Function updateSettings

cli/src/persistence.ts:90–153

(
  updater: (current: Settings) => Settings | Promise<Settings>
)

 * @returns The updated settings
 */
export async function updateSettings(
  updater: (current: Settings) => Settings | Promise<Settings>
): Promise<Settings> {
  // Timing constants
  const LOCK_RETRY_INTERVAL_MS = 100;  // How long to wait between lock attempts
  const MAX_LOCK_ATTEMPTS = 50;        // Maximum number of attempts (5 seconds total)
  const STALE_LOCK_TIMEOUT_MS = 10000; // Consider lock stale after 10 seconds

  if (!existsSync(configuration.happyHomeDir)) {
    await mkdir(configuration.happyHomeDir, { recursive: true });
  }

  const lockFile = configuration.settingsFile + '.lock';
  const tmpFile = configuration.settingsFile + '.tmp';
  let fileHandle;
  let attempts = 0;

  // Acquire exclusive lock with retries
  while (attempts < MAX_LOCK_ATTEMPTS) {
    try {
      // 'wx' = create exclusively, fail if exists (cross-platform compatible)
      fileHandle = await open(lockFile, 'wx');
      break;
    } catch (err: any) {
      if (err.code === 'EEXIST') {
        // Lock file exists, wait and retry
        attempts++;
        await new Promise(resolve => setTimeout(resolve, LOCK_RETRY_INTERVAL_MS));

        // Check for stale lock
        try {
          const stats = await stat(lockFile);
          if (Date.now() - stats.mtimeMs > STALE_LOCK_TIMEOUT_MS) {
            await unlink(lockFile).catch(() => { });
          }
        } catch { }
      } else {
        throw err;
      }
    }
  }

  if (!fileHandle) {
    throw new Error(`Failed to acquire settings lock after ${MAX_LOCK_ATTEMPTS * LOCK_RETRY_INTERVAL_MS / 1000} seconds`);
  }

  try {
    // Read current settings with defaults
    const current = await readSettings() || { ...defaultSettings };

    // Apply update
    const updated = await updater(current);

    // Write atomically using rename
    await writeFile(tmpFile, JSON.stringify(updated, null, 2));
    await rename(tmpFile, configuration.settingsFile); // Atomic on POSIX

    return updated;