website

import fs from "node:fs";
import path from "node:path";
import { fileURLToPath } from "node:url";

const __dirname = path.dirname(fileURLToPath(import.meta.url));
const CACHE_DIR = path.resolve(__dirname, "..", "..", ".cache");

const cachePath = (key) => path.join(CACHE_DIR, `${key}.json`);

/**
 * Disk cache for the expensive per-commit/per-file git data (diffs,
 * history, blame, syntax highlighting) computed in repoCommits.js/
 * repoFiles.js. Keyed by the repo's current HEAD sha rather than by
 * content hash — cheap to check (one `git rev-parse` per repo) and
 * correct as long as callers only read the cache for a clean working
 * tree (see isDirty() in gitRepos.js): if HEAD hasn't moved and there
 * are no uncommitted changes, none of this data could have changed.
 */
export const readCache = (key, sha) => {
  try {
    const { sha: cachedSha, data } = JSON.parse(fs.readFileSync(cachePath(key), "utf8"));
    return cachedSha === sha ? data : null;
  } catch {
    return null;
  }
};

export const writeCache = (key, sha, data) => {
  try {
    fs.mkdirSync(CACHE_DIR, { recursive: true });
    fs.writeFileSync(cachePath(key), JSON.stringify({ sha, data }));
  } catch {
    // best-effort — a failed cache write shouldn't fail the build
  }
};