fix: harden payment resume and wxpay webhook routing

backend/internal/handler/payment_webhook_handler.go

@@ -1,6 +1,8 @@
 package handler
 
 import (
+	"context"
+	"fmt"
 	"io"
 	"log/slog"
 	"net/http"
@@ -77,9 +79,13 @@ func (h *PaymentWebhookHandler) handleNotify(c *gin.Context, providerKey string)
 	// This is needed when multiple instances of the same provider exist (e.g. multiple EasyPay accounts).
 	outTradeNo := extractOutTradeNo(rawBody, providerKey)
 
-	provider, err := h.paymentService.GetWebhookProvider(c.Request.Context(), providerKey, outTradeNo)
+	providers, err := h.paymentService.GetWebhookProviders(c.Request.Context(), providerKey, outTradeNo)
 	if err != nil {
 		slog.Warn("[Payment Webhook] provider not found", "provider", providerKey, "outTradeNo", outTradeNo, "error", err)
+		if providerKey == payment.TypeWxpay {
+			c.String(http.StatusBadRequest, "verify failed")
+			return
+		}
 		writeSuccessResponse(c, providerKey)
 		return
 	}
@@ -89,7 +95,7 @@ func (h *PaymentWebhookHandler) handleNotify(c *gin.Context, providerKey string)
 		headers[strings.ToLower(k)] = c.GetHeader(k)
 	}
 
-	notification, err := provider.VerifyNotification(c.Request.Context(), rawBody, headers)
+	resolvedProviderKey, notification, err := verifyNotificationWithProviders(c.Request.Context(), providers, rawBody, headers)
 	if err != nil {
 		truncatedBody := rawBody
 		if len(truncatedBody) > webhookLogTruncateLen {
@@ -103,17 +109,17 @@ func (h *PaymentWebhookHandler) handleNotify(c *gin.Context, providerKey string)
 
 	// nil notification means irrelevant event (e.g. Stripe non-payment event); return success.
 	if notification == nil {
-		writeSuccessResponse(c, providerKey)
+		writeSuccessResponse(c, resolvedProviderKey)
 		return
 	}
 
-	if err := h.paymentService.HandlePaymentNotification(c.Request.Context(), notification, providerKey); err != nil {
-		slog.Error("[Payment Webhook] handle notification failed", "provider", providerKey, "error", err)
+	if err := h.paymentService.HandlePaymentNotification(c.Request.Context(), notification, resolvedProviderKey); err != nil {
+		slog.Error("[Payment Webhook] handle notification failed", "provider", resolvedProviderKey, "error", err)
 		c.String(http.StatusInternalServerError, "handle failed")
 		return
 	}
 
-	writeSuccessResponse(c, providerKey)
+	writeSuccessResponse(c, resolvedProviderKey)
 }
 
 // extractOutTradeNo parses the webhook body to find the out_trade_no.
@@ -131,6 +137,25 @@ func extractOutTradeNo(rawBody, providerKey string) string {
 	return ""
 }
 
+func verifyNotificationWithProviders(ctx context.Context, providers []payment.Provider, rawBody string, headers map[string]string) (string, *payment.PaymentNotification, error) {
+	var lastErr error
+	for _, provider := range providers {
+		if provider == nil {
+			continue
+		}
+		notification, err := provider.VerifyNotification(ctx, rawBody, headers)
+		if err != nil {
+			lastErr = err
+			continue
+		}
+		return provider.ProviderKey(), notification, nil
+	}
+	if lastErr != nil {
+		return "", nil, lastErr
+	}
+	return "", nil, fmt.Errorf("no webhook provider could verify notification")
+}
+
 // wxpaySuccessResponse is the JSON response expected by WeChat Pay webhook.
 type wxpaySuccessResponse struct {
 	Code    string `json:"code"`

backend/internal/handler/payment_webhook_handler_test.go

@@ -3,11 +3,14 @@
 package handler
 
 import (
+	"context"
 	"encoding/json"
+	"errors"
 	"net/http"
 	"net/http/httptest"
 	"testing"
 
+	"github.com/Wei-Shaw/sub2api/internal/payment"
 	"github.com/gin-gonic/gin"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -131,3 +134,70 @@ func TestExtractOutTradeNo(t *testing.T) {
 		})
 	}
 }
+
+func TestVerifyNotificationWithProvidersReturnsMatchedProvider(t *testing.T) {
+	firstErr := errors.New("wrong provider")
+	providers := []payment.Provider{
+		webhookHandlerProviderStub{
+			key:       payment.TypeWxpay,
+			verifyErr: firstErr,
+		},
+		webhookHandlerProviderStub{
+			key: payment.TypeWxpay,
+			notification: &payment.PaymentNotification{
+				OrderID: "sub2_42",
+				TradeNo: "trade-42",
+				Status:  payment.NotificationStatusSuccess,
+			},
+		},
+	}
+
+	providerKey, notification, err := verifyNotificationWithProviders(context.Background(), providers, "{}", map[string]string{"wechatpay-signature": "sig"})
+	require.NoError(t, err)
+	require.Equal(t, payment.TypeWxpay, providerKey)
+	require.NotNil(t, notification)
+	require.Equal(t, "sub2_42", notification.OrderID)
+}
+
+func TestVerifyNotificationWithProvidersFailsWhenAllProvidersReject(t *testing.T) {
+	providers := []payment.Provider{
+		webhookHandlerProviderStub{
+			key:       payment.TypeWxpay,
+			verifyErr: errors.New("verify failed a"),
+		},
+		webhookHandlerProviderStub{
+			key:       payment.TypeWxpay,
+			verifyErr: errors.New("verify failed b"),
+		},
+	}
+
+	_, _, err := verifyNotificationWithProviders(context.Background(), providers, "{}", nil)
+	require.Error(t, err)
+}
+
+type webhookHandlerProviderStub struct {
+	key          string
+	notification *payment.PaymentNotification
+	verifyErr    error
+}
+
+func (p webhookHandlerProviderStub) Name() string { return p.key }
+func (p webhookHandlerProviderStub) ProviderKey() string { return p.key }
+func (p webhookHandlerProviderStub) SupportedTypes() []payment.PaymentType {
+	return []payment.PaymentType{payment.PaymentType(p.key)}
+}
+func (p webhookHandlerProviderStub) CreatePayment(context.Context, payment.CreatePaymentRequest) (*payment.CreatePaymentResponse, error) {
+	panic("unexpected call")
+}
+func (p webhookHandlerProviderStub) QueryOrder(context.Context, string) (*payment.QueryOrderResponse, error) {
+	panic("unexpected call")
+}
+func (p webhookHandlerProviderStub) VerifyNotification(context.Context, string, map[string]string) (*payment.PaymentNotification, error) {
+	if p.verifyErr != nil {
+		return nil, p.verifyErr
+	}
+	return p.notification, nil
+}
+func (p webhookHandlerProviderStub) Refund(context.Context, payment.RefundRequest) (*payment.RefundResponse, error) {
+	panic("unexpected call")
+}