package filewebdav

import (
	"log/slog"
	"net/http"
	"os"
	"path/filepath"
	"sync"

	"github.com/yourusername/caldav-server/internal/auth"
	"github.com/yourusername/caldav-server/internal/config"
	xwebdav "golang.org/x/net/webdav"
)

// NewHandler returns an http.Handler that provides standard WebDAV file access,
// mounted at the fixed URL /files/ for every user and rooted at
// dataDir/<username>/files/ on disk. The URL is the same for all users —
// which user's directory is served is resolved from the Basic Auth identity
// in the request context, not from the URL.
//
// A dedicated xwebdav.Handler (with its own persistent LockSystem) is created
// once per user and cached, so LOCK/UNLOCK state survives across requests
// instead of being reset on every call.
func NewHandler(cfg *config.Config, dataDir string, logger *slog.Logger) http.Handler {
	var (
		mu       sync.Mutex
		handlers = make(map[string]http.Handler)
	)

	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		p := auth.FromContext(r.Context())
		if p == nil {
			w.WriteHeader(http.StatusUnauthorized)
			return
		}

		mu.Lock()
		h, ok := handlers[p.Username]
		if !ok {
			username := p.Username
			userDir := filepath.Join(dataDir, username, "files")
			if err := os.MkdirAll(userDir, 0o755); err != nil {
				mu.Unlock()
				logger.Error("creating user WebDAV dir", "user", username, "error", err)
				http.Error(w, "internal server error", http.StatusInternalServerError)
				return
			}

			// Each user gets their own isolated WebDAV handler (and lock
			// system) so paths and locks don't bleed between users, even
			// though they all share the same "/files/" URL.
			h = &xwebdav.Handler{
				FileSystem: xwebdav.Dir(userDir),
				LockSystem: xwebdav.NewMemLS(),
				Logger: func(r *http.Request, err error) {
					if err != nil {
						logger.Warn("WebDAV error",
							"user", username,
							"method", r.Method,
							"path", r.URL.Path,
							"error", err)
					}
				},
				Prefix: "/files",
			}
			handlers[username] = h
		}
		mu.Unlock()

		h.ServeHTTP(w, r)
	})
}