legex/scrapers/au.py

import logging
import re
from datetime import date

from datasets import load_dataset

from legex.models.base import Case
from legex.scrapers.base import BaseScraper

DATASET_NAME = "isaacus/high-court-of-australia-cases"
log = logging.getLogger(__name__)

_RE_CITATION = re.compile(r"\[(\d{4})\]\s*HCA\s*(\d+)")
# HCA docket, for example"S94/2025", "P7/2024", "B15/2024". Registry letters seen: S/B/C/P/M/H/D.
_RE_DOCKET = re.compile(r"\b([SBCPMHD])(\d+)/(\d{4})\b")
HCOURT_URL_TEMPLATE = "https://www.hcourt.gov.au/cases-and-judgments/cases/decided/case-{letter}{num}{year}"


class AUScraper(BaseScraper):
    country = "Australia"

    def scrape(
        self,
        start_date: date | None = None,
        end_date: date | None = None,
    ) -> list[Case]:
        log.info(f"Loading {DATASET_NAME} …")
        dataset = load_dataset(DATASET_NAME, split="corpus")
        cases = [self._row_to_case(row) for row in dataset]
        cases = [c for c in cases if c is not None]

        if start_date or end_date:
            cases = [
                c for c in cases
                if (start_date is None or c.decision_date >= start_date)
                and (end_date is None or c.decision_date <= end_date)
            ]
        cases.sort(key=lambda c: c.decision_date or date.min, reverse=True)
        log.info(f"{len(cases)} cases after filtering")
        return cases

    @staticmethod
    def _row_to_case(row: dict) -> Case | None:
        raw_date = row.get("date")
        if not raw_date:
            return None
        citation = row.get("citation") or ""
        m = _RE_CITATION.search(citation)
        case_id = f"[{m.group(1)}] HCA {m.group(2)}" if m else citation or None
        decision_date = raw_date.date() if hasattr(raw_date, "date") else date.fromisoformat(str(raw_date)[:10])

        # We prefer the authoritative hcourt.gov.au per-case URL, built from the docket
        # number found in the first 2000 chars of the decision text. This gives around 95% hit rate.
        # For the remaining ~5% with no docket match we fall back to the dataset URL.
        text = row.get("text") or ""
        d = _RE_DOCKET.search(text[:2000])
        if d:
            docket = f"{d.group(1)}{d.group(2)}/{d.group(3)}"
            link = HCOURT_URL_TEMPLATE.format(
                letter=d.group(1).lower(), num=d.group(2), year=d.group(3)
            )
        else:
            docket = ""
            link = row.get("url")

        return Case(
            case_id=case_id,
            link=link,
            decision_date=decision_date,
            jurisdiction="au",
            language="en",
            full_text=text or None,
            metadata={"citation": citation, "docket": docket},
        )

    @staticmethod
    def civil_filter(cases: list[Case]) -> list[Case]:
        # HCA is mixed civil/criminal/constitutional. Exclude the explicit criminal
        # pattern "v The King" / "v The Queen", everything else we treat as civil.
        return [
            c for c in cases
            if " v The King" not in (c.metadata or {}).get("citation", "")
            and " v The Queen" not in (c.metadata or {}).get("citation", "")
        ]