package main

import (
	"encoding/binary"
	"io"
	"log"
	"net"
	"sync"
)

type CartServer struct {
	*TCPCartServerMux
}

func CartListen(address string) (*CartServer, error) {
	listener, err := net.Listen("tcp", address)
	server := &CartServer{
		NewCartTCPServerMux(100),
	}

	if err != nil {
		return nil, err
	}
	go func() {
		for {
			conn, err := listener.Accept()
			if err != nil {
				log.Printf("Error accepting connection: %v\n", err)
				continue
			}
			go server.HandleConnection(conn)
		}
	}()
	return server, nil
}

type TCPCartServerMux struct {
	mu        sync.RWMutex
	listeners map[uint16]func(CartId, []byte) error
	functions map[uint16]func(CartId, []byte) (uint16, []byte, error)
}

func NewCartTCPServerMux(maxClients int) *TCPCartServerMux {
	m := &TCPCartServerMux{
		mu:        sync.RWMutex{},
		listeners: make(map[uint16]func(CartId, []byte) error),
		functions: make(map[uint16]func(CartId, []byte) (uint16, []byte, error)),
	}

	return m
}

func (m *TCPCartServerMux) handleListener(messageType uint16, id CartId, data []byte) (bool, error) {
	m.mu.RLock()
	handler, ok := m.listeners[messageType]
	m.mu.RUnlock()
	if ok {
		err := handler(id, data)
		if err != nil {
			return true, err
		}
	}
	return false, nil
}

func (m *TCPCartServerMux) handleFunction(connection net.Conn, messageType uint16, id CartId, data []byte) (bool, error) {
	m.mu.RLock()
	function, ok := m.functions[messageType]
	m.mu.RUnlock()
	if ok {
		responseType, responseData, err := function(id, data)
		if err != nil {
			return true, err
		}
		err = binary.Write(connection, binary.LittleEndian, CartPacket{
			Version:     1,
			MessageType: responseType,
			DataLength:  uint16(len(responseData)),
			Id:          id,
		})
		if err != nil {
			return true, err
		}
		packetsSent.Inc()
		_, err = connection.Write(responseData)
		return true, err
	}
	return false, nil
}

func (m *TCPCartServerMux) HandleConnection(connection net.Conn) error {
	var packet CartPacket
	var err error
	defer connection.Close()
	for {
		err = ReadPacket(connection, &packet)
		if err != nil {
			if err == io.EOF {
				return nil
			}
			log.Printf("Error receiving packet: %v\n", err)
			return err
		}

		data, err := GetPacketData(connection, packet.DataLength)
		if err != nil {
			log.Printf("Error getting packet data: %v\n", err)
		}
		status, err := m.handleListener(packet.MessageType, packet.Id, data)
		if err != nil {
			log.Printf("Error handling listener: %v\n", err)
		}
		if !status {
			status, err = m.handleFunction(connection, packet.MessageType, packet.Id, data)
			if err != nil {
				log.Printf("Error handling function: %v\n", err)
			}
			if !status {
				log.Printf("Unknown message type: %d\n", packet.MessageType)
			}
		}
	}
}

func (m *TCPCartServerMux) ListenFor(messageType uint16, handler func(CartId, []byte) error) {
	m.mu.Lock()
	m.listeners[messageType] = handler
	m.mu.Unlock()
}

func (m *TCPCartServerMux) HandleCall(messageType uint16, handler func(CartId, []byte) (uint16, []byte, error)) {
	m.mu.Lock()
	m.functions[messageType] = handler
	m.mu.Unlock()
}