promises, link

app/api/download/[jobId]/route.ts

@@ -1,7 +1,6 @@
 import { createReadStream } from "node:fs";
-import { rm } from "node:fs/promises";
 import { Readable } from "node:stream";
-import { takeJob } from "@/lib/jobs";
+import { getJobZip } from "@/lib/jobs";
 
 export const runtime = "nodejs";
 export const dynamic = "force-dynamic";
@@ -11,22 +10,18 @@ export async function GET(
   context: { params: Promise<{ jobId: string }> },
 ): Promise<Response> {
   const { jobId } = await context.params;
-  const job = takeJob(jobId);
+  const job = await getJobZip(jobId);
   if (!job) {
-    return Response.json({ error: "Download expired or not found" }, { status: 404 });
+    return Response.json(
+      { error: "Download expired or not found" },
+      { status: 404 },
+    );
   }
 
-  const file = createReadStream(job.zipPath);
-  file.on("close", () => {
-    void rm(job.dir, { recursive: true, force: true });
-  });
-  file.on("error", () => {
-    void rm(job.dir, { recursive: true, force: true });
-  });
-
-  return new Response(Readable.toWeb(file) as ReadableStream, {
+  return new Response(Readable.toWeb(createReadStream(job.zipPath)) as ReadableStream, {
     headers: {
       "Content-Type": "application/zip",
+      "Content-Length": String(job.size),
       "Content-Disposition": 'attachment; filename="ids.zip"',
       "Cache-Control": "no-store",
     },

app/api/generate/route.ts

@@ -1,12 +1,10 @@
-import { createCanvas, loadImage, GlobalFonts } from "@napi-rs/canvas";
 import { createWriteStream } from "node:fs";
-import { mkdir, mkdtemp, rm, writeFile } from "node:fs/promises";
-import { tmpdir } from "node:os";
+import { writeFile } from "node:fs/promises";
 import path from "node:path";
 import { finished } from "node:stream/promises";
 import { createZipArchive } from "@/lib/create-zip";
-import { drawIdText } from "@/lib/draw-id";
-import { isPresetFont } from "@/lib/fonts";
+import { PRESET_FONTS, isPresetFont } from "@/lib/fonts";
+import { generatePngsInWorkers, type WorkerFont } from "@/lib/generate-pool";
 import {
   CUSTOM_FONT_FAMILY,
   formatUserId,
@@ -16,9 +14,8 @@ import {
   sanitizeFilename,
   toIdDrawStyle,
 } from "@/lib/id-config";
-import { saveJob } from "@/lib/jobs";
+import { createJobDir } from "@/lib/jobs";
 import type { GenerateProgressEvent } from "@/lib/progress";
-import { registerPresetFonts } from "@/lib/register-fonts";
 
 export const runtime = "nodejs";
 export const maxDuration = 300;
@@ -28,6 +25,14 @@ function jsonError(message: string, status = 400): Response {
   return Response.json({ error: message }, { status });
 }
 
+function presetFonts(): WorkerFont[] {
+  const dir = path.join(process.cwd(), "public", "fonts");
+  return PRESET_FONTS.flatMap((font) => [
+    { path: path.join(dir, font.regular), family: font.id },
+    { path: path.join(dir, font.bold), family: font.id },
+  ]);
+}
+
 export async function POST(req: Request): Promise<Response> {
   try {
     const form = await req.formData();
@@ -71,35 +76,28 @@ export async function POST(req: Request): Promise<Response> {
     const encoder = new TextEncoder();
     const stream = new ReadableStream<Uint8Array>({
       async start(controller) {
-        let tmpDir: string | null = null;
         const send = (event: GenerateProgressEvent) => {
           controller.enqueue(encoder.encode(`${JSON.stringify(event)}\n`));
         };
 
         try {
-          tmpDir = await mkdtemp(path.join(tmpdir(), "kk-card-"));
-          const pngDir = path.join(tmpDir, "png");
-          await mkdir(pngDir);
-
-          registerPresetFonts();
-          const style = toIdDrawStyle(config);
+          const job = await createJobDir();
+          const imagePath = `${job.imagePath}.bin`;
+          await writeFile(imagePath, Buffer.from(await imageFile.arrayBuffer()));
 
