// Store API quota seen by a command, passed to `storebound serve` (the desktop's read scheduler) as one marked stderr
// line per change: App Store Connect's X-Rate-Limit header ("user-hour-lim:3600;user-hour-rem:3412;") and 429 /
// RESOURCE_EXHAUSTED answers of the Google APIs. Outside serve (STOREBOUND_MACHINE unset) nothing is printed.

/** Prefix of the quota line on stderr; runner.ts takes it out of the output. */
export const QUOTA_MARK = '\u001estorebound-quota ';

export interface QuotaInfo {
  store: 'apple' | 'play';
  /** Requests per hour of this key (App Store Connect). */
  limit?: number;
  /** Requests left in the current hour. */
  remaining?: number;
  /** The store answered 429 / RESOURCE_EXHAUSTED at least once in this run. */
  throttled?: boolean;
}

/** "user-hour-lim:3600;user-hour-rem:3412;" -> { limit: 3600, remaining: 3412 }; null when it is not there. */
export function parseAscRateLimit(header: string | null | undefined): { limit: number; remaining: number } | null {
  if (!header) return null;
  const lim = /user-hour-lim:(\d+)/i.exec(header), rem = /user-hour-rem:(\d+)/i.exec(header);
  return lim && rem ? { limit: Number(lim[1]), remaining: Number(rem[1]) } : null;
}

let last = '';
function emit(q: QuotaInfo): void {
  if (process.env.STOREBOUND_MACHINE !== '1') return;
  const line = JSON.stringify(q);
  if (line === last) return;
  last = line;
  process.stderr.write(QUOTA_MARK + line + '\n');
}

/** After every App Store Connect answer. */
export function noteAsc(r: { status: number; headers: { get(n: string): string | null } }): void {
  const rl = parseAscRateLimit(r.headers.get('x-rate-limit'));
  if (rl) emit({ store: 'apple', ...rl, ...(r.status === 429 ? { throttled: true } : {}) });
  else if (r.status === 429) emit({ store: 'apple', throttled: true });
}

/** After every Google answer (Play Developer API, Reporting API). */
export function noteGoogle(status: number): void {
  if (status === 429) emit({ store: 'play', throttled: true });
}

/** Folds the marked lines of one run into one value (the latest counts; throttled if any line said so). */
export function mergeQuota(a: QuotaInfo | undefined, b: QuotaInfo): QuotaInfo {
  if (!a || a.store !== b.store) return b;
  const remaining = b.remaining ?? a.remaining, limit = b.limit ?? a.limit;
  return { store: b.store, ...(limit === undefined ? {} : { limit }), ...(remaining === undefined ? {} : { remaining }), ...(a.throttled || b.throttled ? { throttled: true } : {}) };
}