package server

import (
	"bufio"
	"bytes"
	"fmt"
	"net"
	"net/http"
	"strings"
	"sync"
	"time"

	"github.com/gorilla/websocket"
	log "github.com/sirupsen/logrus"
	"reichard.io/conduit/types"
)

type TunnelConnection struct {
	*websocket.Conn
	name    string
	streams map[string]chan []byte // StreamID -> data channel
}

type Server struct {
	tunnels  map[string]*TunnelConnection
	mu       sync.RWMutex
	upgrader websocket.Upgrader
}

func NewServer() *Server {
	return &Server{
		tunnels: make(map[string]*TunnelConnection),
		upgrader: websocket.Upgrader{
			CheckOrigin: func(r *http.Request) bool {
				return true
			},
		},
	}
}

func (s *Server) Start(addr string) error {
	// Raw TCP listener instead of http.ListenAndServe
	listener, err := net.Listen("tcp", addr)
	if err != nil {
		return err
	}
	defer listener.Close()

	log.Infof("Conduit server listening on %s", addr)

	for {
		conn, err := listener.Accept()
		if err != nil {
			log.Printf("Error accepting connection: %v", err)
			continue
		}

		go s.handleRawConnection(conn)
	}
}

func (s *Server) extractSubdomain(host string) string {
	if idx := strings.Index(host, ":"); idx != -1 {
		host = host[:idx]
	}

	parts := strings.Split(host, ".")
	if len(parts) >= 1 {
		return parts[0]
	}

	return ""
}

func (s *Server) getStatus(conn net.Conn) {
	s.mu.RLock()
	count := len(s.tunnels)
	s.mu.RUnlock()

	response := fmt.Sprintf(
		"HTTP/1.1 200 OK\r\n"+
			"Content-Type: application/json\r\n"+
			"Content-Length: %d\r\n\r\n"+
			`{"tunnels": %d}`,
		len(fmt.Sprintf(`{"tunnels": %d}`, count)), count)

	conn.Write([]byte(response))
}

func (s *Server) extractHostFromHTTP(data []byte) string {
	// Simple HTTP header parsing
	lines := strings.Split(string(data), "\r\n")
	for _, line := range lines {
		if strings.HasPrefix(strings.ToLower(line), "host:") {
			parts := strings.SplitN(line, ":", 2)
			if len(parts) == 2 {
				return strings.TrimSpace(parts[1])
			}
		}
	}
	return ""
}

func (s *Server) proxyRawConnection(clientConn net.Conn, tunnelConn *TunnelConnection, initialData []byte) {
	defer clientConn.Close()

	// Generate a unique stream ID for this connection
	streamID := fmt.Sprintf("stream_%d", time.Now().UnixNano())

	// Send initial data with stream ID
	msg := types.Message{
		Type:     "data",
		StreamID: streamID,
		Data:     initialData,
	}

	if err := tunnelConn.WriteJSON(msg); err != nil {
		log.Errorf("Error sending initial data: %v", err)
		return
	}

	// Create a channel for this stream's responses
	responseChan := make(chan []byte, 100)

	// Register this stream
	s.mu.Lock()
	if tunnelConn.streams == nil {
		tunnelConn.streams = make(map[string]chan []byte)
	}
	tunnelConn.streams[streamID] = responseChan
	s.mu.Unlock()

	// Clean up when done
	defer func() {
		s.mu.Lock()
		delete(tunnelConn.streams, streamID)
		close(responseChan)
		s.mu.Unlock()

		// Send close message
		closeMsg := types.Message{
			Type:     "close",
			StreamID: streamID,
		}
		tunnelConn.WriteJSON(closeMsg)
	}()

	// Handle client -> tunnel
	go func() {
		buffer := make([]byte, 4096)
		for {
			n, err := clientConn.Read(buffer)
			if err != nil {
				return
			}

			msg := types.Message{
				Type:     "data",
				StreamID: streamID,
				Data:     buffer[:n],
			}

			if err := tunnelConn.WriteJSON(msg); err != nil {
				return
			}
		}
	}()

	// Return Client Response Data
	for data := range responseChan {
		if _, err := clientConn.Write(data); err != nil {
			break
		}
	}
}

func (s *Server) handleRawConnection(conn net.Conn) {
	defer conn.Close()

	// Read enough to get the Host header
	buffer := make([]byte, 4096)
	n, err := conn.Read(buffer)
	if err != nil {
		return
	}

	// Extract host
	host := s.extractHostFromHTTP(buffer[:n])
	subdomain := s.extractSubdomain(host)

