package ymt_v3

import (
	"bytes"
	"crypto"
	"crypto/aes"
	"crypto/rand"
	"crypto/rsa"
	"crypto/sha256"
	"crypto/x509"
	"encoding/base64"
	"encoding/json"
	"encoding/pem"
	"fmt"
	"io"
	"reflect"
	"sort"
	"strings"
	"time"
)

// ============================================================
// 时间戳工具
// ============================================================

// GenerateTimestamp 生成格式为 yyyy-MM-dd HH:mm:ss 的时间戳
func GenerateTimestamp() string {
	return time.Now().Format("2006-01-02 15:04:05")
}

// ============================================================
// PKCS7 填充/去填充
// ============================================================

func pkcs7Padding(data []byte, blockSize int) []byte {
	padding := blockSize - len(data)%blockSize
	padText := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(data, padText...)
}

func pkcs7UnPadding(data []byte) ([]byte, error) {
	length := len(data)
	if length == 0 {
		return nil, fmt.Errorf("数据为空")
	}
	padding := int(data[length-1])
	if padding > length || padding == 0 {
		return nil, fmt.Errorf("无效的填充")
	}
	for i := length - padding; i < length; i++ {
		if data[i] != byte(padding) {
			return nil, fmt.Errorf("无效的填充")
		}
	}
	return data[:length-padding], nil
}

// ============================================================
// AES-ECB 加密/解密
// ============================================================

// AESECBEncrypt AES-ECB模式加密，返回base64编码
func AESECBEncrypt(plaintext []byte, key []byte) (string, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return "", fmt.Errorf("创建AES cipher失败: %v", err)
	}

	padded := pkcs7Padding(plaintext, aes.BlockSize)

	ciphertext := make([]byte, len(padded))
	for i := 0; i < len(padded); i += aes.BlockSize {
		block.Encrypt(ciphertext[i:i+aes.BlockSize], padded[i:i+aes.BlockSize])
	}

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

// AESECBDecrypt AES-ECB模式解密，输入base64编码
func AESECBDecrypt(encryptedData string, key []byte) ([]byte, error) {
	ciphertext, err := base64.StdEncoding.DecodeString(encryptedData)
	if err != nil {
		return nil, fmt.Errorf("base64解码失败: %v", err)
	}

	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, fmt.Errorf("创建AES cipher失败: %v", err)
	}

	if len(ciphertext)%aes.BlockSize != 0 {
		return nil, fmt.Errorf("密文长度不是块大小的整数倍")
	}

	plaintext := make([]byte, len(ciphertext))
	for i := 0; i < len(ciphertext); i += aes.BlockSize {
		block.Decrypt(plaintext[i:i+aes.BlockSize], ciphertext[i:i+aes.BlockSize])
	}

	plaintext, err = pkcs7UnPadding(plaintext)
	if err != nil {
		return nil, fmt.Errorf("去除填充失败: %v", err)
	}

	return plaintext, nil
}

// ============================================================
// SM4-CBC 加密/解密（纯Go实现，无外部依赖）
// ============================================================

// SM4CBCEncrypt SM4-CBC模式加密，返回base64编码（IV前置）
func SM4CBCEncrypt(plaintext []byte, key []byte) (string, error) {
	if len(key) != 16 {
		return "", fmt.Errorf("SM4密钥长度必须为16字节")
	}

	block, err := newSM4Cipher(key)
	if err != nil {
		return "", fmt.Errorf("创建SM4 cipher失败: %v", err)
	}

	padded := pkcs7Padding(plaintext, block.BlockSize())

	iv := make([]byte, block.BlockSize())
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		return "", fmt.Errorf("生成IV失败: %v", err)
	}

	mode := newCBCEncrypter(block, iv)
	ciphertext := make([]byte, len(padded))
	mode.CryptBlocks(ciphertext, padded)

	result := append(iv, ciphertext...)
	return base64.StdEncoding.EncodeToString(result), nil
}

