package api

import (
	"context"
	"fmt"
	"net/http"
	"strings"

	"github.com/golang-jwt/jwt/v5"
	"workorders/internal/model"
)

var roleLevel = map[string]int{
	"admin": 4, "dispatcher": 3, "field_tech": 2, "viewer": 1,
}

// JWTAuth validates a locally-issued HMAC-signed JWT in the Authorization header.
func JWTAuth(secret string) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			auth := r.Header.Get("Authorization")
			if !strings.HasPrefix(auth, "Bearer ") {
				jsonError(w, "unauthorized", http.StatusUnauthorized)
				return
			}
			raw := strings.TrimPrefix(auth, "Bearer ")

			var claims model.LocalClaims
			_, err := jwt.ParseWithClaims(raw, &claims, func(t *jwt.Token) (any, error) {
				if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
					return nil, fmt.Errorf("unexpected signing method: %v", t.Header["alg"])
				}
				return []byte(secret), nil
			}, jwt.WithExpirationRequired())

			if err != nil {
				jsonError(w, "invalid token", http.StatusUnauthorized)
				return
			}

			user := model.UserClaims{
				UserID:      claims.UserID,
				Username:    claims.Username,
				Email:       claims.Email,
				DisplayName: claims.DisplayName,
				Role:        claims.Role,
			}
			ctx := context.WithValue(r.Context(), model.CtxUserKey, user)
			next.ServeHTTP(w, r.WithContext(ctx))
		})
	}
}

// RequireRole blocks requests where the user's role is below the required level.
func RequireRole(minRole string) func(http.Handler) http.Handler {
	minLevel := roleLevel[minRole]
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			user := UserFromCtx(r)
			if roleLevel[user.Role] >= minLevel {
				next.ServeHTTP(w, r)
				return
			}
			jsonError(w, "forbidden", http.StatusForbidden)
		})
	}
}

func CORS(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Access-Control-Allow-Origin", "*")
		w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
		w.Header().Set("Access-Control-Allow-Headers", "Authorization, Content-Type")
		if r.Method == http.MethodOptions {
			w.WriteHeader(http.StatusNoContent)
			return
		}
		next.ServeHTTP(w, r)
	})
}

func jsonError(w http.ResponseWriter, msg string, code int) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(code)
	fmt.Fprintf(w, `{"error":%q}`, msg)
}

func UserFromCtx(r *http.Request) model.UserClaims {
	u, _ := r.Context().Value(model.CtxUserKey).(model.UserClaims)
	return u
}