	// If we have a registered tunnel for this subdomain, relay it
	if subdomain != "" {
		s.mu.RLock()
		tunnelConn, exists := s.tunnels[subdomain]
		s.mu.RUnlock()

		if exists {
			log.Infof("Relaying %s to tunnel", subdomain)
			s.proxyRawConnection(conn, tunnelConn, buffer[:n])
			return
		}
	}

	// Otherwise, handle as control server (recreate HTTP request and use net/http)
	s.handleAsHTTP(conn, buffer[:n])
}

func (s *Server) handleAsHTTP(conn net.Conn, initialData []byte) {
	// Create a fake HTTP request from the raw data
	reader := bufio.NewReader(bytes.NewReader(initialData))
	req, err := http.ReadRequest(reader)
	if err != nil {
		_, _ = conn.Write([]byte("HTTP/1.1 400 Bad Request\r\n\r\n"))
		return
	}

	// Handle Control Endpoints
	switch req.URL.Path {
	case "/_conduit/tunnel":
		s.createTunnel(conn, req)
	case "/_conduit/status":
		s.getStatus(conn)
	default:
		_, _ = conn.Write([]byte("HTTP/1.1 404 Not Found\r\n\r\n"))
	}
}

func (s *Server) handleTunnelMessages(tunnel *TunnelConnection) {
	for {
		var msg types.Message
		err := tunnel.ReadJSON(&msg)
		if err != nil {
			break
		}

		// Route message to appropriate stream
		if msg.Type == "data" && msg.StreamID != "" {
			s.mu.RLock()
			if streamChan, exists := tunnel.streams[msg.StreamID]; exists {
				select {
				case streamChan <- msg.Data:
				case <-time.After(time.Second):
					log.Infof("Stream %s channel full, dropping data", msg.StreamID)
				}
			}
			s.mu.RUnlock()
		}
	}
}
func (s *Server) createTunnel(conn net.Conn, req *http.Request) {
	// Get Tunnel Name
	tunnelName := req.URL.Query().Get("tunnelName")
	if tunnelName == "" {
		conn.Write([]byte("HTTP/1.1 400 Bad Request\r\n\r\nMissing tunnelName parameter"))
		return
	}

	// Validate Unique
	if _, exists := s.tunnels[tunnelName]; exists {
		conn.Write([]byte("HTTP/1.1 409 Conflict\r\n\r\nTunnel already registered"))
		return
	}

	// Upgrade Connection
	wsConn, err := s.upgrader.Upgrade(&rawResponseWriter{conn: conn}, req, nil)
	if err != nil {
		log.Errorf("WebSocket upgrade failed: %v", err)
		return
	}

	// Create & Cache TunnelConnection
	tunnel := &TunnelConnection{
		Conn:    wsConn,
		name:    tunnelName,
		streams: make(map[string]chan []byte),
	}
	s.mu.Lock()
	s.tunnels[tunnelName] = tunnel
	s.mu.Unlock()
	log.Infof("Tunnel established: %s", tunnelName)

	// Keep connection alive and handle cleanup
	defer func() {
		s.mu.Lock()
		delete(s.tunnels, tunnelName)
		s.mu.Unlock()
		wsConn.Close()
		log.Infof("Tunnel closed: %s", tunnelName)
	}()

	// Handle tunnel messages
	s.handleTunnelMessages(tunnel)
}

type rawResponseWriter struct {
	conn   net.Conn
	header http.Header
}

func (f *rawResponseWriter) Header() http.Header {
	if f.header == nil {
		f.header = make(http.Header)
	}
	return f.header
}

func (f *rawResponseWriter) Write(data []byte) (int, error) {
	return f.conn.Write(data)
}

func (f *rawResponseWriter) WriteHeader(statusCode int) {
	// Write Status
	status := fmt.Sprintf("HTTP/1.1 %d %s\r\n", statusCode, http.StatusText(statusCode))
	_, _ = f.conn.Write([]byte(status))

	// Write Headers
	for key, values := range f.header {
		for _, value := range values {
			_, _ = fmt.Fprintf(f.conn, "%s: %s\r\n", key, value)
		}
	}

	// End Headers
	_, _ = f.conn.Write([]byte("\r\n"))
}

func (f *rawResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
	// Return Raw Connection & ReadWriter
	rw := bufio.NewReadWriter(bufio.NewReader(f.conn), bufio.NewWriter(f.conn))
	return f.conn, rw, nil
}