// SM4CBCDecrypt SM4-CBC模式解密，输入base64编码
func SM4CBCDecrypt(encryptedData string, key []byte) ([]byte, error) {
	if len(key) != 16 {
		return nil, fmt.Errorf("SM4密钥长度必须为16字节")
	}

	data, err := base64.StdEncoding.DecodeString(encryptedData)
	if err != nil {
		return nil, fmt.Errorf("base64解码失败: %v", err)
	}

	block, err := newSM4Cipher(key)
	if err != nil {
		return nil, fmt.Errorf("创建SM4 cipher失败: %v", err)
	}

	blockSize := block.BlockSize()
	if len(data) < blockSize {
		return nil, fmt.Errorf("数据长度不足")
	}
	iv := data[:blockSize]
	ciphertext := data[blockSize:]

	mode := newCBCDecrypter(block, iv)
	plaintext := make([]byte, len(ciphertext))
	mode.CryptBlocks(plaintext, ciphertext)

	plaintext, err = pkcs7UnPadding(plaintext)
	if err != nil {
		return nil, fmt.Errorf("去除填充失败: %v", err)
	}

	return plaintext, nil
}

// ============================================================
// SM4 纯Go实现
// ============================================================

type sm4Cipher struct {
	sk [32]uint32
}

func newSM4Cipher(key []byte) (*sm4Cipher, error) {
	if len(key) != 16 {
		return nil, fmt.Errorf("SM4密钥长度必须为16字节")
	}
	c := &sm4Cipher{}
	c.sm4KeyInit(key)
	return c, nil
}

func (c *sm4Cipher) BlockSize() int { return 16 }

func (c *sm4Cipher) Encrypt(dst, src []byte) {
	c.sm4OneRound(dst, src, c.sk)
}

func (c *sm4Cipher) Decrypt(dst, src []byte) {
	var rk [32]uint32
	for i := 0; i < 32; i++ {
		rk[i] = c.sk[31-i]
	}
	c.sm4OneRound(dst, src, rk)
}

type sm4CBCEncrypter struct {
	b  *sm4Cipher
	iv []byte
}

func newCBCEncrypter(b *sm4Cipher, iv []byte) *sm4CBCEncrypter {
	return &sm4CBCEncrypter{b: b, iv: append([]byte{}, iv...)}
}

func (c *sm4CBCEncrypter) CryptBlocks(dst, src []byte) {
	blockSize := c.b.BlockSize()
	iv := make([]byte, blockSize)
	copy(iv, c.iv)
	for i := 0; i < len(src); i += blockSize {
		for j := 0; j < blockSize; j++ {
			dst[i+j] = src[i+j] ^ iv[j]
		}
		c.b.Encrypt(dst[i:i+blockSize], dst[i:i+blockSize])
		copy(iv, dst[i:i+blockSize])
	}
}

type sm4CBCDecrypter struct {
	b  *sm4Cipher
	iv []byte
}

func newCBCDecrypter(b *sm4Cipher, iv []byte) *sm4CBCDecrypter {
	return &sm4CBCDecrypter{b: b, iv: append([]byte{}, iv...)}
}

func (c *sm4CBCDecrypter) CryptBlocks(dst, src []byte) {
	blockSize := c.b.BlockSize()
	iv := make([]byte, blockSize)
	copy(iv, c.iv)
	for i := 0; i < len(src); i += blockSize {
		c.b.Decrypt(dst[i:i+blockSize], src[i:i+blockSize])
		for j := 0; j < blockSize; j++ {
			dst[i+j] ^= iv[j]
		}
		copy(iv, src[i:i+blockSize])
	}
}

