fix(subscriptions): reject concurrent duplicate rules

Fixes #66

internal/database/schema_subscription_identity.go

@@ -0,0 +1,54 @@
+package database
+
+import (
+	"time"
+
+	"gorm.io/gorm"
+
+	"github.com/ShukeBta/MediaStationGo/internal/model"
+)
+
+const duplicateSubscriptionMigrationReason = "迁移合并重复订阅规则"
+
+func ensureSubscriptionIdentityUniqueness(db *gorm.DB) error {
+	if db == nil || !db.Migrator().HasTable(&model.Subscription{}) {
+		return nil
+	}
+	return db.Transaction(func(tx *gorm.DB) error {
+		var rows []model.Subscription
+		if err := tx.Unscoped().Order("created_at asc, id asc").Find(&rows).Error; err != nil {
+			return err
+		}
+		seen := make(map[string]string)
+		for i := range rows {
+			row := &rows[i]
+			key := model.RefreshSubscriptionIdentity(row)
+			updates := map[string]any{"identity_key": key}
+			if !row.DeletedAt.Valid && row.ArchivedAt == nil {
+				activeKey := row.UserID + "\x00" + key
+				if _, duplicate := seen[activeKey]; duplicate {
+					archivedAt := row.UpdatedAt
+					if archivedAt.IsZero() {
+						archivedAt = row.CreatedAt
+					}
+					if archivedAt.IsZero() {
+						archivedAt = time.Now()
+					}
+					updates["enabled"] = false
+					updates["archived_at"] = &archivedAt
+					updates["archive_reason"] = duplicateSubscriptionMigrationReason
+				} else {
+					seen[activeKey] = row.ID
+				}
+			}
+			if err := tx.Unscoped().Model(&model.Subscription{}).Where("id = ?", row.ID).Updates(updates).Error; err != nil {
+				return err
+			}
+		}
+		return tx.Exec(`
+CREATE UNIQUE INDEX IF NOT EXISTS idx_subscriptions_user_identity_active
+ON subscriptions(user_id, identity_key)
+WHERE deleted_at IS NULL AND archived_at IS NULL AND identity_key <> ''
+`).Error
+	})
+}