// File: ymt_v3/go.mod
```go
module ymt_v3

go 1.21
```

// File: ymt_v3/errors.go
```go
package ymt_v3

import "fmt"

// APIError 表示API返回的错误信息
type APIError struct {
	Code    int32  `json:"code"`
	Message string `json:"message"`
	Reason  string `json:"reason,omitempty"`
}

func (e *APIError) Error() string {
	if e.Reason != "" {
		return fmt.Sprintf("code=%d, message=%s, reason=%s", e.Code, e.Message, e.Reason)
	}
	return fmt.Sprintf("code=%d, message=%s", e.Code, e.Message)
}
```

// File: ymt_v3/types.go
```go
package ymt_v3

// OrderRequest 获取券码请求（业务明文参数）
type OrderRequest struct {
	OutBizNo   string `json:"out_biz_no"`
	ActivityNo string `json:"activity_no"`
	Account    string `json:"account,omitempty"`
	NotifyURL  string `json:"notify_url,omitempty"`
}

// OrderResponse 获取券码/券码查询响应（解密后）
type OrderResponse struct {
	OutBizNo        string  `json:"out_biz_no"`
	TradeNo         string  `json:"trade_no"`
	Key             string  `json:"key,omitempty"`
	URL             string  `json:"url,omitempty"`
	ValidBeginTime  string  `json:"valid_begin_time,omitempty"`
	ValidEndTime    string  `json:"valid_end_time,omitempty"`
	UsableNum       uint32  `json:"usable_num"`
	UsageNum        uint32  `json:"usage_num"`
	Status          uint32  `json:"status"`
	SettlementPrice float64 `json:"settlement_price,omitempty"`
	Account         string  `json:"account,omitempty"`
}

// QueryRequest 券码查询请求（业务明文参数）
type QueryRequest struct {
	OutBizNo string `json:"out_biz_no,omitempty"`
	TradeNo  string `json:"trade_no,omitempty"`
}

// DiscardRequest 券码作废请求（业务明文参数）
type DiscardRequest struct {
	OutBizNo string `json:"out_biz_no,omitempty"`
	TradeNo  string `json:"trade_no,omitempty"`
}

// DiscardResponse 券码作废响应（解密后）
type DiscardResponse struct {
	OutBizNo string `json:"out_biz_no"`
	TradeNo  string `json:"trade_no"`
	Status   uint32 `json:"status"`
}

// BatchOrderRequest 批量发卡请求（业务明文参数）
type BatchOrderRequest struct {
	OutBizNo   string `json:"out_biz_no"`
	ActivityNo string `json:"activity_no"`
	Number     int32  `json:"number"`
	NotifyURL  string `json:"notify_url,omitempty"`
}

// BatchOrderResponse 批量发卡响应（解密后）
type BatchOrderResponse struct {
	OutBizNo string `json:"out_biz_no"`
	TradeNo  string `json:"trade_no"`
	Status   string `json:"status"`
}

// BatchQueryRequest 批量查询请求（业务明文参数）
type BatchQueryRequest struct {
	OutBizNo string `json:"out_biz_no,omitempty"`
	TradeNo  string `json:"trade_no,omitempty"`
}

// BatchQueryResponse 批量查询响应（解密后）
type BatchQueryResponse struct {
	OutBizNo    string `json:"out_biz_no"`
	TradeNo     string `json:"trade_no"`
	Status      string `json:"status"`
	DownloadURL string `json:"download_url,omitempty"`
	ZipPassword string `json:"zip_password,omitempty"`
}

// EncryptedRequest 公共加密请求体
type EncryptedRequest struct {
	Ciphertext string `json:"ciphertext"`
}

// EncryptedResponse 公共加密响应体
type EncryptedResponse struct {
	Code    int32           `json:"code"`
	Message string          `json:"message"`
	Reason  string          `json:"reason,omitempty"`
	Data    *EncryptedData  `json:"data,omitempty"`
}

// EncryptedData 加密数据包装
type EncryptedData struct {
	Ciphertext string `json:"ciphertext"`
}
```

