package tools

import (
	"crypto"
	"crypto/rand"
	"crypto/rsa"
	"crypto/sha256"
	"crypto/x509"
	"encoding/base64"
	"encoding/pem"
	"errors"
)

// RSA2私钥签名
func Rsa2PriSign(signContent string, privateKey string, hash crypto.Hash) string {
	shaNew := hash.New()
	shaNew.Write([]byte(signContent))
	hashed := shaNew.Sum(nil)
	priKey, err := ParsePrivateKey(privateKey)
	if err != nil {
		return ""
	}

	signature, err := rsa.SignPKCS1v15(rand.Reader, priKey, hash, hashed)
	if err != nil {
		return ""
	}
	return base64.StdEncoding.EncodeToString(signature)
}

// 解析私钥
func ParsePrivateKey(privateKey string) (*rsa.PrivateKey, error) {
	block, _ := pem.Decode([]byte(privateKey))
	if block == nil {
		return nil, errors.New("私钥信息错误！")
	}
	priKey, err := x509.ParsePKCS1PrivateKey(block.Bytes)
	if err != nil {
		return nil, err
	}
	return priKey, nil
}

// RSA2公钥验证签名
func Rsa2PubCheckSign(source, sign, publicKey string, hash crypto.Hash) (bool, error) {
	hashed := sha256.Sum256([]byte(source))
	pubKey, err := ParsePublicKey(publicKey)
	if err != nil {
		return false, err
	}
	sig, _ := base64.StdEncoding.DecodeString(sign)
	err = rsa.VerifyPKCS1v15(pubKey, hash, hashed[:], sig)
	if err != nil {
		return false, err
	}
	return true, nil
}

// 解析公钥
func ParsePublicKey(publicKey string) (*rsa.PublicKey, error) {
	block, _ := pem.Decode([]byte(publicKey))
	if block == nil {
		return nil, errors.New("公钥信息错误！")
	}
	pubKey, err := x509.ParsePKIXPublicKey(block.Bytes)
	if err != nil {
		return nil, err
	}
	return pubKey.(*rsa.PublicKey), nil
}