package tcp

import (
	"context"
	gotls "crypto/tls"
	"strings"
	"time"

	"github.com/v2fly/v2ray-core/v4/common"
	"github.com/v2fly/v2ray-core/v4/common/net"
	"github.com/v2fly/v2ray-core/v4/common/serial"
	"github.com/v2fly/v2ray-core/v4/common/session"
	"github.com/v2fly/v2ray-core/v4/transport/internet"
	"github.com/v2fly/v2ray-core/v4/transport/internet/tls"
)

// Listener is an internet.Listener that listens for TCP connections.
type Listener struct {
	listener   net.Listener
	tlsConfig  *gotls.Config
	authConfig internet.ConnectionAuthenticator
	config     *Config
	addConn    internet.ConnHandler
	locker     *internet.FileLocker // for unix domain socket
}

// ListenTCP creates a new Listener based on configurations.
func ListenTCP(ctx context.Context, address net.Address, port net.Port, streamSettings *internet.MemoryStreamConfig, handler internet.ConnHandler) (internet.Listener, error) {
	l := &Listener{
		addConn: handler,
	}
	tcpSettings := streamSettings.ProtocolSettings.(*Config)
	l.config = tcpSettings
	if l.config != nil {
		if streamSettings.SocketSettings == nil {
			streamSettings.SocketSettings = &internet.SocketConfig{}
		}
		streamSettings.SocketSettings.AcceptProxyProtocol = l.config.AcceptProxyProtocol
	}
	var listener net.Listener
	var err error
	if port == net.Port(0) { // unix
		listener, err = internet.ListenSystem(ctx, &net.UnixAddr{
			Name: address.Domain(),
			Net:  "unix",
		}, streamSettings.SocketSettings)
		if err != nil {
			return nil, newError("failed to listen Unix Domain Socket on ", address).Base(err)
		}
		newError("listening Unix Domain Socket on ", address).WriteToLog(session.ExportIDToError(ctx))
		locker := ctx.Value(address.Domain())
		if locker != nil {
			l.locker = locker.(*internet.FileLocker)
		}
	} else {
		listener, err = internet.ListenSystem(ctx, &net.TCPAddr{
			IP:   address.IP(),
			Port: int(port),
		}, streamSettings.SocketSettings)
		if err != nil {
			return nil, newError("failed to listen TCP on ", address, ":", port).Base(err)
		}
		newError("listening TCP on ", address, ":", port).WriteToLog(session.ExportIDToError(ctx))
	}

	if streamSettings.SocketSettings != nil && streamSettings.SocketSettings.AcceptProxyProtocol {
		newError("accepting PROXY protocol").AtWarning().WriteToLog(session.ExportIDToError(ctx))
	}

	l.listener = listener

	if config := tls.ConfigFromStreamSettings(streamSettings); config != nil {
		l.tlsConfig = config.GetTLSConfig()
	}

	if tcpSettings.HeaderSettings != nil {
		headerConfig, err := serial.GetInstanceOf(tcpSettings.HeaderSettings)
		if err != nil {
			return nil, newError("invalid header settings").Base(err).AtError()
		}
		auth, err := internet.CreateConnectionAuthenticator(headerConfig)
		if err != nil {
			return nil, newError("invalid header settings.").Base(err).AtError()
		}
		l.authConfig = auth
	}

	go l.keepAccepting()
	return l, nil
}

func (v *Listener) keepAccepting() {
	for {
		conn, err := v.listener.Accept()
		if err != nil {
			errStr := err.Error()
			if strings.Contains(errStr, "closed") {
				break
			}
			newError("failed to accepted raw connections").Base(err).AtWarning().WriteToLog()
			if strings.Contains(errStr, "too many") {
				time.Sleep(time.Millisecond * 500)
			}
			continue
		}

		if v.tlsConfig != nil {
			conn = tls.Server(conn, v.tlsConfig)
		}
		if v.authConfig != nil {
			conn = v.authConfig.Server(conn)
		}

		v.addConn(internet.Connection(conn))
	}
}

// Addr implements internet.Listener.Addr.
func (v *Listener) Addr() net.Addr {
	return v.listener.Addr()
}

// Close implements internet.Listener.Close.
func (v *Listener) Close() error {
	if v.locker != nil {
		v.locker.Release()
	}
	return v.listener.Close()
}

func init() {
	common.Must(internet.RegisterTransportListener(protocolName, ListenTCP))
}