package shadowsocks

import (
	"io"

	"github.com/v2ray/v2ray-core/common/alloc"
	"github.com/v2ray/v2ray-core/common/log"
	v2net "github.com/v2ray/v2ray-core/common/net"
	"github.com/v2ray/v2ray-core/common/serial"
	"github.com/v2ray/v2ray-core/transport"
)

const (
	AddrTypeIPv4   = 1
	AddrTypeIPv6   = 4
	AddrTypeDomain = 3
)

type Request struct {
	Address    v2net.Address
	Port       v2net.Port
	OTA        bool
	UDPPayload *alloc.Buffer
}

func ReadRequest(reader io.Reader, auth *Authenticator, udp bool) (*Request, error) {
	buffer := alloc.NewSmallBuffer()
	defer buffer.Release()

	_, err := io.ReadFull(reader, buffer.Value[:1])
	if err != nil {
		log.Error("Shadowsocks: Failed to read address type: ", err)
		return nil, transport.ErrorCorruptedPacket
	}
	lenBuffer := 1

	request := new(Request)

	addrType := (buffer.Value[0] & 0x0F)
	if (buffer.Value[0] & 0x10) == 0x10 {
		request.OTA = true
	}
	switch addrType {
	case AddrTypeIPv4:
		_, err := io.ReadFull(reader, buffer.Value[lenBuffer:lenBuffer+4])
		if err != nil {
			log.Error("Shadowsocks: Failed to read IPv4 address: ", err)
			return nil, transport.ErrorCorruptedPacket
		}
		request.Address = v2net.IPAddress(buffer.Value[lenBuffer : lenBuffer+4])
		lenBuffer += 4
	case AddrTypeIPv6:
		_, err := io.ReadFull(reader, buffer.Value[lenBuffer:lenBuffer+16])
		if err != nil {
			log.Error("Shadowsocks: Failed to read IPv6 address: ", err)
			return nil, transport.ErrorCorruptedPacket
		}
		request.Address = v2net.IPAddress(buffer.Value[lenBuffer : lenBuffer+16])
		lenBuffer += 16
	case AddrTypeDomain:
		_, err := io.ReadFull(reader, buffer.Value[lenBuffer:lenBuffer+1])
		if err != nil {
			log.Error("Shadowsocks: Failed to read domain lenth: ", err)
			return nil, transport.ErrorCorruptedPacket
		}
		domainLength := int(buffer.Value[lenBuffer])
		lenBuffer++
		_, err = io.ReadFull(reader, buffer.Value[lenBuffer:lenBuffer+domainLength])
		if err != nil {
			log.Error("Shadowsocks: Failed to read domain: ", err)
			return nil, transport.ErrorCorruptedPacket
		}
		request.Address = v2net.DomainAddress(string(buffer.Value[lenBuffer : lenBuffer+domainLength]))
		lenBuffer += domainLength
	default:
		log.Error("Shadowsocks: Unknown address type: ", addrType)
		return nil, transport.ErrorCorruptedPacket
	}

	_, err = io.ReadFull(reader, buffer.Value[lenBuffer:lenBuffer+2])
	if err != nil {
		log.Error("Shadowsocks: Failed to read port: ", err)
		return nil, transport.ErrorCorruptedPacket
	}

	request.Port = v2net.PortFromBytes(buffer.Value[lenBuffer : lenBuffer+2])
	lenBuffer += 2

	var authBytes []byte

	if udp {
		nBytes, err := reader.Read(buffer.Value[lenBuffer:])
		if err != nil {
			log.Error("Shadowsocks: Failed to read UDP payload: ", err)
		}
		buffer.Slice(0, lenBuffer+nBytes)
		if request.OTA {
			authBytes = buffer.Value[lenBuffer+nBytes-AuthSize:]
			request.UDPPayload = alloc.NewSmallBuffer().Clear().Append(buffer.Value[lenBuffer : lenBuffer+nBytes-AuthSize])
			lenBuffer = lenBuffer + nBytes - AuthSize
		} else {
			request.UDPPayload = alloc.NewSmallBuffer().Clear().Append(buffer.Value[lenBuffer:])
		}
	} else {
		if request.OTA {
			authBytes = buffer.Value[lenBuffer : lenBuffer+AuthSize]
			_, err = io.ReadFull(reader, authBytes)
			if err != nil {
				log.Error("Shadowsocks: Failed to read OTA: ", err)
				return nil, transport.ErrorCorruptedPacket
			}
		}
	}

	if request.OTA {
		actualAuth := auth.Authenticate(nil, buffer.Value[0:lenBuffer])
		if !serial.BytesLiteral(actualAuth).Equals(serial.BytesLiteral(authBytes)) {
			log.Error("Shadowsocks: Invalid OTA: ", actualAuth)
			return nil, transport.ErrorCorruptedPacket
		}
	}

	return request, nil
}