sub-cli/internal/format/lrc/lrc.go

package lrc

import (
	"bufio"
	"fmt"
	"os"
	"regexp"
	"strconv"
	"strings"

	"sub-cli/internal/model"
)

// Parse parses an LRC file and returns a Lyrics struct
func Parse(filePath string) (model.Lyrics, error) {
	lyrics := model.Lyrics{
		Metadata: make(map[string]string),
	}

	file, err := os.Open(filePath)
	if err != nil {
		return lyrics, err
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)
	metadataRegex := regexp.MustCompile(`\[([\w:]+):(.*?)\]`)
	timestampRegex := regexp.MustCompile(`\[(\d+:\d+(?:\.\d+)?)\]`)

	for scanner.Scan() {
		line := scanner.Text()

		// Extract metadata
		metadataMatches := metadataRegex.FindAllStringSubmatch(line, -1)
		for _, match := range metadataMatches {
			if len(match) >= 3 {
				key := match[1]
				value := match[2]
				lyrics.Metadata[key] = value
			}
		}

		// Extract timestamp and content
		timestampMatches := timestampRegex.FindAllStringSubmatch(line, -1)
		if len(timestampMatches) > 0 {
			var timestamps []model.Timestamp
			lineContent := line

			for _, match := range timestampMatches {
				if len(match) >= 2 {
					timestamp, err := ParseTimestamp(match[1])
					if err == nil {
						timestamps = append(timestamps, timestamp)
					}
					lineContent = strings.Replace(lineContent, match[0], "", 1)
				}
			}

			lineContent = strings.TrimSpace(lineContent)
			if lineContent != "" {
				for range timestamps {
					lyrics.Timeline = append(lyrics.Timeline, timestamps...)
					lyrics.Content = append(lyrics.Content, lineContent)
				}
			}
		}
	}

	return lyrics, nil
}

// ParseTimestamp parses an LRC timestamp string into a Timestamp struct
func ParseTimestamp(timeStr string) (model.Timestamp, error) {
	// remove brackets
	timeStr = strings.Trim(timeStr, "[]")

	parts := strings.Split(timeStr, ":")
	var hours, minutes, seconds, milliseconds int
	var err error

	switch len(parts) {
	case 2: // minutes:seconds.milliseconds
		minutes, err = strconv.Atoi(parts[0])
		if err != nil {
			return model.Timestamp{}, err
		}
		secParts := strings.Split(parts[1], ".")
		seconds, err = strconv.Atoi(secParts[0])
		if err != nil {
			return model.Timestamp{}, err
		}
		if len(secParts) > 1 {
			milliseconds, err = strconv.Atoi(secParts[1])
			if err != nil {
				return model.Timestamp{}, err
			}
			// adjust milliseconds based on the number of digits
			switch len(secParts[1]) {
			case 1:
				milliseconds *= 100
			case 2:
				milliseconds *= 10
			}
		}
	case 3: // hours:minutes:seconds.milliseconds
		hours, err = strconv.Atoi(parts[0])
		if err != nil {
			return model.Timestamp{}, err
		}
		minutes, err = strconv.Atoi(parts[1])
		if err != nil {
			return model.Timestamp{}, err
		}
		secParts := strings.Split(parts[2], ".")
		seconds, err = strconv.Atoi(secParts[0])
		if err != nil {
			return model.Timestamp{}, err
		}
		if len(secParts) > 1 {
			milliseconds, err = strconv.Atoi(secParts[1])
			if err != nil {
				return model.Timestamp{}, err
			}
			// adjust milliseconds based on the number of digits
			switch len(secParts[1]) {
			case 1:
				milliseconds *= 100
			case 2:
				milliseconds *= 10
			}
		}
	default:
		return model.Timestamp{}, fmt.Errorf("invalid timestamp format: %s", timeStr)
	}

	return model.Timestamp{
		Hours:        hours,
		Minutes:      minutes,
		Seconds:      seconds,
		Milliseconds: milliseconds,
	}, nil
}

// Generate generates an LRC file from a Lyrics struct
func Generate(lyrics model.Lyrics, filePath string) error {
	file, err := os.Create(filePath)
	if err != nil {
		return err
	}
	defer file.Close()

	// Write metadata
	for key, value := range lyrics.Metadata {
		fmt.Fprintf(file, "[%s:%s]\n", key, value)
	}
	
	// Write content with timestamps
	for i, content := range lyrics.Content {
		if i < len(lyrics.Timeline) {
			timestamp := lyrics.Timeline[i]
			fmt.Fprintf(file, "[%02d:%02d.%03d]%s\n", 
				timestamp.Minutes, 
				timestamp.Seconds, 
				timestamp.Milliseconds,
				content)
		} else {
			fmt.Fprintln(file, content)
		}
	}

	return nil
}

// Format formats an LRC file
func Format(filePath string) error {
	lyrics, err := Parse(filePath)
	if err != nil {
		return err
	}
	
	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)
}