/**
 * Static-source regression guards for live-browser.js.
 *
 * `source/skills/impeccable/scripts/live-browser.js` is a self-contained
 * IIFE served directly to user pages by live-server.mjs (no bundle step,
 * no module exports). That makes its internal helpers untestable via
 * normal import — but a few behaviors have failed in real-world live
 * sessions in ways that are easy to express as "this exact code shape
 * MUST NOT come back." This file pins those down.
 *
 * Add a guard whenever a bug we fix has a one-line "anti-pattern" cause
 * that's easy to reintroduce on an unrelated edit.
 */

import { describe, it } from 'node:test';
import assert from 'node:assert/strict';
import fs from 'node:fs';
import path from 'node:path';
import { fileURLToPath } from 'node:url';

const __dirname = path.dirname(fileURLToPath(import.meta.url));
const LIVE_BROWSER = path.resolve(
  __dirname,
  '..',
  'source/skills/impeccable/scripts/live-browser.js',
);
const SOURCE = fs.readFileSync(LIVE_BROWSER, 'utf-8');

describe('live-browser.js regression guards', () => {
  it('resolveCanvasBackground does not fall back to `getComputedStyle(...).backgroundColor || ...`', () => {
    // The browser returns the literal string `"rgba(0, 0, 0, 0)"` for an
    // unset body/html background. That string is non-empty and truthy, so a
    // `||` chain short-circuits to transparent-black, which modern-screenshot
    // hands to its WebGL shader as the canvas color and the screenshot
    // overlay flashes solid black during loading on any page that doesn't
    // explicitly set its own background. Forbid the pattern outright; the
    // correct fallback is a literal `'#ffffff'` (the browser's default
    // canvas color).
    const buggy =
      /getComputedStyle\(document\.(?:body|documentElement)\)\.backgroundColor\s*\|\|/;
    assert.ok(
      !buggy.test(SOURCE),
      'live-browser.js must not chain `getComputedStyle(...).backgroundColor || ...` — that returns transparent-black for default-bg pages and renders the screenshot overlay as solid black during loading. Use a literal fallback (`#ffffff`) instead.',
    );
  });

  it('detectPageTheme honors alpha when reading body / html backgroundColor', () => {
    // Equivalent trap: `rgba(0, 0, 0, 0)` parsed naively as `(0,0,0)` makes
    // a perfectly white default page register as "dark," which flips the
    // chrome to the wrong palette. The fix introduced an alpha guard
    // (function readOpaque) — keep that signature in source.
    assert.match(
      SOURCE,
      /function detectPageTheme\b[\s\S]{0,1500}?function readOpaque\b/,
      'detectPageTheme must keep its readOpaque helper that filters out fully-transparent backgrounds before computing luminance',
    );
  });
});