#!/usr/bin/env python3
"""Fail-closed freshness checks for the local AUTO_GEN product-pack mirror."""

from __future__ import annotations

import json
import subprocess
from datetime import datetime, timezone
from pathlib import Path
from typing import Any


REPO_ROOT = Path(__file__).resolve().parents[2]
PRODUCT_PACK_ROOT = REPO_ROOT / "packs" / "AUTO_GEN_Product-pack"
LOCAL_LAST_GENERATED = PRODUCT_PACK_ROOT / ".last-generated.json"
LIVE_BRANCH = "origin/product-pack-live"
LIVE_LAST_GENERATED_PATH = "packs/AUTO_GEN_Product-pack/.last-generated.json"


def _load_json(path: Path) -> dict[str, Any]:
    return json.loads(path.read_text(encoding="utf-8"))


def _parse_generated_at(payload: dict[str, Any], source: str) -> datetime:
    raw = str(payload.get("generatedAt") or "").strip()
    if not raw:
        raise RuntimeError(f"missing generatedAt in {source}")
    try:
        return datetime.fromisoformat(raw.replace("Z", "+00:00")).astimezone(timezone.utc)
    except ValueError as exc:
        raise RuntimeError(f"invalid generatedAt in {source}: {raw}") from exc


def _git_show(ref_and_path: str) -> str | None:
    result = subprocess.run(
        ["git", "show", ref_and_path],
        cwd=REPO_ROOT,
        text=True,
        capture_output=True,
        check=False,
    )
    if result.returncode != 0:
        return None
    return result.stdout


def ensure_local_mirror_is_fresh() -> None:
    if not LOCAL_LAST_GENERATED.exists():
        raise RuntimeError(f"missing local mirror freshness marker: {LOCAL_LAST_GENERATED}")

    local_payload = _load_json(LOCAL_LAST_GENERATED)
    local_generated_at = _parse_generated_at(local_payload, str(LOCAL_LAST_GENERATED))

    remote_raw = _git_show(f"{LIVE_BRANCH}:{LIVE_LAST_GENERATED_PATH}")
    if remote_raw is None:
        return

    remote_payload = json.loads(remote_raw)
    remote_generated_at = _parse_generated_at(remote_payload, f"{LIVE_BRANCH}:{LIVE_LAST_GENERATED_PATH}")

    if local_generated_at < remote_generated_at:
        raise RuntimeError(
            "local AUTO_GEN product-pack mirror is stale: "
            f"local generatedAt={local_generated_at.isoformat()} < "
            f"{LIVE_BRANCH} generatedAt={remote_generated_at.isoformat()}. "
            "Refresh from origin/product-pack-live or re-run sync-product-pack before generating diffs."
        )