+
+	t.Run("a couple fast jobs added, still returns immediately", func(*testing.T) {
+		cron := newWithSeconds()
+		cron.AddFunc("* * * * * *", func() {})
+		cron.Start()
+		cron.AddFunc("* * * * * *", func() {})
+		cron.AddFunc("* * * * * *", func() {})
+		cron.AddFunc("* * * * * *", func() {})
+		time.Sleep(time.Second)
+		ctx := cron.Stop()
+		select {
+		case <-ctx.Done():
+		case <-time.After(time.Millisecond):
+			t.Error("context was not done immediately")
+		}
+	})
+
+	t.Run("a couple fast jobs and a slow job added, waits for slow job", func(*testing.T) {
+		cron := newWithSeconds()
+		cron.AddFunc("* * * * * *", func() {})
+		cron.Start()
+		cron.AddFunc("* * * * * *", func() { time.Sleep(2 * time.Second) })
+		cron.AddFunc("* * * * * *", func() {})
+		time.Sleep(time.Second)
+
+		ctx := cron.Stop()
+
+		// Verify that it is not done for at least 750ms
+		select {
+		case <-ctx.Done():
+			t.Error("context was done too quickly immediately")
+		case <-time.After(750 * time.Millisecond):
+			// expected, because the job sleeping for 1 second is still running
+		}
+
+		// Verify that it IS done in the next 500ms (giving 250ms buffer)
+		select {
+		case <-ctx.Done():
+			// expected
+		case <-time.After(1500 * time.Millisecond):
+			t.Error("context not done after job should have completed")
+		}
+	})
+
+	t.Run("repeated calls to stop, waiting for completion and after", func(*testing.T) {
+		cron := newWithSeconds()
+		cron.AddFunc("* * * * * *", func() {})
+		cron.AddFunc("* * * * * *", func() { time.Sleep(2 * time.Second) })
+		cron.Start()
+		cron.AddFunc("* * * * * *", func() {})
+		time.Sleep(time.Second)
+		ctx := cron.Stop()
+		ctx2 := cron.Stop()
+
+		// Verify that it is not done for at least 1500ms
+		select {
+		case <-ctx.Done():
+			t.Error("context was done too quickly immediately")
+		case <-ctx2.Done():
+			t.Error("context2 was done too quickly immediately")
+		case <-time.After(1500 * time.Millisecond):
+			// expected, because the job sleeping for 2 seconds is still running
+		}
+
+		// Verify that it IS done in the next 1s (giving 500ms buffer)
+		select {
+		case <-ctx.Done():
+			// expected
+		case <-time.After(time.Second):
+			t.Error("context not done after job should have completed")
+		}
+
+		// Verify that ctx2 is also done.
+		select {
+		case <-ctx2.Done():
+			// expected
+		case <-time.After(time.Millisecond):
+			t.Error("context2 not done even though context1 is")
+		}
+
+		// Verify that a new context retrieved from stop is immediately done.
+		ctx3 := cron.Stop()
+		select {
+		case <-ctx3.Done():
+			// expected
+		case <-time.After(time.Millisecond):
+			t.Error("context not done even when cron Stop is completed")
+		}
+	})
+}
+
+func TestMultiThreadedStartAndStop(t *testing.T) {
+	cron := New()
+	go cron.Run()
+	time.Sleep(2 * time.Millisecond)
+	cron.Stop()
+}
+
+func wait(wg *sync.WaitGroup) chan bool {
+	ch := make(chan bool)
+	go func() {
+		wg.Wait()
+		ch <- true
+	}()
+	return ch
+}
+
+func stop(cron *Cron) chan bool {
+	ch := make(chan bool)
+	go func() {
+		cron.Stop()
+		ch <- true
+	}()
+	return ch
+}
+
+// newWithSeconds returns a Cron with the seconds field enabled.
+func newWithSeconds() *Cron {
+	return New(WithParser(secondParser), WithChain())
+}

plugin/cron/logger.go

@@ -0,0 +1,86 @@
+package cron
+
+import (
+	"io"
+	"log"
+	"os"
+	"strings"
+	"time"
+)
+
+// DefaultLogger is used by Cron if none is specified.
+var DefaultLogger = PrintfLogger(log.New(os.Stdout, "cron: ", log.LstdFlags))
+
+// DiscardLogger can be used by callers to discard all log messages.
+var DiscardLogger = PrintfLogger(log.New(io.Discard, "", 0))
+
+// Logger is the interface used in this package for logging, so that any backend
+// can be plugged in. It is a subset of the github.com/go-logr/logr interface.
+type Logger interface {
+	// Info logs routine messages about cron's operation.
+	Info(msg string, keysAndValues ...interface{})
+	// Error logs an error condition.
+	Error(err error, msg string, keysAndValues ...interface{})
+}
+
+// PrintfLogger wraps a Printf-based logger (such as the standard library "log")
+// into an implementation of the Logger interface which logs errors only.
+func PrintfLogger(l interface{ Printf(string, ...interface{}) }) Logger {
+	return printfLogger{l, false}
+}
+
+// VerbosePrintfLogger wraps a Printf-based logger (such as the standard library
+// "log") into an implementation of the Logger interface which logs everything.
+func VerbosePrintfLogger(l interface{ Printf(string, ...interface{}) }) Logger {
+	return printfLogger{l, true}
+}
+
+type printfLogger struct {
+	logger  interface{ Printf(string, ...interface{}) }
+	logInfo bool
+}
+
+func (pl printfLogger) Info(msg string, keysAndValues ...interface{}) {
+	if pl.logInfo {
+		keysAndValues = formatTimes(keysAndValues)
+		pl.logger.Printf(
+			formatString(len(keysAndValues)),
+			append([]interface{}{msg}, keysAndValues...)...)
+	}
+}
+
+func (pl printfLogger) Error(err error, msg string, keysAndValues ...interface{}) {
+	keysAndValues = formatTimes(keysAndValues)
+	pl.logger.Printf(
+		formatString(len(keysAndValues)+2),
+		append([]interface{}{msg, "error", err}, keysAndValues...)...)
+}
+
+// formatString returns a logfmt-like format string for the number of
+// key/values.
+func formatString(numKeysAndValues int) string {
+	var sb strings.Builder
+	sb.WriteString("%s")
+	if numKeysAndValues > 0 {
+		sb.WriteString(", ")
+	}
+	for i := 0; i < numKeysAndValues/2; i++ {
+		if i > 0 {
+			sb.WriteString(", ")
+		}
+		sb.WriteString("%v=%v")
+	}
+	return sb.String()
+}
+
+// formatTimes formats any time.Time values as RFC3339.
+func formatTimes(keysAndValues []interface{}) []interface{} {
+	var formattedArgs []interface{}
+	for _, arg := range keysAndValues {
+		if t, ok := arg.(time.Time); ok {
+			arg = t.Format(time.RFC3339)
+		}
+		formattedArgs = append(formattedArgs, arg)
+	}
+	return formattedArgs
+}

plugin/cron/option.go

@@ -0,0 +1,45 @@
+package cron
+
+import (
+	"time"
+)
+
+// Option represents a modification to the default behavior of a Cron.
+type Option func(*Cron)
+
+// WithLocation overrides the timezone of the cron instance.
+func WithLocation(loc *time.Location) Option {
+	return func(c *Cron) {
+		c.location = loc
+	}
+}
+
+// WithSeconds overrides the parser used for interpreting job schedules to
+// include a seconds field as the first one.
+func WithSeconds() Option {
+	return WithParser(NewParser(
+		Second | Minute | Hour | Dom | Month | Dow | Descriptor,
+	))
+}
+
+// WithParser overrides the parser used for interpreting job schedules.
+func WithParser(p ScheduleParser) Option {
+	return func(c *Cron) {
+		c.parser = p
+	}
+}
+
+// WithChain specifies Job wrappers to apply to all jobs added to this cron.
+// Refer to the Chain* functions in this package for provided wrappers.
+func WithChain(wrappers ...JobWrapper) Option {
+	return func(c *Cron) {
+		c.chain = NewChain(wrappers...)
+	}
+}
+
+// WithLogger uses the provided logger.
+func WithLogger(logger Logger) Option {
+	return func(c *Cron) {
+		c.logger = logger
+	}
+}

plugin/cron/option_test.go

@@ -0,0 +1,43 @@
+//nolint:all
+package cron
+
+import (
+	"log"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestWithLocation(t *testing.T) {
+	c := New(WithLocation(time.UTC))
+	if c.location != time.UTC {
+		t.Errorf("expected UTC, got %v", c.location)
+	}
+}
+
+func TestWithParser(t *testing.T) {
+	var parser = NewParser(Dow)
+	c := New(WithParser(parser))
+	if c.parser != parser {
+		t.Error("expected provided parser")
+	}
+}
+
+func TestWithVerboseLogger(t *testing.T) {
+	var buf syncWriter
+	var logger = log.New(&buf, "", log.LstdFlags)
+	c := New(WithLogger(VerbosePrintfLogger(logger)))
+	if c.logger.(printfLogger).logger != logger {
+		t.Error("expected provided logger")
+	}
+
+	c.AddFunc("@every 1s", func() {})
+	c.Start()
+	time.Sleep(OneSecond)
+	c.Stop()
+	out := buf.String()
+	if !strings.Contains(out, "schedule,") ||
+		!strings.Contains(out, "run,") {
+		t.Error("expected to see some actions, got:", out)
+	}
+}

