feat(v2): Stripe adapter 落地 RefundingProvider(session→payment_intent→Refunds.New,refund_id 作幂等键)

internal/provider/stripe/stripe.go

@@ -42,12 +42,45 @@ func (p *Provider) Method() string { return "stripe" }
 func (p *Provider) Capabilities() provider.Capabilities {
 	return provider.Capabilities{
 		RenderTypes:      []provider.RenderType{provider.RenderRedirect},
-		SupportsRefund:   false, // P4
+		SupportsRefund:   true, // P4:/v1/refunds
 		SettleCurrencies: []string{supportedCurrency},
 		Regions:          []string{"global"},
 	}
 }
 
+// Refund 经 Checkout Session 取 PaymentIntent 再退款。refundID 作 Idempotency-Key。
+// 不传 Stripe Reason(仅收枚举);业务文案只落 pay 本地。
+func (p *Provider) Refund(_ context.Context, providerRef, refundID string, amountMinor int64, _ string) (string, provider.PaidStatus, error) {
+	sess, err := p.sc.CheckoutSessions.Get(providerRef, nil)
+	if err != nil {
+		return "", provider.PaidFailed, fmt.Errorf("stripe: 取 session 失败: %w", err)
+	}
+	if sess.PaymentIntent == nil || sess.PaymentIntent.ID == "" {
+		return "", provider.PaidFailed, fmt.Errorf("stripe: session %s 无 payment_intent,无法退款", providerRef)
+	}
+	params := &gostripe.RefundParams{
+		PaymentIntent: gostripe.String(sess.PaymentIntent.ID),
+		Amount:        gostripe.Int64(amountMinor), // cent = USD minor,直传
+	}
+	params.SetIdempotencyKey(refundID)
+	rf, err := p.sc.Refunds.New(params)
+	if err != nil {
+		return "", provider.PaidFailed, fmt.Errorf("stripe: 退款请求失败: %w", err)
+	}
+	return rf.ID, mapRefundStatus(rf.Status), nil
+}
+
+func mapRefundStatus(s gostripe.RefundStatus) provider.PaidStatus {
+	switch s {
+	case gostripe.RefundStatusSucceeded:
+		return provider.PaidSucceeded
+	case gostripe.RefundStatusFailed, gostripe.RefundStatusCanceled:
+		return provider.PaidFailed
+	default: // pending / requires_action → 异步,交上层保持 processing
+		return provider.PaidPending
+	}
+}
+
 func (p *Provider) Create(_ context.Context, req provider.CreateRequest) (*provider.Session, error) {
 	if req.Currency != supportedCurrency {
 		return nil, fmt.Errorf("stripe: 仅支持 %s, got %s", supportedCurrency, req.Currency)

internal/provider/stripe/stripe_refund_test.go

@@ -0,0 +1,55 @@
+package stripe_test
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	gostripe "github.com/stripe/stripe-go/v79"
+	"github.com/stripe/stripe-go/v79/client"
+
+	"github.com/wangjia/pay/internal/provider"
+	st "github.com/wangjia/pay/internal/provider/stripe"
+)
+
+func fakeStripeRefundAPI(t *testing.T) *httptest.Server {
+	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		switch {
+		case r.Method == http.MethodGet && strings.Contains(r.URL.Path, "/v1/checkout/sessions/cs_test_123"):
+			// 未展开:payment_intent 是字符串 id,SDK 反序列化进 *PaymentIntent{ID}
+			fmt.Fprint(w, `{"id":"cs_test_123","object":"checkout.session","payment_intent":"pi_test_456","amount_total":2999,"currency":"usd","payment_status":"paid"}`)
+		case r.Method == http.MethodPost && strings.HasPrefix(r.URL.Path, "/v1/refunds"):
+			fmt.Fprint(w, `{"id":"re_test_789","object":"refund","amount":2999,"currency":"usd","payment_intent":"pi_test_456","status":"succeeded"}`)
+		default:
+			http.Error(w, `{"error":{"message":"not found"}}`, http.StatusNotFound)
+		}
+	}))
+}
+
+func newStripeRefund(t *testing.T, ts *httptest.Server) *st.Provider {
+	backends := &gostripe.Backends{
+		API: gostripe.GetBackendWithConfig(gostripe.APIBackend, &gostripe.BackendConfig{URL: gostripe.String(ts.URL)}),
+	}
+	return st.New(client.New("sk_test_x", backends), "whsec_test_secret")
+}
+
+func TestStripeRefundSuccess(t *testing.T) {
+	ts := fakeStripeRefundAPI(t)
+	defer ts.Close()
+	p := newStripeRefund(t, ts)
+
+	if !p.Capabilities().SupportsRefund {
+		t.Fatal("stripe Capabilities.SupportsRefund 应为 true")
+	}
+	ref, status, err := p.Refund(context.Background(), "cs_test_123", "rf-999", 2999, "requested_by_customer")
+	if err != nil {
+		t.Fatalf("refund: %v", err)
+	}
+	if status != provider.PaidSucceeded || ref != "re_test_789" {
+		t.Fatalf("refund result: ref=%s status=%s", ref, status)
+	}
+}