// File: ymt_v3/crypto.go
```go
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
	}
}
```

// File: ymt_v3/client.go
```go
package ymt_v3

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"sort"
	"strings"
)

// Config 客户端配置
type Config struct {
	AppID       string // 应用ID
	PrivateKey  string // 应用私钥（PEM格式），用于请求签名
	PublicKey   string // 平台公钥（PEM格式），用于响应验签
	Key         string // 业务参数加密密钥
	EncryptType string // 加密类型：aes 或 sm4
	BaseURL     string // 接口地址
	HTTPClient  *http.Client
}

// Client SDK客户端
type Client struct {
	config *Config
	client *http.Client
}

// NewClient 创建新的SDK客户端
func NewClient(config *Config) *Client {
	if config.HTTPClient == nil {
		config.HTTPClient = http.DefaultClient
	}
	return &Client{
		config: config,
		client: config.HTTPClient,
	}
}

// doRequest 发送请求并处理响应
func (c *Client) doRequest(ctx context.Context, path string, bizParams interface{}, result interface{}) error {
	// 1. 加密业务参数
	ciphertext, err := EncryptBizParams(bizParams, []byte(c.config.Key), c.config.EncryptType)
	if err != nil {
		return fmt.Errorf("加密业务参数失败: %v", err)
	}

	// 2. 生成时间戳
	timestamp := GenerateTimestamp()

	// 3. 拼接签名字符串：app_id + timestamp + ciphertext
	signStr := c.config.AppID + timestamp + ciphertext

	// 4. 使用应用私钥签名
	sign, err := SignWithRSA(signStr, c.config.PrivateKey)
	if err != nil {
		return fmt.Errorf("签名失败: %v", err)
	}

	// 5. 构建请求体
	reqBody := EncryptedRequest{
		Ciphertext: ciphertext,
	}
	bodyBytes, err := json.Marshal(reqBody)
	if err != nil {
		return fmt.Errorf("序列化请求体失败: %v", err)
	}

	// 6. 创建HTTP请求
	url := strings.TrimRight(c.config.BaseURL, "/") + path
	req, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewReader(bodyBytes))
	if err != nil {
		return fmt.Errorf("创建请求失败: %v", err)
	}

	// 7. 设置Header
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Appid", c.config.AppID)
	req.Header.Set("Timestamp", timestamp)
	req.Header.Set("Sign", sign)

	// 8. 发送请求
	resp, err := c.client.Do(req)
	if err != nil {
		return fmt.Errorf("发送请求失败: %v", err)
	}
	defer resp.Body.Close()

	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return fmt.Errorf("读取响应失败: %v", err)
	}

	// 9. 解析响应
	var encryptedResp EncryptedResponse
	if err := json.Unmarshal(respBody, &encryptedResp); err != nil {
		return fmt.Errorf("解析响应失败: %v", err)
	}

	// 10. 检查错误码
	if encryptedResp.Code != 200 {
		return &APIError{
			Code:    encryptedResp.Code,
			Message: encryptedResp.Message,
			Reason:  encryptedResp.Reason,
		}
	}

	// 11. 解密响应数据
	if encryptedResp.Data == nil || encryptedResp.Data.Ciphertext == "" {
		return fmt.Errorf("响应数据为空")
	}

	plaintext, err := DecryptBizParams(encryptedResp.Data.Ciphertext, []byte(c.config.Key), c.config.EncryptType)
	if err != nil {
		return fmt.Errorf("解密响应数据失败: %v", err)
	}

	// 12. 解析解密后的数据到结果结构体
	if err := json.Unmarshal(plaintext, result); err != nil {
		return fmt.Errorf("解析解密数据失败: %v", err)
	}

