package main

import (
	"encoding/binary"
	"log"
	"time"

	"github.com/goccy/go-json"
	"github.com/panjf2000/gnet/v2"
)

type TCPServer struct {
	gnet.BuiltinEventEngine
	server  *LoginServer
	clients *ClientManager
	worlds  *WorldManager
}

func (s *TCPServer) OnBoot(eng gnet.Engine) gnet.Action {
	log.Printf("TCP server started on %s", eng.Addr())
	return gnet.None
}

func (s *TCPServer) OnOpen(c gnet.Conn) ([]byte, gnet.Action) {
	addr := c.RemoteAddr().String()
	log.Printf("New connection from %s", addr)

	client := &Client{
		conn:      c,
		address:   addr,
		connected: time.Now(),
		state:     StateConnected,
		version:   0,
	}

	s.clients.AddClient(c.Fd(), client)
	return nil, gnet.None
}

func (s *TCPServer) OnClose(c gnet.Conn, err error) gnet.Action {
	s.clients.RemoveClient(c.Fd())
	if err != nil {
		log.Printf("Connection closed with error: %v", err)
	}
	return gnet.None
}

func (s *TCPServer) OnTraffic(c gnet.Conn) gnet.Action {
	client := s.clients.GetClient(c.Fd())
	if client == nil {
		return gnet.Close
	}

	for {
		packet, err := s.readPacket(c)
		if err != nil {
			if err != ErrIncompletePacket {
				log.Printf("Error reading packet: %v", err)
				return gnet.Close
			}
			break
		}

		if err := s.handlePacket(client, packet); err != nil {
			log.Printf("Error handling packet: %v", err)
			return gnet.Close
		}
	}

	return gnet.None
}

func (s *TCPServer) readPacket(c gnet.Conn) (*EQ2Packet, error) {
	// Read packet header (2 bytes length + 2 bytes opcode)
	if c.InboundBuffered() < 4 {
		return nil, ErrIncompletePacket
	}

	header := make([]byte, 4)
	if _, err := c.Peek(header); err != nil {
		return nil, err
	}

	length := binary.LittleEndian.Uint16(header[0:2])
	opcode := binary.LittleEndian.Uint16(header[2:4])

	totalLength := int(length) + 4 // Add header size
	if c.InboundBuffered() < totalLength {
		return nil, ErrIncompletePacket
	}

	// Read complete packet
	data := make([]byte, totalLength)
	if _, err := c.Read(data); err != nil {
		return nil, err
	}

	return &EQ2Packet{
		Opcode: opcode,
		Size:   length,
		Data:   data[4:], // Skip header
	}, nil
}

func (s *TCPServer) handlePacket(client *Client, packet *EQ2Packet) error {
	switch packet.Opcode {
	case OpLoginRequest:
		return s.handleLoginRequest(client, packet)
	case OpWorldListRequest:
		return s.handleWorldListRequest(client, packet)
	case OpCharacterListRequest:
		return s.handleCharacterListRequest(client, packet)
	case OpCreateCharacter:
		return s.handleCreateCharacter(client, packet)
	case OpDeleteCharacter:
		return s.handleDeleteCharacter(client, packet)
	case OpPlayCharacter:
		return s.handlePlayCharacter(client, packet)
	default:
		log.Printf("Unknown opcode: 0x%04X", packet.Opcode)
	}
	return nil
}

func (s *TCPServer) handleLoginRequest(client *Client, packet *EQ2Packet) error {
	var loginReq LoginRequest
	if err := json.Unmarshal(packet.Data, &loginReq); err != nil {
		return s.sendLoginDenied(client, "Invalid login data")
	}

	account, err := s.server.db.Get(s.server.ctx)
	if err != nil {
		return s.sendLoginDenied(client, "Database error")
	}
	defer s.server.db.Put(account)

	// Authenticate user
	authenticated, accountID, err := authenticateUser(account, loginReq.Username, loginReq.Password, s.server.config.Game.AllowAccountCreation)
	if err != nil {
		return s.sendLoginDenied(client, "Authentication failed")
	}

	if !authenticated {
		return s.sendLoginDenied(client, "Invalid credentials")
	}

	client.accountID = accountID
	client.accountName = loginReq.Username
	client.state = StateAuthenticated
	client.version = loginReq.Version

