#!/usr/bin/env node
const fs = require('fs');
const path = require('path');
const puppeteer = require('puppeteer');
const PNG = require('pngjs').PNG;
const pixelmatch = require('pixelmatch');

async function capture(fileUrl, outPath, width=1280, height=720) {
  const browser = await puppeteer.launch({args: ['--no-sandbox','--disable-setuid-sandbox']});
  const page = await browser.newPage();
  await page.setViewport({ width, height });
  await page.goto(fileUrl, { waitUntil: 'networkidle0' });
  // wait a bit for scripts to run
  await page.waitForTimeout(500);
  await page.screenshot({ path: outPath, fullPage: false });
  await browser.close();
}

function compare(imgAPath, imgBPath, diffOut) {
  const imgA = PNG.sync.read(fs.readFileSync(imgAPath));
  const imgB = PNG.sync.read(fs.readFileSync(imgBPath));
  if (imgA.width !== imgB.width || imgA.height !== imgB.height) {
    throw new Error('Images must have same dimensions');
  }
  const { width, height } = imgA;
  const diff = new PNG({ width, height });
  const mismatched = pixelmatch(imgA.data, imgB.data, diff.data, width, height, { threshold: 0.1 });
  fs.writeFileSync(diffOut, PNG.sync.write(diff));
  return { mismatched, total: width*height, ratio: mismatched / (width*height) };
}

(async () => {
  try {
    const outDir = '/tmp';
    const fileArg = process.argv[2] || `file://${path.resolve(process.cwd(),'docs/prejoin_template.html')}`;
    const outFile = path.join(outDir, 'prejoin_capture_1280x720.png');
    console.log('Capturing', fileArg, '->', outFile);
    await capture(fileArg, outFile, 1280, 720);
    console.log('Saved capture to', outFile);
    // If baseline exists in repo root under baselines/, compare
    const baselineA = path.resolve(process.cwd(), 'baselines/prejoin_regen_1280x720.png');
    const baselineB = path.resolve(process.cwd(), 'baselines/prejoin_browserless_1280x720.png');
    let result = { captured: outFile, compared: false };
    if (fs.existsSync(baselineA)) {
      const diffOut = path.join(outDir, 'prejoin_diff_1280x720.png');
      const metrics = compare(outFile, baselineA, diffOut);
      result.compared = true; result.baseline = baselineA; result.diff = diffOut; result.metrics = metrics;
      console.log('Compared with', baselineA, 'metrics=', metrics);
    } else if (fs.existsSync(baselineB)) {
      const diffOut = path.join(outDir, 'prejoin_diff_1280x720.png');
      const metrics = compare(outFile, baselineB, diffOut);
      result.compared = true; result.baseline = baselineB; result.diff = diffOut; result.metrics = metrics;
      console.log('Compared with', baselineB, 'metrics=', metrics);
    } else {
      console.log('No baseline found (checked baselines/prejoin_regen_1280x720.png and baselines/prejoin_browserless_1280x720.png)');
    }
    fs.writeFileSync(path.join('/tmp','prejoin_capture_report.json'), JSON.stringify(result, null, 2));
    console.log('Report written to /tmp/prejoin_capture_report.json');
  } catch (err) {
    console.error('Failed:', err);
    process.exit(2);
  }
})();