#!/usr/bin/env node
// Compare the *rendered* text of a legacy page against its Astro replacement.
//
//   node .agents/scripts/rendered-text-diff.mjs full-guide
//
// Why this exists: scripts/verify.mjs reads the legacy files, so a migrated
// page can drop half its content and still pass the gate. Task 15d shipped
// /full-guide/ missing 86 rendered spans -- the entire verification section,
// the hands-on exercise brief, and both "Clone from Gitea" links -- and every
// check was green.
//
// Static HTML comparison is useless here: the guide's tab panels are injected
// by an island at runtime, so half the legacy page's markup has no static
// counterpart. This walks the live DOM instead and skips anything the browser
// is not painting -- which also drops the hidden Portuguese half of each
// bilingual pair, so the two sides line up.
//
// Requires playwright (devDependency) and two static servers; it starts both.
import { spawn } from 'node:child_process';
import { cpSync, mkdtempSync, rmSync } from 'node:fs';
import { tmpdir } from 'node:os';
import { join } from 'node:path';
import { chromium } from 'playwright';

// `index` is the landing page: it lives at the repository root, not in a
// directory of its own, so it needs a different path on the legacy side.
const route = process.argv[2];
if (!route) {
  console.error('usage: rendered-text-diff.mjs <route>   e.g. full-guide, or index');
  process.exit(2);
}
const legacyPath = route === 'index' ? 'index.html' : `${route}/index.html`;
const astroPath = route === 'index' ? '' : `${route}/`;

// The built site expects to be served under the configured base path.
const staging = mkdtempSync(join(tmpdir(), 'af-rtd-'));
cpSync('dist', join(staging, 'ai-for-dummies'), { recursive: true });

const serve = (dir, port) =>
  spawn('python3', ['-m', 'http.server', String(port), '-d', dir], { stdio: 'ignore' });
const servers = [serve('.', 4197), serve(staging, 4196)];
const stop = () => {
  servers.forEach((s) => s.kill());
  rmSync(staging, { recursive: true, force: true });
};

// Visible text nodes, in document order, whitespace collapsed.
const visibleText = () => {
  const out = [];
  const walk = (node) => {
    for (const child of node.childNodes) {
      if (child.nodeType === Node.TEXT_NODE) {
        const text = child.textContent.replace(/\s+/g, ' ').trim();
        if (text) out.push(text);
        continue;
      }
      if (child.nodeType !== Node.ELEMENT_NODE) continue;
      if (child.tagName === 'SCRIPT' || child.tagName === 'STYLE') continue;
      const style = getComputedStyle(child);
      if (child.hidden || style.display === 'none' || style.visibility === 'hidden') continue;
      walk(child);
    }
  };
  walk(document.body);
  return out;
};

try {
  await new Promise((r) => setTimeout(r, 1500));
  const browser = await chromium.launch();
  const grab = async (url) => {
    const page = await browser.newPage({ viewport: { width: 1400, height: 1000 } });
    await page.goto(url, { waitUntil: 'load' });
    // The islands hydrate and render their initial panel on load; without this
    // every panel's copy reads as missing.
    await page.waitForTimeout(1200);
    const spans = await page.evaluate(visibleText);
    await page.close();
    return spans;
  };

  const legacy = await grab(`http://localhost:4197/${legacyPath}`);
  const astro = await grab(`http://localhost:4196/ai-for-dummies/${astroPath}`);
  await browser.close();

  const rendered = new Set(astro);
  const missing = legacy.filter((span) => !rendered.has(span));

  console.log(
    `legacy ${legacy.length} spans · astro ${astro.length} spans · missing ${missing.length}`,
  );
  for (const span of missing) console.log(`  - ${span}`);
  process.exitCode = missing.length === 0 ? 0 : 1;
} finally {
  stop();
}