var sm4Sbox = [256]byte{
	0xd6, 0x90, 0xe9, 0xfe, 0xcc, 0xe1, 0x3d, 0xb7, 0x16, 0xb6, 0x14, 0xc2, 0x28, 0xfb, 0x2c, 0x05,
	0x2b, 0x67, 0x9a, 0x76, 0x2a, 0xbe, 0x04, 0xc3, 0xaa, 0x44, 0x13, 0x26, 0x49, 0x86, 0x06, 0x99,
	0x9c, 0x42, 0x50, 0xf4, 0x91, 0xef, 0x98, 0x7a, 0x33, 0x54, 0x0b, 0x43, 0xed, 0xcf, 0xac, 0x62,
	0xe4, 0xb3, 0x1c, 0xa9, 0xc9, 0x08, 0xe8, 0x95, 0x80, 0xdf, 0x94, 0xfa, 0x75, 0x8f, 0x3f, 0xa6,
	0x47, 0x07, 0xa7, 0xfc, 0xf3, 0x73, 0x17, 0xba, 0x83, 0x59, 0x3c, 0x19, 0xe6, 0x85, 0x4f, 0xa8,
	0x68, 0x6b, 0x81, 0xb2, 0x71, 0x64, 0xda, 0x8b, 0xf8, 0xeb, 0x0f, 0x4b, 0x70, 0x56, 0x9d, 0x35,
	0x1e, 0x24, 0x0e, 0x5e, 0x63, 0x58, 0xd1, 0xa2, 0x25, 0x22, 0x7c, 0x3b, 0x01, 0x21, 0x78, 0x87,
	0xd4, 0x00, 0x46, 0x57, 0x9f, 0xd3, 0x27, 0x52, 0x4c, 0x36, 0x02, 0xe7, 0xa0, 0xc4, 0xc8, 0x9e,
	0xea, 0xbf, 0x8a, 0xd2, 0x40, 0xc7, 0x38, 0xb5, 0xa3, 0xf7, 0xf2, 0xce, 0xf9, 0x61, 0x15, 0xa1,
	0xe0, 0xae, 0x5d, 0xa4, 0x9b, 0x34, 0x1a, 0x55, 0xad, 0x93, 0x32, 0x30, 0xf5, 0x8c, 0xb1, 0xe3,
	0x1d, 0xf6, 0xe2, 0x2e, 0x82, 0x66, 0xca, 0x60, 0xc0, 0x29, 0x23, 0xab, 0x0d, 0x53, 0x4e, 0x6f,
	0xd5, 0xdb, 0x37, 0x45, 0xde, 0xfd, 0x8e, 0x2f, 0x03, 0xff, 0x6a, 0x72, 0x6d, 0x6c, 0x5b, 0x51,
	0x8d, 0x1b, 0xaf, 0x92, 0xbb, 0xdd, 0xbc, 0x7f, 0x11, 0xd9, 0x5c, 0x41, 0x1f, 0x10, 0x5a, 0xd8,
	0x0a, 0xc1, 0x31, 0x88, 0xa5, 0xcd, 0x7b, 0xbd, 0x2d, 0x74, 0xd0, 0x12, 0xb8, 0xe5, 0xb4, 0xb0,
	0x89, 0x69, 0x97, 0x4a, 0x0c, 0x96, 0x77, 0x7e, 0x65, 0xb9, 0xf1, 0x09, 0xc5, 0x6e, 0xc6, 0x84,
	0x18, 0xf0, 0x7d, 0xec, 0x3a, 0xdc, 0x4d, 0x20, 0x79, 0xee, 0x5f, 0x3e, 0xd7, 0xcb, 0x39, 0x48,
}

var sm4FK = [4]uint32{0xa3b1bac6, 0x56aa3350, 0x677d9197, 0xb27022dc}

var sm4CK = [32]uint32{
	0x00070e15, 0x1c232a31, 0x383f464d, 0x545b6269,
	0x70777e85, 0x8c939aa1, 0xa8afb6bd, 0xc4cbd2d9,
	0xe0e7eef5, 0xfc030a11, 0x181f262d, 0x343b4249,
	0x50575e65, 0x6c737a81, 0x888f969d, 0xa4abb2b9,
	0xc0c7ced5, 0xdce3eaf1, 0xf8ff060d, 0x141b2229,
	0x30373e45, 0x4c535a61, 0x686f767d, 0x848b9299,
	0xa0a7aeb5, 0xbcc3cad1, 0xd8dfe6ed, 0xf4fb0209,
	0x10171e25, 0x2c333a41, 0x484f565d, 0x646b7279,
}

