package main

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"os/signal"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"syscall"
	"time"

	//	"strings"

	"github.com/gorilla/websocket"
)

var upgrader = websocket.Upgrader{
	CheckOrigin: func(r *http.Request) bool {
		origin := r.Header.Get("Origin")
		return origin == "https://ddlion.net" || origin == "https://ddln.app"
	},
}

func websocketCloseHandler(code int, text string) error {
	log.Print("Client closed websocket.")
	return nil
}

type Message struct {
	Type string `json:"type"`
}

type MessageHandler func([]byte, *Peer) ([]byte, error)

var messageHandlers = make(map[string]MessageHandler)

func registerHandler(messageType string, handler MessageHandler) {
	messageHandlers[messageType] = handler
}

func dispatchMessage(message []byte, peer *Peer) ([]byte, error) {
	var msg Message
	if err := json.Unmarshal(message, &msg); err != nil {
		return nil, err
	}

	handler, ok := messageHandlers[msg.Type]
	if !ok {
		err := fmt.Errorf("no handler registered for message type: %s", msg.Type)
		return []byte(fmt.Sprintf(`{"type":"error", "message": "%s"}`, err.Error())), nil
	}

	return handler(message, peer)
}

const (
	writeWait = 120 * time.Second
)

type Peer struct {
	conn       *websocket.Conn
	send       chan []byte
	lastActive time.Time
	closeOnce  sync.Once
}

func removePeer(peerID string, peer *Peer) {
	delete(peerConnections, peerID)

	for userID, peers := range userPeers {
		delete(peers, peerID)
		if len(peers) == 0 {
			delete(userPeers, userID) // not safe need mutex
		}
	}

	delete(connectionPeers, peer.conn)

	// Close the peer's send channel safely
	peer.closeOnce.Do(func() {
		close(peer.send)
	})
}

func handleWebSocket(w http.ResponseWriter, r *http.Request) {
	log.Println("Websocket connection!", r.RemoteAddr)

	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Println("Upgrade error:", err)
		return
	}
	defer conn.Close()

	conn.SetCloseHandler(websocketCloseHandler)

	// Create a Peer object with a buffered channel for sending messages
	peer := &Peer{
		conn:       conn,
		send:       make(chan []byte, 256),
		lastActive: time.Now(),
	}

	// Start the write loop in a separate goroutine
	go writePump(peer)

	for {
		_, message, err := conn.ReadMessage()
		if err != nil {
			log.Println("ReadMessage error:", err, connectionPeers[conn])
			break
		}

		peer.lastActive = time.Now()

		// fmt.Println("ws<-", connectionPeers[conn], ":", string(message[:min(80, len(message))]))

		response, err := dispatchMessage(message, peer)

		if err != nil {
			log.Printf("Error dispatching message: %v", err)
		}

		if response != nil {
			// Send the response to the write loop
			peer.send <- response
		}
	}

	// Clean up when the connection is closed
	peer.closeOnce.Do(func() {
		close(peer.send)
	})

	peerID := connectionPeers[peer.conn]
	if peerID != "" {
		delete(peerConnections, peerID)
	}
}

func writePump(peer *Peer) {
	defer func() {
		peer.conn.Close()
	}()
	for {
		select {
		case message, ok := <-peer.send:
			if !ok {
				// Channel closed, close the connection
				peer.conn.WriteMessage(websocket.CloseMessage, []byte{})
				return
			}
			peer.conn.SetWriteDeadline(time.Now().Add(writeWait))
			// fmt.Println("ws->", connectionPeers[peer.conn], ":", string(message[:min(80, len(message))]))

			err := peer.conn.WriteMessage(websocket.TextMessage, message)
			if err != nil {
				log.Println("WriteMessage error:", err)
				return
			}
		}
	}
}

func handlePing(message []byte, peer *Peer) ([]byte, error) {
	var pingMsg struct {
		Type   string `json:"type"`
		PeerID string `json:"peer_id"`
	}

	if err := json.Unmarshal(message, &pingMsg); err != nil {
		return nil, err
	}

	// log.Printf("Received ping from peer: %s", pingMsg.PeerID)

