import { ensureApiGatewayReady, invalidateApiGatewayReady } from '@/lib/api';

const GATEWAY_RETRY_STATUS = new Set([502, 503, 504]);
const MEDIA_FETCH_MAX_ATTEMPTS = 8;
const MEDIA_SLOW_LOAD_WARN_MS = 8_000;

function sleep(ms: number): Promise<void> {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

function warnSlowMediaLoad(label: string, startedAt: number, error: unknown) {
  if (Date.now() - startedAt < MEDIA_SLOW_LOAD_WARN_MS) return;
  const detail = error instanceof Error ? error.message : 'неизвестная ошибка';
  console.warn(`[media] ${label}: не удалось загрузить за ${Math.round((Date.now() - startedAt) / 1000)} с (${detail})`);
}

export async function fetchMediaBlobWithRetry(
  accessUrl: string,
  token: string,
  options?: { mimeType?: string; label?: string }
): Promise<Blob> {
  const startedAt = Date.now();
  const label = options?.label ?? 'изображение';
  let lastError: unknown;

  for (let attempt = 0; attempt < MEDIA_FETCH_MAX_ATTEMPTS; attempt += 1) {
    try {
      await ensureApiGatewayReady();
      const response = await fetch(accessUrl, {
        headers: { Authorization: `Bearer ${token}` },
        cache: 'no-store'
      });

      if (GATEWAY_RETRY_STATUS.has(response.status) && attempt + 1 < MEDIA_FETCH_MAX_ATTEMPTS) {
        invalidateApiGatewayReady();
        await sleep(350 * (attempt + 1));
        continue;
      }

      if (!response.ok) {
        throw new Error(`HTTP ${response.status}`);
      }

      const raw = await response.blob();
      const mimeType = options?.mimeType;
      if (mimeType && (!raw.type || raw.type === 'application/octet-stream')) {
        return new Blob([await raw.arrayBuffer()], { type: mimeType });
      }
      return raw;
    } catch (error) {
      lastError = error;
      if (attempt + 1 < MEDIA_FETCH_MAX_ATTEMPTS) {
        await sleep(350 * (attempt + 1));
      }
    }
  }

  warnSlowMediaLoad(label, startedAt, lastError);
  throw lastError instanceof Error ? lastError : new Error('Не удалось загрузить файл');
}