package shadowsocks_2022

import (
	"io"

	B "github.com/sagernet/sing/common/buf"
	E "github.com/sagernet/sing/common/exceptions"
	M "github.com/sagernet/sing/common/metadata"
	"github.com/xtls/xray-core/common/buf"
	"github.com/xtls/xray-core/common/net"
)

//go:generate go run github.com/xtls/xray-core/common/errors/errorgen

func toDestination(socksaddr M.Socksaddr, network net.Network) net.Destination {
	if socksaddr.IsFqdn() {
		return net.Destination{
			Network: network,
			Address: net.DomainAddress(socksaddr.Fqdn),
			Port:    net.Port(socksaddr.Port),
		}
	} else {
		return net.Destination{
			Network: network,
			Address: net.IPAddress(socksaddr.Addr.AsSlice()),
			Port:    net.Port(socksaddr.Port),
		}
	}
}

func toSocksaddr(destination net.Destination) M.Socksaddr {
	var addr M.Socksaddr
	switch destination.Address.Family() {
	case net.AddressFamilyDomain:
		addr.Fqdn = destination.Address.Domain()
	default:
		addr.Addr = M.AddrFromIP(destination.Address.IP())
	}
	addr.Port = uint16(destination.Port)
	return addr
}

type pipeConnWrapper struct {
	R io.Reader
	W buf.Writer
	net.Conn
}

func (w *pipeConnWrapper) Close() error {
	return nil
}

func (w *pipeConnWrapper) Read(b []byte) (n int, err error) {
	return w.R.Read(b)
}

func (w *pipeConnWrapper) Write(p []byte) (n int, err error) {
	n = len(p)
	var mb buf.MultiBuffer
	pLen := len(p)
	for pLen > 0 {
		buffer := buf.New()
		if pLen > buf.Size {
			_, err = buffer.Write(p[:buf.Size])
			p = p[buf.Size:]
		} else {
			buffer.Write(p)
		}
		pLen -= int(buffer.Len())
		mb = append(mb, buffer)
	}
	err = w.W.WriteMultiBuffer(mb)
	if err != nil {
		n = 0
		buf.ReleaseMulti(mb)
	}
	return
}

type packetConnWrapper struct {
	buf.Reader
	buf.Writer
	net.Conn
	Dest   net.Destination
	cached buf.MultiBuffer
}

func (w *packetConnWrapper) ReadPacket(buffer *B.Buffer) (M.Socksaddr, error) {
	if w.cached != nil {
		mb, bb := buf.SplitFirst(w.cached)
		if bb == nil {
			w.cached = nil
		} else {
			buffer.Write(bb.Bytes())
			w.cached = mb
			var destination net.Destination
			if bb.UDP != nil {
				destination = *bb.UDP
			} else {
				destination = w.Dest
			}
			bb.Release()
			return toSocksaddr(destination), nil
		}
	}
	mb, err := w.ReadMultiBuffer()
	if err != nil {
		return M.Socksaddr{}, err
	}
	nb, bb := buf.SplitFirst(mb)
	if bb == nil {
		return M.Socksaddr{}, nil
	} else {
		buffer.Write(bb.Bytes())
		w.cached = nb
		var destination net.Destination
		if bb.UDP != nil {
			destination = *bb.UDP
		} else {
			destination = w.Dest
		}
		bb.Release()
		return toSocksaddr(destination), nil
	}
}

func (w *packetConnWrapper) WritePacket(buffer *B.Buffer, destination M.Socksaddr) error {
	vBuf := buf.New()
	vBuf.Write(buffer.Bytes())
	endpoint := toDestination(destination, net.Network_UDP)
	vBuf.UDP = &endpoint
	return w.Writer.WriteMultiBuffer(buf.MultiBuffer{vBuf})
}

func (w *packetConnWrapper) Close() error {
	buf.ReleaseMulti(w.cached)
	return nil
}

func returnError(err error) error {
	if E.IsClosed(err) {
		return nil
	}
	return err
}