plugin/cron/parser.go

@@ -0,0 +1,435 @@
+package cron
+
+import (
+	"math"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/pkg/errors"
+)
+
+// Configuration options for creating a parser. Most options specify which
+// fields should be included, while others enable features. If a field is not
+// included the parser will assume a default value. These options do not change
+// the order fields are parse in.
+type ParseOption int
+
+const (
+	Second         ParseOption = 1 << iota // Seconds field, default 0
+	SecondOptional                         // Optional seconds field, default 0
+	Minute                                 // Minutes field, default 0
+	Hour                                   // Hours field, default 0
+	Dom                                    // Day of month field, default *
+	Month                                  // Month field, default *
+	Dow                                    // Day of week field, default *
+	DowOptional                            // Optional day of week field, default *
+	Descriptor                             // Allow descriptors such as @monthly, @weekly, etc.
+)
+
+var places = []ParseOption{
+	Second,
+	Minute,
+	Hour,
+	Dom,
+	Month,
+	Dow,
+}
+
+var defaults = []string{
+	"0",
+	"0",
+	"0",
+	"*",
+	"*",
+	"*",
+}
+
+// A custom Parser that can be configured.
+type Parser struct {
+	options ParseOption
+}
+
+// NewParser creates a Parser with custom options.
+//
+// It panics if more than one Optional is given, since it would be impossible to
+// correctly infer which optional is provided or missing in general.
+//
+// Examples
+//
+//	// Standard parser without descriptors
+//	specParser := NewParser(Minute | Hour | Dom | Month | Dow)
+//	sched, err := specParser.Parse("0 0 15 */3 *")
+//
+//	// Same as above, just excludes time fields
+//	specParser := NewParser(Dom | Month | Dow)
+//	sched, err := specParser.Parse("15 */3 *")
+//
+//	// Same as above, just makes Dow optional
+//	specParser := NewParser(Dom | Month | DowOptional)
+//	sched, err := specParser.Parse("15 */3")
+func NewParser(options ParseOption) Parser {
+	optionals := 0
+	if options&DowOptional > 0 {
+		optionals++
+	}
+	if options&SecondOptional > 0 {
+		optionals++
+	}
+	if optionals > 1 {
+		panic("multiple optionals may not be configured")
+	}
+	return Parser{options}
+}
+
+// Parse returns a new crontab schedule representing the given spec.
+// It returns a descriptive error if the spec is not valid.
+// It accepts crontab specs and features configured by NewParser.
+func (p Parser) Parse(spec string) (Schedule, error) {
+	if len(spec) == 0 {
+		return nil, errors.New("empty spec string")
+	}
+
+	// Extract timezone if present
+	var loc = time.Local
+	if strings.HasPrefix(spec, "TZ=") || strings.HasPrefix(spec, "CRON_TZ=") {
+		var err error
+		i := strings.Index(spec, " ")
+		eq := strings.Index(spec, "=")
+		if loc, err = time.LoadLocation(spec[eq+1 : i]); err != nil {
+			return nil, errors.Wrap(err, "provided bad location")
+		}
+		spec = strings.TrimSpace(spec[i:])
+	}
+
+	// Handle named schedules (descriptors), if configured
+	if strings.HasPrefix(spec, "@") {
+		if p.options&Descriptor == 0 {
+			return nil, errors.New("descriptors not enabled")
+		}
+		return parseDescriptor(spec, loc)
+	}
+
+	// Split on whitespace.
+	fields := strings.Fields(spec)
+
+	// Validate & fill in any omitted or optional fields
+	var err error
+	fields, err = normalizeFields(fields, p.options)
+	if err != nil {
+		return nil, err
+	}
+
+	field := func(field string, r bounds) uint64 {
+		if err != nil {
+			return 0
+		}
+		var bits uint64
+		bits, err = getField(field, r)
+		return bits
+	}
+
+	var (
+		second     = field(fields[0], seconds)
+		minute     = field(fields[1], minutes)
+		hour       = field(fields[2], hours)
+		dayofmonth = field(fields[3], dom)
+		month      = field(fields[4], months)
+		dayofweek  = field(fields[5], dow)
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	return &SpecSchedule{
+		Second:   second,
+		Minute:   minute,
+		Hour:     hour,
+		Dom:      dayofmonth,
+		Month:    month,
+		Dow:      dayofweek,
+		Location: loc,
+	}, nil
+}
+
+// normalizeFields takes a subset set of the time fields and returns the full set
+// with defaults (zeroes) populated for unset fields.
+//
+// As part of performing this function, it also validates that the provided
+// fields are compatible with the configured options.
+func normalizeFields(fields []string, options ParseOption) ([]string, error) {
+	// Validate optionals & add their field to options
+	optionals := 0
+	if options&SecondOptional > 0 {
+		options |= Second
+		optionals++
+	}
+	if options&DowOptional > 0 {
+		options |= Dow
+		optionals++
+	}
+	if optionals > 1 {
+		return nil, errors.New("multiple optionals may not be configured")
+	}
+
+	// Figure out how many fields we need
+	max := 0
+	for _, place := range places {
+		if options&place > 0 {
+			max++
+		}
+	}
+	min := max - optionals
+
+	// Validate number of fields
+	if count := len(fields); count < min || count > max {
+		if min == max {
+			return nil, errors.New("incorrect number of fields")
+		}
+		return nil, errors.New("incorrect number of fields, expected " + strconv.Itoa(min) + "-" + strconv.Itoa(max))
+	}
+
+	// Populate the optional field if not provided
+	if min < max && len(fields) == min {
+		switch {
+		case options&DowOptional > 0:
+			fields = append(fields, defaults[5]) // TODO: improve access to default
+		case options&SecondOptional > 0:
+			fields = append([]string{defaults[0]}, fields...)
+		default:
+			return nil, errors.New("unexpected optional field")
+		}
+	}
+
+	// Populate all fields not part of options with their defaults
+	n := 0
+	expandedFields := make([]string, len(places))
+	copy(expandedFields, defaults)
+	for i, place := range places {
+		if options&place > 0 {
+			expandedFields[i] = fields[n]
+			n++
+		}
+	}
+	return expandedFields, nil
+}
+
+var standardParser = NewParser(
+	Minute | Hour | Dom | Month | Dow | Descriptor,
+)
+
+// ParseStandard returns a new crontab schedule representing the given
+// standardSpec (https://en.wikipedia.org/wiki/Cron). It requires 5 entries
+// representing: minute, hour, day of month, month and day of week, in that
+// order. It returns a descriptive error if the spec is not valid.
+//
+// It accepts
+//   - Standard crontab specs, e.g. "* * * * ?"
+//   - Descriptors, e.g. "@midnight", "@every 1h30m"
+func ParseStandard(standardSpec string) (Schedule, error) {
+	return standardParser.Parse(standardSpec)
+}
+
+// getField returns an Int with the bits set representing all of the times that
+// the field represents or error parsing field value.  A "field" is a comma-separated
+// list of "ranges".
+func getField(field string, r bounds) (uint64, error) {
+	var bits uint64
+	ranges := strings.FieldsFunc(field, func(r rune) bool { return r == ',' })
+	for _, expr := range ranges {
+		bit, err := getRange(expr, r)
+		if err != nil {
+			return bits, err
+		}
+		bits |= bit
+	}
+	return bits, nil
+}
+
+// getRange returns the bits indicated by the given expression:
+//
+//	number | number "-" number [ "/" number ]
+//
+// or error parsing range.
+func getRange(expr string, r bounds) (uint64, error) {
+	var (
+		start, end, step uint
+		rangeAndStep     = strings.Split(expr, "/")
+		lowAndHigh       = strings.Split(rangeAndStep[0], "-")
+		singleDigit      = len(lowAndHigh) == 1
+		err              error
+	)
+
+	var extra uint64
+	if lowAndHigh[0] == "*" || lowAndHigh[0] == "?" {
+		start = r.min
+		end = r.max
+		extra = starBit
+	} else {
+		start, err = parseIntOrName(lowAndHigh[0], r.names)
+		if err != nil {
+			return 0, err
+		}
+		switch len(lowAndHigh) {
+		case 1:
+			end = start
+		case 2:
+			end, err = parseIntOrName(lowAndHigh[1], r.names)
+			if err != nil {
+				return 0, err
+			}
+		default:
+			return 0, errors.New("too many hyphens: " + expr)
+		}
+	}
+
+	switch len(rangeAndStep) {
+	case 1:
+		step = 1
+	case 2:
+		step, err = mustParseInt(rangeAndStep[1])
+		if err != nil {
+			return 0, err
+		}
+
+		// Special handling: "N/step" means "N-max/step".
+		if singleDigit {
+			end = r.max
+		}
+		if step > 1 {
+			extra = 0
+		}
+	default:
+		return 0, errors.New("too many slashes: " + expr)
+	}
+
+	if start < r.min {
+		return 0, errors.New("beginning of range below minimum: " + expr)
+	}
+	if end > r.max {
+		return 0, errors.New("end of range above maximum: " + expr)
+	}
+	if start > end {
+		return 0, errors.New("beginning of range after end: " + expr)
+	}
+	if step == 0 {
+		return 0, errors.New("step cannot be zero: " + expr)
+	}
+
+	return getBits(start, end, step) | extra, nil
+}
+
+// parseIntOrName returns the (possibly-named) integer contained in expr.
+func parseIntOrName(expr string, names map[string]uint) (uint, error) {
+	if names != nil {
+		if namedInt, ok := names[strings.ToLower(expr)]; ok {
+			return namedInt, nil
+		}
+	}
+	return mustParseInt(expr)
+}
+
+// mustParseInt parses the given expression as an int or returns an error.
+func mustParseInt(expr string) (uint, error) {
+	num, err := strconv.Atoi(expr)
+	if err != nil {
+		return 0, errors.Wrap(err, "failed to parse number")
+	}
+	if num < 0 {
+		return 0, errors.New("number must be positive")
+	}
+
+	return uint(num), nil
+}
+
+// getBits sets all bits in the range [min, max], modulo the given step size.
+func getBits(min, max, step uint) uint64 {
+	var bits uint64
+
+	// If step is 1, use shifts.
+	if step == 1 {
+		return ^(math.MaxUint64 << (max + 1)) & (math.MaxUint64 << min)
+	}
+
+	// Else, use a simple loop.
+	for i := min; i <= max; i += step {
+		bits |= 1 << i
+	}
+	return bits
+}
+
+// all returns all bits within the given bounds.
+func all(r bounds) uint64 {
+	return getBits(r.min, r.max, 1) | starBit
+}
+
+// parseDescriptor returns a predefined schedule for the expression, or error if none matches.
+func parseDescriptor(descriptor string, loc *time.Location) (Schedule, error) {
+	switch descriptor {
+	case "@yearly", "@annually":
+		return &SpecSchedule{
+			Second:   1 << seconds.min,
+			Minute:   1 << minutes.min,
+			Hour:     1 << hours.min,
+			Dom:      1 << dom.min,
+			Month:    1 << months.min,
+			Dow:      all(dow),
+			Location: loc,
+		}, nil
+
+	case "@monthly":
+		return &SpecSchedule{
+			Second:   1 << seconds.min,
+			Minute:   1 << minutes.min,
+			Hour:     1 << hours.min,
+			Dom:      1 << dom.min,
+			Month:    all(months),
+			Dow:      all(dow),
+			Location: loc,
+		}, nil
+
+	case "@weekly":
+		return &SpecSchedule{
+			Second:   1 << seconds.min,
+			Minute:   1 << minutes.min,
+			Hour:     1 << hours.min,
+			Dom:      all(dom),
+			Month:    all(months),
+			Dow:      1 << dow.min,
+			Location: loc,
+		}, nil
+
+	case "@daily", "@midnight":
+		return &SpecSchedule{
+			Second:   1 << seconds.min,
+			Minute:   1 << minutes.min,
+			Hour:     1 << hours.min,
+			Dom:      all(dom),
+			Month:    all(months),
+			Dow:      all(dow),
+			Location: loc,
+		}, nil
+
+	case "@hourly":
+		return &SpecSchedule{
+			Second:   1 << seconds.min,
+			Minute:   1 << minutes.min,
+			Hour:     all(hours),
+			Dom:      all(dom),
+			Month:    all(months),
+			Dow:      all(dow),
+			Location: loc,
+		}, nil
+	}
+
+	const every = "@every "
+	if strings.HasPrefix(descriptor, every) {
+		duration, err := time.ParseDuration(descriptor[len(every):])
+		if err != nil {
+			return nil, errors.Wrap(err, "failed to parse duration")
+		}
+		return Every(duration), nil
+	}
+
+	return nil, errors.New("unrecognized descriptor: " + descriptor)
+}

plugin/cron/parser_test.go

@@ -0,0 +1,384 @@
+//nolint:all
+package cron
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+var secondParser = NewParser(Second | Minute | Hour | Dom | Month | DowOptional | Descriptor)
+
+func TestRange(t *testing.T) {
+	zero := uint64(0)
+	ranges := []struct {
+		expr     string
+		min, max uint
+		expected uint64
+		err      string
+	}{
+		{"5", 0, 7, 1 << 5, ""},
+		{"0", 0, 7, 1 << 0, ""},
+		{"7", 0, 7, 1 << 7, ""},
+
+		{"5-5", 0, 7, 1 << 5, ""},
+		{"5-6", 0, 7, 1<<5 | 1<<6, ""},
+		{"5-7", 0, 7, 1<<5 | 1<<6 | 1<<7, ""},
+
+		{"5-6/2", 0, 7, 1 << 5, ""},
+		{"5-7/2", 0, 7, 1<<5 | 1<<7, ""},
+		{"5-7/1", 0, 7, 1<<5 | 1<<6 | 1<<7, ""},
+
+		{"*", 1, 3, 1<<1 | 1<<2 | 1<<3 | starBit, ""},
+		{"*/2", 1, 3, 1<<1 | 1<<3, ""},
+
+		{"5--5", 0, 0, zero, "too many hyphens"},
+		{"jan-x", 0, 0, zero, `failed to parse number: strconv.Atoi: parsing "jan": invalid syntax`},
+		{"2-x", 1, 5, zero, `failed to parse number: strconv.Atoi: parsing "x": invalid syntax`},
+		{"*/-12", 0, 0, zero, "number must be positive"},
+		{"*//2", 0, 0, zero, "too many slashes"},
+		{"1", 3, 5, zero, "below minimum"},
+		{"6", 3, 5, zero, "above maximum"},
+		{"5-3", 3, 5, zero, "beginning of range after end: 5-3"},
+		{"*/0", 0, 0, zero, "step cannot be zero: */0"},
+	}
+
+	for _, c := range ranges {
+		actual, err := getRange(c.expr, bounds{c.min, c.max, nil})
+		if len(c.err) != 0 && (err == nil || !strings.Contains(err.Error(), c.err)) {
+			t.Errorf("%s => expected %v, got %v", c.expr, c.err, err)
+		}
+		if len(c.err) == 0 && err != nil {
+			t.Errorf("%s => unexpected error %v", c.expr, err)
+		}
+		if actual != c.expected {
+			t.Errorf("%s => expected %d, got %d", c.expr, c.expected, actual)
+		}
+	}
+}
+
+func TestField(t *testing.T) {
+	fields := []struct {
+		expr     string
+		min, max uint
+		expected uint64
+	}{
+		{"5", 1, 7, 1 << 5},
+		{"5,6", 1, 7, 1<<5 | 1<<6},
+		{"5,6,7", 1, 7, 1<<5 | 1<<6 | 1<<7},
+		{"1,5-7/2,3", 1, 7, 1<<1 | 1<<5 | 1<<7 | 1<<3},
+	}
+
+	for _, c := range fields {
+		actual, _ := getField(c.expr, bounds{c.min, c.max, nil})
+		if actual != c.expected {
+			t.Errorf("%s => expected %d, got %d", c.expr, c.expected, actual)
+		}
+	}
+}
+
+func TestAll(t *testing.T) {
+	allBits := []struct {
+		r        bounds
+		expected uint64
+	}{
+		{minutes, 0xfffffffffffffff}, // 0-59: 60 ones
+		{hours, 0xffffff},            // 0-23: 24 ones
+		{dom, 0xfffffffe},            // 1-31: 31 ones, 1 zero
+		{months, 0x1ffe},             // 1-12: 12 ones, 1 zero
+		{dow, 0x7f},                  // 0-6: 7 ones
+	}
+
+	for _, c := range allBits {
+		actual := all(c.r) // all() adds the starBit, so compensate for that..
+		if c.expected|starBit != actual {
+			t.Errorf("%d-%d/%d => expected %b, got %b",
+				c.r.min, c.r.max, 1, c.expected|starBit, actual)
+		}
+	}
+}
+
+func TestBits(t *testing.T) {
+	bits := []struct {
+		min, max, step uint
+		expected       uint64
+	}{
+		{0, 0, 1, 0x1},
+		{1, 1, 1, 0x2},
+		{1, 5, 2, 0x2a}, // 101010
+		{1, 4, 2, 0xa},  // 1010
+	}
+
+	for _, c := range bits {
+		actual := getBits(c.min, c.max, c.step)
+		if c.expected != actual {
+			t.Errorf("%d-%d/%d => expected %b, got %b",
+				c.min, c.max, c.step, c.expected, actual)
+		}
+	}
+}
+
+func TestParseScheduleErrors(t *testing.T) {
+	var tests = []struct{ expr, err string }{
+		{"* 5 j * * *", `failed to parse number: strconv.Atoi: parsing "j": invalid syntax`},
+		{"@every Xm", "failed to parse duration"},
+		{"@unrecognized", "unrecognized descriptor"},
+		{"* * * *", "incorrect number of fields, expected 5-6"},
+		{"", "empty spec string"},
+	}
+	for _, c := range tests {
+		actual, err := secondParser.Parse(c.expr)
+		if err == nil || !strings.Contains(err.Error(), c.err) {
+			t.Errorf("%s => expected %v, got %v", c.expr, c.err, err)
+		}
+		if actual != nil {
+			t.Errorf("expected nil schedule on error, got %v", actual)
+		}
+	}
+}
+
+func TestParseSchedule(t *testing.T) {
+	tokyo, _ := time.LoadLocation("Asia/Tokyo")
+	entries := []struct {
+		parser   Parser
+		expr     string
+		expected Schedule
+	}{
+		{secondParser, "0 5 * * * *", every5min(time.Local)},
+		{standardParser, "5 * * * *", every5min(time.Local)},
+		{secondParser, "CRON_TZ=UTC  0 5 * * * *", every5min(time.UTC)},
+		{standardParser, "CRON_TZ=UTC  5 * * * *", every5min(time.UTC)},
+		{secondParser, "CRON_TZ=Asia/Tokyo 0 5 * * * *", every5min(tokyo)},
+		{secondParser, "@every 5m", ConstantDelaySchedule{5 * time.Minute}},
+		{secondParser, "@midnight", midnight(time.Local)},
+		{secondParser, "TZ=UTC  @midnight", midnight(time.UTC)},
+		{secondParser, "TZ=Asia/Tokyo @midnight", midnight(tokyo)},
+		{secondParser, "@yearly", annual(time.Local)},
+		{secondParser, "@annually", annual(time.Local)},
+		{
+			parser: secondParser,
+			expr:   "* 5 * * * *",
+			expected: &SpecSchedule{
+				Second:   all(seconds),
+				Minute:   1 << 5,
+				Hour:     all(hours),
+				Dom:      all(dom),
+				Month:    all(months),
+				Dow:      all(dow),
+				Location: time.Local,
+			},
+		},
+	}
+
+	for _, c := range entries {
+		actual, err := c.parser.Parse(c.expr)
+		if err != nil {
+			t.Errorf("%s => unexpected error %v", c.expr, err)
+		}
+		if !reflect.DeepEqual(actual, c.expected) {
+			t.Errorf("%s => expected %b, got %b", c.expr, c.expected, actual)
+		}
+	}
+}
+
+func TestOptionalSecondSchedule(t *testing.T) {
+	parser := NewParser(SecondOptional | Minute | Hour | Dom | Month | Dow | Descriptor)
+	entries := []struct {
+		expr     string
+		expected Schedule
+	}{
+		{"0 5 * * * *", every5min(time.Local)},
+		{"5 5 * * * *", every5min5s(time.Local)},
+		{"5 * * * *", every5min(time.Local)},
+	}
+
+	for _, c := range entries {
+		actual, err := parser.Parse(c.expr)
+		if err != nil {
+			t.Errorf("%s => unexpected error %v", c.expr, err)
+		}
+		if !reflect.DeepEqual(actual, c.expected) {
+			t.Errorf("%s => expected %b, got %b", c.expr, c.expected, actual)
+		}
+	}
+}
+
+func TestNormalizeFields(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    []string
+		options  ParseOption
+		expected []string
+	}{
+		{
+			"AllFields_NoOptional",
+			[]string{"0", "5", "*", "*", "*", "*"},
+			Second | Minute | Hour | Dom | Month | Dow | Descriptor,
+			[]string{"0", "5", "*", "*", "*", "*"},
+		},
+		{
+			"AllFields_SecondOptional_Provided",
+			[]string{"0", "5", "*", "*", "*", "*"},
+			SecondOptional | Minute | Hour | Dom | Month | Dow | Descriptor,
+			[]string{"0", "5", "*", "*", "*", "*"},
+		},
+		{
+			"AllFields_SecondOptional_NotProvided",
+			[]string{"5", "*", "*", "*", "*"},
+			SecondOptional | Minute | Hour | Dom | Month | Dow | Descriptor,
+			[]string{"0", "5", "*", "*", "*", "*"},
+		},
+		{
+			"SubsetFields_NoOptional",
+			[]string{"5", "15", "*"},
+			Hour | Dom | Month,
+			[]string{"0", "0", "5", "15", "*", "*"},
+		},
+		{
+			"SubsetFields_DowOptional_Provided",
+			[]string{"5", "15", "*", "4"},
+			Hour | Dom | Month | DowOptional,
+			[]string{"0", "0", "5", "15", "*", "4"},
+		},
+		{
+			"SubsetFields_DowOptional_NotProvided",
+			[]string{"5", "15", "*"},
+			Hour | Dom | Month | DowOptional,
+			[]string{"0", "0", "5", "15", "*", "*"},
+		},
+		{
+			"SubsetFields_SecondOptional_NotProvided",
+			[]string{"5", "15", "*"},
+			SecondOptional | Hour | Dom | Month,
+			[]string{"0", "0", "5", "15", "*", "*"},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(*testing.T) {
+			actual, err := normalizeFields(test.input, test.options)
+			if err != nil {
+				t.Errorf("unexpected error: %v", err)
+			}
+			if !reflect.DeepEqual(actual, test.expected) {
+				t.Errorf("expected %v, got %v", test.expected, actual)
+			}
+		})
+	}
+}
+
+func TestNormalizeFields_Errors(t *testing.T) {
+	tests := []struct {
+		name    string
+		input   []string
+		options ParseOption
+		err     string
+	}{
+		{
+			"TwoOptionals",
+			[]string{"0", "5", "*", "*", "*", "*"},
+			SecondOptional | Minute | Hour | Dom | Month | DowOptional,
+			"",
+		},
+		{
+			"TooManyFields",
+			[]string{"0", "5", "*", "*"},
+			SecondOptional | Minute | Hour,
+			"",
+		},
+		{
+			"NoFields",
+			[]string{},
+			SecondOptional | Minute | Hour,
+			"",
+		},
+		{
+			"TooFewFields",
+			[]string{"*"},
+			SecondOptional | Minute | Hour,
+			"",
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(*testing.T) {
+			actual, err := normalizeFields(test.input, test.options)
+			if err == nil {
+				t.Errorf("expected an error, got none. results: %v", actual)
+			}
+			if !strings.Contains(err.Error(), test.err) {
+				t.Errorf("expected error %q, got %q", test.err, err.Error())
+			}
+		})
+	}
+}
+
+func TestStandardSpecSchedule(t *testing.T) {
+	entries := []struct {
+		expr     string
+		expected Schedule
+		err      string
+	}{
+		{
+			expr:     "5 * * * *",
+			expected: &SpecSchedule{1 << seconds.min, 1 << 5, all(hours), all(dom), all(months), all(dow), time.Local},
+		},
+		{
+			expr:     "@every 5m",
+			expected: ConstantDelaySchedule{time.Duration(5) * time.Minute},
+		},
+		{
+			expr: "5 j * * *",
+			err:  `failed to parse number: strconv.Atoi: parsing "j": invalid syntax`,
+		},
+		{
+			expr: "* * * *",
+			err:  "incorrect number of fields",
+		},
+	}
+
+	for _, c := range entries {
+		actual, err := ParseStandard(c.expr)
+		if len(c.err) != 0 && (err == nil || !strings.Contains(err.Error(), c.err)) {
+			t.Errorf("%s => expected %v, got %v", c.expr, c.err, err)
+		}
+		if len(c.err) == 0 && err != nil {
+			t.Errorf("%s => unexpected error %v", c.expr, err)
+		}
+		if !reflect.DeepEqual(actual, c.expected) {
+			t.Errorf("%s => expected %b, got %b", c.expr, c.expected, actual)
+		}
+	}
+}
+
+func TestNoDescriptorParser(t *testing.T) {
+	parser := NewParser(Minute | Hour)
+	_, err := parser.Parse("@every 1m")
+	if err == nil {
+		t.Error("expected an error, got none")
+	}
+}
+
+func every5min(loc *time.Location) *SpecSchedule {
+	return &SpecSchedule{1 << 0, 1 << 5, all(hours), all(dom), all(months), all(dow), loc}
+}
+
+func every5min5s(loc *time.Location) *SpecSchedule {
+	return &SpecSchedule{1 << 5, 1 << 5, all(hours), all(dom), all(months), all(dow), loc}
+}
+
+func midnight(loc *time.Location) *SpecSchedule {
+	return &SpecSchedule{1, 1, 1, all(dom), all(months), all(dow), loc}
+}
+
+func annual(loc *time.Location) *SpecSchedule {
+	return &SpecSchedule{
+		Second:   1 << seconds.min,
+		Minute:   1 << minutes.min,
+		Hour:     1 << hours.min,
+		Dom:      1 << dom.min,
+		Month:    1 << months.min,
+		Dow:      all(dow),
+		Location: loc,
+	}
+}

