import fs from 'node:fs';
import path from 'node:path';
import { pathToFileURL } from 'node:url';
import { createRequire } from 'node:module';

const require = createRequire(import.meta.url);
const nodePathEntries = (process.env.NODE_PATH || '')
	.split(path.delimiter)
	.filter(Boolean);
const resolveOptions = nodePathEntries.length > 0 ? { paths: nodePathEntries } : undefined;
const { default: pixelmatch } = await import(pathToFileURL(require.resolve('pixelmatch', resolveOptions)));
const { PNG } = require(require.resolve('pngjs', resolveOptions));

const [expectedPath, actualPath, diffPath = 'docs/ui-baseline/login-diff.png'] = process.argv.slice(2);

if (!expectedPath || !actualPath) {
	console.error('Usage: node tools/compare_ui_baseline.mjs <expected.png> <actual.png> [diff.png]');
	process.exit(2);
}

const expected = PNG.sync.read(fs.readFileSync(expectedPath));
const actual = PNG.sync.read(fs.readFileSync(actualPath));

if (expected.width !== actual.width || expected.height !== actual.height) {
	console.error(JSON.stringify({
		ok: false,
		error: 'Image dimensions differ.',
		expected: { width: expected.width, height: expected.height },
		actual: { width: actual.width, height: actual.height },
	}, null, 2));
	process.exit(1);
}

const diff = new PNG({ width: expected.width, height: expected.height });
const mismatchedPixels = pixelmatch(
	expected.data,
	actual.data,
	diff.data,
	expected.width,
	expected.height,
	{ threshold: 0.1, includeAA: true }
);

fs.mkdirSync(path.dirname(diffPath), { recursive: true });
fs.writeFileSync(diffPath, PNG.sync.write(diff));

const totalPixels = expected.width * expected.height;
const result = {
	ok: mismatchedPixels === 0,
	expected: expectedPath,
	actual: actualPath,
	diff: diffPath,
	width: expected.width,
	height: expected.height,
	mismatchedPixels,
	totalPixels,
	mismatchRatio: Number((mismatchedPixels / totalPixels).toFixed(6)),
};

console.log(JSON.stringify(result, null, 2));
process.exit(result.ok ? 0 : 1);