// Start() the web server
func Start() {
	addr := fmt.Sprintf("%v:%v", webConfig.Ip4address, webConfig.Ip4port)
	server := &http.Server{
		Addr:         addr,
		Handler:      nil,
		ReadTimeout:  60 * time.Second,
		WriteTimeout: 60 * time.Second,
	}

	// We don't use ListenAndServe because it lacks a way to close the listener
	log.LogInfo("HTTP listening on TCP4 %v", addr)
	var err error
	listener, err = net.Listen("tcp", addr)
	if err != nil {
		log.LogError("HTTP failed to start TCP4 listener: %v", err)
		// TODO More graceful early-shutdown procedure
		panic(err)
	}

	err = server.Serve(listener)
	if shutdown {
		log.LogTrace("HTTP server shutting down on request")
	} else if err != nil {
		log.LogError("HTTP server failed: %v", err)
	}
}

// ServeHTTP builds the context and passes onto the real handler
func (h handler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	// Create the context
	ctx, err := NewContext(req)
	if err != nil {
		log.LogError("Failed to create context: %v", err)
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	defer ctx.Close()

	// Run the handler, grab the error, and report it
	buf := new(httpbuf.Buffer)
	log.LogTrace("Web: %v %v %v %v", req.RemoteAddr, req.Proto, req.Method, req.RequestURI)
	err = h(buf, req, ctx)
	if err != nil {
		log.LogError("Error handling %v: %v", req.RequestURI, err)
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	// Save the session
	if err = ctx.Session.Save(req, buf); err != nil {
		log.LogError("Failed to save session: %v", err)
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	// Apply the buffered response to the writer
	buf.Apply(w)
}

// Main listener loop
func (s *Server) Start() {
	cfg := config.GetPop3Config()
	addr, err := net.ResolveTCPAddr("tcp4", fmt.Sprintf("%v:%v",
		cfg.Ip4address, cfg.Ip4port))
	if err != nil {
		log.LogError("POP3 Failed to build tcp4 address: %v", err)
		// TODO More graceful early-shutdown procedure
		panic(err)
	}

	log.LogInfo("POP3 listening on TCP4 %v", addr)
	s.listener, err = net.ListenTCP("tcp4", addr)
	if err != nil {
		log.LogError("POP3 failed to start tcp4 listener: %v", err)
		// TODO More graceful early-shutdown procedure
		panic(err)
	}

	// Handle incoming connections
	var tempDelay time.Duration
	for sid := 1; ; sid++ {
		if conn, err := s.listener.Accept(); err != nil {
			if nerr, ok := err.(net.Error); ok && nerr.Temporary() {
				// Temporary error, sleep for a bit and try again
				if tempDelay == 0 {
					tempDelay = 5 * time.Millisecond
				} else {
					tempDelay *= 2
				}
				if max := 1 * time.Second; tempDelay > max {
					tempDelay = max
				}
				log.LogError("POP3 accept error: %v; retrying in %v", err, tempDelay)
				time.Sleep(tempDelay)
				continue
			} else {
				if s.shutdown {
					log.LogTrace("POP3 listener shutting down on request")
					return
				}
				// TODO Implement a max error counter before shutdown?
				// or maybe attempt to restart POP3
				panic(err)
			}
		} else {
			tempDelay = 0
			s.waitgroup.Add(1)
			go s.startSession(sid, conn)
		}
	}
}

// signalProcessor is a goroutine that handles OS signals
func signalProcessor(c <-chan os.Signal) {
	for {
		sig := <-c
		switch sig {
		case syscall.SIGHUP:
			// Rotate logs if configured
			if logf != nil {
				log.LogInfo("Recieved SIGHUP, cycling logfile")
				closeLogFile()
				openLogFile()
			} else {
				log.LogInfo("Ignoring SIGHUP, logfile not configured")
			}
		case syscall.SIGTERM:
			// Initiate shutdown
			log.LogInfo("Received SIGTERM, shutting down")
			go timedExit()
			web.Stop()
			if smtpServer != nil {
				smtpServer.Stop()
			} else {
				log.LogError("smtpServer was nil during shutdown")
			}
		}
	}
}

func Stop() {
	log.LogTrace("HTTP shutdown requested")
	shutdown = true
	if listener != nil {
		listener.Close()
	} else {
		log.LogError("HTTP listener was nil during shutdown")
	}
}

// RenderPartial fetches the named template and renders it to the provided
// ResponseWriter.
func RenderPartial(name string, w http.ResponseWriter, data interface{}) error {
	t, err := ParseTemplate(name, true)
	if err != nil {
		log.LogError("Error in template '%v': %v", name, err)
		return err
	}
	w.Header().Set("Expires", "-1")
	return t.Execute(w, data)
}

// createDir checks for the presence of the path for this mailbox, creates it if needed
func (mb *FileMailbox) createDir() error {
	if _, err := os.Stat(mb.path); err != nil {
		if err := os.MkdirAll(mb.path, 0770); err != nil {
			log.LogError("Failed to create directory %v, %v", mb.path, err)
			return err
		}
	}
	return nil
}

