Improve handling of moved and added video files (#4598)

* If old file path is not in library, treat as move
* Use existing phash if file with same oshash exists

internal/manager/task_generate_phash.go

@@ -25,19 +25,38 @@ func (t *GeneratePhashTask) Start(ctx context.Context) {
 		return
 	}
 
-	hash, err := videophash.Generate(instance.FFMpeg, t.File)
-	if err != nil {
-		logger.Errorf("error generating phash: %s", err.Error())
-		logErrorOutput(err)
-		return
+	var hash int64
+	set := false
+
+	// #4393 - if there is a file with the same oshash, we can use the same phash
+	// only use this if we're not overwriting
+	if !t.Overwrite {
+		existing, err := t.findExistingPhash(ctx)
+		if err != nil {
+			logger.Warnf("Error finding existing phash: %v", err)
+		} else if existing != nil {
+			logger.Infof("Using existing phash for %s", t.File.Path)
+			hash = existing.(int64)
+			set = true
+		}
+	}
+
+	if !set {
+		generated, err := videophash.Generate(instance.FFMpeg, t.File)
+		if err != nil {
+			logger.Errorf("Error generating phash: %v", err)
+			logErrorOutput(err)
+			return
+		}
+
+		hash = int64(*generated)
 	}
 
 	r := t.repository
 	if err := r.WithTxn(ctx, func(ctx context.Context) error {
-		hashValue := int64(*hash)
 		t.File.Fingerprints = t.File.Fingerprints.AppendUnique(models.Fingerprint{
 			Type:        models.FingerprintTypePhash,
-			Fingerprint: hashValue,
+			Fingerprint: hash,
 		})
 
 		return r.File.Update(ctx, t.File)
@@ -46,6 +65,36 @@ func (t *GeneratePhashTask) Start(ctx context.Context) {
 	}
 }
 
+func (t *GeneratePhashTask) findExistingPhash(ctx context.Context) (interface{}, error) {
+	r := t.repository
+	var ret interface{}
+	if err := r.WithReadTxn(ctx, func(ctx context.Context) error {
+		oshash := t.File.Fingerprints.Get(models.FingerprintTypeOshash)
+
+		// find other files with the same oshash
+		files, err := r.File.FindByFingerprint(ctx, models.Fingerprint{
+			Type:        models.FingerprintTypeOshash,
+			Fingerprint: oshash,
+		})
+		if err != nil {
+			return fmt.Errorf("finding files by oshash: %w", err)
+		}
+
+		// find the first file with a phash
+		for _, file := range files {
+			if phash := file.Base().Fingerprints.Get(models.FingerprintTypePhash); phash != nil {
+				ret = phash
+				return nil
+			}
+		}
+		return nil
+	}); err != nil {
+		return nil, err
+	}
+
+	return ret, nil
+}
+
 func (t *GeneratePhashTask) required() bool {
 	if t.Overwrite {
 		return true