package inbound

import (
	"crypto/md5"
	"io"
	"sync"

	"github.com/v2ray/v2ray-core/app"
	"github.com/v2ray/v2ray-core/app/dispatcher"
	"github.com/v2ray/v2ray-core/app/proxyman"
	"github.com/v2ray/v2ray-core/common/alloc"
	v2crypto "github.com/v2ray/v2ray-core/common/crypto"
	v2io "github.com/v2ray/v2ray-core/common/io"
	"github.com/v2ray/v2ray-core/common/log"
	v2net "github.com/v2ray/v2ray-core/common/net"
	proto "github.com/v2ray/v2ray-core/common/protocol"
	"github.com/v2ray/v2ray-core/common/serial"
	"github.com/v2ray/v2ray-core/common/uuid"
	"github.com/v2ray/v2ray-core/proxy"
	"github.com/v2ray/v2ray-core/proxy/internal"
	vmessio "github.com/v2ray/v2ray-core/proxy/vmess/io"
	"github.com/v2ray/v2ray-core/proxy/vmess/protocol"
	"github.com/v2ray/v2ray-core/transport/hub"
)

type userByEmail struct {
	sync.RWMutex
	cache           map[string]*proto.User
	defaultLevel    proto.UserLevel
	defaultAlterIDs uint16
}

func NewUserByEmail(users []*proto.User, config *DefaultConfig) *userByEmail {
	cache := make(map[string]*proto.User)
	for _, user := range users {
		cache[user.Email] = user
	}
	return &userByEmail{
		cache:           cache,
		defaultLevel:    config.Level,
		defaultAlterIDs: config.AlterIDs,
	}
}

func (this *userByEmail) Get(email string) (*proto.User, bool) {
	var user *proto.User
	var found bool
	this.RLock()
	user, found = this.cache[email]
	this.RUnlock()
	if !found {
		this.Lock()
		user, found = this.cache[email]
		if !found {
			id := proto.NewID(uuid.New())
			user = proto.NewUser(id, this.defaultLevel, this.defaultAlterIDs, email)
			this.cache[email] = user
		}
		this.Unlock()
	}
	return user, found
}

// Inbound connection handler that handles messages in VMess format.
type VMessInboundHandler struct {
	sync.Mutex
	packetDispatcher      dispatcher.PacketDispatcher
	inboundHandlerManager proxyman.InboundHandlerManager
	clients               proto.UserValidator
	usersByEmail          *userByEmail
	accepting             bool
	listener              *hub.TCPHub
	features              *FeaturesConfig
	listeningPort         v2net.Port
}

func (this *VMessInboundHandler) Port() v2net.Port {
	return this.listeningPort
}

func (this *VMessInboundHandler) Close() {
	this.accepting = false
	if this.listener != nil {
		this.Lock()
		this.listener.Close()
		this.listener = nil
		this.Unlock()
	}
}

func (this *VMessInboundHandler) GetUser(email string) *proto.User {
	user, existing := this.usersByEmail.Get(email)
	if !existing {
		this.clients.Add(user)
	}
	return user
}

func (this *VMessInboundHandler) Listen(port v2net.Port) error {
	if this.accepting {
		if this.listeningPort == port {
			return nil
		} else {
			return proxy.ErrorAlreadyListening
		}
	}
	this.listeningPort = port

	tcpListener, err := hub.ListenTCP(port, this.HandleConnection)
	if err != nil {
		log.Error("Unable to listen tcp port ", port, ": ", err)
		return err
	}
	this.accepting = true
	this.Lock()
	this.listener = tcpListener
	this.Unlock()
	return nil
}

func (this *VMessInboundHandler) HandleConnection(connection *hub.TCPConn) {
	defer connection.Close()

	connReader := v2net.NewTimeOutReader(16, connection)
	requestReader := protocol.NewVMessRequestReader(this.clients)

