screenshotBlocksCi.ts

/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

// Compares blocks-ci fixture screenshots from a rendered manifest against the committed markdown.
// Usage: node build/lib/screenshotBlocksCi.ts <manifest-path> <markdown-path> <service-url> [--json]
//
// Exit codes:
//   0 — all screenshots match (or no blocks-ci fixtures)
//   1 — mismatches found
//
// Without --json: prints the full updated markdown to stdout.
// With --json: prints a JSON object with { startLine, endLine, replacement } for a GitHub suggestion.

import * as fs from 'fs';

const HEADER = '<!-- auto-generated by CI — do not edit manually -->';

interface ManifestFixture {
	readonly fixtureId: string;
	readonly imageHash: string;
	readonly labels?: readonly string[];
}

interface Manifest {
	readonly fixtures: readonly ManifestFixture[];
}

function generateMarkdown(fixtures: readonly ManifestFixture[], serviceUrl: string): string {
	const lines: string[] = [HEADER, ''];
	const seen = new Set<string>();
	const sorted = [...fixtures].sort((a, b) => a.fixtureId.localeCompare(b.fixtureId));
	for (const f of sorted) {
		if (f.labels?.includes('blocks-ci') && !seen.has(f.fixtureId)) {
			seen.add(f.fixtureId);
			lines.push(`#### ${f.fixtureId}`);
			lines.push(`![screenshot](${serviceUrl}/images/${f.imageHash})`);
			lines.push('');
		}
	}
	return lines.join('\n');
}

function computeDiff(committedLines: string[], updatedLines: string[]): { startLine: number; endLine: number; replacement: string } {
	let firstDiff = 0;
	while (firstDiff < committedLines.length && firstDiff < updatedLines.length && committedLines[firstDiff] === updatedLines[firstDiff]) {
		firstDiff++;
	}

	let committedEnd = committedLines.length - 1;
	let updatedEnd = updatedLines.length - 1;
	while (committedEnd > firstDiff && updatedEnd > firstDiff && committedLines[committedEnd] === updatedLines[updatedEnd]) {
		committedEnd--;
		updatedEnd--;
	}

	return {
		startLine: firstDiff + 1, // 1-indexed
		endLine: committedEnd + 1, // 1-indexed
		replacement: updatedLines.slice(firstDiff, updatedEnd + 1).join('\n'),
	};
}

function main(): void {
	const args = process.argv.slice(2);
	const jsonMode = args.includes('--json');
	const positional = args.filter(a => a !== '--json');
	const [manifestPath, markdownPath, serviceUrl] = positional;

	if (!manifestPath || !markdownPath || !serviceUrl) {
		console.error('Usage: node build/lib/screenshotBlocksCi.ts <manifest-path> <markdown-path> <service-url> [--json]');
		process.exit(1);
	}

	const manifest: Manifest = JSON.parse(fs.readFileSync(manifestPath, 'utf8'));
	const actual = generateMarkdown(manifest.fixtures, serviceUrl);

	let committed = '';
	if (fs.existsSync(markdownPath)) {
		committed = fs.readFileSync(markdownPath, 'utf8');
	}

	if (actual === committed) {
		process.exit(0);
	}

	console.error('blocks-ci screenshots have changed.');

	if (jsonMode) {
		const diff = computeDiff(committed.split('\n'), actual.split('\n'));
		process.stdout.write(JSON.stringify(diff) + '\n');
	} else {
		process.stdout.write(actual);
	}
	process.exit(1);
}

main();