feat: vtt converting
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7 changed files with 693 additions and 107 deletions
393
internal/format/vtt/vtt.go
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393
internal/format/vtt/vtt.go
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package vtt
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import (
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"bufio"
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"fmt"
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"os"
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"regexp"
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"strconv"
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"strings"
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"time"
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"sub-cli/internal/model"
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)
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// Constants for VTT format
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const (
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VTTHeader = "WEBVTT"
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)
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// Parse parses a WebVTT file into our intermediate Subtitle representation
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func Parse(filePath string) (model.Subtitle, error) {
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subtitle := model.NewSubtitle()
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subtitle.Format = "vtt"
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file, err := os.Open(filePath)
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if err != nil {
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return subtitle, fmt.Errorf("error opening VTT file: %w", err)
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}
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defer file.Close()
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scanner := bufio.NewScanner(file)
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// Check header
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if !scanner.Scan() {
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return subtitle, fmt.Errorf("empty VTT file")
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}
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header := strings.TrimSpace(scanner.Text())
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if !strings.HasPrefix(header, VTTHeader) {
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return subtitle, fmt.Errorf("invalid VTT file: missing WEBVTT header")
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}
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// Get metadata from header
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if strings.Contains(header, " - ") {
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subtitle.Title = strings.TrimSpace(strings.TrimPrefix(header, VTTHeader+" - "))
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}
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// Process file content
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var currentEntry model.SubtitleEntry
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var inCue bool
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var inStyle bool
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var styleBuffer strings.Builder
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var cueTextBuffer strings.Builder
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lineNum := 1
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for scanner.Scan() {
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lineNum++
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line := scanner.Text()
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// Skip empty lines
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if strings.TrimSpace(line) == "" {
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if inCue {
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// End of a cue
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currentEntry.Text = cueTextBuffer.String()
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subtitle.Entries = append(subtitle.Entries, currentEntry)
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currentEntry = model.NewSubtitleEntry()
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cueTextBuffer.Reset()
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inCue = false
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}
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continue
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}
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// Check for style blocks
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if strings.HasPrefix(line, "STYLE") {
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inStyle = true
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continue
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}
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if inStyle {
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if line == "" {
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inStyle = false
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subtitle.Styles["css"] = styleBuffer.String()
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styleBuffer.Reset()
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} else {
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styleBuffer.WriteString(line)
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styleBuffer.WriteString("\n")
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}
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continue
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}
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// Check for NOTE comments
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if strings.HasPrefix(line, "NOTE") {
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comment := strings.TrimSpace(strings.TrimPrefix(line, "NOTE"))
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subtitle.Comments = append(subtitle.Comments, comment)
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continue
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}
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// Check for REGION definitions
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if strings.HasPrefix(line, "REGION") {
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parts := strings.Split(strings.TrimPrefix(line, "REGION"), ":")
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if len(parts) >= 2 {
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regionID := strings.TrimSpace(parts[0])
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region := model.NewSubtitleRegion(regionID)
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settings := strings.Split(parts[1], " ")
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for _, setting := range settings {
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keyValue := strings.Split(setting, "=")
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if len(keyValue) == 2 {
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region.Settings[strings.TrimSpace(keyValue[0])] = strings.TrimSpace(keyValue[1])
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}
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}
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subtitle.Regions = append(subtitle.Regions, region)
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}
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continue
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}
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// Check for timestamp lines
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if strings.Contains(line, "-->") {
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inCue = true
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// Parse timestamps
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timestamps := strings.Split(line, "-->")
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if len(timestamps) != 2 {
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return subtitle, fmt.Errorf("invalid timestamp format at line %d: %s", lineNum, line)
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}
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startTimeStr := strings.TrimSpace(timestamps[0])
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endTimeAndSettings := strings.TrimSpace(timestamps[1])
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endTimeStr := endTimeAndSettings
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settings := ""
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// Check for cue settings after end timestamp
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if spaceIndex := strings.IndexByte(endTimeAndSettings, ' '); spaceIndex != -1 {