	return nil
}

// ============================================================
// API 方法
// ============================================================

// Order 获取券码
func (c *Client) Order(ctx context.Context, req *OrderRequest) (*OrderResponse, error) {
	result := &OrderResponse{}
	if err := c.doRequest(ctx, "/openapi/v1/key/order", req, result); err != nil {
		return nil, err
	}
	return result, nil
}

// Query 券码查询
func (c *Client) Query(ctx context.Context, req *QueryRequest) (*OrderResponse, error) {
	result := &OrderResponse{}
	if err := c.doRequest(ctx, "/openapi/v1/key/query", req, result); err != nil {
		return nil, err
	}
	return result, nil
}

// Discard 券码作废
func (c *Client) Discard(ctx context.Context, req *DiscardRequest) (*DiscardResponse, error) {
	result := &DiscardResponse{}
	if err := c.doRequest(ctx, "/openapi/v1/key/discard", req, result); err != nil {
		return nil, err
	}
	return result, nil
}

// BatchOrder 批量发卡
func (c *Client) BatchOrder(ctx context.Context, req *BatchOrderRequest) (*BatchOrderResponse, error) {
	result := &BatchOrderResponse{}
	if err := c.doRequest(ctx, "/openapi/v1/key/batch_order", req, result); err != nil {
		return nil, err
	}
	return result, nil
}

// BatchQuery 批量查询
func (c *Client) BatchQuery(ctx context.Context, req *BatchQueryRequest) (*BatchQueryResponse, error) {
	result := &BatchQueryResponse{}
	if err := c.doRequest(ctx, "/openapi/v1/key/batch_query", req, result); err != nil {
		return nil, err
	}
	return result, nil
}

// ============================================================
// 回调验签
// ============================================================

// VerifyCallback 验证回调通知的签名
// 参数：
//   - appID: 应用ID
//   - timestamp: 回调请求中的时间戳
//   - sign: 回调请求中的签名
//   - data: 回调请求中的业务数据（明文JSON字符串）
//   - publicKeyPEM: 平台公钥（PEM格式）
//   - key: 业务参数加密密钥
//   - encryptType: 加密类型：aes 或 sm4
func VerifyCallback(appID, timestamp, sign, data, publicKeyPEM string, key []byte, encryptType string) error {
	// 1. 使用key将data加密得到ciphertext
	ciphertext, err := EncryptBizParamsFromJSON(data, key, encryptType)
	if err != nil {
		return fmt.Errorf("加密回调数据失败: %v", err)
	}

	// 2. 拼接签名字符串：app_id + timestamp + ciphertext
	signStr := appID + timestamp + ciphertext

	// 3. 使用平台公钥验签
	return VerifyWithRSA(signStr, sign, publicKeyPEM)
}

// EncryptBizParamsFromJSON 将JSON字符串按规则加密
func EncryptBizParamsFromJSON(jsonStr string, key []byte, encryptType string) (string, error) {
	// 解析JSON
	var data map[string]interface{}
	if err := json.Unmarshal([]byte(jsonStr), &data); err != nil {
		return "", fmt.Errorf("解析JSON失败: %v", err)
	}

	// 去掉零值
	cleaned := make(map[string]interface{})
	for k, v := range data {
		if !isZeroValue(v) {
			cleaned[k] = v
		}
	}

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

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

// File: ymt_v3/example_test.go
```go
package ymt_v3

