package inbound

import (
	"context"
	"net"
	"os"
	"time"

	"github.com/sagernet/sing-box/adapter"
	"github.com/sagernet/sing-box/common/mux"
	"github.com/sagernet/sing-box/common/uot"
	C "github.com/sagernet/sing-box/constant"
	"github.com/sagernet/sing-box/log"
	"github.com/sagernet/sing-box/option"
	"github.com/sagernet/sing-shadowsocks"
	"github.com/sagernet/sing-shadowsocks/shadowaead"
	"github.com/sagernet/sing-shadowsocks/shadowaead_2022"
	"github.com/sagernet/sing/common"
	"github.com/sagernet/sing/common/auth"
	"github.com/sagernet/sing/common/buf"
	E "github.com/sagernet/sing/common/exceptions"
	F "github.com/sagernet/sing/common/format"
	M "github.com/sagernet/sing/common/metadata"
	N "github.com/sagernet/sing/common/network"
	"github.com/sagernet/sing/common/ntp"
)

var (
	_ adapter.Inbound              = (*ShadowsocksMulti)(nil)
	_ adapter.TCPInjectableInbound = (*ShadowsocksMulti)(nil)
)

type ShadowsocksMulti struct {
	myInboundAdapter
	service shadowsocks.MultiService[int]
	users   []option.ShadowsocksUser
}

func newShadowsocksMulti(ctx context.Context, router adapter.Router, logger log.ContextLogger, tag string, options option.ShadowsocksInboundOptions) (*ShadowsocksMulti, error) {
	inbound := &ShadowsocksMulti{
		myInboundAdapter: myInboundAdapter{
			protocol:      C.TypeShadowsocks,
			network:       options.Network.Build(),
			ctx:           ctx,
			router:        uot.NewRouter(router, logger),
			logger:        logger,
			tag:           tag,
			listenOptions: options.ListenOptions,
		},
	}
	inbound.connHandler = inbound
	inbound.packetHandler = inbound
	var err error
	inbound.router, err = mux.NewRouterWithOptions(inbound.router, logger, common.PtrValueOrDefault(options.Multiplex))
	if err != nil {
		return nil, err
	}
	var udpTimeout time.Duration
	if options.UDPTimeout != 0 {
		udpTimeout = time.Duration(options.UDPTimeout)
	} else {
		udpTimeout = C.UDPTimeout
	}
	var service shadowsocks.MultiService[int]
	if common.Contains(shadowaead_2022.List, options.Method) {
		service, err = shadowaead_2022.NewMultiServiceWithPassword[int](
			options.Method,
			options.Password,
			int64(udpTimeout.Seconds()),
			adapter.NewUpstreamHandler(adapter.InboundContext{}, inbound.newConnection, inbound.newPacketConnection, inbound),
			ntp.TimeFuncFromContext(ctx),
		)
	} else if common.Contains(shadowaead.List, options.Method) {
		service, err = shadowaead.NewMultiService[int](
			options.Method,
			int64(udpTimeout.Seconds()),
			adapter.NewUpstreamHandler(adapter.InboundContext{}, inbound.newConnection, inbound.newPacketConnection, inbound),
		)
	} else {
		return nil, E.New("unsupported method: " + options.Method)
	}
	if err != nil {
		return nil, err
	}
	err = service.UpdateUsersWithPasswords(common.MapIndexed(options.Users, func(index int, user option.ShadowsocksUser) int {
		return index
	}), common.Map(options.Users, func(user option.ShadowsocksUser) string {
		return user.Password
	}))
	if err != nil {
		return nil, err
	}
	inbound.service = service
	inbound.packetUpstream = service
	inbound.users = options.Users
	return inbound, err
}

func (h *ShadowsocksMulti) NewConnectionEx(ctx context.Context, conn net.Conn, metadata adapter.InboundContext, onClose N.CloseHandlerFunc) {
	err := h.service.NewConnection(ctx, conn, adapter.UpstreamMetadata(metadata))
	N.CloseOnHandshakeFailure(conn, onClose, err)
	if err != nil {
		h.logger.ErrorContext(ctx, E.Cause(err, "process connection from ", metadata.Source))
	}
}

func (h *ShadowsocksMulti) NewPacketEx(buffer *buf.Buffer, source M.Socksaddr) {
	err := h.service.NewPacket(h.ctx, h.packetConn(), buffer, M.Metadata{Source: source})
	if err != nil {
		h.logger.Error(E.Cause(err, "process packet from ", source))
	}
}

func (h *ShadowsocksMulti) newConnection(ctx context.Context, conn net.Conn, metadata adapter.InboundContext) error {
	userIndex, loaded := auth.UserFromContext[int](ctx)
	if !loaded {
		return os.ErrInvalid
	}
	user := h.users[userIndex].Name
	if user == "" {
		user = F.ToString(userIndex)
	} else {
		metadata.User = user
	}
	h.logger.InfoContext(ctx, "[", user, "] inbound connection to ", metadata.Destination)
	return h.router.RouteConnection(ctx, conn, h.createMetadata(conn, metadata))
}

func (h *ShadowsocksMulti) newPacketConnection(ctx context.Context, conn N.PacketConn, metadata adapter.InboundContext) error {
	userIndex, loaded := auth.UserFromContext[int](ctx)
	if !loaded {
		return os.ErrInvalid
	}
	user := h.users[userIndex].Name
	if user == "" {
		user = F.ToString(userIndex)
	} else {
		metadata.User = user
	}
	ctx = log.ContextWithNewID(ctx)
	h.logger.InfoContext(ctx, "[", user, "] inbound packet connection from ", metadata.Source)
	h.logger.InfoContext(ctx, "[", user, "] inbound packet connection to ", metadata.Destination)
	return h.router.RoutePacketConnection(ctx, conn, h.createPacketMetadata(conn, metadata))
}