#!/usr/bin/env python3
"""Catch high-confidence documentation drift before a Codex turn ends."""

from __future__ import annotations

import json
import subprocess
import sys
from pathlib import Path


def changed_paths(root: Path) -> set[str]:
    result = subprocess.run(
        ["git", "status", "--porcelain"],
        cwd=root,
        capture_output=True,
        text=True,
        timeout=20,
    )
    if result.returncode != 0:
        return set()

    paths: set[str] = set()
    for line in result.stdout.splitlines():
        if not line.strip():
            continue
        path = line[3:].replace("\\", "/")
        if " -> " in path:
            path = path.split(" -> ", 1)[1]
        paths.add(path)
    return paths


def block(reason: str) -> int:
    json.dump({"decision": "block", "reason": reason}, sys.stdout)
    return 0


def main() -> int:
    try:
        payload = json.load(sys.stdin)
    except json.JSONDecodeError:
        return 0

    if payload.get("stop_hook_active"):
        return 0

    root = Path(payload.get("cwd") or ".").resolve()
    paths = changed_paths(root)

    if "requirements.txt" in paths and "docs/TOOLCHAIN.md" not in paths:
        return block(
            "requirements.txt changed without docs/TOOLCHAIN.md. "
            "Update the toolchain notes with dependency compatibility rationale."
        )

    sample_pdf_changed = any(path.startswith("samples/") and path.lower().endswith(".pdf") for path in paths)
    metadata_changed = "samples/metadata.json" in paths
    if sample_pdf_changed and not metadata_changed:
        return block(
            "A sample PDF changed without samples/metadata.json. "
            "Update the sample metadata mapping so quality tests know the corpus traits."
        )

    policy_docs = {
        "docs/ARCHITECTURE.md",
        "docs/CONVERSION_POLICY.md",
        "docs/ADR.md",
    }
    touched_policy_docs = policy_docs.intersection(paths)
    if touched_policy_docs and "PROGRESS.md" not in paths:
        return block(
            "Architecture or conversion policy docs changed without PROGRESS.md. "
            "Record the decision and handoff context in PROGRESS.md."
        )

    return 0


if __name__ == "__main__":
    raise SystemExit(main())