package server

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"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
	upgrader websocket.Upgrader
	mu       sync.RWMutex
}

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(peakReader io.Reader) string {
	// Read Request
	req, err := http.ReadRequest(bufio.NewReader(peakReader))
	if err != nil {
		return ""
	}
	defer req.Body.Close()

	// Extract Host
	host := req.Host
	if idx := strings.Index(host, ":"); idx != -1 {
		host = host[:idx]
	}

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

	return ""
}

func (s *Server) getStatus(w http.ResponseWriter, _ *http.Request) {
	s.mu.RLock()
	count := len(s.tunnels)
	s.mu.RUnlock()

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(200)

	response := fmt.Sprintf(`{"tunnels": %d}`, count)
	_, _ = w.Write([]byte(response))
}

func (s *Server) proxyRawConnection(clientConn net.Conn, tunnelConn *TunnelConnection, dataReader io.Reader) {
	defer clientConn.Close()

	// Create Identifiers
	streamID := fmt.Sprintf("stream_%d", time.Now().UnixNano())
	responseChan := make(chan []byte, 100)

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

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

		// Send Close
		closeMsg := types.Message{
			Type:     types.MessageTypeClose,
			StreamID: streamID,
		}
		_ = tunnelConn.WriteJSON(closeMsg)
	}()

	// Read & Send Chunks
	go func() {
		buffer := make([]byte, 4096)
		for {
			n, err := dataReader.Read(buffer)
			if err != nil {
				return
			}

			if err := tunnelConn.WriteJSON(types.Message{
				Type:     types.MessageTypeData,
				StreamID: streamID,
				Data:     buffer[:n],
			}); err != nil {
				return
			}
		}
	}()

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

// peakData limits how much we read as we only need to determine
// the host to figure out whether we should proxy or not.
func (s *Server) peekData(conn net.Conn) (io.Reader, io.Reader, error) {
	peek := make([]byte, 8192)
	n, err := conn.Read(peek)
	if err != nil {
		return nil, nil, err
	}

	peekedData := peek[:n]
	combinedReader := io.MultiReader(bytes.NewReader(peekedData), conn)

	return bytes.NewReader(peekedData), combinedReader, nil
}

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

	peakReader, allReader, _ := s.peekData(conn)
	if subdomain := s.extractSubdomain(peakReader); 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, allReader)
			return
		}
	}

	// Otherwise, handle as control server (recreate HTTP request and use net/http)
	s.handleAsHTTP(conn, allReader)
}

func (s *Server) handleAsHTTP(conn net.Conn, allReader io.Reader) {
	// Create HTTP Request & Writer
	r, err := http.ReadRequest(bufio.NewReader(allReader))
	if err != nil {
		_, _ = conn.Write([]byte("HTTP/1.1 400 Bad Request\r\n\r\n"))
		return
	}
	w := &connResponseWriter{conn: conn}

	// Handle Control Endpoints
	switch r.URL.Path {
	case "/_conduit/tunnel":
		s.createTunnel(w, r)
	case "/_conduit/status":
		s.getStatus(w, r)
	default:
		w.WriteHeader(http.StatusNotFound)
	}
}

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

		if msg.StreamID == "" {
			log.Infof("Tunnel %s missing streamID", tunnel.name)
			continue
		}

		switch msg.Type {
		case types.MessageTypeClose:
			return
		case types.MessageTypeData:
			s.mu.RLock()
			streamChan, exists := tunnel.streams[msg.StreamID]
			if !exists {
				log.Infof("Stream %s does not exist", msg.StreamID)
				s.mu.RUnlock()
				continue
			}

			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(w http.ResponseWriter, r *http.Request) {
	// Get Tunnel Name
	tunnelName := r.URL.Query().Get("tunnelName")
	if tunnelName == "" {
		w.WriteHeader(http.StatusBadRequest)
		_, _ = w.Write([]byte("Missing tunnelName parameter"))
		return
	}

	// Validate Unique
	if _, exists := s.tunnels[tunnelName]; exists {
		w.WriteHeader(http.StatusConflict)
		_, _ = w.Write([]byte("Tunnel already registered"))
		return
	}

	// Upgrade Connection
	wsConn, err := s.upgrader.Upgrade(w, r, 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)
}