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endTimeStr = endTimeAndSettings[:spaceIndex]
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settings = endTimeAndSettings[spaceIndex+1:]
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}
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// Set timestamps
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currentEntry.StartTime = parseVTTTimestamp(startTimeStr)
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currentEntry.EndTime = parseVTTTimestamp(endTimeStr)
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// Parse cue settings
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if settings != "" {
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settingPairs := strings.Split(settings, " ")
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for _, pair := range settingPairs {
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if pair == "" {
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continue
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}
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if strings.Contains(pair, ":") {
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parts := strings.Split(pair, ":")
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if len(parts) == 2 {
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currentEntry.Styles[strings.TrimSpace(parts[0])] = strings.TrimSpace(parts[1])
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}
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} else {
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// Handle non-key-value settings if any
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currentEntry.FormatData["setting_"+pair] = true
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}
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}
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}
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cueTextBuffer.Reset()
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continue
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}
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// Check if we have identifier before timestamp
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if !inCue && currentEntry.Index == 0 && !strings.Contains(line, "-->") {
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// This might be a cue identifier
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if _, err := strconv.Atoi(line); err == nil {
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// It's likely a numeric identifier
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num, _ := strconv.Atoi(line)
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currentEntry.Index = num
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} else {
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// It's a string identifier, store it in metadata
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currentEntry.Metadata["identifier"] = line
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currentEntry.Index = len(subtitle.Entries) + 1
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}
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continue
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}
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// If we're in a cue, add this line to the text
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if inCue {
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if cueTextBuffer.Len() > 0 {
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cueTextBuffer.WriteString("\n")
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}
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cueTextBuffer.WriteString(line)
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}
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}
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// Don't forget the last entry
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if inCue && cueTextBuffer.Len() > 0 {
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currentEntry.Text = cueTextBuffer.String()
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subtitle.Entries = append(subtitle.Entries, currentEntry)
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}
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// Process cue text to extract styling
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processVTTCueTextStyling(&subtitle)
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if err := scanner.Err(); err != nil {
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return subtitle, fmt.Errorf("error reading VTT file: %w", err)
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}
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return subtitle, nil
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}
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// parseVTTTimestamp parses a VTT timestamp string into our Timestamp model
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func parseVTTTimestamp(timeStr string) model.Timestamp {
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// VTT timestamps format: 00:00:00.000
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re := regexp.MustCompile(`(\d+):(\d+):(\d+)\.(\d+)|\d+:(\d+)\.(\d+)`)
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matches := re.FindStringSubmatch(timeStr)
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var hours, minutes, seconds, milliseconds int
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if len(matches) >= 5 && matches[1] != "" {
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// Full format: 00:00:00.000
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hours, _ = strconv.Atoi(matches[1])
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minutes, _ = strconv.Atoi(matches[2])
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seconds, _ = strconv.Atoi(matches[3])
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msStr := matches[4]
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// Ensure milliseconds are treated correctly
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switch len(msStr) {
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case 1:
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milliseconds, _ = strconv.Atoi(msStr + "00")
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case 2:
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milliseconds, _ = strconv.Atoi(msStr + "0")
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case 3:
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milliseconds, _ = strconv.Atoi(msStr)
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default:
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if len(msStr) > 3 {
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milliseconds, _ = strconv.Atoi(msStr[:3])
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}
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}
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} else if len(matches) >= 7 && matches[5] != "" {
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// Short format: 00:00.000
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minutes, _ = strconv.Atoi(matches[5])
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seconds, _ = strconv.Atoi(matches[6])
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msStr := matches[7]
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// Ensure milliseconds are treated correctly
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switch len(msStr) {
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case 1:
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milliseconds, _ = strconv.Atoi(msStr + "00")
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case 2:
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milliseconds, _ = strconv.Atoi(msStr + "0")
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case 3:
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milliseconds, _ = strconv.Atoi(msStr)
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default:
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if len(msStr) > 3 {
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milliseconds, _ = strconv.Atoi(msStr[:3])
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}
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}
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} else {
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// Try another approach with time.Parse
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layout := "15:04:05.000"
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t, err := time.Parse(layout, timeStr)
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if err == nil {
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hours = t.Hour()
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minutes = t.Minute()
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seconds = t.Second()
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milliseconds = t.Nanosecond() / 1000000