plugin/cron/spec.go

@@ -0,0 +1,188 @@
+package cron
+
+import "time"
+
+// SpecSchedule specifies a duty cycle (to the second granularity), based on a
+// traditional crontab specification. It is computed initially and stored as bit sets.
+type SpecSchedule struct {
+	Second, Minute, Hour, Dom, Month, Dow uint64
+
+	// Override location for this schedule.
+	Location *time.Location
+}
+
+// bounds provides a range of acceptable values (plus a map of name to value).
+type bounds struct {
+	min, max uint
+	names    map[string]uint
+}
+
+// The bounds for each field.
+var (
+	seconds = bounds{0, 59, nil}
+	minutes = bounds{0, 59, nil}
+	hours   = bounds{0, 23, nil}
+	dom     = bounds{1, 31, nil}
+	months  = bounds{1, 12, map[string]uint{
+		"jan": 1,
+		"feb": 2,
+		"mar": 3,
+		"apr": 4,
+		"may": 5,
+		"jun": 6,
+		"jul": 7,
+		"aug": 8,
+		"sep": 9,
+		"oct": 10,
+		"nov": 11,
+		"dec": 12,
+	}}
+	dow = bounds{0, 6, map[string]uint{
+		"sun": 0,
+		"mon": 1,
+		"tue": 2,
+		"wed": 3,
+		"thu": 4,
+		"fri": 5,
+		"sat": 6,
+	}}
+)
+
+const (
+	// Set the top bit if a star was included in the expression.
+	starBit = 1 << 63
+)
+
+// Next returns the next time this schedule is activated, greater than the given
+// time.  If no time can be found to satisfy the schedule, return the zero time.
+func (s *SpecSchedule) Next(t time.Time) time.Time {
+	// General approach
+	//
+	// For Month, Day, Hour, Minute, Second:
+	// Check if the time value matches.  If yes, continue to the next field.
+	// If the field doesn't match the schedule, then increment the field until it matches.
+	// While incrementing the field, a wrap-around brings it back to the beginning
+	// of the field list (since it is necessary to re-verify previous field
+	// values)
+
+	// Convert the given time into the schedule's timezone, if one is specified.
+	// Save the original timezone so we can convert back after we find a time.
+	// Note that schedules without a time zone specified (time.Local) are treated
+	// as local to the time provided.
+	origLocation := t.Location()
+	loc := s.Location
+	if loc == time.Local {
+		loc = t.Location()
+	}
+	if s.Location != time.Local {
+		t = t.In(s.Location)
+	}
+
+	// Start at the earliest possible time (the upcoming second).
+	t = t.Add(1*time.Second - time.Duration(t.Nanosecond())*time.Nanosecond)
+
+	// This flag indicates whether a field has been incremented.
+	added := false
+
+	// If no time is found within five years, return zero.
+	yearLimit := t.Year() + 5
+
+WRAP:
+	if t.Year() > yearLimit {
+		return time.Time{}
+	}
+
+	// Find the first applicable month.
+	// If it's this month, then do nothing.
+	for 1<<uint(t.Month())&s.Month == 0 {
+		// If we have to add a month, reset the other parts to 0.
+		if !added {
+			added = true
+			// Otherwise, set the date at the beginning (since the current time is irrelevant).
+			t = time.Date(t.Year(), t.Month(), 1, 0, 0, 0, 0, loc)
+		}
+		t = t.AddDate(0, 1, 0)
+
+		// Wrapped around.
+		if t.Month() == time.January {
+			goto WRAP
+		}
+	}
+
+	// Now get a day in that month.
+	//
+	// NOTE: This causes issues for daylight savings regimes where midnight does
+	// not exist.  For example: Sao Paulo has DST that transforms midnight on
+	// 11/3 into 1am. Handle that by noticing when the Hour ends up != 0.
+	for !dayMatches(s, t) {
+		if !added {
+			added = true
+			t = time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, loc)
+		}
+		t = t.AddDate(0, 0, 1)
+		// Notice if the hour is no longer midnight due to DST.
+		// Add an hour if it's 23, subtract an hour if it's 1.
+		if t.Hour() != 0 {
+			if t.Hour() > 12 {
+				t = t.Add(time.Duration(24-t.Hour()) * time.Hour)
+			} else {
+				t = t.Add(time.Duration(-t.Hour()) * time.Hour)
+			}
+		}
+
+		if t.Day() == 1 {
+			goto WRAP
+		}
+	}
+
+	for 1<<uint(t.Hour())&s.Hour == 0 {
+		if !added {
+			added = true
+			t = time.Date(t.Year(), t.Month(), t.Day(), t.Hour(), 0, 0, 0, loc)
+		}
+		t = t.Add(1 * time.Hour)
+
+		if t.Hour() == 0 {
+			goto WRAP
+		}
+	}
+
+	for 1<<uint(t.Minute())&s.Minute == 0 {
+		if !added {
+			added = true
+			t = t.Truncate(time.Minute)
+		}
+		t = t.Add(1 * time.Minute)
+
+		if t.Minute() == 0 {
+			goto WRAP
+		}
+	}
+
+	for 1<<uint(t.Second())&s.Second == 0 {
+		if !added {
+			added = true
+			t = t.Truncate(time.Second)
+		}
+		t = t.Add(1 * time.Second)
+
+		if t.Second() == 0 {
+			goto WRAP
+		}
+	}
+
+	return t.In(origLocation)
+}
+
+// dayMatches returns true if the schedule's day-of-week and day-of-month
+// restrictions are satisfied by the given time.
+func dayMatches(s *SpecSchedule, t time.Time) bool {
+	var (
+		domMatch = 1<<uint(t.Day())&s.Dom > 0
+		dowMatch = 1<<uint(t.Weekday())&s.Dow > 0
+	)
+	if s.Dom&starBit > 0 || s.Dow&starBit > 0 {
+		return domMatch && dowMatch
+	}
+	return domMatch || dowMatch
+}