+          const fonts = presetFonts();
           if (config.useCustomFont && fontFile instanceof File) {
             const ext = fontFile.name.toLowerCase().endsWith(".otf")
               ? ".otf"
               : ".ttf";
-            const fontPath = path.join(tmpDir, `custom${ext}`);
+            const fontPath = path.join(job.dir, `custom${ext}`);
             await writeFile(fontPath, Buffer.from(await fontFile.arrayBuffer()));
-            GlobalFonts.registerFromPath(fontPath, CUSTOM_FONT_FAMILY);
+            fonts.push({ path: fontPath, family: CUSTOM_FONT_FAMILY });
           }
 
-          const image = await loadImage(
-            Buffer.from(await imageFile.arrayBuffer()),
-          );
-          const canvas = createCanvas(image.width, image.height);
-          const ctx = canvas.getContext("2d");
+          const style = toIdDrawStyle(config);
           const usedNames = new Set<string>();
-          const files: { name: string; path: string }[] = [];
+          const files: { name: string; path: string; text: string }[] = [];
 
           for (let i = 0; i < config.count; i += 1) {
             const id = formatUserId(
@@ -113,20 +111,30 @@ export async function POST(req: Request): Promise<Response> {
               name = `${sanitizeFilename(id)}-${i}.png`;
             }
             usedNames.add(name);
-
-            ctx.drawImage(image, 0, 0);
-            drawIdText(ctx, id, image.width, image.height, style);
-            const png = await canvas.encode("png");
-            const filePath = path.join(pngDir, name);
-            await writeFile(filePath, png);
-            files.push({ name, path: filePath });
-            send({ phase: "generate", current: i + 1, total: config.count });
+            files.push({
+              name,
+              path: path.join(job.pngDir, name),
+              text: id,
+            });
           }
 
+          send({ phase: "generate", current: 0, total: files.length });
+          await generatePngsInWorkers({
+            imagePath,
+            fonts,
+            style,
+            tasks: files.map((file) => ({
+              text: file.text,
+              outPath: file.path,
+            })),
+            onProgress: (current, total) => {
+              send({ phase: "generate", current, total });
+            },
+          });
+
           send({ phase: "zip", current: 0, total: files.length });
 
-          const zipPath = path.join(tmpDir, "ids.zip");
-          const output = createWriteStream(zipPath);
+          const output = createWriteStream(job.zipPath);
           const archive = createZipArchive();
           archive.on("error", (error: Error) => {
             output.destroy(error);
@@ -147,15 +155,9 @@ export async function POST(req: Request): Promise<Response> {
           await archive.finalize();
           await finished(output);
           send({ phase: "zip", current: files.length, total: files.length });
-
-          const id = saveJob(tmpDir, zipPath);
-          tmpDir = null;
-          send({ phase: "done", id });
+          send({ phase: "done", id: job.id });
           controller.close();
         } catch (error) {
-          if (tmpDir) {
-            await rm(tmpDir, { recursive: true, force: true }).catch(() => {});
-          }
           const message =
             error instanceof Error ? error.message : "Failed to generate images";
           send({ phase: "error", message });

app/editor.tsx

@@ -111,10 +111,11 @@ export function Editor() {
   const [error, setError] = useState<string | null>(null);
   const [status, setStatus] = useState<string | null>(null);
   const [progress, setProgress] = useState<{
-    phase: "generate" | "zip" | "download";
+    phase: "generate" | "zip";
     current: number;
     total: number;
   } | null>(null);
+  const [downloadHref, setDownloadHref] = useState<string | null>(null);
   const [cursor, setCursor] = useState<"grab" | "grabbing" | "default">(
     "default",
   );
@@ -354,6 +355,7 @@ export function Editor() {
     setBusy(true);
     setError(null);
     setStatus(null);
+    setDownloadHref(null);
     setProgress({ phase: "generate", current: 0, total: config.count });
 
     try {
@@ -390,23 +392,9 @@ export function Editor() {
         }
       });
 
