package sudoku

import (
	"context"
	"net"
	"strings"

	"github.com/sagernet/sing-box/adapter"
	"github.com/sagernet/sing-box/adapter/inbound"
	"github.com/sagernet/sing-box/common/listener"
	C "github.com/sagernet/sing-box/constant"
	"github.com/sagernet/sing-box/log"
	"github.com/sagernet/sing-box/option"
	"github.com/sagernet/sing-box/transport/sudoku"
	"github.com/sagernet/sing/common/bufio"
	"github.com/sagernet/sing/common/logger"
	M "github.com/sagernet/sing/common/metadata"
	N "github.com/sagernet/sing/common/network"
)

func RegisterInbound(registry *inbound.Registry) {
	inbound.Register[option.SudokuInboundOptions](registry, C.TypeSudoku, NewInbound)
}

type Inbound struct {
	inbound.Adapter
	router    adapter.ConnectionRouterEx
	logger    logger.ContextLogger
	listener  *listener.Listener
	protoConf sudoku.ProtocolConfig
	tunnelSrv *sudoku.HTTPMaskTunnelServer
	fallback  string
}

func NewInbound(ctx context.Context, router adapter.Router, logger log.ContextLogger, tag string, options option.SudokuInboundOptions) (adapter.Inbound, error) {
	defaultConf := sudoku.DefaultConfig()
	tableType, err := sudoku.NormalizeTableType(options.TableType)
	if err != nil {
		return nil, err
	}
	paddingMin, paddingMax := sudoku.ResolvePadding(options.PaddingMin, options.PaddingMax, defaultConf.PaddingMin, defaultConf.PaddingMax)
	enablePureDownlink := sudoku.DerefBool(options.EnablePureDownlink, defaultConf.EnablePureDownlink)
	handshakeTimeout := sudoku.DerefInt(options.HandshakeTimeout, defaultConf.HandshakeTimeoutSeconds)

	tables, err := sudoku.NewServerTablesWithCustomPatterns(sudoku.ServerAEADSeed(options.Key), tableType, options.CustomTable, options.CustomTables)
	if err != nil {
		return nil, err
	}

	protoConf := sudoku.ProtocolConfig{
		Key:                     options.Key,
		AEADMethod:              defaultConf.AEADMethod,
		PaddingMin:              paddingMin,
		PaddingMax:              paddingMax,
		EnablePureDownlink:      enablePureDownlink,
		HandshakeTimeoutSeconds: handshakeTimeout,
		DisableHTTPMask:         options.DisableHTTPMask,
		HTTPMaskMode:            options.HTTPMaskMode,
		HTTPMaskPathRoot:        strings.TrimSpace(options.PathRoot),
	}
	if len(tables) == 1 {
		protoConf.Table = tables[0]
	} else {
		protoConf.Tables = tables
	}
	if options.AEADMethod != "" {
		protoConf.AEADMethod = options.AEADMethod
	}

	inbound := &Inbound{
		Adapter:   inbound.NewAdapter(C.TypeSudoku, tag),
		router:    router,
		logger:    logger,
		protoConf: protoConf,
		fallback:  strings.TrimSpace(options.Fallback),
	}
	if inbound.fallback != "" {
		inbound.tunnelSrv = sudoku.NewHTTPMaskTunnelServerWithFallback(&inbound.protoConf)
	} else {
		inbound.tunnelSrv = sudoku.NewHTTPMaskTunnelServer(&inbound.protoConf)
	}

	inbound.listener = listener.New(listener.Options{
		Context:           ctx,
		Logger:            logger,
		Network:           []string{N.NetworkTCP},
		Listen:            options.ListenOptions,
		ConnectionHandler: inbound,
	})
	return inbound, nil
}

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

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

func (h *Inbound) NewConnectionEx(ctx context.Context, conn net.Conn, metadata adapter.InboundContext, onClose N.CloseHandlerFunc) {
	h.handleConn(ctx, conn, metadata, onClose)
}

func (h *Inbound) handleConn(ctx context.Context, conn net.Conn, metadata adapter.InboundContext, onClose N.CloseHandlerFunc) {
	handshakeConn := conn
	handshakeCfg := &h.protoConf

	if h.tunnelSrv != nil {
		c, cfg, done, err := h.tunnelSrv.WrapConn(conn)
		if err != nil {
			conn.Close()
			return
		}
		if done {
			return
		}
		if c != nil {
			handshakeConn = c
		}
		if cfg != nil {
			handshakeCfg = cfg
		}
	}

	cConn, meta, err := sudoku.ServerHandshake(handshakeConn, handshakeCfg)
	if err != nil {
		h.logger.DebugContext(ctx, "handshake failed: ", err)
		conn.Close()
		if handshakeConn != conn {
			handshakeConn.Close()
		}
		return
	}

	session, err := sudoku.ReadServerSession(cConn, meta)
	if err != nil {
		h.logger.WarnContext(ctx, "read session failed: ", err)
		cConn.Close()
		return
	}

	switch session.Type {
	case sudoku.SessionTypeUoT:
		h.handleUoT(ctx, session.Conn, metadata, onClose)
	case sudoku.SessionTypeMultiplex:
		mux, err := sudoku.AcceptMultiplexServer(session.Conn)
		if err != nil {
			session.Conn.Close()
			return
		}
		defer mux.Close()
		for {
			stream, target, err := mux.AcceptTCP()
			if err != nil {
				return
			}
			go h.routeTCP(ctx, stream, target, metadata)
		}
	default:
		h.routeTCP(ctx, session.Conn, session.Target, metadata)
	}
}

func (h *Inbound) routeTCP(ctx context.Context, conn net.Conn, target string, metadata adapter.InboundContext) {
	destination := M.ParseSocksaddr(target)
	metadata.Destination = destination
	h.logger.InfoContext(ctx, "inbound connection to ", destination)
	h.router.RouteConnectionEx(ctx, conn, metadata, nil)
}

func (h *Inbound) handleUoT(ctx context.Context, conn net.Conn, metadata adapter.InboundContext, onClose N.CloseHandlerFunc) {
	h.logger.InfoContext(ctx, "inbound packet connection")
	packetConn := sudoku.NewUoTPacketConn(conn)
	h.router.RoutePacketConnectionEx(ctx, bufio.NewPacketConn(packetConn), metadata, onClose)
}