GitManager/internal/mcp/mcp_test.go

package mcp

import (
	"context"
	"encoding/json"
	"io"
	"log/slog"
	"os"
	"os/exec"
	"path/filepath"
	"testing"
	"time"

	mcpsdk "github.com/modelcontextprotocol/go-sdk/mcp"

	"gitmanager/internal/git"
	"gitmanager/internal/repos"
	"gitmanager/internal/service"
)

// TestMCPRoundTrip exercises the full path: a real temp git repo -> scanner ->
// service -> MCP tools, called by an in-memory MCP client.
func TestMCPRoundTrip(t *testing.T) {
	root := t.TempDir()
	repoPath := filepath.Join(root, "myrepo")
	if err := os.Mkdir(repoPath, 0o755); err != nil {
		t.Fatal(err)
	}
	runGit(t, repoPath, "init", "-b", "main")
	runGit(t, repoPath, "config", "user.email", "test@example.com")
	runGit(t, repoPath, "config", "user.name", "Test")
	if err := os.WriteFile(filepath.Join(repoPath, "README.md"), []byte("hi\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	runGit(t, repoPath, "add", "-A")
	runGit(t, repoPath, "commit", "-m", "first commit")

	// Populate the index via the real scanner, then build service + MCP server.
	log := slog.New(slog.NewTextHandler(io.Discard, nil))
	g := git.New("git")
	scanner := repos.NewScanner(g, log, []string{root}, 3, nil, time.Minute, false)
	scanner.Refresh(context.Background())

	svc := service.New(g, scanner.Index)
	srv := NewServer(svc, "test")

	// Wire an in-memory client<->server session.
	ctx := context.Background()
	clientT, serverT := mcpsdk.NewInMemoryTransports()
	serverSession, err := srv.Connect(ctx, serverT, nil)
	if err != nil {
		t.Fatalf("server connect: %v", err)
	}
	defer serverSession.Close()

	client := mcpsdk.NewClient(&mcpsdk.Implementation{Name: "test", Version: "0"}, nil)
	cs, err := client.Connect(ctx, clientT, nil)
	if err != nil {
		t.Fatalf("client connect: %v", err)
	}
	defer cs.Close()

	// list_repos should find our one repo.
	res, err := cs.CallTool(ctx, &mcpsdk.CallToolParams{Name: "list_repos"})
	if err != nil {
		t.Fatalf("list_repos: %v", err)
	}
	var listOut listReposOutput
	decodeResult(t, res, &listOut)
	states := listOut.Repos
	if len(states) != 1 {
		t.Fatalf("expected 1 repo, got %d: %+v", len(states), states)
	}
	if states[0].Name != "myrepo" || states[0].Branch != "main" {
		t.Fatalf("unexpected repo state: %+v", states[0])
	}

	// get_repo should return detail including the commit we made.
	res, err = cs.CallTool(ctx, &mcpsdk.CallToolParams{
		Name:      "get_repo",
		Arguments: map[string]any{"path": states[0].Path},
	})
	if err != nil {
		t.Fatalf("get_repo: %v", err)
	}
	var detail repos.Detail
	decodeResult(t, res, &detail)
	if len(detail.Commits) != 1 || detail.Commits[0].Subject != "first commit" {
		t.Fatalf("unexpected detail commits: %+v", detail.Commits)
	}

	// get_repo with a bad path is a tool error, not a protocol error.
	res, err = cs.CallTool(ctx, &mcpsdk.CallToolParams{
		Name:      "get_repo",
		Arguments: map[string]any{"path": filepath.Join(root, "nope")},
	})
	if err != nil {
		t.Fatalf("get_repo(bad) protocol error: %v", err)
	}
	if !res.IsError {
		t.Fatalf("expected IsError for unknown repo, got success")
	}
}

// decodeResult unmarshals the JSON text content of a tool result into v.
func decodeResult(t *testing.T, res *mcpsdk.CallToolResult, v any) {
	t.Helper()
	for _, c := range res.Content {
		if tc, ok := c.(*mcpsdk.TextContent); ok {
			if err := json.Unmarshal([]byte(tc.Text), v); err != nil {
				t.Fatalf("unmarshal result: %v (text=%s)", err, tc.Text)
			}
			return
		}
	}
	t.Fatalf("no text content in result: %+v", res.Content)
}

func runGit(t *testing.T, dir string, args ...string) {
	t.Helper()
	cmd := exec.Command("git", args...)
	cmd.Dir = dir
	if out, err := cmd.CombinedOutput(); err != nil {
		t.Fatalf("git %v: %v\n%s", args, err, out)
	}
}