lyric_sync/output.py

"""
Output formatters for synchronized lyrics.

Supports multiple standard formats:
- LRC (Enhanced): Word-level timestamps in LRC format
- JSON: Structured word-level data
- SRT: Subtitle format (line-level)
- ASS: Advanced SubStation Alpha (word-level karaoke)
- Plain text with inline timestamps
"""

import json
from typing import Optional

from lyric_sync.transcribe import TimedWord


def to_enhanced_lrc(words: list[TimedWord], line_break_gap: float = 1.0) -> str:
    """
    Format as Enhanced LRC with word-level timestamps.
    
    Enhanced LRC format:
    [MM:SS.cc] <MM:SS.cc> word1 <MM:SS.cc> word2 <MM:SS.cc> word3
    
    Args:
        words: Timed words
        line_break_gap: Seconds of gap to trigger a new line (default 1.0s)
    """
    if not words:
        return ""

    lines = []
    current_line_words = []
    current_line_start = words[0].start

    for i, word in enumerate(words):
        # Detect line breaks based on gaps between words
        if current_line_words:
            prev_end = current_line_words[-1].end
            if word.start - prev_end > line_break_gap:
                # Emit current line
                lines.append(_format_lrc_line(current_line_words, current_line_start))
                current_line_words = []
                current_line_start = word.start

        current_line_words.append(word)

    # Emit final line
    if current_line_words:
        lines.append(_format_lrc_line(current_line_words, current_line_start))

    return "\n".join(lines)


def _format_lrc_line(words: list[TimedWord], line_start: float) -> str:
    """Format a single Enhanced LRC line."""
    line_ts = _format_lrc_timestamp(line_start)
    word_parts = []
    for word in words:
        word_ts = _format_lrc_timestamp(word.start)
        word_parts.append(f"<{word_ts}> {word.word}")
    # Add end timestamp
    end_ts = _format_lrc_timestamp(words[-1].end)
    return f"[{line_ts}] {' '.join(f'<{_format_lrc_timestamp(w.start)}> {w.word}' for w in words)} <{end_ts}>"


def _format_lrc_timestamp(seconds: float) -> str:
    """Format seconds as MM:SS.cc (LRC standard)."""
    minutes = int(seconds // 60)
    secs = seconds % 60
    return f"{minutes:02d}:{secs:05.2f}"


def to_standard_lrc(words: list[TimedWord], line_break_gap: float = 1.0) -> str:
    """
    Format as standard LRC (line-level timestamps only).
    
    [MM:SS.cc] Line of lyrics text
    """
    if not words:
        return ""

    lines = []
    current_line_words = []
    current_line_start = words[0].start

    for word in words:
        if current_line_words:
            prev_end = current_line_words[-1].end
            if word.start - prev_end > line_break_gap:
                ts = _format_lrc_timestamp(current_line_start)
                text = " ".join(w.word for w in current_line_words)
                lines.append(f"[{ts}] {text}")
                current_line_words = []
                current_line_start = word.start

        current_line_words.append(word)

    if current_line_words:
        ts = _format_lrc_timestamp(current_line_start)
        text = " ".join(w.word for w in current_line_words)
        lines.append(f"[{ts}] {text}")

    return "\n".join(lines)


def to_json(words: list[TimedWord], indent: int = 2) -> str:
    """
    Format as JSON array of word objects.
    
    [{"word": "hello", "start": 0.123, "end": 0.456, "confidence": 0.95}, ...]
    """
    data = [
        {
            "word": w.word,
            "start": round(w.start, 3),
            "end": round(w.end, 3),
            "confidence": round(w.confidence, 3),
        }
        for w in words
    ]
    return json.dumps(data, indent=indent, ensure_ascii=False)


def to_srt(words: list[TimedWord], line_break_gap: float = 1.0, max_words_per_line: int = 10) -> str:
    """
    Format as SRT subtitles (line-level).
    
