/**
 * Network throttle simulation via CDP.
 *
 * Simulates different network conditions during crawl to test how the app
 * behaves under slow connections. Useful for detecting loading states, error
 * handling, and performance degradation on poor networks.
 *
 * Conditions mirror Chrome DevTools presets:
 * - slow3g: ~500kbps download, high latency
 * - fast3g: ~1.6Mbps download, medium latency
 * - 4g: ~9Mbps download, low latency
 * - offline: no connectivity
 * - none: no throttle (default)
 */

export type NetworkConditionPreset = 'none' | 'slow3g' | 'fast3g' | '4g' | 'offline';

interface NetworkCondition {
  offline: boolean;
  downloadThroughput: number; // bytes/s
  uploadThroughput: number;   // bytes/s
  latency: number;            // ms
}

const PRESETS: Record<NetworkConditionPreset, NetworkCondition> = {
  none:    { offline: false, downloadThroughput: -1, uploadThroughput: -1, latency: 0 },
  slow3g:  { offline: false, downloadThroughput: 500 * 1024 / 8, uploadThroughput: 500 * 1024 / 8, latency: 2_000 },
  fast3g:  { offline: false, downloadThroughput: 1.6 * 1024 * 1024 / 8, uploadThroughput: 750 * 1024 / 8, latency: 562.5 },
  '4g':    { offline: false, downloadThroughput: 9 * 1024 * 1024 / 8, uploadThroughput: 2.67 * 1024 * 1024 / 8, latency: 85 },
  offline: { offline: true, downloadThroughput: 0, uploadThroughput: 0, latency: 0 },
};

export async function applyNetworkThrottle(
  cdpSession: any,
  preset: NetworkConditionPreset,
): Promise<void> {
  if (!cdpSession?.send) return;
  const condition = PRESETS[preset];
  try {
    await cdpSession.send('Network.enable');
    await cdpSession.send('Network.emulateNetworkConditions', condition);
  } catch { /* non-fatal — CDP may not be available */ }
}

export async function clearNetworkThrottle(cdpSession: any): Promise<void> {
  await applyNetworkThrottle(cdpSession, 'none');
}

export interface ThrottledCrawlOpts {
  /** Network preset to apply during this URL's crawl */
  preset: NetworkConditionPreset;
  /** Restore to 'none' after navigation (default: true) */
  restoreAfter?: boolean;
}

/** Apply throttle, run fn, restore. Returns fn's result. */
export async function withNetworkThrottle<T>(
  cdpSession: any,
  preset: NetworkConditionPreset,
  fn: () => Promise<T>,
  restoreAfter = true,
): Promise<T> {
  await applyNetworkThrottle(cdpSession, preset);
  try {
    return await fn();
  } finally {
    if (restoreAfter) await clearNetworkThrottle(cdpSession).catch(() => {});
  }
}