	return s.sendLoginAccepted(client)
}

func (s *TCPServer) sendLoginAccepted(client *Client) error {
	response := LoginResponse{
		Response:   1,
		AccountID:  client.accountID,
		SubLevel:   s.server.config.Game.DefaultSubscriptionLevel,
		RaceFlag:   s.server.config.Game.EnabledRaces,
		ClassFlag:  0x7FFFFFE,
		Username:   client.accountName,
		Unknown5:   s.server.config.Game.ExpansionFlag,
		CitiesFlag: s.server.config.Game.CitiesFlag,
	}

	return s.sendPacket(client, OpLoginReply, &response)
}

func (s *TCPServer) sendLoginDenied(client *Client, reason string) error {
	response := LoginResponse{
		Response: 0,
		Reason:   reason,
	}
	return s.sendPacket(client, OpLoginReply, &response)
}

func (s *TCPServer) handleWorldListRequest(client *Client, packet *EQ2Packet) error {
	if client.state != StateAuthenticated {
		return s.sendError(client, "Not authenticated")
	}

	worlds := s.worlds.GetWorldList()
	worldList := WorldListResponse{
		NumWorlds: uint32(len(worlds)),
		Worlds:    worlds,
	}

	return s.sendPacket(client, OpWorldListReply, &worldList)
}

func (s *TCPServer) handleCharacterListRequest(client *Client, packet *EQ2Packet) error {
	if client.state != StateAuthenticated {
		return s.sendError(client, "Not authenticated")
	}

	conn := s.server.db.Get(s.server.ctx)
	defer s.server.db.Put(conn)

	characters, err := getCharacterList(conn, client.accountID)
	if err != nil {
		return s.sendError(client, "Failed to load characters")
	}

	charList := CharacterListResponse{
		NumCharacters: uint32(len(characters)),
		Characters:    characters,
		AccountID:     client.accountID,
		MaxChars:      uint32(s.server.config.Game.MaxCharactersPerAccount),
	}

	return s.sendPacket(client, OpCharacterListReply, &charList)
}

func (s *TCPServer) sendPacket(client *Client, opcode uint16, data any) error {
	jsonData, err := json.Marshal(data)
	if err != nil {
		return err
	}

	packet := make([]byte, 4+len(jsonData))
	binary.LittleEndian.PutUint16(packet[0:2], uint16(len(jsonData)))
	binary.LittleEndian.PutUint16(packet[2:4], opcode)
	copy(packet[4:], jsonData)

	_, err = client.conn.Write(packet)
	return err
}

func (s *TCPServer) sendError(client *Client, message string) error {
	return s.sendPacket(client, OpError, map[string]string{"error": message})
}

func (s *TCPServer) handleCreateCharacter(client *Client, packet *EQ2Packet) error {
	var createReq CreateCharacterRequest
	if err := json.Unmarshal(packet.Data, &createReq); err != nil {
		return s.sendError(client, "Invalid character data")
	}

	conn := s.server.db.Get(s.server.ctx)
	defer s.server.db.Put(conn)

	charID, err := createCharacter(conn, client.accountID, &createReq)
	if err != nil {
		return s.sendError(client, "Failed to create character")
	}

	response := CreateCharacterResponse{
		Success:     true,
		CharacterID: charID,
		Name:        createReq.Name,
	}

	return s.sendPacket(client, OpCreateCharacterReply, &response)
}

func (s *TCPServer) handleDeleteCharacter(client *Client, packet *EQ2Packet) error {
	var deleteReq DeleteCharacterRequest
	if err := json.Unmarshal(packet.Data, &deleteReq); err != nil {
		return s.sendError(client, "Invalid delete request")
	}

	conn := s.server.db.Get(s.server.ctx)
	defer s.server.db.Put(conn)

	if err := deleteCharacter(conn, client.accountID, deleteReq.CharacterID); err != nil {
		return s.sendError(client, "Failed to delete character")
	}

	response := DeleteCharacterResponse{
		Success:     true,
		CharacterID: deleteReq.CharacterID,
	}

	return s.sendPacket(client, OpDeleteCharacterReply, &response)
}

func (s *TCPServer) handlePlayCharacter(client *Client, packet *EQ2Packet) error {
	var playReq PlayCharacterRequest
	if err := json.Unmarshal(packet.Data, &playReq); err != nil {
		return s.sendError(client, "Invalid play request")
	}

	world := s.worlds.GetWorld(playReq.ServerID)
	if world == nil {
		return s.sendError(client, "World server not available")
	}

	// Generate session key and send to world server
	sessionKey := generateSessionKey()

	response := PlayCharacterResponse{
		Success:    true,
		ServerIP:   world.Address,
		ServerPort: world.Port,
		SessionKey: sessionKey,
	}

	return s.sendPacket(client, OpPlayCharacterReply, &response)
}