import hashlib
import json
from pathlib import Path
from typing import Any
import os
import time

# TTL for cache entries in seconds (24 hours)
CACHE_TTL = 24 * 60 * 60


CACHE_DIR = Path(__file__).resolve().parents[1] / 'cache'
CACHE_DIR.mkdir(parents=True, exist_ok=True)


def _key_to_filename(key: str) -> Path:
    h = hashlib.sha256(key.encode('utf-8')).hexdigest()
    return CACHE_DIR / f'{h}.json'


def read_cache(key: str) -> Any:
    # avoid returning cached values during pytest runs to keep tests deterministic
    if os.environ.get('PYTEST_CURRENT_TEST'):
        return None
    path = _key_to_filename(key)
    if not path.exists():
        return None
    try:
        with path.open('r', encoding='utf-8') as f:
            payload = json.load(f)
        # payload expected to be {'created_at': <ts>, 'data': <actual>}
        created = payload.get('created_at')
        if created is None:
            return payload.get('data', None)
        # expire after TTL
        if (time.time() - created) > CACHE_TTL:
            try:
                path.unlink()
            except Exception:
                pass
            return None
        return payload.get('data', None)
    except Exception:
        return None


def write_cache(key: str, data: Any) -> None:
    # avoid writing cache during pytest runs to prevent test cross-talk
    if os.environ.get('PYTEST_CURRENT_TEST'):
        return
    path = _key_to_filename(key)
    tmp = path.with_suffix('.tmp')
    try:
        payload = {'created_at': time.time(), 'data': data}
        with tmp.open('w', encoding='utf-8') as f:
            json.dump(payload, f)
        tmp.replace(path)
    except Exception:
        if tmp.exists():
            tmp.unlink()