plugin/cron/spec_test.go

@@ -0,0 +1,301 @@
+//nolint:all
+package cron
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestActivation(t *testing.T) {
+	tests := []struct {
+		time, spec string
+		expected   bool
+	}{
+		// Every fifteen minutes.
+		{"Mon Jul 9 15:00 2012", "0/15 * * * *", true},
+		{"Mon Jul 9 15:45 2012", "0/15 * * * *", true},
+		{"Mon Jul 9 15:40 2012", "0/15 * * * *", false},
+
+		// Every fifteen minutes, starting at 5 minutes.
+		{"Mon Jul 9 15:05 2012", "5/15 * * * *", true},
+		{"Mon Jul 9 15:20 2012", "5/15 * * * *", true},
+		{"Mon Jul 9 15:50 2012", "5/15 * * * *", true},
+
+		// Named months
+		{"Sun Jul 15 15:00 2012", "0/15 * * Jul *", true},
+		{"Sun Jul 15 15:00 2012", "0/15 * * Jun *", false},
+
+		// Everything set.
+		{"Sun Jul 15 08:30 2012", "30 08 ? Jul Sun", true},
+		{"Sun Jul 15 08:30 2012", "30 08 15 Jul ?", true},
+		{"Mon Jul 16 08:30 2012", "30 08 ? Jul Sun", false},
+		{"Mon Jul 16 08:30 2012", "30 08 15 Jul ?", false},
+
+		// Predefined schedules
+		{"Mon Jul 9 15:00 2012", "@hourly", true},
+		{"Mon Jul 9 15:04 2012", "@hourly", false},
+		{"Mon Jul 9 15:00 2012", "@daily", false},
+		{"Mon Jul 9 00:00 2012", "@daily", true},
+		{"Mon Jul 9 00:00 2012", "@weekly", false},
+		{"Sun Jul 8 00:00 2012", "@weekly", true},
+		{"Sun Jul 8 01:00 2012", "@weekly", false},
+		{"Sun Jul 8 00:00 2012", "@monthly", false},
+		{"Sun Jul 1 00:00 2012", "@monthly", true},
+
+		// Test interaction of DOW and DOM.
+		// If both are restricted, then only one needs to match.
+		{"Sun Jul 15 00:00 2012", "* * 1,15 * Sun", true},
+		{"Fri Jun 15 00:00 2012", "* * 1,15 * Sun", true},
+		{"Wed Aug 1 00:00 2012", "* * 1,15 * Sun", true},
+		{"Sun Jul 15 00:00 2012", "* * */10 * Sun", true}, // verifies #70
+
+		// However, if one has a star, then both need to match.
+		{"Sun Jul 15 00:00 2012", "* * * * Mon", false},
+		{"Mon Jul 9 00:00 2012", "* * 1,15 * *", false},
+		{"Sun Jul 15 00:00 2012", "* * 1,15 * *", true},
+		{"Sun Jul 15 00:00 2012", "* * */2 * Sun", true},
+	}
+
+	for _, test := range tests {
+		sched, err := ParseStandard(test.spec)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		actual := sched.Next(getTime(test.time).Add(-1 * time.Second))
+		expected := getTime(test.time)
+		if test.expected && expected != actual || !test.expected && expected == actual {
+			t.Errorf("Fail evaluating %s on %s: (expected) %s != %s (actual)",
+				test.spec, test.time, expected, actual)
+		}
+	}
+}
+
+func TestNext(t *testing.T) {
+	runs := []struct {
+		time, spec string
+		expected   string
+	}{
+		// Simple cases
+		{"Mon Jul 9 14:45 2012", "0 0/15 * * * *", "Mon Jul 9 15:00 2012"},
+		{"Mon Jul 9 14:59 2012", "0 0/15 * * * *", "Mon Jul 9 15:00 2012"},
+		{"Mon Jul 9 14:59:59 2012", "0 0/15 * * * *", "Mon Jul 9 15:00 2012"},
+
+		// Wrap around hours
+		{"Mon Jul 9 15:45 2012", "0 20-35/15 * * * *", "Mon Jul 9 16:20 2012"},
+
+		// Wrap around days
+		{"Mon Jul 9 23:46 2012", "0 */15 * * * *", "Tue Jul 10 00:00 2012"},
+		{"Mon Jul 9 23:45 2012", "0 20-35/15 * * * *", "Tue Jul 10 00:20 2012"},
+		{"Mon Jul 9 23:35:51 2012", "15/35 20-35/15 * * * *", "Tue Jul 10 00:20:15 2012"},
+		{"Mon Jul 9 23:35:51 2012", "15/35 20-35/15 1/2 * * *", "Tue Jul 10 01:20:15 2012"},
+		{"Mon Jul 9 23:35:51 2012", "15/35 20-35/15 10-12 * * *", "Tue Jul 10 10:20:15 2012"},
+
+		{"Mon Jul 9 23:35:51 2012", "15/35 20-35/15 1/2 */2 * *", "Thu Jul 11 01:20:15 2012"},
+		{"Mon Jul 9 23:35:51 2012", "15/35 20-35/15 * 9-20 * *", "Wed Jul 10 00:20:15 2012"},
+		{"Mon Jul 9 23:35:51 2012", "15/35 20-35/15 * 9-20 Jul *", "Wed Jul 10 00:20:15 2012"},
+
+		// Wrap around months
+		{"Mon Jul 9 23:35 2012", "0 0 0 9 Apr-Oct ?", "Thu Aug 9 00:00 2012"},
+		{"Mon Jul 9 23:35 2012", "0 0 0 */5 Apr,Aug,Oct Mon", "Tue Aug 1 00:00 2012"},
+		{"Mon Jul 9 23:35 2012", "0 0 0 */5 Oct Mon", "Mon Oct 1 00:00 2012"},
+
+		// Wrap around years
+		{"Mon Jul 9 23:35 2012", "0 0 0 * Feb Mon", "Mon Feb 4 00:00 2013"},
+		{"Mon Jul 9 23:35 2012", "0 0 0 * Feb Mon/2", "Fri Feb 1 00:00 2013"},
+
+		// Wrap around minute, hour, day, month, and year
+		{"Mon Dec 31 23:59:45 2012", "0 * * * * *", "Tue Jan 1 00:00:00 2013"},
+
+		// Leap year
+		{"Mon Jul 9 23:35 2012", "0 0 0 29 Feb ?", "Mon Feb 29 00:00 2016"},
+
+		// Daylight savings time 2am EST (-5) -> 3am EDT (-4)
+		{"2012-03-11T00:00:00-0500", "TZ=America/New_York 0 30 2 11 Mar ?", "2013-03-11T02:30:00-0400"},
+
+		// hourly job
+		{"2012-03-11T00:00:00-0500", "TZ=America/New_York 0 0 * * * ?", "2012-03-11T01:00:00-0500"},
+		{"2012-03-11T01:00:00-0500", "TZ=America/New_York 0 0 * * * ?", "2012-03-11T03:00:00-0400"},
+		{"2012-03-11T03:00:00-0400", "TZ=America/New_York 0 0 * * * ?", "2012-03-11T04:00:00-0400"},
+		{"2012-03-11T04:00:00-0400", "TZ=America/New_York 0 0 * * * ?", "2012-03-11T05:00:00-0400"},
+
+		// hourly job using CRON_TZ
+		{"2012-03-11T00:00:00-0500", "CRON_TZ=America/New_York 0 0 * * * ?", "2012-03-11T01:00:00-0500"},
+		{"2012-03-11T01:00:00-0500", "CRON_TZ=America/New_York 0 0 * * * ?", "2012-03-11T03:00:00-0400"},
+		{"2012-03-11T03:00:00-0400", "CRON_TZ=America/New_York 0 0 * * * ?", "2012-03-11T04:00:00-0400"},
+		{"2012-03-11T04:00:00-0400", "CRON_TZ=America/New_York 0 0 * * * ?", "2012-03-11T05:00:00-0400"},
+
+		// 1am nightly job
+		{"2012-03-11T00:00:00-0500", "TZ=America/New_York 0 0 1 * * ?", "2012-03-11T01:00:00-0500"},
+		{"2012-03-11T01:00:00-0500", "TZ=America/New_York 0 0 1 * * ?", "2012-03-12T01:00:00-0400"},
+
+		// 2am nightly job (skipped)
+		{"2012-03-11T00:00:00-0500", "TZ=America/New_York 0 0 2 * * ?", "2012-03-12T02:00:00-0400"},
+
+		// Daylight savings time 2am EDT (-4) => 1am EST (-5)
+		{"2012-11-04T00:00:00-0400", "TZ=America/New_York 0 30 2 04 Nov ?", "2012-11-04T02:30:00-0500"},
+		{"2012-11-04T01:45:00-0400", "TZ=America/New_York 0 30 1 04 Nov ?", "2012-11-04T01:30:00-0500"},
+
+		// hourly job
+		{"2012-11-04T00:00:00-0400", "TZ=America/New_York 0 0 * * * ?", "2012-11-04T01:00:00-0400"},
+		{"2012-11-04T01:00:00-0400", "TZ=America/New_York 0 0 * * * ?", "2012-11-04T01:00:00-0500"},
+		{"2012-11-04T01:00:00-0500", "TZ=America/New_York 0 0 * * * ?", "2012-11-04T02:00:00-0500"},
+
+		// 1am nightly job (runs twice)
+		{"2012-11-04T00:00:00-0400", "TZ=America/New_York 0 0 1 * * ?", "2012-11-04T01:00:00-0400"},
+		{"2012-11-04T01:00:00-0400", "TZ=America/New_York 0 0 1 * * ?", "2012-11-04T01:00:00-0500"},
+		{"2012-11-04T01:00:00-0500", "TZ=America/New_York 0 0 1 * * ?", "2012-11-05T01:00:00-0500"},
+
+		// 2am nightly job
+		{"2012-11-04T00:00:00-0400", "TZ=America/New_York 0 0 2 * * ?", "2012-11-04T02:00:00-0500"},
+		{"2012-11-04T02:00:00-0500", "TZ=America/New_York 0 0 2 * * ?", "2012-11-05T02:00:00-0500"},
+
+		// 3am nightly job
+		{"2012-11-04T00:00:00-0400", "TZ=America/New_York 0 0 3 * * ?", "2012-11-04T03:00:00-0500"},
+		{"2012-11-04T03:00:00-0500", "TZ=America/New_York 0 0 3 * * ?", "2012-11-05T03:00:00-0500"},
+
+		// hourly job
+		{"TZ=America/New_York 2012-11-04T00:00:00-0400", "0 0 * * * ?", "2012-11-04T01:00:00-0400"},
+		{"TZ=America/New_York 2012-11-04T01:00:00-0400", "0 0 * * * ?", "2012-11-04T01:00:00-0500"},
+		{"TZ=America/New_York 2012-11-04T01:00:00-0500", "0 0 * * * ?", "2012-11-04T02:00:00-0500"},
+
+		// 1am nightly job (runs twice)
+		{"TZ=America/New_York 2012-11-04T00:00:00-0400", "0 0 1 * * ?", "2012-11-04T01:00:00-0400"},
+		{"TZ=America/New_York 2012-11-04T01:00:00-0400", "0 0 1 * * ?", "2012-11-04T01:00:00-0500"},
+		{"TZ=America/New_York 2012-11-04T01:00:00-0500", "0 0 1 * * ?", "2012-11-05T01:00:00-0500"},
+
+		// 2am nightly job
+		{"TZ=America/New_York 2012-11-04T00:00:00-0400", "0 0 2 * * ?", "2012-11-04T02:00:00-0500"},
+		{"TZ=America/New_York 2012-11-04T02:00:00-0500", "0 0 2 * * ?", "2012-11-05T02:00:00-0500"},
+
+		// 3am nightly job
+		{"TZ=America/New_York 2012-11-04T00:00:00-0400", "0 0 3 * * ?", "2012-11-04T03:00:00-0500"},
+		{"TZ=America/New_York 2012-11-04T03:00:00-0500", "0 0 3 * * ?", "2012-11-05T03:00:00-0500"},
+
+		// Unsatisfiable
+		{"Mon Jul 9 23:35 2012", "0 0 0 30 Feb ?", ""},
+		{"Mon Jul 9 23:35 2012", "0 0 0 31 Apr ?", ""},
+
+		// Monthly job
+		{"TZ=America/New_York 2012-11-04T00:00:00-0400", "0 0 3 3 * ?", "2012-12-03T03:00:00-0500"},
+
+		// Test the scenario of DST resulting in midnight not being a valid time.
+		// https://github.com/robfig/cron/issues/157
+		{"2018-10-17T05:00:00-0400", "TZ=America/Sao_Paulo 0 0 9 10 * ?", "2018-11-10T06:00:00-0500"},
+		{"2018-02-14T05:00:00-0500", "TZ=America/Sao_Paulo 0 0 9 22 * ?", "2018-02-22T07:00:00-0500"},
+	}
+
+	for _, c := range runs {
+		sched, err := secondParser.Parse(c.spec)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		actual := sched.Next(getTime(c.time))
+		expected := getTime(c.expected)
+		if !actual.Equal(expected) {
+			t.Errorf("%s, \"%s\": (expected) %v != %v (actual)", c.time, c.spec, expected, actual)
+		}
+	}
+}
+
+func TestErrors(t *testing.T) {
+	invalidSpecs := []string{
+		"xyz",
+		"60 0 * * *",
+		"0 60 * * *",
+		"0 0 * * XYZ",
+	}
+	for _, spec := range invalidSpecs {
+		_, err := ParseStandard(spec)
+		if err == nil {
+			t.Error("expected an error parsing: ", spec)
+		}
+	}
+}
+
+func getTime(value string) time.Time {
+	if value == "" {
+		return time.Time{}
+	}
+
+	var location = time.Local
+	if strings.HasPrefix(value, "TZ=") {
+		parts := strings.Fields(value)
+		loc, err := time.LoadLocation(parts[0][len("TZ="):])
+		if err != nil {
+			panic("could not parse location:" + err.Error())
+		}
+		location = loc
+		value = parts[1]
+	}
+
+	var layouts = []string{
+		"Mon Jan 2 15:04 2006",
+		"Mon Jan 2 15:04:05 2006",
+	}
+	for _, layout := range layouts {
+		if t, err := time.ParseInLocation(layout, value, location); err == nil {
+			return t
+		}
+	}
+	if t, err := time.ParseInLocation("2006-01-02T15:04:05-0700", value, location); err == nil {
+		return t
+	}
+	panic("could not parse time value " + value)
+}
+
+func TestNextWithTz(t *testing.T) {
+	runs := []struct {
+		time, spec string
+		expected   string
+	}{
+		// Failing tests
+		{"2016-01-03T13:09:03+0530", "14 14 * * *", "2016-01-03T14:14:00+0530"},
+		{"2016-01-03T04:09:03+0530", "14 14 * * ?", "2016-01-03T14:14:00+0530"},
+
+		// Passing tests
+		{"2016-01-03T14:09:03+0530", "14 14 * * *", "2016-01-03T14:14:00+0530"},
+		{"2016-01-03T14:00:00+0530", "14 14 * * ?", "2016-01-03T14:14:00+0530"},
+	}
+	for _, c := range runs {
+		sched, err := ParseStandard(c.spec)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		actual := sched.Next(getTimeTZ(c.time))
+		expected := getTimeTZ(c.expected)
+		if !actual.Equal(expected) {
+			t.Errorf("%s, \"%s\": (expected) %v != %v (actual)", c.time, c.spec, expected, actual)
+		}
+	}
+}
+
+func getTimeTZ(value string) time.Time {
+	if value == "" {
+		return time.Time{}
+	}
+	t, err := time.Parse("Mon Jan 2 15:04 2006", value)
+	if err != nil {
+		t, err = time.Parse("Mon Jan 2 15:04:05 2006", value)
+		if err != nil {
+			t, err = time.Parse("2006-01-02T15:04:05-0700", value)
+			if err != nil {
+				panic(err)
+			}
+		}
+	}
+
+	return t
+}
+
+// https://github.com/robfig/cron/issues/144
+func TestSlash0NoHang(t *testing.T) {
+	schedule := "TZ=America/New_York 15/0 * * * *"
+	_, err := ParseStandard(schedule)
+	if err == nil {
+		t.Error("expected an error on 0 increment")
+	}
+}

