package main

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

type Server struct {
	*TCPServerMux
}

func Listen(address string) (*Server, error) {
	listener, err := net.Listen("tcp", address)
	server := &Server{
		NewTCPServerMux(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 TCPServerMux struct {
	mu        sync.RWMutex
	listeners map[uint16]func(data []byte) error
	functions map[uint16]func(data []byte) (uint16, []byte, error)
}

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

	return m
}

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

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

func (m *TCPServerMux) HandleConnection(connection net.Conn) error {

	defer connection.Close()
	for {
		messageType, data, err := ReceivePacket(connection)
		if err != nil {
			if err == io.EOF {
				return nil
			}
			log.Printf("Error receiving packet: %v\n", err)
			return err
		}

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

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

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