package shadowsocks

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

	"github.com/sagernet/sing-box/adapter"
	"github.com/sagernet/sing-box/adapter/inbound"
	"github.com/sagernet/sing-box/common/listener"
	"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"
	"github.com/sagernet/sing/common/logger"
	M "github.com/sagernet/sing/common/metadata"
	N "github.com/sagernet/sing/common/network"
	"github.com/sagernet/sing/common/ntp"
)

var _ adapter.TCPInjectableInbound = (*MultiInbound)(nil)

type MultiInbound struct {
	inbound.Adapter
	ctx      context.Context
	router   adapter.ConnectionRouterEx
	logger   logger.ContextLogger
	listener *listener.Listener
	service  shadowsocks.MultiService[int]
	users    []option.ShadowsocksUser
}

func newMultiInbound(ctx context.Context, router adapter.Router, logger log.ContextLogger, tag string, options option.ShadowsocksInboundOptions) (*MultiInbound, error) {
	inbound := &MultiInbound{
		Adapter: inbound.NewAdapter(C.TypeShadowsocks, tag),
		ctx:     ctx,
		router:  uot.NewRouter(router, logger),
		logger:  logger,
	}
	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.users = options.Users
	inbound.listener = listener.New(listener.Options{
		Context:                  ctx,
		Logger:                   logger,
		Network:                  options.Network.Build(),
		Listen:                   options.ListenOptions,
		ConnectionHandler:        inbound,
		PacketHandler:            inbound,
		ThreadUnsafePacketWriter: true,
	})
	return inbound, err
}

func (h *MultiInbound) Start(stage adapter.StartStage) error {
	if stage != adapter.StartStateStart {
		return nil
	}
	return h.listener.Start()
}

func (h *MultiInbound) Close() error {
	return h.listener.Close()
}

func (h *MultiInbound) 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 {
		if E.IsClosedOrCanceled(err) {
			h.logger.DebugContext(ctx, "connection closed: ", err)
		} else {
			h.logger.ErrorContext(ctx, E.Cause(err, "process connection from ", metadata.Source))
		}
	}
}

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

func (h *MultiInbound) 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)
	metadata.Inbound = h.Tag()
	metadata.InboundType = h.Type()
	metadata.InboundDetour = h.listener.ListenOptions().Detour
	metadata.InboundOptions = h.listener.ListenOptions().InboundOptions
	return h.router.RouteConnection(ctx, conn, metadata)
}

func (h *MultiInbound) 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)
	metadata.Inbound = h.Tag()
	metadata.InboundType = h.Type()
	metadata.InboundDetour = h.listener.ListenOptions().Detour
	metadata.InboundOptions = h.listener.ListenOptions().InboundOptions
	return h.router.RoutePacketConnection(ctx, conn, metadata)
}

func (h *MultiInbound) NewError(ctx context.Context, err error) {
	NewError(h.logger, ctx, err)
}