package main

import (
"encoding/hex"
"crypto/sha256"
"math/big"
"bytes"
"fmt"
)


//base58編碼
var b58Alphabet = []byte("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz")

func Base58Encode(input []byte
 
) []byte{
var result []byte

	x:= big.NewInt(0).SetBytes(input)

	base := big.NewInt(int64(len(b58Alphabet)))
	zero := big.NewInt(0)

	mod := &big.Int{}
for x.Cmp(zero) != 0 {
		x.DivMod(x,base,mod)  // 對x取餘數
		result =  append(result, b58Alphabet[mod.Int64()])
	}



	ReverseBytes(result)

for _,b:=range input{
 


if b ==0x00{
			result =  append([]byte{b58Alphabet[0]},result...)
		}else{
break
		}
	}


return result

}


//位元組陣列的反轉
func ReverseBytes(data []byte){
for i,j :=0,len(data) - 1;i<j;i,j = i+1,j - 1{
		data[i],data[j] = data[j],data[i]
	}
}
func generatePrivateKey(hexprivatekey string,compressed bool) []byte{
	versionstr :=""
//判斷是否對應的是壓縮的公鑰，如果是，需要在後面加上0x01這個位元組。同時任何的私鑰，我們需要在前方0x80的位元組
if compressed{
		versionstr  = "80" + hexprivatekey + "01"
	}else{
		versionstr  = "80" + hexprivatekey
	}
//字串轉化為16進位制的位元組
	privatekey,_:=hex.DecodeString(versionstr)
//通過 double hash 計算checksum.checksum他是兩次hash256以後的前4個位元組。
	firsthash:=sha256.Sum256(privatekey)

	secondhash:= sha256.Sum256(firsthash[:])

	checksum := secondhash[:4]

//拼接
	result := append(privatekey,checksum...)

//最後進行base58的編碼
	base58result :=Base58Encode(result)
return base58result
}



func Base58Decode(input []byte) []byte{
	result :=  big.NewInt(0)
	zeroBytes :=0
for _,b :=range input{
if b=='1'{
			zeroBytes++
		}else{
break
		}
	}

	payload:= input[zeroBytes:]

for _,b := range payload{
		charIndex := bytes.IndexByte(b58Alphabet,b)  //反推出餘數

		result.Mul(result,big.NewInt(58))   //之前的結果乘以58

		result.Add(result,big.NewInt(int64(charIndex)))  //加上這個餘數

	}

	decoded :=result.Bytes()


	decoded =  append(bytes.Repeat([]byte{0x00},zeroBytes),decoded...)
return decoded
}


//檢查checkWIF是否有效
func checkWIF(wifprivate string) bool{
	rawdata := []byte(wifprivate)
//包含了80、私鑰、checksum
	base58decodedata:= Base58Decode(rawdata)

	fmt.Printf("base58decodedata：%x\n",base58decodedata)
	length :=len(base58decodedata)


if(length <37){
		fmt.Printf("長度小於37，一定有問題")
return false
	}


	private := base58decodedata[:(length-4)]
//得到檢查碼
//fmt.Printf("private：%x\n",private)
	firstsha :=  sha256.Sum256(private)

	secondsha := sha256.Sum256(firstsha[:])

	checksum := secondsha[:4]
//fmt.Printf("%x\n",checksum)
//得到原始的檢查碼
	orignchecksum:= base58decodedata[(length-4):]
//	fmt.Printf("%x\n",orignchecksum)

//[]byte對比
if bytes.Compare(checksum,orignchecksum)==0{
return true
	}

return false

}

//通過wif格式的私鑰，得到原始的私鑰。
func getPrivateKeyfromWIF( wifprivate string) []byte{
if checkWIF(wifprivate){
				rawdata := []byte(wifprivate)
//包含了80、私鑰、checksum
				base58decodedata:= Base58Decode(rawdata)
//私鑰一共32個位元組，排除了0x80
return base58decodedata[1:33]
			}
return []byte{}

}


func main(){
//得到wif格式的私鑰
	wifprivatekey:=generatePrivateKey("18d3e15d48b2df76562fab783eac137aaeb611e6ff0a193e12ceef1354220ac7",false)
	fmt.Printf("%s\n",wifprivatekey)

//【】byte轉換為string
	str := fmt.Sprintf("%s",wifprivatekey)

//得到原始的私鑰
	 privatekey :=getPrivateKeyfromWIF(str)
		fmt.Printf("%x", privatekey)
}