-      setProgress({ phase: "download", current: 1, total: 1 });
-      const zipResponse = await fetch(`/api/download/${jobId}`);
-      if (!zipResponse.ok) {
-        throw new Error("Could not download the zip file");
-      }
-
-      const blob = await zipResponse.blob();
-      const url = URL.createObjectURL(blob);
-      const link = document.createElement("a");
-      link.href = url;
-      link.download = "ids.zip";
-      document.body.appendChild(link);
-      link.click();
-      link.remove();
-      URL.revokeObjectURL(url);
       setProgress(null);
-      setStatus(`Downloaded ids.zip with ${config.count} PNGs`);
+      setDownloadHref(`/api/download/${jobId}`);
+      setStatus(`${config.count} images are ready. Download the zip below.`);
     } catch (err) {
       setProgress(null);
       setStatus(null);
@@ -766,6 +754,15 @@ export function Editor() {
               {status}
             </p>
           ) : null}
+          {downloadHref && !busy ? (
+            <a
+              href={downloadHref}
+              download="ids.zip"
+              className="rounded-xl bg-emerald-500 px-4 py-3 text-center text-sm font-semibold text-white transition hover:bg-emerald-400"
+            >
+              Download ids.zip
+            </a>
+          ) : null}
 
           <button
             type="button"
@@ -785,7 +782,7 @@ export function Editor() {
 
 function progressLabel(
   progress: {
-    phase: "generate" | "zip" | "download";
+    phase: "generate" | "zip";
     current: number;
     total: number;
   } | null,
@@ -795,9 +792,6 @@ function progressLabel(
   if (progress.phase === "zip") {
     return `Zipping ${progress.current} / ${progress.total}`;
   }
-  if (progress.phase === "download") {
-    return "Downloading zip…";
-  }
   return `Generating ${progress.current} / ${progress.total}`;
 }
 
@@ -805,7 +799,7 @@ function ProgressPanel({
   progress,
 }: {
   progress: {
-    phase: "generate" | "zip" | "download";
+    phase: "generate" | "zip";
     current: number;
     total: number;
   };
@@ -814,21 +808,14 @@ function ProgressPanel({
     progress.total > 0
       ? Math.min(100, Math.round((progress.current / progress.total) * 100))
       : 0;
-  const title =
-    progress.phase === "zip"
-      ? "Zipping"
-      : progress.phase === "download"
-        ? "Downloading"
-        : "Generating";
+  const title = progress.phase === "zip" ? "Zipping" : "Generating";
 
   return (
     <div className="rounded-lg border border-indigo-900 bg-indigo-950/50 px-3 py-3 text-sm text-indigo-100">
       <div className="flex items-center justify-between gap-3">
         <span>{title}</span>
         <span className="font-mono text-xs text-indigo-200">
-          {progress.phase === "download"
-            ? "ids.zip"
-            : `${progress.current} / ${progress.total}`}
+          {progress.current} / {progress.total}
         </span>
       </div>
       <div className="mt-2 h-2 overflow-hidden rounded-full bg-zinc-800">