import (
	"context"
	"fmt"
	"testing"
)

// 测试参数（请替换为实际值）
const (
	testAppID       = "xxx"
	testPrivateKey  = `-----BEGIN PRIVATE KEY-----
xxx
-----END PRIVATE KEY-----`
	testPublicKey   = `-----BEGIN PUBLIC KEY-----
xxx
-----END PUBLIC KEY-----`
	testKey         = "xxxx"
	testEncryptType = "aes"
	testBaseURL     = "https://gateway.dev.cdlsxd.cn"
	testActivityNo  = "xxxx"
)

func TestClient_Order(t *testing.T) {
	client := NewClient(&Config{
		AppID:       testAppID,
		PrivateKey:  testPrivateKey,
		PublicKey:   testPublicKey,
		Key:         testKey,
		EncryptType: testEncryptType,
		BaseURL:     testBaseURL,
	})

	resp, err := client.Order(context.Background(), &OrderRequest{
		OutBizNo:   "order_001",
		ActivityNo: testActivityNo,
		Account:    "18666666666",
		NotifyURL:  "https://notify.example.com/openapi",
	})
	if err != nil {
		t.Fatalf("Order failed: %v", err)
	}
	fmt.Printf("Order response: %+v\n", resp)
}

func TestClient_Query(t *testing.T) {
	client := NewClient(&Config{
		AppID:       testAppID,
		PrivateKey:  testPrivateKey,
		PublicKey:   testPublicKey,
		Key:         testKey,
		EncryptType: testEncryptType,
		BaseURL:     testBaseURL,
	})

	resp, err := client.Query(context.Background(), &QueryRequest{
		OutBizNo: "order_001",
	})
	if err != nil {
		t.Fatalf("Query failed: %v", err)
	}
	fmt.Printf("Query response: %+v\n", resp)
}

func TestClient_Discard(t *testing.T) {
	client := NewClient(&Config{
		AppID:       testAppID,
		PrivateKey:  testPrivateKey,
		PublicKey:   testPublicKey,
		Key:         testKey,
		EncryptType: testEncryptType,
		BaseURL:     testBaseURL,
	})

	resp, err := client.Discard(context.Background(), &DiscardRequest{
		TradeNo: "7251449503000383488",
	})
	if err != nil {
		t.Fatalf("Discard failed: %v", err)
	}
	fmt.Printf("Discard response: %+v\n", resp)
}

func TestClient_BatchOrder(t *testing.T) {
	client := NewClient(&Config{
		AppID:       testAppID,
		PrivateKey:  testPrivateKey,
		PublicKey:   testPublicKey,
		Key:         testKey,
		EncryptType: testEncryptType,
		BaseURL:     testBaseURL,
	})

	resp, err := client.BatchOrder(context.Background(), &BatchOrderRequest{
		OutBizNo:   "batch_001",
		ActivityNo: testActivityNo,
		Number:     10,
		NotifyURL:  "https://notify.example.com/openapi",
	})
	if err != nil {
		t.Fatalf("BatchOrder failed: %v", err)
	}
	fmt.Printf("BatchOrder response: %+v\n", resp)
}

func TestClient_BatchQuery(t *testing.T) {
	client := NewClient(&Config{
		AppID:       testAppID,
		PrivateKey:  testPrivateKey,
		PublicKey:   testPublicKey,
		Key:         testKey,
		EncryptType: testEncryptType,
		BaseURL:     testBaseURL,
	})

	resp, err := client.BatchQuery(context.Background(), &BatchQueryRequest{
		TradeNo: "7251449503000383499",
	})
	if err != nil {
		t.Fatalf("BatchQuery failed: %v", err)
	}
	fmt.Printf("BatchQuery response: %+v\n", resp)
}

func TestVerifyCallback(t *testing.T) {
	// 模拟回调参数
	appID := "123456"
	timestamp := "2026-06-22 15:30:00"
	sign := "base64_encoded_signature"
	data := `{"out_biz_no":"batch_001","trade_no":"7251449503000383499","status":"success","download_url":"https://oss.example.com/openapi_7251449503000383499.zip","zip_password":"123456"}`

	err := VerifyCallback(appID, timestamp, sign, data, testPublicKey, []byte(testKey), testEncryptType)
	if err != nil {
		t.Logf("VerifyCallback result: %v (expected if sign is invalid)", err)
	} else {
		t.Log("VerifyCallback success")
	}
}
```