plugin/filter/common_converter.go

@@ -0,0 +1,448 @@
+package filter
+
+import (
+	"fmt"
+	"slices"
+	"strings"
+
+	"github.com/pkg/errors"
+	exprv1 "google.golang.org/genproto/googleapis/api/expr/v1alpha1"
+)
+
+// CommonSQLConverter handles the common CEL to SQL conversion logic.
+type CommonSQLConverter struct {
+	dialect    SQLDialect
+	paramIndex int
+}
+
+// NewCommonSQLConverter creates a new converter with the specified dialect.
+func NewCommonSQLConverter(dialect SQLDialect) *CommonSQLConverter {
+	return &CommonSQLConverter{
+		dialect:    dialect,
+		paramIndex: 1,
+	}
+}
+
+// ConvertExprToSQL converts a CEL expression to SQL using the configured dialect.
+func (c *CommonSQLConverter) ConvertExprToSQL(ctx *ConvertContext, expr *exprv1.Expr) error {
+	if v, ok := expr.ExprKind.(*exprv1.Expr_CallExpr); ok {
+		switch v.CallExpr.Function {
+		case "_||_", "_&&_":
+			return c.handleLogicalOperator(ctx, v.CallExpr)
+		case "!_":
+			return c.handleNotOperator(ctx, v.CallExpr)
+		case "_==_", "_!=_", "_<_", "_>_", "_<=_", "_>=_":
+			return c.handleComparisonOperator(ctx, v.CallExpr)
+		case "@in":
+			return c.handleInOperator(ctx, v.CallExpr)
+		case "contains":
+			return c.handleContainsOperator(ctx, v.CallExpr)
+		}
+	} else if v, ok := expr.ExprKind.(*exprv1.Expr_IdentExpr); ok {
+		return c.handleIdentifier(ctx, v.IdentExpr)
+	}
+	return nil
+}
+
+func (c *CommonSQLConverter) handleLogicalOperator(ctx *ConvertContext, callExpr *exprv1.Expr_Call) error {
+	if len(callExpr.Args) != 2 {
+		return errors.Errorf("invalid number of arguments for %s", callExpr.Function)
+	}
+
+	if _, err := ctx.Buffer.WriteString("("); err != nil {
+		return err
+	}
+
+	if err := c.ConvertExprToSQL(ctx, callExpr.Args[0]); err != nil {
+		return err
+	}
+
+	operator := "AND"
+	if callExpr.Function == "_||_" {
+		operator = "OR"
+	}
+
+	if _, err := ctx.Buffer.WriteString(fmt.Sprintf(" %s ", operator)); err != nil {
+		return err
+	}
+
+	if err := c.ConvertExprToSQL(ctx, callExpr.Args[1]); err != nil {
+		return err
+	}
+
+	if _, err := ctx.Buffer.WriteString(")"); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleNotOperator(ctx *ConvertContext, callExpr *exprv1.Expr_Call) error {
+	if len(callExpr.Args) != 1 {
+		return errors.Errorf("invalid number of arguments for %s", callExpr.Function)
+	}
+
+	if _, err := ctx.Buffer.WriteString("NOT ("); err != nil {
+		return err
+	}
+
+	if err := c.ConvertExprToSQL(ctx, callExpr.Args[0]); err != nil {
+		return err
+	}
+
+	if _, err := ctx.Buffer.WriteString(")"); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleComparisonOperator(ctx *ConvertContext, callExpr *exprv1.Expr_Call) error {
+	if len(callExpr.Args) != 2 {
+		return errors.Errorf("invalid number of arguments for %s", callExpr.Function)
+	}
+
+	// Check if the left side is a function call like size(tags)
+	if leftCallExpr, ok := callExpr.Args[0].ExprKind.(*exprv1.Expr_CallExpr); ok {
+		if leftCallExpr.CallExpr.Function == "size" {
+			return c.handleSizeComparison(ctx, callExpr, leftCallExpr.CallExpr)
+		}
+	}
+
+	identifier, err := GetIdentExprName(callExpr.Args[0])
+	if err != nil {
+		return err
+	}
+
+	if !slices.Contains([]string{"creator_id", "created_ts", "updated_ts", "visibility", "content", "has_task_list"}, identifier) {
+		return errors.Errorf("invalid identifier for %s", callExpr.Function)
+	}
+
+	value, err := GetExprValue(callExpr.Args[1])
+	if err != nil {
+		return err
+	}
+
+	operator := c.getComparisonOperator(callExpr.Function)
+
+	switch identifier {
+	case "created_ts", "updated_ts":
+		return c.handleTimestampComparison(ctx, identifier, operator, value)
+	case "visibility", "content":
+		return c.handleStringComparison(ctx, identifier, operator, value)
+	case "creator_id":
+		return c.handleIntComparison(ctx, identifier, operator, value)
+	case "has_task_list":
+		return c.handleBooleanComparison(ctx, identifier, operator, value)
+	}
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleSizeComparison(ctx *ConvertContext, callExpr *exprv1.Expr_Call, sizeCall *exprv1.Expr_Call) error {
+	if len(sizeCall.Args) != 1 {
+		return errors.New("size function requires exactly one argument")
+	}
+
+	identifier, err := GetIdentExprName(sizeCall.Args[0])
+	if err != nil {
+		return err
+	}
+
+	if identifier != "tags" {
+		return errors.Errorf("size function only supports 'tags' identifier, got: %s", identifier)
+	}
+
+	value, err := GetExprValue(callExpr.Args[1])
+	if err != nil {
+		return err
+	}
+
+	valueInt, ok := value.(int64)
+	if !ok {
+		return errors.New("size comparison value must be an integer")
+	}
+
+	operator := c.getComparisonOperator(callExpr.Function)
+
+	if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s %s",
+		c.dialect.GetJSONArrayLength("$.tags"),
+		operator,
+		c.dialect.GetParameterPlaceholder(c.paramIndex))); err != nil {
+		return err
+	}
+
+	ctx.Args = append(ctx.Args, valueInt)
+	c.paramIndex++
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleInOperator(ctx *ConvertContext, callExpr *exprv1.Expr_Call) error {
+	if len(callExpr.Args) != 2 {
+		return errors.Errorf("invalid number of arguments for %s", callExpr.Function)
+	}
+
+	// Check if this is "element in collection" syntax
+	if identifier, err := GetIdentExprName(callExpr.Args[1]); err == nil {
+		if identifier == "tags" {
+			return c.handleElementInTags(ctx, callExpr.Args[0])
+		}
+		return errors.Errorf("invalid collection identifier for %s: %s", callExpr.Function, identifier)
+	}
+
+	// Original logic for "identifier in [list]" syntax
+	identifier, err := GetIdentExprName(callExpr.Args[0])
+	if err != nil {
+		return err
+	}
+
+	if !slices.Contains([]string{"tag", "visibility"}, identifier) {
+		return errors.Errorf("invalid identifier for %s", callExpr.Function)
+	}
+
+	values := []any{}
+	for _, element := range callExpr.Args[1].GetListExpr().Elements {
+		value, err := GetConstValue(element)
+		if err != nil {
+			return err
+		}
+		values = append(values, value)
+	}
+
+	if identifier == "tag" {
+		return c.handleTagInList(ctx, values)
+	} else if identifier == "visibility" {
+		return c.handleVisibilityInList(ctx, values)
+	}
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleElementInTags(ctx *ConvertContext, elementExpr *exprv1.Expr) error {
+	element, err := GetConstValue(elementExpr)
+	if err != nil {
+		return errors.Errorf("first argument must be a constant value for 'element in tags': %v", err)
+	}
+
+	// Use dialect-specific JSON contains logic
+	sqlExpr := c.dialect.GetJSONContains("$.tags", "element")
+	if _, err := ctx.Buffer.WriteString(sqlExpr); err != nil {
+		return err
+	}
+
+	// For SQLite, we need a different approach since it uses LIKE
+	if _, ok := c.dialect.(*SQLiteDialect); ok {
+		ctx.Args = append(ctx.Args, fmt.Sprintf(`%%"%s"%%`, element))
+	} else {
+		ctx.Args = append(ctx.Args, element)
+	}
+	c.paramIndex++
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleTagInList(ctx *ConvertContext, values []any) error {
+	subconditions := []string{}
+	args := []any{}
+
+	for _, v := range values {
+		if _, ok := c.dialect.(*SQLiteDialect); ok {
+			subconditions = append(subconditions, c.dialect.GetJSONLike("$.tags", "pattern"))
+			args = append(args, fmt.Sprintf(`%%"%s"%%`, v))
+		} else {
+			subconditions = append(subconditions, c.dialect.GetJSONContains("$.tags", "element"))
+			args = append(args, v)
+		}
+		c.paramIndex++
+	}
+
+	if len(subconditions) == 1 {
+		if _, err := ctx.Buffer.WriteString(subconditions[0]); err != nil {
+			return err
+		}
+	} else {
+		if _, err := ctx.Buffer.WriteString(fmt.Sprintf("(%s)", strings.Join(subconditions, " OR "))); err != nil {
+			return err
+		}
+	}
+
+	ctx.Args = append(ctx.Args, args...)
+	return nil
+}
+
+func (c *CommonSQLConverter) handleVisibilityInList(ctx *ConvertContext, values []any) error {
+	placeholders := []string{}
+	for range values {
+		placeholders = append(placeholders, c.dialect.GetParameterPlaceholder(c.paramIndex))
+		c.paramIndex++
+	}
+
+	tablePrefix := c.dialect.GetTablePrefix()
+	if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s.`visibility` IN (%s)", tablePrefix, strings.Join(placeholders, ","))); err != nil {
+		return err
+	}
+
+	ctx.Args = append(ctx.Args, values...)
+	return nil
+}
+
+func (c *CommonSQLConverter) handleContainsOperator(ctx *ConvertContext, callExpr *exprv1.Expr_Call) error {
+	if len(callExpr.Args) != 1 {
+		return errors.Errorf("invalid number of arguments for %s", callExpr.Function)
+	}
+
+	identifier, err := GetIdentExprName(callExpr.Target)
+	if err != nil {
+		return err
+	}
+
+	if identifier != "content" {
+		return errors.Errorf("invalid identifier for %s", callExpr.Function)
+	}
+
+	arg, err := GetConstValue(callExpr.Args[0])
+	if err != nil {
+		return err
+	}
+
+	tablePrefix := c.dialect.GetTablePrefix()
+	if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s.`content` LIKE %s", tablePrefix, c.dialect.GetParameterPlaceholder(c.paramIndex))); err != nil {
+		return err
+	}
+
+	ctx.Args = append(ctx.Args, fmt.Sprintf("%%%s%%", arg))
+	c.paramIndex++
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleIdentifier(ctx *ConvertContext, identExpr *exprv1.Expr_Ident) error {
+	identifier := identExpr.GetName()
+
+	if !slices.Contains([]string{"pinned", "has_task_list"}, identifier) {
+		return errors.Errorf("invalid identifier %s", identifier)
+	}
+
+	if identifier == "pinned" {
+		tablePrefix := c.dialect.GetTablePrefix()
+		if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s.`pinned` IS TRUE", tablePrefix)); err != nil {
+			return err
+		}
+	} else if identifier == "has_task_list" {
+		if _, err := ctx.Buffer.WriteString(c.dialect.GetBooleanCheck("$.property.hasTaskList")); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleTimestampComparison(ctx *ConvertContext, field, operator string, value interface{}) error {
+	valueInt, ok := value.(int64)
+	if !ok {
+		return errors.New("invalid integer timestamp value")
+	}
+
+	timestampField := c.dialect.GetTimestampComparison(field)
+	if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s %s %s", timestampField, operator, c.dialect.GetParameterPlaceholder(c.paramIndex))); err != nil {
+		return err
+	}
+
+	ctx.Args = append(ctx.Args, valueInt)
+	c.paramIndex++
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleStringComparison(ctx *ConvertContext, field, operator string, value interface{}) error {
+	if operator != "=" && operator != "!=" {
+		return errors.Errorf("invalid operator for %s", field)
+	}
+
+	valueStr, ok := value.(string)
+	if !ok {
+		return errors.New("invalid string value")
+	}
+
+	tablePrefix := c.dialect.GetTablePrefix()
+	fieldName := field
+	if field == "visibility" {
+		fieldName = "`visibility`"
+	} else if field == "content" {
+		fieldName = "`content`"
+	}
+
+	if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s.%s %s %s", tablePrefix, fieldName, operator, c.dialect.GetParameterPlaceholder(c.paramIndex))); err != nil {
+		return err
+	}
+
+	ctx.Args = append(ctx.Args, valueStr)
+	c.paramIndex++
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleIntComparison(ctx *ConvertContext, field, operator string, value interface{}) error {
+	if operator != "=" && operator != "!=" {
+		return errors.Errorf("invalid operator for %s", field)
+	}
+
+	valueInt, ok := value.(int64)
+	if !ok {
+		return errors.New("invalid int value")
+	}
+
+	tablePrefix := c.dialect.GetTablePrefix()
+	if _, err := ctx.Buffer.WriteString(fmt.Sprintf("%s.`%s` %s %s", tablePrefix, field, operator, c.dialect.GetParameterPlaceholder(c.paramIndex))); err != nil {
+		return err
+	}
+
+	ctx.Args = append(ctx.Args, valueInt)
+	c.paramIndex++
+
+	return nil
+}
+
+func (c *CommonSQLConverter) handleBooleanComparison(ctx *ConvertContext, field, operator string, value interface{}) error {
+	if operator != "=" && operator != "!=" {
+		return errors.Errorf("invalid operator for %s", field)
+	}
+
+	valueBool, ok := value.(bool)
+	if !ok {
+		return errors.New("invalid boolean value for has_task_list")
+	}
+
+	sqlExpr := c.dialect.GetBooleanComparison("$.property.hasTaskList", valueBool)
+	if _, err := ctx.Buffer.WriteString(sqlExpr); err != nil {
+		return err
+	}
+
+	// For dialects that need parameters (PostgreSQL)
+	if _, ok := c.dialect.(*PostgreSQLDialect); ok {
+		ctx.Args = append(ctx.Args, valueBool)
+		c.paramIndex++
+	}
+
+	return nil
+}
+
+func (*CommonSQLConverter) getComparisonOperator(function string) string {
+	switch function {
+	case "_==_":
+		return "="
+	case "_!=_":
+		return "!="
+	case "_<_":
+		return "<"
+	case "_>_":
+		return ">"
+	case "_<=_":
+		return "<="
+	case "_>=_":
+		return ">="
+	default:
+		return "="
+	}
+}

