import type { CDPSession, Page } from '@playwright/test';
import { createWriteStream, mkdirSync, writeFileSync } from 'node:fs';
import path from 'node:path';

const sessions = new WeakMap<Page, CDPSession>();

async function cdp(page: Page): Promise<CDPSession> {
  let s = sessions.get(page);
  if (!s) {
    s = await page.context().newCDPSession(page);
    sessions.set(page, s);
  }
  return s;
}

/** CPU throttling: rate=1 — без замедления, 4 — в 4 раза медленнее. */
export async function throttle(page: Page, rate: number): Promise<void> {
  await (await cdp(page)).send('Emulation.setCPUThrottlingRate', { rate });
}

export async function startTrace(page: Page): Promise<void> {
  await page.context().browser()!.startTracing(page, {
    categories: ['devtools.timeline', 'disabled-by-default-devtools.timeline', 'v8.execute', 'blink.user_timing'],
    screenshots: false,
  });
}

export async function stopTrace(page: Page, file: string): Promise<void> {
  mkdirSync(path.dirname(file), { recursive: true });
  const buf = await page.context().browser()!.stopTracing();
  writeFileSync(file, buf);
}

export async function gc(page: Page): Promise<void> {
  const s = await cdp(page);
  await s.send('HeapProfiler.enable');
  await s.send('HeapProfiler.collectGarbage');
}

export async function domCounters(page: Page): Promise<{ documents: number; nodes: number; jsEventListeners: number }> {
  return (await (await cdp(page)).send('Memory.getDOMCounters')) as any;
}

/** Размер JS-кучи после GC, байты. */
export async function heapUsed(page: Page): Promise<number> {
  await gc(page);
  const s = await cdp(page);
  await s.send('Runtime.enable');
  const r = (await s.send('Runtime.getHeapUsage')) as { usedSize: number };
  return r.usedSize;
}

export async function heapSnapshot(page: Page, file: string): Promise<void> {
  mkdirSync(path.dirname(file), { recursive: true });
  const s = await cdp(page);
  const out = createWriteStream(file);
  const onChunk = (e: { chunk: string }) => { out.write(e.chunk); };
  s.on('HeapProfiler.addHeapSnapshotChunk', onChunk);
  await s.send('HeapProfiler.enable');
  await s.send('HeapProfiler.takeHeapSnapshot', { reportProgress: false });
  s.off('HeapProfiler.addHeapSnapshotChunk', onChunk);
  await new Promise<void>((res) => out.end(res));
}