// Synchronous fs method implementations
// Served from caches where possible, sync XHR fallback for uncached content.

export function createFsSync(metadataCache, contentCache, transport) {
  return {
    existsSync(path) {
      return metadataCache.has(path);
    },

    statSync(path) {
      const stat = metadataCache.toStat(path);
      if (!stat) {
        const err = new Error(`ENOENT: no such file or directory, stat '${path}'`);
        err.code = 'ENOENT';
        throw err;
      }
      return stat;
    },

    accessSync(path, mode) {
      if (!metadataCache.has(path)) {
        const err = new Error(`ENOENT: no such file or directory, access '${path}'`);
        err.code = 'ENOENT';
        throw err;
      }
    },

    readFileSync(path, encoding) {
      if (typeof encoding === 'object') encoding = encoding?.encoding;

      // Try content cache first
      const cached = contentCache.get(path);
      if (cached !== null) {
        if (encoding === 'utf8' || encoding === 'utf-8') {
          return typeof cached === 'string' ? cached : new TextDecoder().decode(cached);
        }
        return cached;
      }

      // Fallback: synchronous XHR
      console.warn('[shim:fs] readFileSync cache miss, using sync XHR:', path);
      const data = transport.readFileSync(path, encoding);
      contentCache.set(path, data);
      return data;
    },

    writeFileSync(path, data, encoding) {
      if (typeof encoding === 'object') encoding = encoding?.encoding;

      // Write to cache immediately (sync return)
      contentCache.set(path, data);
      const size = typeof data === 'string' ? data.length : (data.byteLength || 0);
      metadataCache.set(path, {
        type: 'file',
        size,
        mtime: Date.now(),
        ctime: metadataCache.get(path)?.ctime || Date.now(),
      });

      // Fire-and-forget async send to server
      transport.writeFile(path, data, encoding).catch((e) => {
        console.error('[shim:fs] writeFileSync background save failed:', path, e);
      });
    },

    unlinkSync(path) {
      contentCache.delete(path);
      metadataCache.delete(path);

      // Fire-and-forget
      transport.unlink(path).catch((e) => {
        console.error('[shim:fs] unlinkSync background delete failed:', path, e);
      });
    },

    readdirSync(path) {
      const entries = metadataCache.readdir(path);
      return entries.map(e => e.name);
    },
  };
}