#!/usr/bin/env python3
"""Fetch the consolidated text of BNatSchG §44 and §45b from
gesetze-im-internet.de and emit a plain-text file suitable for the
bnatschg ingest loader.

Usage:
    python scripts/fetch_bnatschg.py [--out sources/bnatschg/bnatschg.txt]

The output uses one heading line per section ("§ N ..." or "Anlage N ...")
exactly as the bnatschg loader's paragraph splitter expects.

Best-effort HTML scrape. If gesetze-im-internet.de changes layout, paste
text manually instead (see sources/README.md).
"""
from __future__ import annotations

import argparse
import re
import sys
from html.parser import HTMLParser
from pathlib import Path
from urllib.request import Request, urlopen

# §s most relevant for Artenschutzgutachten. Add more as needed.
SECTIONS = [
    ("§ 44 Vorschriften für besonders geschützte und bestimmte andere Tier- und Pflanzenarten",
     "https://www.gesetze-im-internet.de/bnatschg_2009/__44.html"),
    ("§ 45 Ausnahmen; Ermächtigung zum Erlass von Rechtsverordnungen",
     "https://www.gesetze-im-internet.de/bnatschg_2009/__45.html"),
    ("§ 45b Schutz wild lebender Vogelarten bei der Errichtung und dem Betrieb von Windenergieanlagen an Land",
     "https://www.gesetze-im-internet.de/bnatschg_2009/__45b.html"),
    ("Anlage 1 (zu § 45b Absatz 1 bis 5) Liste der bei der Errichtung und dem Betrieb von Windenergieanlagen an Land kollisionsgefährdeten Brutvogelarten",
     "https://www.gesetze-im-internet.de/bnatschg_2009/anlage_1.html"),
]


class TextExtractor(HTMLParser):
    def __init__(self) -> None:
        super().__init__()
        self._buf: list[str] = []
        self._skip = 0  # depth of <script>/<style>

    def handle_starttag(self, tag: str, attrs: list[tuple[str, str | None]]) -> None:
        if tag in {"script", "style"}:
            self._skip += 1
        elif tag in {"br", "p", "div", "li", "tr"}:
            self._buf.append("\n")

    def handle_endtag(self, tag: str) -> None:
        if tag in {"script", "style"} and self._skip:
            self._skip -= 1
        elif tag in {"p", "div", "li", "tr"}:
            self._buf.append("\n")

    def handle_data(self, data: str) -> None:
        if not self._skip:
            self._buf.append(data)

    def value(self) -> str:
        raw = "".join(self._buf)
        # Collapse excess blank lines while preserving paragraph breaks.
        raw = re.sub(r"[ \t]+", " ", raw)
        raw = re.sub(r"\n{3,}", "\n\n", raw)
        return raw.strip()


def fetch(url: str, timeout: float = 30.0) -> str:
    req = Request(url, headers={"User-Agent": "artenschutz-router/0.1 (+fetch_bnatschg)"})
    with urlopen(req, timeout=timeout) as resp:
        raw_bytes = resp.read()
    # gesetze-im-internet.de serves ISO-8859-1; sniff from header if present.
    charset = resp.headers.get_content_charset() or "iso-8859-1"
    return raw_bytes.decode(charset, errors="replace")


def main(argv: list[str] | None = None) -> int:
    parser = argparse.ArgumentParser(prog="fetch_bnatschg")
    parser.add_argument(
        "--out",
        type=Path,
        default=Path("sources/bnatschg/bnatschg.txt"),
        help="Output path (default: %(default)s)",
    )
    args = parser.parse_args(argv)
    args.out.parent.mkdir(parents=True, exist_ok=True)

    chunks: list[str] = []
    for heading, url in SECTIONS:
        print(f"  fetching {heading.split('(')[0].strip()} ...", file=sys.stderr)
        try:
            html = fetch(url)
        except Exception as exc:  # noqa: BLE001
            print(f"    FAILED ({exc}) — skipping", file=sys.stderr)
            continue
        extractor = TextExtractor()
        extractor.feed(html)
        body = extractor.value()
        # Anchor each section with the expected heading on its own line so the
        # paragraph chunker recognises it.
        chunks.append(f"{heading}\n\n{body}\n")

    if not chunks:
        print("No sections fetched — refusing to write empty output", file=sys.stderr)
        return 2

    args.out.write_text("\n\n".join(chunks), encoding="utf-8")
    print(f"Wrote {args.out} ({sum(len(c) for c in chunks):,} chars)", file=sys.stderr)
    return 0


if __name__ == "__main__":
    sys.exit(main())