	return []byte(`{"type":"pong"}`), nil
}

type PeerSet map[string]struct{}

var userPeers = make(map[string]PeerSet)
var peerConnections = make(map[string]*Peer)
var connectionPeers = make(map[*websocket.Conn]string)

func handleHello(message []byte, peer *Peer) ([]byte, error) {

	var m struct {
		Type       string   `json:"type"`
		UserID     string   `json:"user_id"`
		UserName   string   `json:"user_name"`
		PeerID     string   `json:"peer_id"`
		PeerName   string   `json:"peer_name"`
		KnownUsers []string `json:"known_users"`
	}

	if err := json.Unmarshal(message, &m); err != nil {
		return nil, err
	}

	log.Printf("Received hello from peer %s:%s, user %s:%s", m.PeerID[0:5], m.PeerName, m.UserID[0:5], m.UserName)
	if userPeers[m.UserID] == nil {
		userPeers[m.UserID] = make(PeerSet)
	}

	for _, knownUserID := range m.KnownUsers {
		fmt.Printf("Adding user %s for peer %s\n", knownUserID, m.PeerID)
		if userPeers[knownUserID] == nil {
			userPeers[knownUserID] = make(PeerSet)
		}

		userPeers[knownUserID][m.PeerID] = struct{}{}

	}

	userPeers[m.UserID][m.PeerID] = struct{}{}
	peerConnections[m.PeerID] = peer
	connectionPeers[peer.conn] = m.PeerID

	jsonData, _ := json.MarshalIndent(userPeers, "", "  ")
	fmt.Println(string(jsonData), peerConnections)

	// return all the peers we know about, with their user_id and peer_id

	return []byte(fmt.Sprintf(`{"type":"hello", "userPeers": %s}`, string(jsonData))), nil
}

func handlePeerMessage(message []byte, peer *Peer) ([]byte, error) {

	type InnerMessage struct {
		Type   string `json:"type"`
		UserID string `json:"user_id"`
	}

	type PeerMessage struct {
		Type         string       `json:"type"`
		From         string       `json:"from"`
		FromUserName string       `json:"from_username"`
		FromPeerName string       `json:"from_peername"`
		To           string       `json:"to"`
		Message      InnerMessage `json:"message"`
	}
	var m PeerMessage

	if err := json.Unmarshal(message, &m); err != nil {
		return nil, err
	}

	fmt.Printf("peer message type %s from %s:%s:%s to %s with message length %d\n", m.Message.Type, m.From[0:5], m.FromPeerName, m.FromUserName, m.To[0:5], len(message))

	toPeer := peerConnections[m.To]

	if toPeer == nil {
		fmt.Printf("Couldn't find peer %s\n", m.To)
		fmt.Println(peerConnections)
		return nil, nil
	}

	// Send the message to the recipient's send channel
	select {
	case toPeer.send <- message:
	default:
		fmt.Println("Could not send message to peer; channel full or closed")
	}

	// No response for this type of message
	return nil, nil
}

// BrotliResponseWriter wraps http.ResponseWriter to support Brotli compression
type brotliResponseWriter struct {
	http.ResponseWriter
	Writer io.Writer
}

func (w *brotliResponseWriter) Write(b []byte) (int, error) {
	return w.Writer.Write(b)
}

// noDirListing wraps an http.FileServer handler to prevent directory listings
func noDirListing(h http.Handler, root string) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {

		// For anything under /static/, we serve it, unless it's a directory
		// Otherwise we serve index.html and the app does the routing nad rendering.

		log.Printf("%s %s %s", r.URL.Path, r.RemoteAddr, r.UserAgent())

		if r.URL.Path == "/sw.js" {
			http.ServeFile(w, r, filepath.Join(root, "static/sw.js"))
			return
		}

		if r.URL.Path == "/robots.txt" {
			http.ServeFile(w, r, filepath.Join(root, "static/robots.txt"))
			return
		}

		if r.URL.Path == "/favicon.ico" {
			http.ServeFile(w, r, filepath.Join(root, "static/favicon.ico"))
			return
		}

		if strings.Contains(r.URL.Path, "/static/") {
			log.Print("Serving static")

			path := filepath.Join(root, r.URL.Path)
			info, err := os.Stat(path)
			if err != nil || info.IsDir() {
				log.Printf("404 File not found/dir")
				http.NotFound(w, r)
				return
			}

			log.Printf("Serving")
			h.ServeHTTP(w, r)
			return

		}

		// // Serve index.html when root is requested
		// if r.URL.Path == "/" {
		log.Printf("Serving index %s", r.URL.Path)
		http.ServeFile(w, r, filepath.Join(root, "/static/index.html"))
		// return
		// }