plugin/filter/converter.go

@@ -0,0 +1,20 @@
+package filter
+
+import (
+	"strings"
+)
+
+type ConvertContext struct {
+	Buffer strings.Builder
+	Args   []any
+	// The offset of the next argument in the condition string.
+	// Mainly using for PostgreSQL.
+	ArgsOffset int
+}
+
+func NewConvertContext() *ConvertContext {
+	return &ConvertContext{
+		Buffer: strings.Builder{},
+		Args:   []any{},
+	}
+}

plugin/filter/dialect.go

@@ -0,0 +1,212 @@
+package filter
+
+import (
+	"fmt"
+	"strings"
+)
+
+// SQLDialect defines database-specific SQL generation methods.
+type SQLDialect interface {
+	// Basic field access
+	GetTablePrefix() string
+	GetParameterPlaceholder(index int) string
+
+	// JSON operations
+	GetJSONExtract(path string) string
+	GetJSONArrayLength(path string) string
+	GetJSONContains(path, element string) string
+	GetJSONLike(path, pattern string) string
+
+	// Boolean operations
+	GetBooleanValue(value bool) interface{}
+	GetBooleanComparison(path string, value bool) string
+	GetBooleanCheck(path string) string
+
+	// Timestamp operations
+	GetTimestampComparison(field string) string
+	GetCurrentTimestamp() string
+}
+
+// DatabaseType represents the type of database.
+type DatabaseType string
+
+const (
+	SQLite     DatabaseType = "sqlite"
+	MySQL      DatabaseType = "mysql"
+	PostgreSQL DatabaseType = "postgres"
+)
+
+// GetDialect returns the appropriate dialect for the database type.
+func GetDialect(dbType DatabaseType) SQLDialect {
+	switch dbType {
+	case SQLite:
+		return &SQLiteDialect{}
+	case MySQL:
+		return &MySQLDialect{}
+	case PostgreSQL:
+		return &PostgreSQLDialect{}
+	default:
+		return &SQLiteDialect{} // default fallback
+	}
+}
+
+// SQLiteDialect implements SQLDialect for SQLite.
+type SQLiteDialect struct{}
+
+func (*SQLiteDialect) GetTablePrefix() string {
+	return "`memo`"
+}
+
+func (*SQLiteDialect) GetParameterPlaceholder(_ int) string {
+	return "?"
+}
+
+func (d *SQLiteDialect) GetJSONExtract(path string) string {
+	return fmt.Sprintf("JSON_EXTRACT(%s.`payload`, '%s')", d.GetTablePrefix(), path)
+}
+
+func (d *SQLiteDialect) GetJSONArrayLength(path string) string {
+	return fmt.Sprintf("JSON_ARRAY_LENGTH(COALESCE(%s, JSON_ARRAY()))", d.GetJSONExtract(path))
+}
+
+func (d *SQLiteDialect) GetJSONContains(path, _ string) string {
+	return fmt.Sprintf("%s LIKE ?", d.GetJSONExtract(path))
+}
+
+func (d *SQLiteDialect) GetJSONLike(path, _ string) string {
+	return fmt.Sprintf("%s LIKE ?", d.GetJSONExtract(path))
+}
+
+func (*SQLiteDialect) GetBooleanValue(value bool) interface{} {
+	if value {
+		return 1
+	}
+	return 0
+}
+
+func (d *SQLiteDialect) GetBooleanComparison(path string, value bool) string {
+	return fmt.Sprintf("%s = %d", d.GetJSONExtract(path), d.GetBooleanValue(value))
+}
+
+func (d *SQLiteDialect) GetBooleanCheck(path string) string {
+	return fmt.Sprintf("%s IS TRUE", d.GetJSONExtract(path))
+}
+
+func (d *SQLiteDialect) GetTimestampComparison(field string) string {
+	return fmt.Sprintf("%s.`%s`", d.GetTablePrefix(), field)
+}
+
+func (*SQLiteDialect) GetCurrentTimestamp() string {
+	return "strftime('%s', 'now')"
+}
+
+// MySQLDialect implements SQLDialect for MySQL.
+type MySQLDialect struct{}
+
+func (*MySQLDialect) GetTablePrefix() string {
+	return "`memo`"
+}
+
+func (*MySQLDialect) GetParameterPlaceholder(_ int) string {
+	return "?"
+}
+
+func (d *MySQLDialect) GetJSONExtract(path string) string {
+	return fmt.Sprintf("JSON_EXTRACT(%s.`payload`, '%s')", d.GetTablePrefix(), path)
+}
+
+func (d *MySQLDialect) GetJSONArrayLength(path string) string {
+	return fmt.Sprintf("JSON_LENGTH(COALESCE(%s, JSON_ARRAY()))", d.GetJSONExtract(path))
+}
+
+func (d *MySQLDialect) GetJSONContains(path, _ string) string {
+	return fmt.Sprintf("JSON_CONTAINS(%s, ?)", d.GetJSONExtract(path))
+}
+
+func (d *MySQLDialect) GetJSONLike(path, _ string) string {
+	return fmt.Sprintf("%s LIKE ?", d.GetJSONExtract(path))
+}
+
+func (*MySQLDialect) GetBooleanValue(value bool) interface{} {
+	return value
+}
+
+func (d *MySQLDialect) GetBooleanComparison(path string, value bool) string {
+	boolStr := "false"
+	if value {
+		boolStr = "true"
+	}
+	return fmt.Sprintf("%s = CAST('%s' AS JSON)", d.GetJSONExtract(path), boolStr)
+}
+
+func (d *MySQLDialect) GetBooleanCheck(path string) string {
+	return fmt.Sprintf("%s = CAST('true' AS JSON)", d.GetJSONExtract(path))
+}
+
+func (d *MySQLDialect) GetTimestampComparison(field string) string {
+	return fmt.Sprintf("UNIX_TIMESTAMP(%s.`%s`)", d.GetTablePrefix(), field)
+}
+
+func (*MySQLDialect) GetCurrentTimestamp() string {
+	return "UNIX_TIMESTAMP()"
+}
+
+// PostgreSQLDialect implements SQLDialect for PostgreSQL.
+type PostgreSQLDialect struct{}
+
+func (*PostgreSQLDialect) GetTablePrefix() string {
+	return "memo"
+}
+
+func (*PostgreSQLDialect) GetParameterPlaceholder(index int) string {
+	return fmt.Sprintf("$%d", index)
+}
+
+func (d *PostgreSQLDialect) GetJSONExtract(path string) string {
+	// Convert $.property.hasTaskList to payload->'property'->>'hasTaskList'
+	parts := strings.Split(strings.TrimPrefix(path, "$."), ".")
+	result := fmt.Sprintf("%s.payload", d.GetTablePrefix())
+	for i, part := range parts {
+		if i == len(parts)-1 {
+			result += fmt.Sprintf("->>'%s'", part)
+		} else {
+			result += fmt.Sprintf("->'%s'", part)
+		}
+	}
+	return result
+}
+
+func (d *PostgreSQLDialect) GetJSONArrayLength(path string) string {
+	jsonPath := strings.Replace(path, "$.tags", "payload->'tags'", 1)
+	return fmt.Sprintf("jsonb_array_length(COALESCE(%s.%s, '[]'::jsonb))", d.GetTablePrefix(), jsonPath)
+}
+
+func (d *PostgreSQLDialect) GetJSONContains(path, _ string) string {
+	jsonPath := strings.Replace(path, "$.tags", "payload->'tags'", 1)
+	return fmt.Sprintf("%s.%s @> jsonb_build_array(?)", d.GetTablePrefix(), jsonPath)
+}
+
+func (d *PostgreSQLDialect) GetJSONLike(path, _ string) string {
+	jsonPath := strings.Replace(path, "$.tags", "payload->'tags'", 1)
+	return fmt.Sprintf("%s.%s @> jsonb_build_array(?)", d.GetTablePrefix(), jsonPath)
+}
+
+func (*PostgreSQLDialect) GetBooleanValue(value bool) interface{} {
+	return value
+}
+
+func (d *PostgreSQLDialect) GetBooleanComparison(path string, _ bool) string {
+	return fmt.Sprintf("(%s)::boolean = ?", d.GetJSONExtract(path))
+}
+
+func (d *PostgreSQLDialect) GetBooleanCheck(path string) string {
+	return fmt.Sprintf("(%s)::boolean IS TRUE", d.GetJSONExtract(path))
+}
+
+func (d *PostgreSQLDialect) GetTimestampComparison(field string) string {
+	return fmt.Sprintf("EXTRACT(EPOCH FROM %s.%s)", d.GetTablePrefix(), field)
+}
+
+func (*PostgreSQLDialect) GetCurrentTimestamp() string {
+	return "EXTRACT(EPOCH FROM NOW())"
+}

plugin/filter/expr.go

@@ -0,0 +1,127 @@
+package filter
+
+import (
+	"errors"
+	"time"
+
+	exprv1 "google.golang.org/genproto/googleapis/api/expr/v1alpha1"
+)
+
+// GetConstValue returns the constant value of the expression.
+func GetConstValue(expr *exprv1.Expr) (any, error) {
+	v, ok := expr.ExprKind.(*exprv1.Expr_ConstExpr)
+	if !ok {
+		return nil, errors.New("invalid constant expression")
+	}
+
+	switch v.ConstExpr.ConstantKind.(type) {
+	case *exprv1.Constant_StringValue:
+		return v.ConstExpr.GetStringValue(), nil
+	case *exprv1.Constant_Int64Value:
+		return v.ConstExpr.GetInt64Value(), nil
+	case *exprv1.Constant_Uint64Value:
+		return v.ConstExpr.GetUint64Value(), nil
+	case *exprv1.Constant_DoubleValue:
+		return v.ConstExpr.GetDoubleValue(), nil
+	case *exprv1.Constant_BoolValue:
+		return v.ConstExpr.GetBoolValue(), nil
+	default:
+		return nil, errors.New("unexpected constant type")
+	}
+}
+
+// GetIdentExprName returns the name of the identifier expression.
+func GetIdentExprName(expr *exprv1.Expr) (string, error) {
+	_, ok := expr.ExprKind.(*exprv1.Expr_IdentExpr)
+	if !ok {
+		return "", errors.New("invalid identifier expression")
+	}
+	return expr.GetIdentExpr().GetName(), nil
+}
+
+// GetFunctionValue evaluates CEL function calls and returns their value.
+// This is specifically for time functions like now().
+func GetFunctionValue(expr *exprv1.Expr) (any, error) {
+	callExpr, ok := expr.ExprKind.(*exprv1.Expr_CallExpr)
+	if !ok {
+		return nil, errors.New("invalid function call expression")
+	}
+
+	switch callExpr.CallExpr.Function {
+	case "now":
+		if len(callExpr.CallExpr.Args) != 0 {
+			return nil, errors.New("now() function takes no arguments")
+		}
+		return time.Now().Unix(), nil
+	case "_-_":
+		// Handle subtraction for expressions like "now() - 60 * 60 * 24"
+		if len(callExpr.CallExpr.Args) != 2 {
+			return nil, errors.New("subtraction requires exactly two arguments")
+		}
+		left, err := GetExprValue(callExpr.CallExpr.Args[0])
+		if err != nil {
+			return nil, err
+		}
+		right, err := GetExprValue(callExpr.CallExpr.Args[1])
+		if err != nil {
+			return nil, err
+		}
+		leftInt, ok1 := left.(int64)
+		rightInt, ok2 := right.(int64)
+		if !ok1 || !ok2 {
+			return nil, errors.New("subtraction operands must be integers")
+		}
+		return leftInt - rightInt, nil
+	case "_*_":
+		// Handle multiplication for expressions like "60 * 60 * 24"
+		if len(callExpr.CallExpr.Args) != 2 {
+			return nil, errors.New("multiplication requires exactly two arguments")
+		}
+		left, err := GetExprValue(callExpr.CallExpr.Args[0])
+		if err != nil {
+			return nil, err
+		}
+		right, err := GetExprValue(callExpr.CallExpr.Args[1])
+		if err != nil {
+			return nil, err
+		}
+		leftInt, ok1 := left.(int64)
+		rightInt, ok2 := right.(int64)
+		if !ok1 || !ok2 {
+			return nil, errors.New("multiplication operands must be integers")
+		}
+		return leftInt * rightInt, nil
+	case "_+_":
+		// Handle addition
+		if len(callExpr.CallExpr.Args) != 2 {
+			return nil, errors.New("addition requires exactly two arguments")
+		}
+		left, err := GetExprValue(callExpr.CallExpr.Args[0])
+		if err != nil {
+			return nil, err
+		}
+		right, err := GetExprValue(callExpr.CallExpr.Args[1])
+		if err != nil {
+			return nil, err
+		}
+		leftInt, ok1 := left.(int64)
+		rightInt, ok2 := right.(int64)
+		if !ok1 || !ok2 {
+			return nil, errors.New("addition operands must be integers")
+		}
+		return leftInt + rightInt, nil
+	default:
+		return nil, errors.New("unsupported function: " + callExpr.CallExpr.Function)
+	}
+}
+
+// GetExprValue attempts to get a value from an expression, trying constants first, then functions.
+func GetExprValue(expr *exprv1.Expr) (any, error) {
+	// Try to get constant value first
+	if constValue, err := GetConstValue(expr); err == nil {
+		return constValue, nil
+	}
+
+	// If not a constant, try to evaluate as a function
+	return GetFunctionValue(expr)
+}

plugin/filter/filter.go

@@ -0,0 +1,48 @@
+package filter
+
+import (
+	"time"
+
+	"github.com/google/cel-go/cel"
+	"github.com/google/cel-go/common/types"
+	"github.com/google/cel-go/common/types/ref"
+	"github.com/pkg/errors"
+	exprv1 "google.golang.org/genproto/googleapis/api/expr/v1alpha1"
+)
+
+// MemoFilterCELAttributes are the CEL attributes for memo.
+var MemoFilterCELAttributes = []cel.EnvOption{
+	cel.Variable("content", cel.StringType),
+	cel.Variable("creator_id", cel.IntType),
+	cel.Variable("created_ts", cel.IntType),
+	cel.Variable("updated_ts", cel.IntType),
+	cel.Variable("pinned", cel.BoolType),
+	cel.Variable("tag", cel.StringType),
+	cel.Variable("tags", cel.ListType(cel.StringType)),
+	cel.Variable("visibility", cel.StringType),
+	cel.Variable("has_task_list", cel.BoolType),
+	// Current timestamp function.
+	cel.Function("now",
+		cel.Overload("now",
+			[]*cel.Type{},
+			cel.IntType,
+			cel.FunctionBinding(func(_ ...ref.Val) ref.Val {
+				return types.Int(time.Now().Unix())
+			}),
+		),
+	),
+}
+
+// Parse parses the filter string and returns the parsed expression.
+// The filter string should be a CEL expression.
+func Parse(filter string, opts ...cel.EnvOption) (expr *exprv1.ParsedExpr, err error) {
+	e, err := cel.NewEnv(opts...)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to create CEL environment")
+	}
+	ast, issues := e.Compile(filter)
+	if issues != nil {
+		return nil, errors.Errorf("failed to compile filter: %v", issues)
+	}
+	return cel.AstToParsedExpr(ast)
+}

