feat: vtt converting

internal/format/lrc/lrc.go

@@ -180,3 +180,87 @@ func Format(filePath string) error {
 	
 	return Generate(lyrics, filePath)
 }
+
+// ConvertToSubtitle converts LRC file to our intermediate Subtitle representation
+func ConvertToSubtitle(filePath string) (model.Subtitle, error) {
+	lyrics, err := Parse(filePath)
+	if err != nil {
+		return model.Subtitle{}, err
+	}
+
+	subtitle := model.NewSubtitle()
+	subtitle.Format = "lrc"
+	
+	// Copy metadata
+	for key, value := range lyrics.Metadata {
+		subtitle.Metadata[key] = value
+	}
+	
+	// Check for specific LRC metadata we should use for title
+	if title, ok := lyrics.Metadata["ti"]; ok {
+		subtitle.Title = title
+	}
+	
+	// Create entries from timeline and content
+	for i, content := range lyrics.Content {
+		if i >= len(lyrics.Timeline) {
+			break
+		}
+		
+		entry := model.NewSubtitleEntry()
+		entry.Index = i + 1
+		entry.StartTime = lyrics.Timeline[i]
+		
+		// Set end time based on next timeline entry if available, otherwise add a few seconds
+		if i+1 < len(lyrics.Timeline) {
+			entry.EndTime = lyrics.Timeline[i+1]
+		} else {
+			// Default end time: start time + 3 seconds
+			entry.EndTime = model.Timestamp{
+				Hours:        entry.StartTime.Hours,
+				Minutes:      entry.StartTime.Minutes,
+				Seconds:      entry.StartTime.Seconds + 3,
+				Milliseconds: entry.StartTime.Milliseconds,
+			}
+			// Handle overflow
+			if entry.EndTime.Seconds >= 60 {
+				entry.EndTime.Seconds -= 60
+				entry.EndTime.Minutes++
+			}
+			if entry.EndTime.Minutes >= 60 {
+				entry.EndTime.Minutes -= 60
+				entry.EndTime.Hours++
+			}
+		}
+		
+		entry.Text = content
+		subtitle.Entries = append(subtitle.Entries, entry)
+	}
+	
+	return subtitle, nil
+}
+
+// ConvertFromSubtitle converts our intermediate Subtitle representation to LRC format
+func ConvertFromSubtitle(subtitle model.Subtitle, filePath string) error {
+	lyrics := model.Lyrics{
+		Metadata: make(map[string]string),
+	}
+	
+	// Copy metadata
+	for key, value := range subtitle.Metadata {
+		lyrics.Metadata[key] = value
+	}
+	
+	// Add title if present and not already in metadata
+	if subtitle.Title != "" && lyrics.Metadata["ti"] == "" {
+		lyrics.Metadata["ti"] = subtitle.Title
+	}
+	
+	// Convert entries to timeline and content
+	for _, entry := range subtitle.Entries {
+		lyrics.Timeline = append(lyrics.Timeline, entry.StartTime)
+		lyrics.Content = append(lyrics.Content, entry.Text)
+	}
+	
+	return Generate(lyrics, filePath)
+}