// Document-start check for an app's page runtime: the built runtime injected the way the app does
// it, as an init script that runs before the parser has created <html>, into static fixtures of the
// site. Every feature flag is switched on, then off, then back to its default; any console error,
// any message with the app's `[label]` prefix or any page error fails the check. Not a live test.
//
//   import { chromium } from 'playwright';
//   import { runtimeStartCheck } from '<waybetter>/dev-tools/runtime-start-check.mjs';
//   const { problems, checked } = await runtimeStartCheck({
//     chromium, runtime: code, global: 'MyApp', label: 'wayBetter for Site', origin: 'https://site.test',
//     queued: 'window.__btPane={redundantNav:true};',       // what native code queues before the runtime exists
//     featureDefaults: { someFlag: true },
//     pages: [{ name: 'home', path: '/home', html: '<!doctype html>…' }],
//     verify: { expression: '({ … })', check: (result, page) => 'a problem' | null },
//   });

/** Runs the check; resolves to `{ problems, checked }`. */
export async function runtimeStartCheck(options) {
  const { chromium, runtime, global, label, origin, pages, featureDefaults = {}, queued = '', verify } = options;
  const browser = await chromium.launch();
  const context = await browser.newContext({ viewport: { width: 1100, height: 800 } });
  if (queued) await context.addInitScript({ content: queued });
  await context.addInitScript({ content: runtime });
  const problems = [];
  let checked = 0;
  try {
    for (const item of pages) {
      const page = await context.newPage();
      page.on('console', message => { if (message.type() === 'error' || message.text().includes(`[${label}]`)) problems.push(`${item.name}: ${message.text().slice(0, 240)}`); });
      page.on('pageerror', error => problems.push(`${item.name}: page error ${String(error).slice(0, 240)}`));
      await page.route(`${origin}/**`, route => route.fulfill({ contentType: 'text/html', body: item.html }));
      await page.goto(`${origin}${item.path}`);
      const result = await page.evaluate(async ({ name, defaults, expression }) => {
        const runtime = window[name];
        if (!runtime) return { runtime: false };
        const all = value => Object.fromEntries(Object.keys(defaults).map(key => [key, value]));
        runtime.features.apply(all(true));
        await new Promise(resolve => setTimeout(resolve, 200));
        runtime.features.apply(all(false));
        await new Promise(resolve => setTimeout(resolve, 100));
        runtime.features.apply(defaults);
        await new Promise(resolve => setTimeout(resolve, 300));
        // The app's own expression over the page (what it expects to be there after the toggles).
        return { runtime: true, details: expression ? (0, eval)(expression) : null };
      }, { name: global, defaults: featureDefaults, expression: verify?.expression ?? '' });
      if (!result.runtime) problems.push(`${item.name}: runtime did not install`);
      else {
        const problem = verify?.check?.(result.details, item);
        if (problem) problems.push(`${item.name}: ${problem}`);
      }
      checked += 1;
      await page.close();
    }
  } finally {
    await browser.close();
  }
  return { problems, checked };
}