		//		w.Header().Set("Cache-Control", "no-cache")

		// Check if client supports Brotli encoding
		//		if strings.Contains(r.Header.Get("Accept-Encoding"), "br") {
		// if false {
		// 	w.Header().Set("Content-Encoding", "br")
		// 	w.Header().Del("Content-Length") // Cannot know content length with compressed data

		// 	// Wrap the ResponseWriter with Brotli writer
		// 	brWriter := brotli.NewWriter(w)
		// 	defer brWriter.Close()

		// 	// Create a ResponseWriter that writes to brWriter
		// 	bw := &brotliResponseWriter{
		// 		ResponseWriter: w,
		// 		Writer:         brWriter,
		// 	}

		// 	// Serve the file using http.ServeFile
		// 	http.ServeFile(bw, r, path)
		// 	return
		// }

		// h.ServeHTTP(w, r)
	}
}

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func main() {
	// Create a channel to receive OS signals for graceful shutdown
	sigChan := make(chan os.Signal, 1)
	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)

	// Create a channel to signal when the program should shut down
	done := make(chan bool)

	// Define the directory to serve and the port to listen on
	dir := "./"
	port := 6789

	addr := ":" + strconv.Itoa(port)
	log.Printf("Starting server on %s", addr)

	// Register message handlers
	registerHandler("hello", handleHello)
	registerHandler("ping", handlePing)
	registerHandler("peer_message", handlePeerMessage)

	// Set up file server and WebSocket endpoint
	fs := http.FileServer(http.Dir(dir))
	http.Handle("/", noDirListing(fs, dir))

	http.HandleFunc("/ws", handleWebSocket)

	// Configure the HTTP server
	server := &http.Server{
		Addr:    addr,
		Handler: nil, // Use the default ServeMux
	}

	// Start the inactivity monitor goroutine
	go func() {
		ticker := time.NewTicker(10 * time.Second)
		defer ticker.Stop()

		for {
			select {
			case <-done:
				return
			case <-ticker.C:
				now := time.Now()

				// Collect inactive peers
				var inactivePeers []string
				for peerID, peer := range peerConnections {
					if now.Sub(peer.lastActive) > 60*time.Second {
						inactivePeers = append(inactivePeers, peerID)
					}
				}

				// Remove inactive peers
				for _, peerID := range inactivePeers {
					peer := peerConnections[peerID]

					if peer != nil {
						log.Printf("Peer %s inactive for more than 60 seconds. Closing connection.", peerID)
						peer.conn.Close()
						removePeer(peerID, peer)
					}
				}
			}
		}
	}()

	// Run a goroutine to handle graceful shutdown
	go func() {
		sig := <-sigChan
		fmt.Println()
		fmt.Println("Received signal:", sig)

		// Perform cleanup here
		fmt.Println("Shutting down gracefully...")

		// Create a context with timeout for the shutdown
		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		defer cancel()

		// Attempt to gracefully shut down the server
		if err := server.Shutdown(ctx); err != nil {
			log.Fatalf("Server Shutdown Failed:%+v", err)
		}

		// Signal that shutdown is complete
		close(done)
	}()

	// Start the HTTP server in a separate goroutine
	go func() {
		log.Printf("Server is configured and serving on port %d...", port)
		if err := server.ListenAndServeTLS(
			"/etc/letsencrypt/live/ddlion.net/fullchain.pem",
			"/etc/letsencrypt/live/ddlion.net/privkey.pem",
		); err != nil && err != http.ErrServerClosed {
			log.Fatalf("Could not listen on %s: %v\n", addr, err)
		}
	}()

	fmt.Println("Program is running. Press Ctrl+C to exit.")

	// Wait for the shutdown signal
	<-done
	fmt.Println("Program has exited.")
}