package main

import (
	"bufio"
	"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(),
	}

	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
	sendMux   sync.Mutex
	listeners map[PoolMessage]func(data []byte) error
	functions map[PoolMessage]func(data []byte) (PoolMessage, []byte, error)
}

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

	return m
}

func (m *TCPServerMux) handleListener(messageType PoolMessage, 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 PoolMessage, data []byte) (bool, error) {
	m.mu.RLock()
	function, ok := m.functions[messageType]
	m.mu.RUnlock()
	m.sendMux.Lock()
	defer m.sendMux.Unlock()
	if ok {
		connection.Write(header[:])
		responseType, responseData, err := function(data)
		if err != nil {
			errData := []byte(err.Error())
			err = binary.Write(connection, binary.LittleEndian, Packet{
				Version:     CurrentPacketVersion,
				MessageType: responseType,
				StatusCode:  500,
				DataLength:  uint32(len(errData)),
			})
			_, err = connection.Write(errData)
			return true, err
		}
		err = binary.Write(connection, binary.LittleEndian, Packet{
			Version:     CurrentPacketVersion,
			MessageType: responseType,
			StatusCode:  200,
			DataLength:  uint32(len(responseData)),
		})
		if err != nil {
			return true, err
		}
		packetsSent.Inc()
		_, err = connection.Write(responseData)
		return true, err
	} else {
		log.Printf("No pool handler for type: %d\n", messageType)
	}
	return false, nil
}

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

	defer connection.Close()
	var packet Packet
	reader := bufio.NewReader(connection)
	for {
		err := ReadPacket(reader, &packet)
		if err != nil {
			if err == io.EOF {
				return nil
			}
			log.Printf("Error receiving packet: %v\n", err)
			return err
		}
		if packet.Version != CurrentPacketVersion {
			log.Printf("Incorrect package version: %v\n", err)
			continue
		}
		data, err := GetPacketData(reader, packet.DataLength)
		if err != nil {
			log.Printf("Error receiving packet data: %v\n", err)
			return err
		}
		go m.HandleData(connection, packet.MessageType, data)
	}
}

func (m *TCPServerMux) HandleData(connection net.Conn, t PoolMessage, data []byte) {
	// listener := m.listeners[t]
	// handler := m.functions[t]
	status, err := m.handleListener(t, data)
	if err != nil {
		log.Printf("Error handling listener: %v\n", err)
	}
	if !status {
		status, err = m.handleFunction(connection, t, data)
		if err != nil {
			log.Printf("Error handling function: %v\n", err)
		}
		if !status {
			log.Printf("Unknown message type: %d\n", t)
		}
	}
}

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

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