"""Disk cache for macro expansion results — keyed by content hash."""

from __future__ import annotations

import hashlib
import json
from pathlib import Path

CACHE_DIR = Path("data/cache/expansions")


class ExpansionCache:
    def __init__(self, cache_dir: Path | None = None):
        self.cache_dir = cache_dir or CACHE_DIR
        self.cache_dir.mkdir(parents=True, exist_ok=True)

    def _key(self, library: str, macro_name: str, call_form: str) -> str:
        content = f"{library}:{macro_name}:{call_form}"
        return hashlib.sha256(content.encode()).hexdigest()[:16]

    def get(self, library: str, macro_name: str, call_form: str) -> dict | None:
        key = self._key(library, macro_name, call_form)
        path = self.cache_dir / f"{key}.json"
        if path.exists():
            try:
                return json.loads(path.read_text())
            except json.JSONDecodeError:
                return None
        return None

    def put(self, library: str, macro_name: str, call_form: str, result: dict) -> None:
        key = self._key(library, macro_name, call_form)
        path = self.cache_dir / f"{key}.json"
        path.write_text(json.dumps(result))

    def invalidate_library(self, library: str) -> None:
        prefix = hashlib.sha256(f"{library}:".encode()).hexdigest()[:8]
        for p in self.cache_dir.glob(f"{prefix}*.json"):
            p.unlink(missing_ok=True)