#!/usr/bin/env python3
"""Convert VTT or SRT subtitle files to Markdown plain text."""
import re
import sys
from pathlib import Path


def strip_html(text):
    return re.sub(r'<[^>]+>', '', text)


def parse_vtt(content):
    blocks = re.split(r'\n{2,}', content.strip())
    cues = []
    for block in blocks:
        lines = block.strip().splitlines()
        if not lines:
            continue
        if lines[0].startswith('WEBVTT'):
            continue
        if lines[0].startswith('NOTE') or lines[0].startswith('STYLE'):
            continue
        ts_idx = next((i for i, l in enumerate(lines) if '-->' in l), None)
        if ts_idx is None:
            continue
        text = ' '.join(
            strip_html(l).strip()
            for l in lines[ts_idx + 1:]
            if strip_html(l).strip()
        )
        if text:
            cues.append(text)
    return cues


def parse_srt(content):
    blocks = re.split(r'\n{2,}', content.strip())
    cues = []
    for block in blocks:
        lines = block.strip().splitlines()
        text_lines = []
        for line in lines:
            line = line.strip()
            if re.match(r'^\d+$', line):
                continue
            if re.match(r'\d{2}:\d{2}:\d{2}[,\.]\d{3}\s*-->', line):
                continue
            cleaned = strip_html(line)
            if cleaned:
                text_lines.append(cleaned)
        if text_lines:
            cues.append(' '.join(text_lines))
    return cues


def deduplicate(cues):
    result = []
    prev = None
    for cue in cues:
        if cue != prev:
            result.append(cue)
            prev = cue
    return result


def to_markdown(cues):
    cues = deduplicate(cues)
    if not cues:
        return ''
    full = ' '.join(cues)
    sentences = re.split(r'(?<=[.!?…])\s+', full)
    paragraphs = []
    for i in range(0, len(sentences), 8):
        paragraphs.append(' '.join(sentences[i:i + 8]))
    return '\n\n'.join(paragraphs)


def convert(input_path):
    content = input_path.read_text(encoding='utf-8', errors='replace')
    suffix = input_path.suffix.lower()
    if suffix == '.vtt':
        cues = parse_vtt(content)
    elif suffix == '.srt':
        cues = parse_srt(content)
    else:
        raise ValueError(f'Unsupported format: {suffix}')
    return to_markdown(cues)


if __name__ == '__main__':
    if len(sys.argv) < 2:
        print(f'Usage: {sys.argv[0]} <file.vtt|file.srt> [output.md]', file=sys.stderr)
        sys.exit(1)

    input_path = Path(sys.argv[1])
    if not input_path.exists():
        print(f'File not found: {input_path}', file=sys.stderr)
        sys.exit(1)

    md = convert(input_path)

    output_path = Path(sys.argv[2]) if len(sys.argv) >= 3 else input_path.with_suffix('.md')
    output_path.write_text(md, encoding='utf-8')
    print(f'Saved: {output_path}')