package shadowsocks_2022

import (
	"context"
	"encoding/base64"

	"github.com/sagernet/sing-shadowsocks"
	"github.com/sagernet/sing-shadowsocks/shadowaead_2022"
	B "github.com/sagernet/sing/common/buf"
	"github.com/sagernet/sing/common/bufio"
	M "github.com/sagernet/sing/common/metadata"
	N "github.com/sagernet/sing/common/network"
	"github.com/xtls/xray-core/common"
	"github.com/xtls/xray-core/common/buf"
	"github.com/xtls/xray-core/common/log"
	"github.com/xtls/xray-core/common/net"
	"github.com/xtls/xray-core/common/protocol"
	"github.com/xtls/xray-core/common/session"
	"github.com/xtls/xray-core/common/uuid"
	"github.com/xtls/xray-core/features/routing"
	"github.com/xtls/xray-core/transport/internet/stat"
)

func init() {
	common.Must(common.RegisterConfig((*MultiUserServerConfig)(nil), func(ctx context.Context, config interface{}) (interface{}, error) {
		return NewMultiServer(ctx, config.(*MultiUserServerConfig))
	}))
}

type MultiUserInbound struct {
	networks []net.Network
	users    []*User
	service  *shadowaead_2022.MultiService[int]
}

func NewMultiServer(ctx context.Context, config *MultiUserServerConfig) (*MultiUserInbound, error) {
	networks := config.Network
	if len(networks) == 0 {
		networks = []net.Network{
			net.Network_TCP,
			net.Network_UDP,
		}
	}
	inbound := &MultiUserInbound{
		networks: networks,
		users:    config.Users,
	}
	if config.Key == "" {
		return nil, newError("missing key")
	}
	psk, err := base64.StdEncoding.DecodeString(config.Key)
	if err != nil {
		return nil, newError("parse config").Base(err)
	}
	service, err := shadowaead_2022.NewMultiService[int](config.Method, psk, 500, inbound)
	if err != nil {
		return nil, newError("create service").Base(err)
	}

	for i, user := range config.Users {
		if user.Email == "" {
			u := uuid.New()
			user.Email = "(user with empty email - " + u.String() + ")"
		}
		uPSK, err := base64.StdEncoding.DecodeString(user.Key)
		if err != nil {
			return nil, newError("parse user key for ", user.Email).Base(err)
		}
		err = service.AddUser(i, uPSK)
		if err != nil {
			return nil, newError("add user").Base(err)
		}
	}

	inbound.service = service
	return inbound, nil
}

func (i *MultiUserInbound) Network() []net.Network {
	return i.networks
}

func (i *MultiUserInbound) Process(ctx context.Context, network net.Network, connection stat.Connection, dispatcher routing.Dispatcher) error {
	inbound := session.InboundFromContext(ctx)

	var metadata M.Metadata
	if inbound.Source.IsValid() {
		metadata.Source = M.ParseSocksaddr(inbound.Source.NetAddr())
	}

	ctx = session.ContextWithDispatcher(ctx, dispatcher)

	if network == net.Network_TCP {
		return i.service.NewConnection(ctx, connection, metadata)
	} else {
		reader := buf.NewReader(connection)
		pc := &natPacketConn{connection}
		for {
			mb, err := reader.ReadMultiBuffer()
			if err != nil {
				return err
			}
			for _, buffer := range mb {
				err = i.service.NewPacket(ctx, pc, B.As(buffer.Bytes()), metadata)
				if err != nil {
					return err
				}
			}
		}
	}
}

func (i *MultiUserInbound) NewConnection(ctx context.Context, conn net.Conn, metadata M.Metadata) error {
	userCtx := ctx.(*shadowsocks.UserContext[int])
	inbound := session.InboundFromContext(ctx)
	user := i.users[userCtx.User]
	inbound.User = &protocol.MemoryUser{
		Email: user.Email,
		Level: uint32(user.Level),
	}
	ctx = log.ContextWithAccessMessage(userCtx.Context, &log.AccessMessage{
		From:   metadata.Source,
		To:     metadata.Destination,
		Status: log.AccessAccepted,
		Email:  user.Email,
	})
	newError("tunnelling request to tcp:", metadata.Destination).WriteToLog(session.ExportIDToError(ctx))
	dispatcher := session.DispatcherFromContext(ctx)
	link, err := dispatcher.Dispatch(ctx, toDestination(metadata.Destination, net.Network_TCP))
	if err != nil {
		return err
	}
	outConn := &pipeConnWrapper{
		&buf.BufferedReader{Reader: link.Reader},
		link.Writer,
		conn,
	}
	return bufio.CopyConn(ctx, conn, outConn)
}

func (i *MultiUserInbound) NewPacketConnection(ctx context.Context, conn N.PacketConn, metadata M.Metadata) error {
	userCtx := ctx.(*shadowsocks.UserContext[int])
	inbound := session.InboundFromContext(ctx)
	user := i.users[userCtx.User]
	inbound.User = &protocol.MemoryUser{
		Email: user.Email,
		Level: uint32(user.Level),
	}
	ctx = log.ContextWithAccessMessage(userCtx.Context, &log.AccessMessage{
		From:   metadata.Source,
		To:     metadata.Destination,
		Status: log.AccessAccepted,
		Email:  user.Email,
	})
	newError("tunnelling request to udp:", metadata.Destination).WriteToLog(session.ExportIDToError(ctx))
	dispatcher := session.DispatcherFromContext(ctx)
	destination := toDestination(metadata.Destination, net.Network_UDP)
	link, err := dispatcher.Dispatch(ctx, destination)
	if err != nil {
		return err
	}
	outConn := &packetConnWrapper{
		Reader: link.Reader,
		Writer: link.Writer,
		Dest:   destination,
	}
	return bufio.CopyPacketConn(ctx, conn, outConn)
}

func (i *MultiUserInbound) HandleError(err error) {
	newError(err).AtWarning().WriteToLog()
}