Function variants

design/src/variants.ts:140–214

(options: VariantsOptions)

 * Generate N variants with staggered parallel execution.
 */
export async function variants(options: VariantsOptions): Promise<void> {
  const apiKey = requireApiKey();
  const baseBrief = options.briefFile
    ? parseBrief(options.briefFile, true)
    : parseBrief(options.brief!, false);

  const quality = options.quality || "high";

  fs.mkdirSync(options.outputDir, { recursive: true });

  // If viewports specified, generate responsive variants instead of style variants
  if (options.viewports) {
    await generateResponsiveVariants(apiKey, baseBrief, options.outputDir, options.viewports, quality);
    return;
  }

  const count = Math.min(options.count, 7); // Cap at 7 style variations
  const size = options.size || "1536x1024";

  console.error(`Generating ${count} variants...`);
  const startTime = Date.now();

  // Staggered parallel: start each call 1.5s apart
  const promises: Promise<{ path: string; success: boolean; error?: string }>[] = [];

  for (let i = 0; i < count; i++) {
    const variation = STYLE_VARIATIONS[i] || "";
    const prompt = variation
      ? `${baseBrief}\n\nStyle direction: ${variation}`
      : baseBrief;

    const outputPath = path.join(options.outputDir, `variant-${String.fromCharCode(65 + i)}.png`);

    // Stagger: wait 1.5s between launches
    const delay = i * 1500;
    promises.push(
      new Promise(resolve => setTimeout(resolve, delay))
        .then(() => {
          console.error(`  Starting variant ${String.fromCharCode(65 + i)}...`);
          return generateVariant(apiKey, prompt, outputPath, size, quality);
        })
    );
  }

  const results = await Promise.allSettled(promises);
  const elapsed = ((Date.now() - startTime) / 1000).toFixed(1);

  const succeeded: string[] = [];
  const failed: string[] = [];

  for (const result of results) {
    if (result.status === "fulfilled" && result.value.success) {
      const size = fs.statSync(result.value.path).size;
      console.error(`  ✓ ${path.basename(result.value.path)} (${(size / 1024).toFixed(0)}KB)`);
      succeeded.push(result.value.path);
    } else {
      const error = result.status === "fulfilled" ? result.value.error : (result.reason as Error).message;
      const filePath = result.status === "fulfilled" ? result.value.path : "unknown";