"""YouTube transcript retrieval without downloading video media."""

from __future__ import annotations

import re


def video_id(url: str) -> str:
    match = re.search(r"(?:v=|youtu\.be/|shorts/)([A-Za-z0-9_-]{11})", url)
    if not match:
        raise ValueError("Could not parse a YouTube video id")
    return match.group(1)


def fetch_youtube_transcript(url: str, languages: tuple[str, ...] = ("en",)) -> str:
    """Return a timestamped YouTube transcript using the public transcript API."""
    from youtube_transcript_api import YouTubeTranscriptApi

    identifier = video_id(url)
    api = YouTubeTranscriptApi()
    fetched = api.fetch(identifier, languages=list(languages))
    snippets = []
    for item in fetched:
        start = float(getattr(item, "start", 0.0))
        text = str(getattr(item, "text", "")).replace("\n", " ").strip()
        snippets.append(f"[{start:.1f}s] {text}")
    if not snippets:
        raise RuntimeError("YouTube returned an empty transcript")
    return "\n".join(snippets)


def find_transcript_context(transcript: str, quote: str, window: int = 3) -> str:
    """Find a quoted dialogue line and return nearby timestamped transcript lines."""
    lines = transcript.splitlines()
    needle = re.sub(r"[^a-z0-9 ]", "", quote.lower())
    for index, line in enumerate(lines):
        haystack = re.sub(r"[^a-z0-9 ]", "", line.lower())
        if needle and needle in haystack:
            return "\n".join(lines[max(0, index - window) : index + window + 1])
    return transcript