/**
 * Does the page actually run in a browser?
 *
 * Serves dist/ and opens it in headless Chrome (hardware WebGPU if there is
 * any, SwiftShader otherwise), then waits for the simulation to report that it
 * has taken steps and the frame loop to turn. Any console error, page error or
 * failed request fails the run.
 *
 * This checks that the app *works*, not that it looks right — a headless
 * browser has no opinion about whether the wavefronts are in the right place.
 * Run it after `vite build`:  node scripts/smoke.mjs
 */
import { createServer } from 'node:http';
import { readFile } from 'node:fs/promises';
import { extname, join } from 'node:path';
import puppeteer from 'puppeteer-core';

const DIST = new URL('../dist/', import.meta.url).pathname;
const CHROME = process.env.CHROME_PATH ?? '/usr/bin/google-chrome';
const MIME = {
  '.html': 'text/html',
  '.js': 'text/javascript',
  '.css': 'text/css',
  '.json': 'application/json',
};

const server = createServer(async (req, res) => {
  try {
    const path = req.url === '/' ? '/index.html' : req.url.split('?')[0];
    const data = await readFile(join(DIST, path));
    res.writeHead(200, { 'content-type': MIME[extname(path)] ?? 'application/octet-stream' });
    res.end(data);
  } catch {
    res.writeHead(404);
    res.end('not found');
  }
});
await new Promise((r) => server.listen(0, '127.0.0.1', r));
const port = server.address().port;

const flagSets = [
  ['--headless=new', '--no-sandbox', '--enable-unsafe-webgpu', '--enable-features=Vulkan'],
  [
    '--headless=new',
    '--no-sandbox',
    '--enable-unsafe-webgpu',
    '--use-webgpu-adapter=swiftshader',
    '--enable-unsafe-swiftshader',
  ],
];

let ok = false;
let lastFailure = 'never ran';
for (const flags of flagSets) {
  const browser = await puppeteer.launch({
    executablePath: CHROME,
    args: [...flags],
    protocolTimeout: 600_000,
  });
  const problems = [];
  try {
    const page = await browser.newPage();
    page.on('console', (m) => {
      if (m.type() === 'error') problems.push(`console: ${m.text()}`);
    });
    page.on('pageerror', (e) => problems.push(`pageerror: ${e.message}`));
    page.on('requestfailed', (r) => problems.push(`request failed: ${r.url()}`));

    await page.goto(`http://127.0.0.1:${port}/index.html`, { waitUntil: 'load' });

    // The page loads paused; the stats line says so once the loop is turning.
    await page.waitForFunction(
      () => /paused/.test(document.getElementById('stats')?.textContent ?? ''),
      { timeout: 120_000, polling: 250 },
    );
    await page.click('#runpause');

    /** The stats line reports the step count, so waiting on it says both that
     *  the solver ran and that the frame loop is turning. */
    const running = async (label) => {
      await page.waitForFunction(
        () => {
          const m = /step (\d+)/.exec(document.getElementById('stats')?.textContent ?? '');
          return m ? Number(m[1]) > 20 : false;
        },
        { timeout: 180_000, polling: 500 },
      );
      console.log(`  ${label}: ${(await page.$eval('#stats', (n) => n.textContent)).trim()}`);
    };
    await running('start');

    // The timestep slider must reach the solver: halving the CFL fraction
    // halves dt, which the stats line reports.
    const dtNow = async () =>
      Number(/dt = ([0-9.e+-]+)/.exec(await page.$eval('#stats', (n) => n.textContent ?? ''))?.[1]);
    const dtBefore = await dtNow();
    await page.evaluate(() => {
      const slider = document.getElementById('cfl');
      slider.value = '0.25';
      slider.dispatchEvent(new Event('input'));
    });
    await page.waitForFunction(
      (before) => {
        const m = /dt = ([0-9.e+-]+)/.exec(document.getElementById('stats')?.textContent ?? '');
        return m ? Math.abs(Number(m[1]) - before / 2) < before / 20 : false;
      },
      { timeout: 30_000, polling: 250 },
      dtBefore,
    );
    console.log(
      `  timestep: dt ${dtBefore.toExponential(2)} -> ${(await dtNow()).toExponential(2)} at half the CFL`,
    );

    // The microphone must be recording, one sample per timestep. (Both
    // numbers are host-side counters, so this checks the wiring, not the GPU
    // trace — that would need a readback the page only does on Listen.)
    await page.waitForFunction(
      () => /[\d,]+ samples/.test(document.getElementById('recinfo')?.textContent ?? ''),
      { timeout: 60_000, polling: 250 },
    );
    const recorded = Number(
      /([\d,]+) samples/
        .exec(await page.$eval('#recinfo', (n) => n.textContent ?? ''))?.[1]
        .replace(/,/g, ''),
    );
    const stepsSoFar = Number(
      /step (\d+)/.exec(await page.$eval('#stats', (n) => n.textContent ?? ''))?.[1],
    );
    console.log(`  microphone: ${(await page.$eval('#recinfo', (n) => n.textContent ?? '')).trim()}`);
    if (!(recorded > 0) || recorded > stepsSoFar) {
      problems.push(`microphone recorded ${recorded} samples in ${stepsSoFar} steps`);
    }

    // Swapping the scene rebuilds the medium. The aperture screen is slower
    // than the background (the smoothing keeps the grid minimum above the
    // nominal 0.2), so a reported cmin below 1 is the evidence.
    await page.select('#scene', 'aperture');
    await page.waitForFunction(
      () => /c ∈ \[0\./.test(document.getElementById('stats')?.textContent ?? ''),
      { timeout: 60_000, polling: 250 },
    );
    await running('after scene swap');

    const report = await page.evaluate(() => ({
      stats: document.getElementById('stats')?.textContent ?? '',
      err: document.getElementById('err')?.textContent ?? '',
      painted: (() => {
        const canvas = document.getElementById('view');
        return canvas instanceof HTMLCanvasElement && canvas.width > 0;
      })(),
    }));

    console.log(`flags: ${flags.join(' ')}`);
    console.log(report.stats.trim());
    if (report.err) problems.push(`page error box: ${report.err}`);
    if (!report.painted) problems.push('canvas was never sized');
    if (problems.length === 0) {
      ok = true;
    } else {
      lastFailure = problems.join('\n');
    }
  } catch (e) {
    lastFailure = [`${e}`, ...problems].join('\n');
  } finally {
    await browser.close();
  }
  if (ok) break;
}

server.close();
if (!ok) {
  console.error(`smoke: FAILED\n${lastFailure}`);
  process.exit(1);
}
console.log('smoke: the page runs');
process.exit(0);