    1
    00:00:01,230 --> 00:00:03,456
    Line of lyrics text
    """
    if not words:
        return ""

    entries = []
    current_words = []
    current_start = words[0].start

    for word in words:
        if current_words:
            prev_end = current_words[-1].end
            if word.start - prev_end > line_break_gap or len(current_words) >= max_words_per_line:
                entries.append((current_start, current_words[-1].end, current_words))
                current_words = []
                current_start = word.start
        current_words.append(word)

    if current_words:
        entries.append((current_start, current_words[-1].end, current_words))

    srt_lines = []
    for idx, (start, end, line_words) in enumerate(entries, 1):
        start_ts = _format_srt_timestamp(start)
        end_ts = _format_srt_timestamp(end)
        text = " ".join(w.word for w in line_words)
        srt_lines.append(f"{idx}\n{start_ts} --> {end_ts}\n{text}\n")

    return "\n".join(srt_lines)


def _format_srt_timestamp(seconds: float) -> str:
    """Format seconds as HH:MM:SS,mmm (SRT standard)."""
    hours = int(seconds // 3600)
    minutes = int((seconds % 3600) // 60)
    secs = seconds % 60
    millis = int((secs % 1) * 1000)
    return f"{hours:02d}:{minutes:02d}:{int(secs):02d},{millis:03d}"


def to_ass_karaoke(
    words: list[TimedWord],
    line_break_gap: float = 1.0,
    style_name: str = "Default",
) -> str:
    """
    Format as ASS (Advanced SubStation Alpha) with karaoke timing.
    
    Uses \\k tags for word-level karaoke highlighting.
    Each \\kN tag specifies duration in centiseconds until next word highlights.
    """
    if not words:
        return ""

    header = f"""[Script Info]
Title: Synced Lyrics
ScriptType: v4.00+
PlayResX: 1920
PlayResY: 1080

[V4+ Styles]
Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding
Style: {style_name},Arial,48,&H00FFFFFF,&H000000FF,&H00000000,&H64000000,-1,0,0,0,100,100,0,0,1,2,1,2,10,10,40,1

[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
"""

    # Group words into lines
    line_groups = []
    current_line = []
    for word in words:
        if current_line:
            prev_end = current_line[-1].end
            if word.start - prev_end > line_break_gap:
                line_groups.append(current_line)
                current_line = []
        current_line.append(word)
    if current_line:
        line_groups.append(current_line)

    events = []
    for line_words in line_groups:
        start = _format_ass_timestamp(line_words[0].start)
        end = _format_ass_timestamp(line_words[-1].end)

        # Build karaoke text with \k tags
        karaoke_parts = []
        for w in line_words:
            duration_cs = int(w.duration * 100)  # centiseconds
            karaoke_parts.append(f"{{\\kf{duration_cs}}}{w.word}")

        text = " ".join(karaoke_parts)
        events.append(f"Dialogue: 0,{start},{end},{style_name},,0,0,0,,{text}")

    return header + "\n".join(events)


def _format_ass_timestamp(seconds: float) -> str:
    """Format seconds as H:MM:SS.cc (ASS standard)."""
    hours = int(seconds // 3600)
    minutes = int((seconds % 3600) // 60)
    secs = seconds % 60
    centis = int((secs % 1) * 100)
    return f"{hours}:{minutes:02d}:{int(secs):02d}.{centis:02d}"


def to_plain_inline(words: list[TimedWord], line_break_gap: float = 1.0) -> str:
    """
    Plain text with inline timestamps for readability.
    
    [0:01.23] Hello world [0:02.45] this is a song
    """
    if not words:
        return ""

    parts = []
    prev_end = 0.0

    for word in words:
        if word.start - prev_end > line_break_gap:
            parts.append("\n")
        ts = _format_lrc_timestamp(word.start)
        parts.append(f"[{ts}] {word.word}")
        prev_end = word.end

    return " ".join(parts).replace(" \n ", "\n")