// 提供CRC8校验和计算功能。
package crc8

import (
	"encoding/hex"
	"fmt"
	"os"

	"github.com/sigurn/crc8"
)

// 根据提供的校验表名称生成对应的校验表
func hasherSelect(table string) *crc8.Table {
	switch table {
	case "CRC8":
		return crc8.MakeTable(crc8.CRC8)
	case "CDMA2000":
		return crc8.MakeTable(crc8.CRC8_CDMA2000)
	case "DARC":
		return crc8.MakeTable(crc8.CRC8_DARC)
	case "DVB-S2":
		return crc8.MakeTable(crc8.CRC8_DVB_S2)
	case "EBU":
		return crc8.MakeTable(crc8.CRC8_EBU)
	case "I-CODE":
		return crc8.MakeTable(crc8.CRC8_I_CODE)
	case "ITU":
		return crc8.MakeTable(crc8.CRC8_ITU)
	case "MAXIM":
		return crc8.MakeTable(crc8.CRC8_MAXIM)
	case "ROHC":
		return crc8.MakeTable(crc8.CRC8_ROHC)
	case "WCDMA":
		return crc8.MakeTable(crc8.CRC8_WCDMA)
	default:
		return crc8.MakeTable(crc8.CRC8)
	}
}

// 计算给定字节数组的CRC8校验和，返回字节数组
func CRC8(data []byte, table ...string) []byte {
	crcTable := append(table, "CRC8")
	return []byte{crc8.Checksum(data, hasherSelect(crcTable[0]))}
}

// 计算给定字节数组的CRC8校验和，返回十六进制字符串
func CRC8Hex(data []byte, table ...string) string {
	return hex.EncodeToString(CRC8(data, table...))
}

// 计算指定文件的CRC8校验和，返回字节数组
func SumFile(file string, table ...string) ([]byte, error) {
	f, err := os.Open(file)
	if err != nil {
		return nil, fmt.Errorf("未能打开指定文件，%w", err)
	}
	defer f.Close()

	crcTable := append(table, "CRC8")
	var buf = make([]byte, 0)
	if _, err := f.Read(buf); err != nil {
		return nil, fmt.Errorf("读取指定文件内容出错，%w", err)
	}
	return []byte{crc8.Checksum(buf, hasherSelect(crcTable[0]))}, nil
}

// 计算指定文件的CRC8校验和，返回十六进制字符串
func SumFileHex(file string, table ...string) (string, error) {
	crc, err := SumFile(file, table...)
	if err != nil {
		return "", err
	}
	return hex.EncodeToString(crc), nil
}