lib/generate-pool.ts

@@ -0,0 +1,81 @@
+import { createRequire } from "node:module";
+import os from "node:os";
+import path from "node:path";
+import type { IdDrawStyle } from "./id-config";
+
+export type WorkerFont = {
+  path: string;
+  family: string;
+};
+
+export type GenerateTask = {
+  text: string;
+  outPath: string;
+};
+
+const nodeRequire = createRequire(path.join(process.cwd(), "package.json"));
+
+function spawnWorker(workerPath: string, workerData: unknown) {
+  const threads = nodeRequire("node:worker_threads") as typeof import("node:worker_threads");
+  return new threads.Worker(workerPath, { workerData });
+}
+
+function workerCount(taskCount: number): number {
+  const cpus =
+    typeof os.availableParallelism === "function"
+      ? os.availableParallelism()
+      : os.cpus().length;
+  return Math.max(1, Math.min(cpus, 8, taskCount));
+}
+
+function splitTasks<T>(items: T[], parts: number): T[][] {
+  const chunks: T[][] = Array.from({ length: parts }, () => []);
+  items.forEach((item, index) => {
+    chunks[index % parts]?.push(item);
+  });
+  return chunks.filter((chunk) => chunk.length > 0);
+}
+
+export async function generatePngsInWorkers(options: {
+  imagePath: string;
+  fonts: WorkerFont[];
+  style: IdDrawStyle;
+  tasks: GenerateTask[];
+  onProgress: (completed: number, total: number) => void;
+}): Promise<void> {
+  const { imagePath, fonts, style, tasks, onProgress } = options;
+  if (tasks.length === 0) return;
+
+  const workerPath = path.join(process.cwd(), "workers", "generate-id.cjs");
+  const chunks = splitTasks(tasks, workerCount(tasks.length));
+  let completed = 0;
+
+  await Promise.all(
+    chunks.map(
+      (chunk) =>
+        new Promise<void>((resolve, reject) => {
+          const worker = spawnWorker(workerPath, {
+            imagePath,
+            fonts,
+            style,
+            tasks: chunk,
+          });
+
+          worker.on("message", (message: { type?: string }) => {
+            if (message?.type !== "progress") return;
+            completed += 1;
+            onProgress(completed, tasks.length);
+          });
+
+          worker.once("error", reject);
+          worker.once("exit", (code) => {
+            if (code === 0) {
+              resolve();
+              return;
+            }
+            reject(new Error(`Image worker stopped with code ${code}`));
+          });
+        }),
+    ),
+  );
+}

lib/jobs.ts

@@ -1,33 +1,78 @@
-import { rm } from "node:fs/promises";
-
-type Job = {
-  dir: string;
-  zipPath: string;
-  createdAt: number;
-};
+import { mkdir, readdir, rm, stat } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import path from "node:path";
 
 const JOB_TTL_MS = 15 * 60 * 1000;
-const jobs = new Map<string, Job>();
+const JOBS_ROOT = path.join(tmpdir(), "kk-card-jobs");
+const JOB_ID_RE =
+  /^[0-9a-f]{8}-[0-9a-f]{4}-[1-8][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;
+
+export function isJobId(id: string): boolean {
+  return JOB_ID_RE.test(id);
+}
+
+export function jobDir(id: string): string {
+  return path.join(JOBS_ROOT, id);
+}
+
+export function jobZipPath(id: string): string {
+  return path.join(jobDir(id), "ids.zip");
+}
+
+export async function sweepExpiredJobs(): Promise<void> {
+  let names: string[] = [];
+  try {
+    names = await readdir(JOBS_ROOT);
+  } catch {
+    return;
+  }
 
-function sweepExpiredJobs(): void {
   const cutoff = Date.now() - JOB_TTL_MS;
-  for (const [id, job] of jobs) {
-    if (job.createdAt > cutoff) continue;
-    jobs.delete(id);
-    void rm(job.dir, { recursive: true, force: true });
+  await Promise.all(
+    names.map(async (name) => {
+      const dir = path.join(JOBS_ROOT, name);
+      try {
+        const info = await stat(dir);
+        if (info.mtimeMs >= cutoff) return;
+        await rm(dir, { recursive: true, force: true });
+      } catch {
+        // ignore missing or locked job folders
+      }
+    }),
+  );
+}
+
+export async function createJobDir(): Promise<{
+  id: string;
+  dir: string;
+  pngDir: string;
+  imagePath: string;
+  zipPath: string;
+}> {
+  await sweepExpiredJobs();
+  const id = crypto.randomUUID();
+  const dir = jobDir(id);
+  const pngDir = path.join(dir, "png");
+  await mkdir(pngDir, { recursive: true });
+  return {
+    id,
+    dir,
+    pngDir,
+    imagePath: path.join(dir, "base"),
+    zipPath: jobZipPath(id),
+  };
+}
+
+export async function getJobZip(
+  id: string,
+): Promise<{ zipPath: string; size: number } | null> {
+  if (!isJobId(id)) return null;
+  const zipPath = jobZipPath(id);
+  try {
+    const info = await stat(zipPath);
+    if (!info.isFile() || info.size === 0) return null;
+    return { zipPath, size: info.size };
+  } catch {
+    return null;
   }
 }
-
-export function saveJob(dir: string, zipPath: string): string {
-  sweepExpiredJobs();
-  const id = crypto.randomUUID();
-  jobs.set(id, { dir, zipPath, createdAt: Date.now() });
-  return id;
-}
-
-export function takeJob(id: string): Job | null {
-  const job = jobs.get(id);
-  if (!job) return null;
-  jobs.delete(id);
-  return job;
-}