plugin/filter/templates.go

@@ -0,0 +1,146 @@
+package filter
+
+import (
+	"fmt"
+)
+
+// SQLTemplate holds database-specific SQL fragments.
+type SQLTemplate struct {
+	SQLite     string
+	MySQL      string
+	PostgreSQL string
+}
+
+// TemplateDBType represents the database type for templates.
+type TemplateDBType string
+
+const (
+	SQLiteTemplate     TemplateDBType = "sqlite"
+	MySQLTemplate      TemplateDBType = "mysql"
+	PostgreSQLTemplate TemplateDBType = "postgres"
+)
+
+// SQLTemplates contains common SQL patterns for different databases.
+var SQLTemplates = map[string]SQLTemplate{
+	"json_extract": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '%s')",
+		MySQL:      "JSON_EXTRACT(`memo`.`payload`, '%s')",
+		PostgreSQL: "memo.payload%s",
+	},
+	"json_array_length": {
+		SQLite:     "JSON_ARRAY_LENGTH(COALESCE(JSON_EXTRACT(`memo`.`payload`, '$.tags'), JSON_ARRAY()))",
+		MySQL:      "JSON_LENGTH(COALESCE(JSON_EXTRACT(`memo`.`payload`, '$.tags'), JSON_ARRAY()))",
+		PostgreSQL: "jsonb_array_length(COALESCE(memo.payload->'tags', '[]'::jsonb))",
+	},
+	"json_contains_element": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.tags') LIKE ?",
+		MySQL:      "JSON_CONTAINS(JSON_EXTRACT(`memo`.`payload`, '$.tags'), ?)",
+		PostgreSQL: "memo.payload->'tags' @> jsonb_build_array(?)",
+	},
+	"json_contains_tag": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.tags') LIKE ?",
+		MySQL:      "JSON_CONTAINS(JSON_EXTRACT(`memo`.`payload`, '$.tags'), ?)",
+		PostgreSQL: "memo.payload->'tags' @> jsonb_build_array(?)",
+	},
+	"boolean_true": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') = 1",
+		MySQL:      "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') = CAST('true' AS JSON)",
+		PostgreSQL: "(memo.payload->'property'->>'hasTaskList')::boolean = true",
+	},
+	"boolean_false": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') = 0",
+		MySQL:      "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') = CAST('false' AS JSON)",
+		PostgreSQL: "(memo.payload->'property'->>'hasTaskList')::boolean = false",
+	},
+	"boolean_not_true": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') != 1",
+		MySQL:      "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') != CAST('true' AS JSON)",
+		PostgreSQL: "(memo.payload->'property'->>'hasTaskList')::boolean != true",
+	},
+	"boolean_not_false": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') != 0",
+		MySQL:      "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') != CAST('false' AS JSON)",
+		PostgreSQL: "(memo.payload->'property'->>'hasTaskList')::boolean != false",
+	},
+	"boolean_compare": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') %s ?",
+		MySQL:      "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') %s CAST(? AS JSON)",
+		PostgreSQL: "(memo.payload->'property'->>'hasTaskList')::boolean %s ?",
+	},
+	"boolean_check": {
+		SQLite:     "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') IS TRUE",
+		MySQL:      "JSON_EXTRACT(`memo`.`payload`, '$.property.hasTaskList') = CAST('true' AS JSON)",
+		PostgreSQL: "(memo.payload->'property'->>'hasTaskList')::boolean IS TRUE",
+	},
+	"table_prefix": {
+		SQLite:     "`memo`",
+		MySQL:      "`memo`",
+		PostgreSQL: "memo",
+	},
+	"timestamp_field": {
+		SQLite:     "`memo`.`%s`",
+		MySQL:      "UNIX_TIMESTAMP(`memo`.`%s`)",
+		PostgreSQL: "EXTRACT(EPOCH FROM memo.%s)",
+	},
+	"content_like": {
+		SQLite:     "`memo`.`content` LIKE ?",
+		MySQL:      "`memo`.`content` LIKE ?",
+		PostgreSQL: "memo.content ILIKE ?",
+	},
+	"visibility_in": {
+		SQLite:     "`memo`.`visibility` IN (%s)",
+		MySQL:      "`memo`.`visibility` IN (%s)",
+		PostgreSQL: "memo.visibility IN (%s)",
+	},
+}
+
+// GetSQL returns the appropriate SQL for the given template and database type.
+func GetSQL(templateName string, dbType TemplateDBType) string {
+	template, exists := SQLTemplates[templateName]
+	if !exists {
+		return ""
+	}
+
+	switch dbType {
+	case SQLiteTemplate:
+		return template.SQLite
+	case MySQLTemplate:
+		return template.MySQL
+	case PostgreSQLTemplate:
+		return template.PostgreSQL
+	default:
+		return template.SQLite
+	}
+}
+
+// GetParameterPlaceholder returns the appropriate parameter placeholder for the database.
+func GetParameterPlaceholder(dbType TemplateDBType, index int) string {
+	switch dbType {
+	case PostgreSQLTemplate:
+		return fmt.Sprintf("$%d", index)
+	default:
+		return "?"
+	}
+}
+
+// GetParameterValue returns the appropriate parameter value for the database.
+func GetParameterValue(dbType TemplateDBType, templateName string, value interface{}) interface{} {
+	switch templateName {
+	case "json_contains_element", "json_contains_tag":
+		if dbType == SQLiteTemplate {
+			return fmt.Sprintf(`%%"%s"%%`, value)
+		}
+		return value
+	default:
+		return value
+	}
+}
+
+// FormatPlaceholders formats a list of placeholders for the given database type.
+func FormatPlaceholders(dbType TemplateDBType, count int, startIndex int) []string {
+	placeholders := make([]string, count)
+	for i := 0; i < count; i++ {
+		placeholders[i] = GetParameterPlaceholder(dbType, startIndex+i)
+	}
+	return placeholders
+}

plugin/httpgetter/html_meta.go

@@ -0,0 +1,166 @@
+package httpgetter
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+
+	"github.com/pkg/errors"
+	"golang.org/x/net/html"
+	"golang.org/x/net/html/atom"
+)
+
+var ErrInternalIP = errors.New("internal IP addresses are not allowed")
+
+var httpClient = &http.Client{
+	CheckRedirect: func(req *http.Request, via []*http.Request) error {
+		if err := validateURL(req.URL.String()); err != nil {
+			return errors.Wrap(err, "redirect to internal IP")
+		}
+		if len(via) >= 10 {
+			return errors.New("too many redirects")
+		}
+		return nil
+	},
+}
+
+type HTMLMeta struct {
+	Title       string `json:"title"`
+	Description string `json:"description"`
+	Image       string `json:"image"`
+}
+
+func GetHTMLMeta(urlStr string) (*HTMLMeta, error) {
+	if err := validateURL(urlStr); err != nil {
+		return nil, err
+	}
+
+	response, err := httpClient.Get(urlStr)
+	if err != nil {
+		return nil, err
+	}
+	defer response.Body.Close()
+
+	mediatype, err := getMediatype(response)
+	if err != nil {
+		return nil, err
+	}
+	if mediatype != "text/html" {
+		return nil, errors.New("not a HTML page")
+	}
+
+	// TODO: limit the size of the response body
+
+	htmlMeta := extractHTMLMeta(response.Body)
+	enrichSiteMeta(response.Request.URL, htmlMeta)
+	return htmlMeta, nil
+}
+
+func extractHTMLMeta(resp io.Reader) *HTMLMeta {
+	tokenizer := html.NewTokenizer(resp)
+	htmlMeta := new(HTMLMeta)
+
+	for {
+		tokenType := tokenizer.Next()
+		if tokenType == html.ErrorToken {
+			break
+		} else if tokenType == html.StartTagToken || tokenType == html.SelfClosingTagToken {
+			token := tokenizer.Token()
+			if token.DataAtom == atom.Body {
+				break
+			}
+
+			if token.DataAtom == atom.Title {
+				tokenizer.Next()
+				token := tokenizer.Token()
+				htmlMeta.Title = token.Data
+			} else if token.DataAtom == atom.Meta {
+				description, ok := extractMetaProperty(token, "description")
+				if ok {
+					htmlMeta.Description = description
+				}
+
+				ogTitle, ok := extractMetaProperty(token, "og:title")
+				if ok {
+					htmlMeta.Title = ogTitle
+				}
+
+				ogDescription, ok := extractMetaProperty(token, "og:description")
+				if ok {
+					htmlMeta.Description = ogDescription
+				}
+
+				ogImage, ok := extractMetaProperty(token, "og:image")
+				if ok {
+					htmlMeta.Image = ogImage
+				}
+			}
+		}
+	}
+
+	return htmlMeta
+}
+
+func extractMetaProperty(token html.Token, prop string) (content string, ok bool) {
+	content, ok = "", false
+	for _, attr := range token.Attr {
+		if attr.Key == "property" && attr.Val == prop {
+			ok = true
+		}
+		if attr.Key == "content" {
+			content = attr.Val
+		}
+	}
+	return content, ok
+}
+
+func validateURL(urlStr string) error {
+	u, err := url.Parse(urlStr)
+	if err != nil {
+		return errors.New("invalid URL format")
+	}
+
+	if u.Scheme != "http" && u.Scheme != "https" {
+		return errors.New("only http/https protocols are allowed")
+	}
+
+	host := u.Hostname()
+	if host == "" {
+		return errors.New("empty hostname")
+	}
+
+	// check if the hostname is an IP
+	if ip := net.ParseIP(host); ip != nil {
+		if ip.IsLoopback() || ip.IsPrivate() || ip.IsLinkLocalUnicast() {
+			return errors.Wrap(ErrInternalIP, ip.String())
+		}
+		return nil
+	}
+
+	// check if it's a hostname, resolve it and check all returned IPs
+	ips, err := net.LookupIP(host)
+	if err != nil {
+		return errors.Errorf("failed to resolve hostname: %v", err)
+	}
+
+	for _, ip := range ips {
+		if ip.IsLoopback() || ip.IsPrivate() || ip.IsLinkLocalUnicast() {
+			return errors.Wrapf(ErrInternalIP, "host=%s, ip=%s", host, ip.String())
+		}
+	}
+
+	return nil
+}
+
+func enrichSiteMeta(url *url.URL, meta *HTMLMeta) {
+	if url.Hostname() == "www.youtube.com" {
+		if url.Path == "/watch" {
+			vid := url.Query().Get("v")
+			if vid != "" {
+				meta.Image = fmt.Sprintf("https://img.youtube.com/vi/%s/mqdefault.jpg", vid)
+			}
+		}
+	}
+}

plugin/httpgetter/html_meta_test.go

@@ -0,0 +1,32 @@
+package httpgetter
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestGetHTMLMeta(t *testing.T) {
+	tests := []struct {
+		urlStr   string
+		htmlMeta HTMLMeta
+	}{}
+	for _, test := range tests {
+		metadata, err := GetHTMLMeta(test.urlStr)
+		require.NoError(t, err)
+		require.Equal(t, test.htmlMeta, *metadata)
+	}
+}
+
+func TestGetHTMLMetaForInternal(t *testing.T) {
+	// test for internal IP
+	if _, err := GetHTMLMeta("http://192.168.0.1"); !errors.Is(err, ErrInternalIP) {
+		t.Errorf("Expected error for internal IP, got %v", err)
+	}
+
+	// test for resolved internal IP
+	if _, err := GetHTMLMeta("http://localhost"); !errors.Is(err, ErrInternalIP) {
+		t.Errorf("Expected error for resolved internal IP, got %v", err)
+	}
+}

plugin/httpgetter/http_getter.go

@@ -0,0 +1 @@
+package httpgetter

plugin/httpgetter/image.go

@@ -0,0 +1,45 @@
+package httpgetter
+
+import (
+	"errors"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+)
+
+type Image struct {
+	Blob      []byte
+	Mediatype string
+}
+
+func GetImage(urlStr string) (*Image, error) {
+	if _, err := url.Parse(urlStr); err != nil {
+		return nil, err
+	}
+
+	response, err := http.Get(urlStr)
+	if err != nil {
+		return nil, err
+	}
+	defer response.Body.Close()
+
+	mediatype, err := getMediatype(response)
+	if err != nil {
+		return nil, err
+	}
+	if !strings.HasPrefix(mediatype, "image/") {
+		return nil, errors.New("wrong image mediatype")
+	}
+
+	bodyBytes, err := io.ReadAll(response.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	image := &Image{
+		Blob:      bodyBytes,
+		Mediatype: mediatype,
+	}
+	return image, nil
+}

plugin/httpgetter/util.go

@@ -0,0 +1,15 @@
+package httpgetter
+
+import (
+	"mime"
+	"net/http"
+)
+
+func getMediatype(response *http.Response) (string, error) {
+	contentType := response.Header.Get("content-type")
+	mediatype, _, err := mime.ParseMediaType(contentType)
+	if err != nil {
+		return "", err
+	}
+	return mediatype, nil
+}

plugin/idp/idp.go

@@ -0,0 +1,8 @@
+package idp
+
+type IdentityProviderUserInfo struct {
+	Identifier  string
+	DisplayName string
+	Email       string
+	AvatarURL   string
+}

