微信支付 - 退款通知 (#359)

* 🆕 发起退款 - 添加notify_url参数

* 🆕 退款通知

pay/notify/refund.go

@@ -0,0 +1,77 @@
+package notify
+
+import (
+	"crypto/md5"
+	"encoding/base64"
+	"encoding/hex"
+	"encoding/xml"
+	"errors"
+
+	"github.com/silenceper/wechat/v2/util"
+)
+
+// reference: https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=9_16&index=10
+
+// RefundedResult 退款回调
+type RefundedResult struct {
+	ReturnCode *string `xml:"return_code"`
+	ReturnMsg  *string `xml:"return_msg"`
+
+	AppID    *string `xml:"appid"`
+	MchID    *string `xml:"mch_id"`
+	NonceStr *string `xml:"nonce_str"`
+	ReqInfo  *string `xml:"req_info"`
+}
+
+// RefundedReqInfo 退款结果（明文）
+type RefundedReqInfo struct {
+	TransactionID       *string `xml:"transaction_id"`
+	OutTradeNO          *string `xml:"out_trade_no"`
+	RefundID            *string `xml:"refund_id"`
+	OutRefundNO         *string `xml:"out_refund_no"`
+	TotalFee            *int    `xml:"total_fee"`
+	SettlementTotalFee  *int    `xml:"settlement_total_fee"`
+	RefundFee           *int    `xml:"refund_fee"`
+	SettlementRefundFee *int    `xml:"settlement_refund_fee"`
+	RefundStatus        *string `xml:"refund_status"`
+	SuccessTime         *string `xml:"success_time"`
+	RefundRecvAccount   *string `xml:"refund_recv_account"`
+	RefundAccount       *string `xml:"refund_account"`
+	RefundRequestSource *string `xml:"refund_request_source"`
+}
+
+// RefundedResp 消息通知返回
+type RefundedResp struct {
+	ReturnCode string `xml:"return_code"`
+	ReturnMsg  string `xml:"return_msg"`
+}
+
+// DecryptReqInfo 对退款结果进行解密
+func (notify *Notify) DecryptReqInfo(result *RefundedResult) (*RefundedReqInfo, error) {
+	var err error
+	if result == nil || result.ReqInfo == nil {
+		return nil, errors.New("empty refunded_result or req_info")
+	}
+
+	base64Decode, err := base64.StdEncoding.DecodeString(*result.ReqInfo)
+	if err != nil {
+		return nil, err
+	}
+
+	hash := md5.New()
+	if _, err = hash.Write([]byte(notify.Key)); err != nil {
+		return nil, err
+	}
+	md5APIKey := hex.EncodeToString(hash.Sum(nil))
+
+	data, err := util.AesECBDecrypt(base64Decode, []byte(md5APIKey))
+	if err != nil {
+		return nil, err
+	}
+
+	res := &RefundedReqInfo{}
+	if err = xml.Unmarshal(data, res); err != nil {
+		return nil, err
+	}
+	return res, nil
+}