	request, err := requestReader.Read(connReader)
	if err != nil {
		log.Access(connection.RemoteAddr(), serial.StringLiteral(""), log.AccessRejected, serial.StringLiteral(err.Error()))
		log.Warning("VMessIn: Invalid request from ", connection.RemoteAddr(), ": ", err)
		return
	}
	log.Access(connection.RemoteAddr(), request.Destination(), log.AccessAccepted, serial.StringLiteral(""))
	log.Debug("VMessIn: Received request for ", request.Destination())

	ray := this.packetDispatcher.DispatchToOutbound(v2net.NewPacket(request.Destination(), nil, true))
	input := ray.InboundInput()
	output := ray.InboundOutput()
	var readFinish, writeFinish sync.Mutex
	readFinish.Lock()
	writeFinish.Lock()

	userSettings := proto.GetUserSettings(request.User.Level)
	connReader.SetTimeOut(userSettings.PayloadReadTimeout)
	go handleInput(request, connReader, input, &readFinish)

	responseKey := md5.Sum(request.RequestKey)
	responseIV := md5.Sum(request.RequestIV)

	aesStream := v2crypto.NewAesEncryptionStream(responseKey[:], responseIV[:])
	responseWriter := v2crypto.NewCryptionWriter(aesStream, connection)

	// Optimize for small response packet
	buffer := alloc.NewLargeBuffer().Clear()
	defer buffer.Release()
	buffer.AppendBytes(request.ResponseHeader, byte(0))
	this.generateCommand(request, buffer)

	if data, open := <-output; open {
		if request.IsChunkStream() {
			vmessio.Authenticate(data)
		}
		buffer.Append(data.Value)
		data.Release()
		responseWriter.Write(buffer.Value)
		go func(finish *sync.Mutex) {
			var writer v2io.Writer = v2io.NewAdaptiveWriter(responseWriter)
			if request.IsChunkStream() {
				writer = vmessio.NewAuthChunkWriter(writer)
			}
			v2io.ChanToWriter(writer, output)
			finish.Unlock()
		}(&writeFinish)
		writeFinish.Lock()
	}

	connection.CloseWrite()
	readFinish.Lock()
}

func handleInput(request *protocol.VMessRequest, reader io.Reader, input chan<- *alloc.Buffer, finish *sync.Mutex) {
	defer close(input)
	defer finish.Unlock()

	aesStream := v2crypto.NewAesDecryptionStream(request.RequestKey, request.RequestIV)
	descriptionReader := v2crypto.NewCryptionReader(aesStream, reader)
	var requestReader v2io.Reader
	if request.IsChunkStream() {
		requestReader = vmessio.NewAuthChunkReader(descriptionReader)
	} else {
		requestReader = v2io.NewAdaptiveReader(descriptionReader)
	}
	v2io.ReaderToChan(input, requestReader)
}

func init() {
	internal.MustRegisterInboundHandlerCreator("vmess",
		func(space app.Space, rawConfig interface{}) (proxy.InboundHandler, error) {
			if !space.HasApp(dispatcher.APP_ID) {
				return nil, internal.ErrorBadConfiguration
			}
			config := rawConfig.(*Config)

			allowedClients := proto.NewTimedUserValidator(protocol.IDHash)
			for _, user := range config.AllowedUsers {
				allowedClients.Add(user)
			}

			handler := &VMessInboundHandler{
				packetDispatcher: space.GetApp(dispatcher.APP_ID).(dispatcher.PacketDispatcher),
				clients:          allowedClients,
				features:         config.Features,
				usersByEmail:     NewUserByEmail(config.AllowedUsers, config.Defaults),
			}

			if space.HasApp(proxyman.APP_ID_INBOUND_MANAGER) {
				handler.inboundHandlerManager = space.GetApp(proxyman.APP_ID_INBOUND_MANAGER).(proxyman.InboundHandlerManager)
			}

			return handler, nil
		})
}