package market

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

// getSignString 使用 xx=aa&yy=bb 的字符串拼接
func getSignString(data map[string]interface{}) string {
	keys := make([]string, 0, len(data))
	for key := range data {
		keys = append(keys, key)
	}
	sort.Strings(keys)

	signString := ""
	separator := ""
	for _, key := range keys {
		value := data[key]
		if key == "sign" || value == nil {
			continue
		}
		signString += fmt.Sprintf("%s%s=%v", separator, key, value)
		separator = "&"
	}
	return signString
}

// VerifyRsaSign 签名验证
func VerifyRsaSign(publicKey string, data map[string]interface{}) (map[string]interface{}, error) {
	// 对 sign nonce timestamp appId 升序排序
	// 使用 xx=aa&yy=bb 的字符串拼接
	// 商户的公钥验签 RSA2验签
	signString := getSignString(data)

	rsaPubKey, err := parseRSAPublicKeyFromPEM([]byte(publicKey))
	if err != nil {
		return nil, err
	}

	signature, err := base64.StdEncoding.DecodeString(data["sign"].(string))
	if err != nil {
		return nil, err
	}

	hashed := sha256.Sum256([]byte(signString))
	err = rsa.VerifyPKCS1v15(rsaPubKey, crypto.SHA256, hashed[:], signature)
	if err != nil {
		return nil, errors.New("签名验证失败")
	}

	return data, nil
}

// MakeRsaSign 生成签名
func MakeRsaSign(privateKey string, data map[string]interface{}) (string, error) {
	// 对 sign nonce timestamp appId 升序排序
	// 使用 xx=aa&yy=bb 的字符串拼接
	// 营销系统生成的私钥生成签名 RSA2加签
	signString := getSignString(data)

	privKey, err := parseRSAPrivateKeyFromPEM([]byte(privateKey))
	if err != nil {
		return "", errors.New("私钥解析失败")
	}

	hashed := sha256.Sum256([]byte(signString))
	signature, err := rsa.SignPKCS1v15(rand.Reader, privKey, crypto.SHA256, hashed[:])
	if err != nil {
		return "", errors.New("签名失败")
	}

	return base64.StdEncoding.EncodeToString(signature), nil
}

// ParseRSAPrivateKeyFromPEM 解析私钥
func parseRSAPrivateKeyFromPEM(key []byte) (*rsa.PrivateKey, error) {
	var err error

	// Parse PEM block
	var block *pem.Block
	if block, _ = pem.Decode(key); block == nil {
		return nil, errors.New("私钥解析失败: 无效的PEM格式")
	}

	var parsedKey interface{}
	if parsedKey, err = x509.ParsePKCS1PrivateKey(block.Bytes); err != nil {
		if parsedKey, err = x509.ParsePKCS8PrivateKey(block.Bytes); err != nil {
			return nil, err
		}
	}

	var pkey *rsa.PrivateKey
	var ok bool
	if pkey, ok = parsedKey.(*rsa.PrivateKey); !ok {
		return nil, errors.New("密钥不是有效的RSA私钥")
	}

	return pkey, nil
}

// parseRSAPublicKeyFromPEM parses a PEM encoded PKCS1 or PKCS8 public key
func parseRSAPublicKeyFromPEM(key []byte) (*rsa.PublicKey, error) {
	var err error

	// Parse PEM block
	var block *pem.Block
	if block, _ = pem.Decode(key); block == nil {
		return nil, errors.New("公钥解析失败: 无效的PEM格式")
	}

	// Parse the key
	var parsedKey interface{}
	if parsedKey, err = x509.ParsePKIXPublicKey(block.Bytes); err != nil {
		if cert, err := x509.ParseCertificate(block.Bytes); err == nil {
			parsedKey = cert.PublicKey
		} else {
			return nil, err
		}
	}

	var pkey *rsa.PublicKey
	var ok bool
	if pkey, ok = parsedKey.(*rsa.PublicKey); !ok {
		return nil, errors.New("密钥不是有效的RSA公钥")
	}

	return pkey, nil
}