Update the Catalog sync to delete the removed resources info from exi…

…sting db

This patch includes following changes

- Adds `OnDelete:CASECADE` constraint on resource_tags and
  resource_categories table
- Update the catalog sync which compares hosted catalog resources to
  existing db info of resources for same catalog while syncing catalogs and delete
  resources info from the db if any resources from the hosted catalog are removed

Signed-off-by: Shiv Verma <shverma@redhat.com>

api/pkg/db/model/model.go

@@ -60,10 +60,10 @@ type (
 		Kind       string `gorm:"not null;default:null"`
 		Rating     float64
 		Catalog    Catalog
-		Categories []*Category `gorm:"many2many:resource_categories;"`
+		Categories []*Category `gorm:"many2many:resource_categories;constraint:OnDelete:CASCADE;"`
 		CatalogID  uint
 		Versions   []ResourceVersion
-		Tags       []*Tag `gorm:"many2many:resource_tags;"`
+		Tags       []*Tag `gorm:"many2many:resource_tags;constraint:OnDelete:CASCADE;"`
 	}
 
 	ResourceVersion struct {

api/pkg/service/catalog/syncer.go

@@ -208,6 +208,11 @@ func (s *syncer) updateJob(syncJob model.SyncJob, sha string, res []parser.Resou
 	}
 	catalog.SHA = sha
 
+	if err := s.deleteDBResources(txn, log, &catalog, res); err != nil {
+		txn.Rollback()
+		return err
+	}
+
 	rerr, err := s.updateResources(txn, log, &catalog, res)
 	if err != nil {
 		txn.Rollback()
@@ -362,3 +367,94 @@ func (s *syncer) updateCatalogResult(
 	}
 	return nil
 }
+
+// Delete all versions of a resources and resource as well
+func (s *syncer) deleteResourceAndVersion(txn *gorm.DB, log *zap.SugaredLogger, id uint) error {
+
+	if err := txn.Unscoped().Where(&model.ResourceVersion{ResourceID: id}).Delete(&model.ResourceVersion{}).Error; err != nil {
+		return err
+	}
+	if err := txn.Unscoped().Where("id = ?", id).Delete(&model.Resource{}).Error; err != nil {
+		return err
+	}
+
+	log.Infof("Resource with ID: %d has been deleted", id)
+
+	return nil
+
+}
+
+// Delete the categories which doesn't belongs to any existing resources
+func (s *syncer) deleteCategory(txn *gorm.DB, log *zap.SugaredLogger, categories []model.ResourceCategory) error {
+
+	for _, c := range categories {
+		var resCat []model.ResourceCategory
+		txn.Where(&model.ResourceCategory{CategoryID: c.CategoryID}).Find(&resCat)
+
+		if len(resCat) == 0 {
+			if err := txn.Unscoped().Where("id = ?", c.CategoryID).Delete(&model.Category{}).Error; err != nil {
+				return err
+			}
+			log.Infof("Category with ID: %d has been deleted", c.CategoryID)
+		}
+	}
+	return nil
+}
+
+// Delete the tags which doesn't belongsto any existing resources
+func (s *syncer) deleteTag(txn *gorm.DB, log *zap.SugaredLogger, tags []model.ResourceTag) error {
+
+	for _, t := range tags {
+		var resTag []model.ResourceTag
+		txn.Where(&model.ResourceTag{TagID: t.TagID}).Find(&resTag)
+
+		if len(resTag) == 0 {
+			if err := txn.Unscoped().Where("id = ?", t.TagID).Delete(&model.Tag{}).Error; err != nil {
+				return err
+			}
+			log.Infof("Tag with ID: %d has been deleted", t.TagID)
+		}
+	}
+	return nil
+}
+
+func (s *syncer) deleteDBResources(
+	txn *gorm.DB, log *zap.SugaredLogger,
+	catalog *model.Catalog, res []parser.Resource) error {
+
+	if len(res) == 0 {
+		return nil
+	}
+
+	var dbResource []model.Resource
+	var dbResID []uint
+
+	txn.Model(&model.Resource{}).Where(&model.Resource{CatalogID: catalog.ID}).Find(&dbResource)
+
+	// Compare db resources to catalog resources to get removed resources info
+	for _, dbRes := range dbResource {
+		var flag bool
+		for _, catalogRes := range res {
+			if dbRes.Name == catalogRes.Name {
+				flag = true
+			}
+		}
+		if flag == false {
+			dbResID = append(dbResID, dbRes.ID)
+		}
+	}
+
+	for _, id := range dbResID {
+
+		var tags []model.ResourceTag
+		var categories []model.ResourceCategory
+
+		txn.Where(&model.ResourceTag{ResourceID: id}).Find(&tags)
+		txn.Where(&model.ResourceCategory{ResourceID: id}).Find(&categories)
+
+		s.deleteResourceAndVersion(txn, log, id)
+		s.deleteCategory(txn, log, categories)
+		s.deleteTag(txn, log, tags)
+	}
+	return nil
+}