func (c *sm4Cipher) sm4KeyInit(key []byte) {
	var mk [4]uint32
	for i := 0; i < 4; i++ {
		mk[i] = uint32(key[4*i])<<24 | uint32(key[4*i+1])<<16 | uint32(key[4*i+2])<<8 | uint32(key[4*i+3])
	}

	var k [36]uint32
	for i := 0; i < 4; i++ {
		k[i] = mk[i] ^ sm4FK[i]
	}

	for i := 0; i < 32; i++ {
		k[i+4] = k[i] ^ sm4L1(k[i+1]^k[i+2]^k[i+3]^sm4CK[i])
		c.sk[i] = k[i+4]
	}
}

func (c *sm4Cipher) sm4OneRound(dst, src []byte, sk [32]uint32) {
	var x [36]uint32
	for i := 0; i < 4; i++ {
		x[i] = uint32(src[4*i])<<24 | uint32(src[4*i+1])<<16 | uint32(src[4*i+2])<<8 | uint32(src[4*i+3])
	}

	for i := 0; i < 32; i++ {
		x[i+4] = x[i] ^ sm4L2(x[i+1]^x[i+2]^x[i+3]^sk[i])
	}

	for i := 0; i < 4; i++ {
		dst[4*i] = byte(x[35-i] >> 24)
		dst[4*i+1] = byte(x[35-i] >> 16)
		dst[4*i+2] = byte(x[35-i] >> 8)
		dst[4*i+3] = byte(x[35-i])
	}
}

func sm4L1(b uint32) uint32 {
	return b ^ sm4Rotl(b, 2) ^ sm4Rotl(b, 10) ^ sm4Rotl(b, 18) ^ sm4Rotl(b, 24)
}

func sm4L2(b uint32) uint32 {
	return b ^ sm4Rotl(b, 13) ^ sm4Rotl(b, 23)
}

func sm4Rotl(x uint32, n uint32) uint32 {
	return (x << n) | (x >> (32 - n))
}

// ============================================================
// RSA 签名与验签
// ============================================================

// SignWithRSA 使用RSA私钥对字符串进行签名，返回base64编码
func SignWithRSA(signStr string, privateKeyPEM string) (string, error) {
	block, _ := pem.Decode([]byte(privateKeyPEM))
	if block == nil {
		return "", fmt.Errorf("解析PEM私钥失败")
	}

	privateKey, err := x509.ParsePKCS8PrivateKey(block.Bytes)
	if err != nil {
		privateKey, err = x509.ParsePKCS1PrivateKey(block.Bytes)
		if err != nil {
			return "", fmt.Errorf("解析私钥失败: %v", err)
		}
	}

	rsaPrivateKey, ok := privateKey.(*rsa.PrivateKey)
	if !ok {
		return "", fmt.Errorf("不是RSA私钥")
	}

	h := sha256.New()
	h.Write([]byte(signStr))
	hashed := h.Sum(nil)

	signature, err := rsa.SignPKCS1v15(rand.Reader, rsaPrivateKey, crypto.SHA256, hashed)
	if err != nil {
		return "", fmt.Errorf("签名失败: %v", err)
	}

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

// VerifyWithRSA 使用RSA公钥验证签名
func VerifyWithRSA(signStr string, sign string, publicKeyPEM string) error {
	block, _ := pem.Decode([]byte(publicKeyPEM))
	if block == nil {
		return fmt.Errorf("解析PEM公钥失败")
	}

	publicKey, err := x509.ParsePKIXPublicKey(block.Bytes)
	if err != nil {
		publicKey, err = x509.ParsePKCS1PublicKey(block.Bytes)
		if err != nil {
			return fmt.Errorf("解析公钥失败: %v", err)
		}
	}

	rsaPublicKey, ok := publicKey.(*rsa.PublicKey)
	if !ok {
		return fmt.Errorf("不是RSA公钥")
	}

	signBytes, err := base64.StdEncoding.DecodeString(sign)
	if err != nil {
		return fmt.Errorf("base64解码签名失败: %v", err)
	}

	h := sha256.New()
	h.Write([]byte(signStr))
	hashed := h.Sum(nil)

	return rsa.VerifyPKCS1v15(rsaPublicKey, crypto.SHA256, hashed, signBytes)
}

// ============================================================
// 业务参数加密/解密
// ============================================================