plugin/idp/oauth2/oauth2.go

@@ -0,0 +1,123 @@
+// Package oauth2 is the plugin for OAuth2 Identity Provider.
+package oauth2
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+
+	"github.com/pkg/errors"
+	"golang.org/x/oauth2"
+
+	"github.com/usememos/memos/plugin/idp"
+	storepb "github.com/usememos/memos/proto/gen/store"
+)
+
+// IdentityProvider represents an OAuth2 Identity Provider.
+type IdentityProvider struct {
+	config *storepb.OAuth2Config
+}
+
+// NewIdentityProvider initializes a new OAuth2 Identity Provider with the given configuration.
+func NewIdentityProvider(config *storepb.OAuth2Config) (*IdentityProvider, error) {
+	for v, field := range map[string]string{
+		config.ClientId:                "clientId",
+		config.ClientSecret:            "clientSecret",
+		config.TokenUrl:                "tokenUrl",
+		config.UserInfoUrl:             "userInfoUrl",
+		config.FieldMapping.Identifier: "fieldMapping.identifier",
+	} {
+		if v == "" {
+			return nil, errors.Errorf(`the field "%s" is empty but required`, field)
+		}
+	}
+
+	return &IdentityProvider{
+		config: config,
+	}, nil
+}
+
+// ExchangeToken returns the exchanged OAuth2 token using the given authorization code.
+func (p *IdentityProvider) ExchangeToken(ctx context.Context, redirectURL, code string) (string, error) {
+	conf := &oauth2.Config{
+		ClientID:     p.config.ClientId,
+		ClientSecret: p.config.ClientSecret,
+		RedirectURL:  redirectURL,
+		Scopes:       p.config.Scopes,
+		Endpoint: oauth2.Endpoint{
+			AuthURL:   p.config.AuthUrl,
+			TokenURL:  p.config.TokenUrl,
+			AuthStyle: oauth2.AuthStyleInParams,
+		},
+	}
+
+	token, err := conf.Exchange(ctx, code)
+	if err != nil {
+		return "", errors.Wrap(err, "failed to exchange access token")
+	}
+
+	accessToken, ok := token.Extra("access_token").(string)
+	if !ok {
+		return "", errors.New(`missing "access_token" from authorization response`)
+	}
+
+	return accessToken, nil
+}
+
+// UserInfo returns the parsed user information using the given OAuth2 token.
+func (p *IdentityProvider) UserInfo(token string) (*idp.IdentityProviderUserInfo, error) {
+	client := &http.Client{}
+	req, err := http.NewRequest(http.MethodGet, p.config.UserInfoUrl, nil)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to new http request")
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", token))
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to get user information")
+	}
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to read response body")
+	}
+	defer resp.Body.Close()
+
+	var claims map[string]any
+	if err := json.Unmarshal(body, &claims); err != nil {
+		return nil, errors.Wrap(err, "failed to unmarshal response body")
+	}
+	slog.Info("user info claims", "claims", claims)
+	userInfo := &idp.IdentityProviderUserInfo{}
+	if v, ok := claims[p.config.FieldMapping.Identifier].(string); ok {
+		userInfo.Identifier = v
+	}
+	if userInfo.Identifier == "" {
+		return nil, errors.Errorf("the field %q is not found in claims or has empty value", p.config.FieldMapping.Identifier)
+	}
+
+	// Best effort to map optional fields
+	if p.config.FieldMapping.DisplayName != "" {
+		if v, ok := claims[p.config.FieldMapping.DisplayName].(string); ok {
+			userInfo.DisplayName = v
+		}
+	}
+	if userInfo.DisplayName == "" {
+		userInfo.DisplayName = userInfo.Identifier
+	}
+	if p.config.FieldMapping.Email != "" {
+		if v, ok := claims[p.config.FieldMapping.Email].(string); ok {
+			userInfo.Email = v
+		}
+	}
+	if p.config.FieldMapping.AvatarUrl != "" {
+		if v, ok := claims[p.config.FieldMapping.AvatarUrl].(string); ok {
+			userInfo.AvatarURL = v
+		}
+	}
+	slog.Info("user info", "userInfo", userInfo)
+	return userInfo, nil
+}

plugin/idp/oauth2/oauth2_test.go

@@ -0,0 +1,163 @@
+package oauth2
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/usememos/memos/plugin/idp"
+	storepb "github.com/usememos/memos/proto/gen/store"
+)
+
+func TestNewIdentityProvider(t *testing.T) {
+	tests := []struct {
+		name        string
+		config      *storepb.OAuth2Config
+		containsErr string
+	}{
+		{
+			name: "no tokenUrl",
+			config: &storepb.OAuth2Config{
+				ClientId:     "test-client-id",
+				ClientSecret: "test-client-secret",
+				AuthUrl:      "",
+				TokenUrl:     "",
+				UserInfoUrl:  "https://example.com/api/user",
+				FieldMapping: &storepb.FieldMapping{
+					Identifier: "login",
+				},
+			},
+			containsErr: `the field "tokenUrl" is empty but required`,
+		},
+		{
+			name: "no userInfoUrl",
+			config: &storepb.OAuth2Config{
+				ClientId:     "test-client-id",
+				ClientSecret: "test-client-secret",
+				AuthUrl:      "",
+				TokenUrl:     "https://example.com/token",
+				UserInfoUrl:  "",
+				FieldMapping: &storepb.FieldMapping{
+					Identifier: "login",
+				},
+			},
+			containsErr: `the field "userInfoUrl" is empty but required`,
+		},
+		{
+			name: "no field mapping identifier",
+			config: &storepb.OAuth2Config{
+				ClientId:     "test-client-id",
+				ClientSecret: "test-client-secret",
+				AuthUrl:      "",
+				TokenUrl:     "https://example.com/token",
+				UserInfoUrl:  "https://example.com/api/user",
+				FieldMapping: &storepb.FieldMapping{
+					Identifier: "",
+				},
+			},
+			containsErr: `the field "fieldMapping.identifier" is empty but required`,
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(*testing.T) {
+			_, err := NewIdentityProvider(test.config)
+			assert.ErrorContains(t, err, test.containsErr)
+		})
+	}
+}
+
+func newMockServer(t *testing.T, code, accessToken string, userinfo []byte) *httptest.Server {
+	mux := http.NewServeMux()
+
+	var rawIDToken string
+	mux.HandleFunc("/oauth2/token", func(w http.ResponseWriter, r *http.Request) {
+		require.Equal(t, http.MethodPost, r.Method)
+
+		body, err := io.ReadAll(r.Body)
+		require.NoError(t, err)
+		vals, err := url.ParseQuery(string(body))
+		require.NoError(t, err)
+
+		require.Equal(t, code, vals.Get("code"))
+		require.Equal(t, "authorization_code", vals.Get("grant_type"))
+
+		w.Header().Set("Content-Type", "application/json")
+		err = json.NewEncoder(w).Encode(map[string]any{
+			"access_token": accessToken,
+			"token_type":   "Bearer",
+			"expires_in":   3600,
+			"id_token":     rawIDToken,
+		})
+		require.NoError(t, err)
+	})
+	mux.HandleFunc("/oauth2/userinfo", func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		_, err := w.Write(userinfo)
+		require.NoError(t, err)
+	})
+
+	s := httptest.NewServer(mux)
+
+	return s
+}
+
+func TestIdentityProvider(t *testing.T) {
+	ctx := context.Background()
+
+	const (
+		testClientID    = "test-client-id"
+		testCode        = "test-code"
+		testAccessToken = "test-access-token"
+		testSubject     = "123456789"
+		testName        = "John Doe"
+		testEmail       = "john.doe@example.com"
+	)
+	userInfo, err := json.Marshal(
+		map[string]any{
+			"sub":   testSubject,
+			"name":  testName,
+			"email": testEmail,
+		},
+	)
+	require.NoError(t, err)
+
+	s := newMockServer(t, testCode, testAccessToken, userInfo)
+
+	oauth2, err := NewIdentityProvider(
+		&storepb.OAuth2Config{
+			ClientId:     testClientID,
+			ClientSecret: "test-client-secret",
+			TokenUrl:     fmt.Sprintf("%s/oauth2/token", s.URL),
+			UserInfoUrl:  fmt.Sprintf("%s/oauth2/userinfo", s.URL),
+			FieldMapping: &storepb.FieldMapping{
+				Identifier:  "sub",
+				DisplayName: "name",
+				Email:       "email",
+			},
+		},
+	)
+	require.NoError(t, err)
+
+	redirectURL := "https://example.com/oauth/callback"
+	oauthToken, err := oauth2.ExchangeToken(ctx, redirectURL, testCode)
+	require.NoError(t, err)
+	require.Equal(t, testAccessToken, oauthToken)
+
+	userInfoResult, err := oauth2.UserInfo(oauthToken)
+	require.NoError(t, err)
+
+	wantUserInfo := &idp.IdentityProviderUserInfo{
+		Identifier:  testSubject,
+		DisplayName: testName,
+		Email:       testEmail,
+	}
+	assert.Equal(t, wantUserInfo, userInfoResult)
+}

plugin/storage/s3/s3.go

@@ -0,0 +1,92 @@
+package s3
+
+import (
+	"context"
+	"io"
+	"time"
+
+	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/config"
+	"github.com/aws/aws-sdk-go-v2/credentials"
+	"github.com/aws/aws-sdk-go-v2/feature/s3/manager"
+	"github.com/aws/aws-sdk-go-v2/service/s3"
+	"github.com/pkg/errors"
+
+	storepb "github.com/usememos/memos/proto/gen/store"
+)
+
+type Client struct {
+	Client *s3.Client
+	Bucket *string
+}
+
+func NewClient(ctx context.Context, s3Config *storepb.StorageS3Config) (*Client, error) {
+	cfg, err := config.LoadDefaultConfig(ctx,
+		config.WithCredentialsProvider(credentials.NewStaticCredentialsProvider(s3Config.AccessKeyId, s3Config.AccessKeySecret, "")),
+		config.WithRegion(s3Config.Region),
+	)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to load s3 config")
+	}
+
+	client := s3.NewFromConfig(cfg, func(o *s3.Options) {
+		o.BaseEndpoint = aws.String(s3Config.Endpoint)
+		o.UsePathStyle = s3Config.UsePathStyle
+		o.RequestChecksumCalculation = aws.RequestChecksumCalculationWhenRequired
+		o.ResponseChecksumValidation = aws.ResponseChecksumValidationWhenRequired
+	})
+	return &Client{
+		Client: client,
+		Bucket: aws.String(s3Config.Bucket),
+	}, nil
+}
+
+// UploadObject uploads an object to S3.
+func (c *Client) UploadObject(ctx context.Context, key string, fileType string, content io.Reader) (string, error) {
+	uploader := manager.NewUploader(c.Client)
+	putInput := s3.PutObjectInput{
+		Bucket:      c.Bucket,
+		Key:         aws.String(key),
+		ContentType: aws.String(fileType),
+		Body:        content,
+	}
+	result, err := uploader.Upload(ctx, &putInput)
+	if err != nil {
+		return "", err
+	}
+
+	resultKey := result.Key
+	if resultKey == nil || *resultKey == "" {
+		return "", errors.New("failed to get file key")
+	}
+	return *resultKey, nil
+}
+
+// PresignGetObject presigns an object in S3.
+func (c *Client) PresignGetObject(ctx context.Context, key string) (string, error) {
+	presignClient := s3.NewPresignClient(c.Client)
+	presignResult, err := presignClient.PresignGetObject(ctx, &s3.GetObjectInput{
+		Bucket: aws.String(*c.Bucket),
+		Key:    aws.String(key),
+	}, func(opts *s3.PresignOptions) {
+		// Set the expiration time of the presigned URL to 5 days.
+		// Reference: https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-query-string-auth.html
+		opts.Expires = time.Duration(5 * 24 * time.Hour)
+	})
+	if err != nil {
+		return "", errors.Wrap(err, "failed to presign put object")
+	}
+	return presignResult.URL, nil
+}
+
+// DeleteObject deletes an object in S3.
+func (c *Client) DeleteObject(ctx context.Context, key string) error {
+	_, err := c.Client.DeleteObject(ctx, &s3.DeleteObjectInput{
+		Bucket: c.Bucket,
+		Key:    aws.String(key),
+	})
+	if err != nil {
+		return errors.Wrap(err, "failed to delete object")
+	}
+	return nil
+}

plugin/webhook/webhook.go

@@ -0,0 +1,90 @@
+package webhook
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"log/slog"
+	"net/http"
+	"time"
+
+	"github.com/pkg/errors"
+
+	v1pb "github.com/usememos/memos/proto/gen/api/v1"
+)
+
+var (
+	// timeout is the timeout for webhook request. Default to 30 seconds.
+	timeout = 30 * time.Second
+)
+
+type WebhookRequestPayload struct {
+	// The target URL for the webhook request.
+	URL string `json:"url"`
+	// The type of activity that triggered this webhook.
+	ActivityType string `json:"activityType"`
+	// The resource name of the creator. Format: users/{user}
+	Creator string `json:"creator"`
+	// The memo that triggered this webhook (if applicable).
+	Memo *v1pb.Memo `json:"memo"`
+}
+
+// Post posts the message to webhook endpoint.
+func Post(requestPayload *WebhookRequestPayload) error {
+	body, err := json.Marshal(requestPayload)
+	if err != nil {
+		return errors.Wrapf(err, "failed to marshal webhook request to %s", requestPayload.URL)
+	}
+
+	req, err := http.NewRequest("POST", requestPayload.URL, bytes.NewBuffer(body))
+	if err != nil {
+		return errors.Wrapf(err, "failed to construct webhook request to %s", requestPayload.URL)
+	}
+
+	req.Header.Set("Content-Type", "application/json")
+	client := &http.Client{
+		Timeout: timeout,
+	}
+	resp, err := client.Do(req)
+	if err != nil {
+		return errors.Wrapf(err, "failed to post webhook to %s", requestPayload.URL)
+	}
+
+	b, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return errors.Wrapf(err, "failed to read webhook response from %s", requestPayload.URL)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode < 200 || resp.StatusCode > 299 {
+		return errors.Errorf("failed to post webhook %s, status code: %d, response body: %s", requestPayload.URL, resp.StatusCode, b)
+	}
+
+	response := &struct {
+		Code    int    `json:"code"`
+		Message string `json:"message"`
+	}{}
+	if err := json.Unmarshal(b, response); err != nil {
+		return errors.Wrapf(err, "failed to unmarshal webhook response from %s", requestPayload.URL)
+	}
+
+	if response.Code != 0 {
+		return errors.Errorf("receive error code sent by webhook server, code %d, msg: %s", response.Code, response.Message)
+	}
+
+	return nil
+}
+
+// PostAsync posts the message to webhook endpoint asynchronously.
+// It spawns a new goroutine to handle the request and does not wait for the response.
+func PostAsync(requestPayload *WebhookRequestPayload) {
+	go func() {
+		if err := Post(requestPayload); err != nil {
+			// Since we're in a goroutine, we can only log the error
+			slog.Warn("Failed to dispatch webhook asynchronously",
+				slog.String("url", requestPayload.URL),
+				slog.String("activityType", requestPayload.ActivityType),
+				slog.Any("err", err))
+		}
+	}()
+}

plugin/webhook/webhook_test.go

@@ -0,0 +1 @@
+package webhook