workers/generate-id.cjs

@@ -0,0 +1,95 @@
+const { createCanvas, loadImage, GlobalFonts } = require("@napi-rs/canvas");
+const { writeFile } = require("node:fs/promises");
+const { parentPort, workerData } = require("node:worker_threads");
+
+function clamp(value, min, max) {
+  return Math.min(max, Math.max(min, value));
+}
+
+function hexToRgba(hex, opacity) {
+  let value = hex.replace("#", "");
+  if (value.length === 3) {
+    value = value
+      .split("")
+      .map((char) => char + char)
+      .join("");
+  }
+
+  let alpha = clamp(opacity, 0, 1);
+  if (value.length === 8) {
+    alpha *= parseInt(value.slice(6, 8), 16) / 255;
+    value = value.slice(0, 6);
+  }
+
+  const r = parseInt(value.slice(0, 2), 16);
+  const g = parseInt(value.slice(2, 4), 16);
+  const b = parseInt(value.slice(4, 6), 16);
+  return `rgba(${r}, ${g}, ${b}, ${alpha})`;
+}
+
+function buildCanvasFont(style) {
+  const italic = style.italic ? "italic " : "";
+  const weight = style.bold ? "700 " : "400 ";
+  return `${italic}${weight}${style.fontSize}px "${style.fontFamily}"`;
+}
+
+function drawIdText(ctx, text, imageWidth, imageHeight, style) {
+  const x = (style.xPercent / 100) * imageWidth;
+  const y = (style.yPercent / 100) * imageHeight;
+  ctx.font = buildCanvasFont(style);
+  ctx.textAlign = style.align;
+  ctx.textBaseline = "alphabetic";
+  const metrics = ctx.measureText(text);
+  const ascent = metrics.actualBoundingBoxAscent ?? style.fontSize * 0.8;
+  const descent = metrics.actualBoundingBoxDescent ?? style.fontSize * 0.2;
+  const baselineY = y + (ascent - descent) / 2;
+
+  ctx.save();
+  ctx.fillStyle = style.color;
+  if (style.shadowEnabled) {
+    ctx.shadowColor = hexToRgba(style.shadowColor, style.shadowOpacity);
+    ctx.shadowBlur = style.shadowBlur;
+    ctx.shadowOffsetX = style.shadowOffsetX;
+    ctx.shadowOffsetY = style.shadowOffsetY;
+  } else {
+    ctx.shadowColor = "transparent";
+    ctx.shadowBlur = 0;
+    ctx.shadowOffsetX = 0;
+    ctx.shadowOffsetY = 0;
+  }
+
+  if (style.outlineEnabled && style.outlineWidth > 0) {
+    ctx.strokeStyle = hexToRgba(style.outlineColor, style.outlineOpacity);
+    ctx.lineWidth = style.outlineWidth;
+    ctx.lineJoin = "round";
+    ctx.miterLimit = 2;
+    ctx.strokeText(text, x, baselineY);
+    ctx.shadowColor = "transparent";
+  }
+
+  ctx.fillText(text, x, baselineY);
+  ctx.restore();
+}
+
+async function run() {
+  const { imagePath, fonts, style, tasks } = workerData;
+
+  for (const font of fonts) {
+    GlobalFonts.registerFromPath(font.path, font.family);
+  }
+
+  const image = await loadImage(imagePath);
+  const canvas = createCanvas(image.width, image.height);
+  const ctx = canvas.getContext("2d");
+
+  for (const task of tasks) {
+    ctx.drawImage(image, 0, 0);
+    drawIdText(ctx, task.text, image.width, image.height, style);
+    await writeFile(task.outPath, await canvas.encode("png"));
+    parentPort?.postMessage({ type: "progress" });
+  }
+}
+
+run().catch((error) => {
+  throw error;
+});