// EncryptBizParams 加密业务参数
// 将业务参数去掉零值，按字母排序，转JSON，然后用指定算法加密
func EncryptBizParams(params interface{}, key []byte, encryptType string) (string, error) {
	// 将结构体转为map，去掉零值
	m, err := structToMap(params)
	if err != nil {
		return "", fmt.Errorf("转换参数失败: %v", err)
	}

	// 按key排序
	keys := make([]string, 0, len(m))
	for k := range m {
		keys = append(keys, k)
	}
	sort.Strings(keys)

	// 构建有序map
	orderedMap := make(map[string]interface{})
	for _, k := range keys {
		orderedMap[k] = m[k]
	}

	// 转JSON
	plaintext, err := json.Marshal(orderedMap)
	if err != nil {
		return "", fmt.Errorf("JSON序列化失败: %v", err)
	}

	// 加密
	switch encryptType {
	case "aes":
		return AESECBEncrypt(plaintext, key)
	case "sm4":
		return SM4CBCEncrypt(plaintext, key)
	default:
		return "", fmt.Errorf("不支持的加密类型: %s", encryptType)
	}
}

// DecryptBizParams 解密业务参数
func DecryptBizParams(ciphertext string, key []byte, encryptType string) ([]byte, error) {
	switch encryptType {
	case "aes":
		return AESECBDecrypt(ciphertext, key)
	case "sm4":
		return SM4CBCDecrypt(ciphertext, key)
	default:
		return nil, fmt.Errorf("不支持的加密类型: %s", encryptType)
	}
}

// structToMap 将结构体转为map，去掉零值
func structToMap(obj interface{}) (map[string]interface{}, error) {
	result := make(map[string]interface{})

	v := reflect.ValueOf(obj)
	if v.Kind() == reflect.Ptr {
		v = v.Elem()
	}
	if v.Kind() != reflect.Struct {
		return nil, fmt.Errorf("不是结构体")
	}

	t := v.Type()
	for i := 0; i < t.NumField(); i++ {
		field := t.Field(i)
		value := v.Field(i)

		// 获取json tag
		jsonTag := field.Tag.Get("json")
		if jsonTag == "" || jsonTag == "-" {
			continue
		}
		name := strings.Split(jsonTag, ",")[0]

		// 检查omitempty
		opts := strings.Split(jsonTag, ",")
		omitempty := false
		for _, opt := range opts[1:] {
			if opt == "omitempty" {
				omitempty = true
				break
			}
		}

		// 获取实际值
		var val interface{}
		switch value.Kind() {
		case reflect.String:
			val = value.String()
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			val = value.Int()
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			val = value.Uint()
		case reflect.Float32, reflect.Float64:
			val = value.Float()
		case reflect.Bool:
			val = value.Bool()
		case reflect.Slice, reflect.Map:
			if value.IsNil() {
				if omitempty {
					continue
				}
				val = value.Interface()
			} else {
				val = value.Interface()
			}
		case reflect.Ptr, reflect.Interface:
			if value.IsNil() {
				if omitempty {
					continue
				}
				val = nil
			} else {
				val = value.Elem().Interface()
			}
		default:
			val = value.Interface()
		}

		// 检查零值
		if omitempty && isZeroValue(val) {
			continue
		}

		result[name] = val
	}

	return result, nil
}

// isZeroValue 判断值是否为零值
func isZeroValue(v interface{}) bool {
	if v == nil {
		return true
	}
	rv := reflect.ValueOf(v)
	switch rv.Kind() {
	case reflect.String:
		return rv.String() == ""
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return rv.Int() == 0
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		return rv.Uint() == 0
	case reflect.Float32, reflect.Float64:
		return rv.Float() == 0
	case reflect.Bool:
		return !rv.Bool()
	default:
		return false
	}
}