package main

import (
	"context"
	"fmt"
	"log/slog"
	"net"
	"net/http"
	"os"
	"os/signal"
	"path/filepath"
	"syscall"
	"time"

	"git.arnef.de/arnef/nidus/internal/auth"
	"git.arnef.de/arnef/nidus/internal/caldav"
	"git.arnef.de/arnef/nidus/internal/carddav"
	"git.arnef.de/arnef/nidus/internal/config"
	"git.arnef.de/arnef/nidus/internal/db"
	"git.arnef.de/arnef/nidus/internal/store"
	"git.arnef.de/arnef/nidus/internal/web"
	filewebdav "git.arnef.de/arnef/nidus/internal/webdav"
	webstatic "git.arnef.de/arnef/nidus/web"
)

func main() {
	// ---- Configuration ----
	cfg, err := config.Load()
	if err != nil {
		fmt.Fprintf(os.Stderr, "error loading config: %v\n", err)
		os.Exit(1)
	}

	// ---- Logging ----
	logger := buildLogger(cfg)
	logger.Info("starting DAV server",
		"host", cfg.Server.Host,
		"port", cfg.Server.Port,
		"base_url", cfg.Server.BaseURL)

	// ---- Storage ----
	st, err := store.NewStore(cfg.Storage.DataDir)
	if err != nil {
		logger.Error("initialising store", "error", err)
		os.Exit(1)
	}

	// ---- Run migration if data directory needs restructuring ----
	if err := st.Migrate(); err != nil {
		logger.Error("migration failed", "error", err)
		os.Exit(1)
	}
	logger.Info("data directory migration completed")

	// ---- Database (users, calendars, address books, sharing) ----
	dbPath := filepath.Join(cfg.Storage.DataDir, "nidus.db")
	dbase, err := db.Open(dbPath)
	if err != nil {
		logger.Error("initialising database", "error", err)
		os.Exit(1)
	}
	defer dbase.Close()

	if n, err := dbase.UserCount(); err != nil {
		logger.Error("counting users", "error", err)
		os.Exit(1)
	} else if n == 0 {
		logger.Warn("no users exist yet — create one with: nidusctl user create <username>")
	}

	// Pre-create on-disk collections for every registered calendar/address
	// book, in case they were added via nidusctl/web UI while the server
	// wasn't running.
	users, err := dbase.ListUsers()
	if err != nil {
		logger.Error("listing users", "error", err)
		os.Exit(1)
	}
	for _, user := range users {
		cals, err := dbase.ListCalendars(user.Username)
		if err != nil {
			logger.Warn("listing calendars", "user", user.Username, "error", err)
			continue
		}
		for _, cal := range cals {
			if err := st.EnsureCollection(user.Username, "cal-"+cal.Name); err != nil {
				logger.Warn("creating calendar collection", "user", user.Username, "cal", cal.Name, "error", err)
			}
		}
		books, err := dbase.ListAddressBooks(user.Username)
		if err != nil {
			logger.Warn("listing address books", "user", user.Username, "error", err)
			continue
		}
		for _, book := range books {
			if err := st.EnsureCollection(user.Username, "card-"+book); err != nil {
				logger.Warn("creating address book collection", "user", user.Username, "book", book, "error", err)
			}
		}
	}

	// ---- Middleware ----
	authMw := auth.NewMiddleware(cfg, dbase, logger)

	// ---- Handlers ----
	calHandler := caldav.NewHandler(cfg, st, dbase, logger)
	cardHandler := carddav.NewHandler(cfg, st, dbase, logger)
	fileHandler := filewebdav.NewHandler(cfg, cfg.Storage.DataDir, logger)
	webUI := web.NewServer(cfg, st, dbase, logger)

	mux := buildMux(cfg, authMw, calHandler, cardHandler, fileHandler, webUI, logger)

	// ---- HTTP Server ----
	addr := net.JoinHostPort(cfg.Server.Host, fmt.Sprintf("%d", cfg.Server.Port))
	srv := &http.Server{
		Addr:         addr,
		Handler:      withRequestLogging(mux, logger),
		ReadTimeout:  30 * time.Second,
		WriteTimeout: 30 * time.Second,
		IdleTimeout:  120 * time.Second,
	}

	// ---- Graceful shutdown ----
	idleConnsClosed := make(chan struct{})
	go func() {
		quit := make(chan os.Signal, 1)
		signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
		<-quit

		logger.Info("shutting down...")
		ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
		defer cancel()
		if err := srv.Shutdown(ctx); err != nil {
			logger.Error("graceful shutdown failed", "error", err)
		}
		close(idleConnsClosed)
	}()

	logger.Info("server ready", "addr", addr)
	err = srv.ListenAndServe()
	if err != nil && err != http.ErrServerClosed {
		logger.Error("server error", "error", err)
		os.Exit(1)
	}

