fix(canvas): 素材库 - 拒绝空字节数并提供历史数据修复工具

backend/internal/canvas/repair_asset_bytes.go

@@ -0,0 +1,116 @@
+package canvas
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"infinite-canvas/backend/internal/model"
+
+	"gorm.io/gorm"
+	"gorm.io/gorm/logger"
+)
+
+type AssetBytesRepairIssue struct {
+	AssetID string `json:"assetId"`
+	Reason  string `json:"reason"`
+}
+
+type AssetBytesRepairReport struct {
+	Apply      bool                    `json:"apply"`
+	Scanned    int                     `json:"scanned"`
+	Repairable int                     `json:"repairable"`
+	Repaired   int                     `json:"repaired"`
+	Unresolved []AssetBytesRepairIssue `json:"unresolved"`
+}
+
+// RepairAssetBytes is an explicit offline maintenance operation, not a read fallback.
+// Only an owned, ready resource with a known positive size can repair a record.
+func RepairAssetBytes(db *gorm.DB, apply bool) (AssetBytesRepairReport, error) {
+	report := AssetBytesRepairReport{Apply: apply, Unresolved: []AssetBytesRepairIssue{}}
+	// Payloads may contain private media URLs; never include SQL parameters in logs.
+	err := db.Session(&gorm.Session{Logger: logger.Default.LogMode(logger.Silent)}).Transaction(func(tx *gorm.DB) error {
+		after := ""
+		for {
+			var rows []model.Asset
+			if err := tx.Where("id > ? AND kind IN ?", after, []string{"image", "video", "audio", "model"}).Order("id ASC").Limit(100).Find(&rows).Error; err != nil {
+				return errors.New("读取素材失败，未提交修复")
+			}
+			if len(rows) == 0 {
+				return nil
+			}
+			for _, asset := range rows {
+				after = asset.ID
+				report.Scanned++
+				issue := func(reason string) {
+					report.Unresolved = append(report.Unresolved, AssetBytesRepairIssue{AssetID: asset.ID, Reason: reason})
+				}
+				var payload map[string]json.RawMessage
+				var data map[string]json.RawMessage
+				if json.Unmarshal([]byte(asset.PayloadJSON), &payload) != nil || json.Unmarshal(payload["data"], &data) != nil || data == nil {
+					issue("素材 JSON 或 data 无效，需人工核查")
+					continue
+				}
+				if _, err := requiredJSONNumberField(data, "bytes"); err == nil {
+					continue
+				}
+				var kind, key string
+				_ = json.Unmarshal(payload["kind"], &kind)
+				_ = json.Unmarshal(data["storageKey"], &key)
+				key = strings.TrimSpace(key)
+				if strings.TrimSpace(asset.UserID) == "" || kind != asset.Kind || !strings.HasPrefix(key, "resource:") || strings.TrimPrefix(key, "resource:") == "" {
+					issue("类型不一致或缺少明确的 resource: 引用，不能推测文件大小")
+					continue
+				}
+				var resource model.Resource
+				err := tx.Where("id = ? AND user_id = ? AND kind = ? AND status = ? AND size > 0", strings.TrimPrefix(key, "resource:"), asset.UserID, kind, model.ResourceStatusReady).Take(&resource).Error
+				if errors.Is(err, gorm.ErrRecordNotFound) {
+					issue("未找到同用户、同类型、就绪且大小已知的资源")
+					continue
+				}
+				if err != nil {
+					return errors.New("读取资源失败，未提交修复")
+				}
+				data["bytes"], err = json.Marshal(resource.Size)
+				if err != nil {
+					return err
+				}
+				payload["data"], err = json.Marshal(data)
+				if err != nil {
+					return err
+				}
+				now := time.Now().UTC()
+				payload["updatedAt"], err = json.Marshal(now.Format(time.RFC3339Nano))
+				if err != nil {
+					return err
+				}
+				encoded, err := json.Marshal(payload)
+				if err != nil {
+					return err
+				}
+				if err := validateUserAssetDocument(encoded); err != nil {
+					issue("素材仍有其他合同错误，未修改，请另行核查")
+					continue
+				}
+				report.Repairable++
+				if !apply {
+					continue
+				}
+				result := tx.Model(&model.Asset{}).Where("id = ? AND user_id = ? AND payload_json = ? AND updated_at = ?", asset.ID, asset.UserID, asset.PayloadJSON, asset.UpdatedAt).Updates(map[string]any{"payload_json": string(encoded), "updated_at": now})
+				if result.Error != nil {
+					return errors.New("更新素材失败，未提交修复")
+				}
+				if result.RowsAffected != 1 {
+					return fmt.Errorf("素材 %s 已变化，整批修复回滚，请停止写入后重试", asset.ID)
+				}
+				report.Repaired++
+			}
+		}
+	})
+	if err != nil {
+		report.Repaired = 0
+	}
+	return report, err
+}