fix(subscriptions): reject concurrent duplicate rules

Fixes #66

internal/handler/subscription_errors.go

@@ -0,0 +1,22 @@
+package handler
+
+import (
+	"errors"
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+
+	"github.com/ShukeBta/MediaStationGo/internal/service"
+)
+
+func writeSubscriptionConflict(c *gin.Context, err error) bool {
+	if !errors.Is(err, service.ErrSubscriptionAlreadyExists) {
+		return false
+	}
+	body := gin.H{"error": "subscription already exists"}
+	if existingID := service.SubscriptionAlreadyExistsID(err); existingID != "" {
+		body["existing_id"] = existingID
+	}
+	c.JSON(http.StatusConflict, body)
+	return true
+}

internal/handler/subscription_errors_test.go

@@ -0,0 +1,32 @@
+package handler
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+
+	"github.com/ShukeBta/MediaStationGo/internal/service"
+)
+
+func TestWriteSubscriptionConflictReturns409WithExistingID(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	err := &service.SubscriptionAlreadyExistsError{ExistingID: "existing-sub"}
+	if !writeSubscriptionConflict(c, err) {
+		t.Fatal("expected conflict to be handled")
+	}
+	if w.Code != http.StatusConflict {
+		t.Fatalf("status = %d body=%s", w.Code, w.Body.String())
+	}
+	var body map[string]any
+	if err := json.Unmarshal(w.Body.Bytes(), &body); err != nil {
+		t.Fatal(err)
+	}
+	if body["existing_id"] != "existing-sub" {
+		t.Fatalf("body = %#v", body)
+	}
+}

internal/handler/subscription_extra.go

@@ -58,14 +58,14 @@ func updateSubscriptionHandler(svc *service.Container) gin.HandlerFunc {
 			c.Status(http.StatusNoContent)
 			return
 		}
-		if err := svc.Repo.DB.WithContext(c.Request.Context()).
-			Model(&model.Subscription{}).
-			Where("id = ?", c.Param("id")).
-			Updates(updates).Error; err != nil {
+		if err := svc.Subscription.Update(c.Request.Context(), c.Param("id"), updates); err != nil {
 			logSubscriptionWarn(svc, "subscription update failed",
 				zap.String("user_id", subscriptionRequestUserID(c)),
 				zap.String("subscription_id", c.Param("id")),
 				zap.Error(err))
+			if writeSubscriptionConflict(c, err) {
+				return
+			}
 			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
 			return
 		}

internal/handler/subscriptions.go

@@ -97,6 +97,9 @@ func createSubscriptionHandler(svc *service.Container) gin.HandlerFunc {
 				zap.String("feed_kind", subscriptionFeedKind(req.FeedURL)),
 				zap.Bool("enabled", enabled),
 				zap.Error(err))
+			if writeSubscriptionConflict(c, err) {
+				return
+			}
 			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
 			return
 		}
@@ -199,6 +202,9 @@ func restoreSubscriptionHandler(svc *service.Container) gin.HandlerFunc {
 				zap.String("user_id", subscriptionRequestUserID(c)),
 				zap.String("subscription_id", c.Param("id")),
 				zap.Error(err))
+			if writeSubscriptionConflict(c, err) {
+				return
+			}
 			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
 			return
 		}