package protocol

import (
	"bytes"
	"encoding/binary"
	"encoding/hex"
	"errors"
	"fmt"
	"openess/internal/log"
)

type ForwardWriteReq struct {
	DevAddr    byte
	FuncNumber byte
	Address    uint16
	Data       []byte
}

type ForwardReadReq struct {
	DevAddr    byte
	FuncNumber byte
	Address    uint16
	Length     uint16
}

type ForwardRsp struct {
	Data []byte
}

func NewWriteForwardReq(devAddr byte, funcNumber byte, addr uint16, value []byte) Request[ForwardRsp, ForwardWriteReq] {
	header := Header{
		TID:      1,
		DevCode:  1,
		DevAddr:  devAddr, // devAddrs[0]
		FuncCode: 4,
	}

	body := ForwardWriteReq{
		DevAddr:    devAddr,
		FuncNumber: funcNumber,
		Address:    addr,
		Data:       value,
	}

	req := Request[ForwardRsp, ForwardWriteReq]{
		Header: header,
		Body:   body,
	}

	return req
}

func NewReadForwardReq(devAddr byte, funcNumber byte, start uint16, length uint16) Request[ForwardRsp, ForwardReadReq] {
	header := Header{
		TID:      1,
		DevCode:  1,
		DevAddr:  devAddr, // devAddrs[0]
		FuncCode: 4,
	}

	body := ForwardReadReq{
		DevAddr:    devAddr,
		FuncNumber: funcNumber,
		Address:    start,
		Length:     length,
	}

	req := Request[ForwardRsp, ForwardReadReq]{
		Header: header,
		Body:   body,
	}

	return req
}

var CRC16HI []byte = []byte{
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,
	0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
	0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01,
	0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81,
	0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
	0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01,
	0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,
	0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
	0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01,
	0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,
	0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
	0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01,
	0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,
	0x40,
}

var CRC16LO []byte = []byte{
	0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7, 0x05, 0xC5, 0xC4,
	0x04, 0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09,
	0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD,
	0x1D, 0x1C, 0xDC, 0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
	0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32, 0x36, 0xF6, 0xF7,
	0x37, 0xF5, 0x35, 0x34, 0xF4, 0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A,
	0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE,
	0x2E, 0x2F, 0xEF, 0x2D, 0xED, 0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
	0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60, 0x61, 0xA1, 0x63, 0xA3, 0xA2,
	0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4, 0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F,
	0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68, 0x78, 0xB8, 0xB9, 0x79, 0xBB,
	0x7B, 0x7A, 0xBA, 0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
	0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0, 0x50, 0x90, 0x91,
	0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C,
	0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, 0x88,
	0x48, 0x49, 0x89, 0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
	0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83, 0x41, 0x81, 0x80,
	0x40,
}

func getCrc16(data []byte) uint16 {
	var hi byte = 0xff
	var lo byte = 0xff
	var index = 0
	for _, c := range data {
		index = int(hi ^ c)
		hi = lo ^ CRC16HI[index]
		lo = CRC16LO[index]
	}
	return (uint16(hi)<<8 | uint16(lo))
}

func (req ForwardWriteReq) EncodeRequest() ([]byte, error) {
	buf := new(bytes.Buffer)
	buf.WriteByte(req.DevAddr)                       // devAddr
	buf.WriteByte(req.FuncNumber)                    // funcNumber
	binary.Write(buf, binary.BigEndian, req.Address) // startAddress
	buf.Write(req.Data)
	crc := getCrc16(buf.Bytes())
	binary.Write(buf, binary.BigEndian, crc)

	log.PrDebug("msg_forward: write request %s\n", hex.EncodeToString(buf.Bytes()))

	return buf.Bytes(), nil
}

func (req ForwardWriteReq) DecodeResponse(data []byte) (ForwardRsp, error) {
	var rsp ForwardRsp

	buf := bytes.NewBuffer(data)

	devAddr, err := buf.ReadByte()
	if err != nil {
		return rsp, err
	}

	funcNumber, err := buf.ReadByte()
	if err != nil {
		return rsp, err
	}

	if devAddr != req.DevAddr || funcNumber != req.FuncNumber {
		return rsp, errors.New(fmt.Sprintf("invalid devaddr or funcNumber in response: %d, %d (expected %d/%d)",
			devAddr, funcNumber, req.DevAddr, req.FuncNumber))
	}

	var addr uint16
	err = binary.Read(buf, binary.BigEndian, &addr)
	if err != nil {
		return rsp, err
	}

	if addr != req.Address {
		return rsp, errors.New(fmt.Sprintf("invalid response address: %d (expected %d)", addr, req.Address))
	}

	rsp.Data = make([]byte, 2)

	_, err = buf.Read(rsp.Data)
	if err != nil {
		return rsp, err
	}

	crcLocal := getCrc16(data)

	if crcLocal != 0 {
		return rsp, errors.New(fmt.Sprintf("crc check failed: payload = %s\n", hex.EncodeToString(data)))
	}

	return rsp, nil
}

func (req ForwardReadReq) EncodeRequest() ([]byte, error) {
	buf := new(bytes.Buffer)
	buf.WriteByte(req.DevAddr)                       // devAddr
	buf.WriteByte(req.FuncNumber)                    // funcNumber
	binary.Write(buf, binary.BigEndian, req.Address) // startAddress
	binary.Write(buf, binary.BigEndian, req.Length)  // length
	crc := getCrc16(buf.Bytes())
	binary.Write(buf, binary.BigEndian, crc)

	log.PrDebug("msg_forward: read request %s\n", hex.EncodeToString(buf.Bytes()))

	return buf.Bytes(), nil
}

func (req ForwardReadReq) DecodeResponse(data []byte) (ForwardRsp, error) {
	var rsp ForwardRsp

	buf := bytes.NewBuffer(data)

	devAddr, err := buf.ReadByte()
	if err != nil {
		return rsp, err
	}

	funcNumber, err := buf.ReadByte()
	if err != nil {
		return rsp, err
	}

	if devAddr != req.DevAddr || funcNumber != req.FuncNumber {
		return rsp, errors.New(fmt.Sprintf("invalid devaddr or funcNumber in response: %d, %d (expected %d/%d)",
			devAddr, funcNumber, req.DevAddr, req.FuncNumber))
	}

	byteCount, err := buf.ReadByte()
	if err != nil {
		return rsp, err
	}

    // Issue #3:
    // Some invertors send extra zeros after the response,
    // so we don't expect the full length match
	if int(byteCount) > len(data) - 5 {
		return rsp, errors.New(fmt.Sprintf("invalid response length: %d (expected %d)", byteCount, len(data) - 5))
	}

	rsp.Data = make([]byte, byteCount)

	_, err = buf.Read(rsp.Data)
	if err != nil {
		return rsp, err
	}

	crcLocal := getCrc16(data[:byteCount + 5])

	if crcLocal != 0 {
		return rsp, errors.New(fmt.Sprintf("crc check failed: payload = %s\n", hex.EncodeToString(data)))
	}

	return rsp, nil
}