	<-idleConnsClosed
	logger.Info("server stopped")
}

// buildMux creates the top-level HTTP multiplexer.
func buildMux(
	cfg *config.Config,
	authMw *auth.Middleware,
	calHandler, cardHandler, fileHandler http.Handler,
	webUI *web.Server,
	logger *slog.Logger,
) *http.ServeMux {
	mux := http.NewServeMux()

	// Web UI (own cookie-based auth, not Basic Auth) — dashboard, login,
	// share management. Mounted at "/web/"; /cal/, /card/, /files/ keep
	// their own dedicated prefixes.
	mux.Handle("/web/", http.StripPrefix("/web", webUI.Handler(webstatic.FS())))

	// /.well-known/ redirects for auto-discovery
	mux.HandleFunc("/.well-known/caldav", func(w http.ResponseWriter, r *http.Request) {
		http.Redirect(w, r, cfg.Server.BaseURL+"/cal/", http.StatusMovedPermanently)
	})
	mux.HandleFunc("/.well-known/carddav", func(w http.ResponseWriter, r *http.Request) {
		http.Redirect(w, r, cfg.Server.BaseURL+"/card/", http.StatusMovedPermanently)
	})

	// Health check (unauthenticated)
	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusOK)
		_, _ = w.Write([]byte(`{"status":"ok"}`))
	})

	// CalDAV, CardDAV, and file WebDAV — all behind Basic Auth
	mux.Handle("/cal/", authMw.Wrap(calHandler))
	mux.Handle("/card/", authMw.Wrap(cardHandler))
	mux.Handle("/files/", authMw.Wrap(fileHandler))

	// Root — simple HTML welcome page (unauthenticated)
	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/" {
			http.NotFound(w, r)
			return
		}
		// Only plain GET/HEAD get the welcome page. Any other method
		// (PROPFIND, LOCK, PUT, ...) hitting "/" means a client is pointed
		// at the wrong URL — reject it explicitly instead of returning a
		// misleading 200 OK, which breaks WebDAV clients expecting 207.
		if r.Method != http.MethodGet && r.Method != http.MethodHead {
			w.Header().Set("Allow", "GET, HEAD")
			http.Error(w, "not a WebDAV collection; use /cal/, /card/ or /files/", http.StatusMethodNotAllowed)
			return
		}
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		fmt.Fprintf(w, welcomePage, cfg.Server.BaseURL, cfg.Server.BaseURL, cfg.Server.BaseURL, cfg.Server.BaseURL, cfg.Server.BaseURL)
	})

	return mux
}

// withRequestLogging wraps a handler with access-log middleware.
func withRequestLogging(next http.Handler, logger *slog.Logger) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		rw := &responseWriter{ResponseWriter: w, code: http.StatusOK}
		next.ServeHTTP(rw, r)
		logger.Info("request",
			"method", r.Method,
			"path", r.URL.Path,
			"status", rw.code,
			"duration_ms", time.Since(start).Milliseconds(),
			"remote_addr", r.RemoteAddr,
		)
	})
}

// responseWriter captures the status code for logging.
type responseWriter struct {
	http.ResponseWriter
	code int
}

func (rw *responseWriter) WriteHeader(code int) {
	rw.code = code
	rw.ResponseWriter.WriteHeader(code)
}

// buildLogger creates a slog.Logger based on config.
func buildLogger(cfg *config.Config) *slog.Logger {
	level := slog.LevelInfo
	switch cfg.Logging.Level {
	case "debug":
		level = slog.LevelDebug
	case "warn":
		level = slog.LevelWarn
	case "error":
		level = slog.LevelError
	}

	var handler slog.Handler
	opts := &slog.HandlerOptions{Level: level}
	if cfg.Logging.Format == "json" {
		handler = slog.NewJSONHandler(os.Stdout, opts)
	} else {
		handler = slog.NewTextHandler(os.Stdout, opts)
	}
	return slog.New(handler)
}

const welcomePage = `<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>DAV Server</title>
<style>
  body { font-family: system-ui, sans-serif; max-width: 640px; margin: 4rem auto; padding: 0 1rem; }
  h1   { color: #333; }
  code { background: #f4f4f4; padding: 2px 6px; border-radius: 3px; }
  ul   { line-height: 2; }
</style>
</head>
<body>
<h1>🗓 DAV Server</h1>
<p>This server provides CalDAV, CardDAV, and WebDAV access.</p>
<h2>Endpoints</h2>
<ul>
  <li><strong>CalDAV</strong>  — <code>%s/cal/</code></li>
  <li><strong>CardDAV</strong> — <code>%s/card/</code></li>
  <li><strong>WebDAV files</strong> — <code>%s/files/</code></li>
</ul>
<h2>Auto-discovery</h2>
<ul>
  <li><code>%s/.well-known/caldav</code></li>
  <li><code>%s/.well-known/carddav</code></li>
</ul>
<p><em>Authentication: HTTP Basic Auth</em></p>
<p><a href="/web/">Open the web dashboard →</a></p>
</body>
</html>`