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}
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}
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return model.Timestamp{
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Hours: hours,
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Minutes: minutes,
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Seconds: seconds,
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Milliseconds: milliseconds,
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}
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}
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// processVTTCueTextStyling processes the cue text to extract styling tags
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func processVTTCueTextStyling(subtitle *model.Subtitle) {
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for i, entry := range subtitle.Entries {
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// Look for basic HTML tags in the text and extract them to styling attributes
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text := entry.Text
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// Process <b>, <i>, <u>, etc. tags to collect styling information
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// For simplicity, we'll just note that styling exists, but we won't modify the text
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if strings.Contains(text, "<") && strings.Contains(text, ">") {
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entry.FormatData["has_html_tags"] = true
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}
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// Update the entry
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subtitle.Entries[i] = entry
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}
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}
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// Generate generates a WebVTT file from our intermediate Subtitle representation
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func Generate(subtitle model.Subtitle, filePath string) error {
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file, err := os.Create(filePath)
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if err != nil {
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return fmt.Errorf("error creating VTT file: %w", err)
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}
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defer file.Close()
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// Write header
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if subtitle.Title != "" {
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fmt.Fprintf(file, "%s - %s\n\n", VTTHeader, subtitle.Title)
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} else {
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fmt.Fprintf(file, "%s\n\n", VTTHeader)
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}
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// Write styles if any
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if cssStyle, ok := subtitle.Styles["css"]; ok && cssStyle != "" {
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fmt.Fprintln(file, "STYLE")
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fmt.Fprintln(file, cssStyle)
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fmt.Fprintln(file)
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}
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// Write regions if any
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for _, region := range subtitle.Regions {
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fmt.Fprintf(file, "REGION %s:", region.ID)
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for key, value := range region.Settings {
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fmt.Fprintf(file, " %s=%s", key, value)
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}
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fmt.Fprintln(file)
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}
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// Write comments if any
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for _, comment := range subtitle.Comments {
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fmt.Fprintf(file, "NOTE %s\n", comment)
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}
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if len(subtitle.Comments) > 0 {
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fmt.Fprintln(file)
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}
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// Write cues
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for i, entry := range subtitle.Entries {
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// Write identifier if available
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if identifier, ok := entry.Metadata["identifier"]; ok && identifier != "" {
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fmt.Fprintln(file, identifier)
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} else if entry.Index > 0 {
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fmt.Fprintln(file, entry.Index)
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} else {
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fmt.Fprintln(file, i+1)
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}
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// Write timestamps and settings
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fmt.Fprintf(file, "%s --> %s", formatVTTTimestamp(entry.StartTime), formatVTTTimestamp(entry.EndTime))
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// Add cue settings
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for key, value := range entry.Styles {
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fmt.Fprintf(file, " %s:%s", key, value)
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}
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fmt.Fprintln(file)
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// Write cue text
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fmt.Fprintln(file, entry.Text)
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fmt.Fprintln(file)
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}
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return nil
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}
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// formatVTTTimestamp formats a Timestamp struct as a VTT timestamp string
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func formatVTTTimestamp(ts model.Timestamp) string {
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return fmt.Sprintf("%02d:%02d:%02d.%03d",
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ts.Hours,
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ts.Minutes,
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ts.Seconds,
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ts.Milliseconds)
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}
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// Format standardizes and formats a VTT file
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func Format(filePath string) error {
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// Parse the file
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subtitle, err := Parse(filePath)
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if err != nil {
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return fmt.Errorf("error parsing VTT file: %w", err)
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}
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// Standardize entry numbering
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for i := range subtitle.Entries {
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subtitle.Entries[i].Index = i + 1
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}
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// Write back the formatted content
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return Generate(subtitle, filePath)
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}
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// ConvertToSubtitle converts VTT entries to our intermediate Subtitle structure
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func ConvertToSubtitle(filePath string) (model.Subtitle, error) {
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return Parse(filePath)
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}
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// ConvertFromSubtitle converts our intermediate Subtitle to VTT format
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func ConvertFromSubtitle(subtitle model.Subtitle, filePath string) error {
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return Generate(subtitle, filePath)
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}
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