// NewFileDataStore creates a new DataStore object using the specified path
func NewFileDataStore(cfg config.DataStoreConfig) DataStore {
	path := cfg.Path
	if path == "" {
		log.LogError("No value configured for datastore path")
		return nil
	}
	mailPath := filepath.Join(path, "mail")
	if _, err := os.Stat(mailPath); err != nil {
		// Mail datastore does not yet exist
		os.MkdirAll(mailPath, 0770)
	}
	return &FileDataStore{path: path, mailPath: mailPath, messageCap: cfg.MailboxMsgCap}
}

// Reversable routing function (shared with templates)
func reverse(name string, things ...interface{}) string {
	// Convert the things to strings
	strs := make([]string, len(things))
	for i, th := range things {
		strs[i] = fmt.Sprint(th)
	}
	// Grab the route
	u, err := Router.Get(name).URL(strs...)
	if err != nil {
		log.LogError("Failed to reverse route: %v", err)
		return "/ROUTE-ERROR"
	}
	return u.Path
}

func retentionScanner(ds DataStore, maxAge time.Duration, sleep time.Duration) {
	start := time.Now()
	for {
		// Prevent scanner from running more than once a minute
		since := time.Since(start)
		if since < time.Minute {
			dur := time.Minute - since
			log.LogTrace("Retention scanner sleeping for %v", dur)
			time.Sleep(dur)
		}
		start = time.Now()

		// Kickoff scan
		if err := doRetentionScan(ds, maxAge, sleep); err != nil {
			log.LogError("Error during retention scan: %v", err)
		}
	}
}

// doRetentionScan does a single pass of all mailboxes looking for messages that can be purged
func doRetentionScan(ds DataStore, maxAge time.Duration, sleep time.Duration) error {
	log.LogTrace("Starting retention scan")
	cutoff := time.Now().Add(-1 * maxAge)
	mboxes, err := ds.AllMailboxes()
	if err != nil {
		return err
	}

	retained := 0
	for _, mb := range mboxes {
		messages, err := mb.GetMessages()
		if err != nil {
			return err
		}
		for _, msg := range messages {
			if msg.Date().Before(cutoff) {
				log.LogTrace("Purging expired message %v", msg.Id())
				err = msg.Delete()
				if err != nil {
					// Log but don't abort
					log.LogError("Failed to purge message %v: %v", msg.Id(), err)
				} else {
					expRetentionDeletesTotal.Add(1)
				}
			} else {
				retained++
			}
		}
		// Sleep after completing a mailbox
		time.Sleep(sleep)
	}

	setRetentionScanCompleted(time.Now())
	expRetainedCurrent.Set(int64(retained))

	return nil
}

func (ses *Session) logError(msg string, args ...interface{}) {
	// Update metrics
	//expErrorsTotal.Add(1)
	log.LogError("POP3[%v]<%v> %v", ses.remoteHost, ses.id, fmt.Sprintf(msg, args...))
}

func main() {
	config.VERSION = VERSION
	config.BUILD_DATE = BUILD_DATE

	flag.Parse()
	if *help {
		flag.Usage()
		return
	}

	// Load & Parse config
	if flag.NArg() != 1 {
		flag.Usage()
		os.Exit(1)
	}
	err := config.LoadConfig(flag.Arg(0))
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to parse config: %v\n", err)
		os.Exit(1)
	}

	// Setup signal handler
	sigChan := make(chan os.Signal)
	signal.Notify(sigChan, syscall.SIGHUP, syscall.SIGTERM)
	go signalProcessor(sigChan)

	// Configure logging, close std* fds
	level, _ := config.Config.String("logging", "level")
	log.SetLogLevel(level)

	if *logfile != "stderr" {
		// stderr is the go logging default
		if *logfile == "stdout" {
			// set to stdout
			golog.SetOutput(os.Stdout)
		} else {
			err = openLogFile()
			if err != nil {
				fmt.Fprintf(os.Stderr, "%v", err)
				os.Exit(1)
			}
			defer closeLogFile()

			// close std* streams
			os.Stdout.Close()
			os.Stderr.Close() // Warning: this will hide panic() output
			os.Stdin.Close()
			os.Stdout = logf
			os.Stderr = logf
		}
	}

	log.LogInfo("Inbucket %v (%v) starting...", config.VERSION, config.BUILD_DATE)

	// Write pidfile if requested
	// TODO: Probably supposed to remove pidfile during shutdown
	if *pidfile != "none" {
		pidf, err := os.Create(*pidfile)
		if err != nil {
			log.LogError("Failed to create %v: %v", *pidfile, err)
			os.Exit(1)
		}
		defer pidf.Close()
		fmt.Fprintf(pidf, "%v\n", os.Getpid())
	}

	// Grab our datastore
	ds := smtpd.DefaultFileDataStore()

	// Start HTTP server
	web.Initialize(config.GetWebConfig(), ds)
	go web.Start()

	// Start POP3 server
	pop3Server = pop3d.New()
	go pop3Server.Start()

	// Startup SMTP server, block until it exits
	smtpServer = smtpd.NewSmtpServer(config.GetSmtpConfig(), ds)
	smtpServer.Start()

	// Wait for active connections to finish
	smtpServer.Drain()
	pop3Server.Drain()
}

// timedExit is called as a goroutine during shutdown, it will force an exit after 15 seconds
func timedExit() {
	time.Sleep(15 * time.Second)
	log.LogError("Inbucket clean shutdown timed out, forcing exit")
	os.Exit(0)
}