perf: offload SWF→Nitro conversion to a worker-thread pool

The synchronous convertSwfToNitro / extractIconFromSwf calls (pure CPU,
no DB/network) now run in a small worker pool so the main Node event
loop stays free during imports — the dominant import-time CPU spike is
moved off the request thread. The pool degrades gracefully to a
synchronous fallback if workers can't be created, and is skipped in the
test environment.

src/lib/services/furni-import.test.ts

@@ -24,10 +24,20 @@ vi.mock("@/lib/services/import/core/download", () => ({
 	validateSwfBytes: vi.fn(),
 }));
 
-vi.mock("@/lib/services/swf-to-nitro", () => ({
-	convertSwfToNitro: vi.fn(),
-	extractIconFromSwf: vi.fn(),
-}));
+vi.mock("@/lib/services/swf-to-nitro", () => {
+	const convertSwfToNitro = vi.fn();
+	const extractIconFromSwf = vi.fn();
+	return {
+		convertSwfToNitro,
+		extractIconFromSwf,
+		convertSwfToNitroAsync: vi.fn(async (buffer: Buffer, classname: string) =>
+			convertSwfToNitro(buffer, classname),
+		),
+		extractIconFromSwfAsync: vi.fn(async (buffer: Buffer, classname: string) =>
+			extractIconFromSwf(buffer, classname),
+		),
+	};
+});
 
 import {
 	autoPriceFurni,

src/lib/services/furni-import.ts

@@ -34,8 +34,8 @@ import {
 } from "@/lib/services/import/core/download";
 import {
 	type ConversionResult,
-	convertSwfToNitro,
-	extractIconFromSwf,
+	convertSwfToNitroAsync,
+	extractIconFromSwfAsync,
 	parseNitroBundle,
 } from "@/lib/services/swf-to-nitro";
 import type { ImportSingleResult } from "@/types/furni";
@@ -766,7 +766,7 @@ export async function importSingleFurni(params: {
 	if (!iconOk && (swfOk || existsSync(/*turbopackIgnore: true*/ swfPath))) {
 		try {
 			const swfBuf = await fs.readFile(/*turbopackIgnore: true*/ swfPath);
-			const iconPng = extractIconFromSwf(swfBuf, baseClassname);
+			const iconPng = await extractIconFromSwfAsync(swfBuf, baseClassname);
 			if (iconPng) {
 				await fs.writeFile(/*turbopackIgnore: true*/ iconPath, iconPng);
 				iconOk = true;
@@ -795,7 +795,10 @@ export async function importSingleFurni(params: {
 		try {
 			if (existsSync(/*turbopackIgnore: true*/ swfPath)) {
 				const swfBuffer = await fs.readFile(/*turbopackIgnore: true*/ swfPath);
-				conversionResult = convertSwfToNitro(swfBuffer, baseClassname);
+				conversionResult = await convertSwfToNitroAsync(
+					swfBuffer,
+					baseClassname,
+				);
 				await fs.writeFile(
 					/*turbopackIgnore: true*/ nitroPath,
 					conversionResult.bundle,

src/lib/services/import-live.test.ts

@@ -43,8 +43,8 @@ vi.mock("@/lib/services/import/core/download", async () => {
 	};
 });
 
-vi.mock("@/lib/services/swf-to-nitro", () => ({
-	convertSwfToNitro: vi.fn(() => ({
+vi.mock("@/lib/services/swf-to-nitro", () => {
+	const convertSwfToNitro = vi.fn((_buffer: Buffer, _classname: string) => ({
 		bundle: Buffer.alloc(256, 0x42),
 		classname: "n/a",
 		dimensions: { x: 1, y: 1, z: 1 },
@@ -61,10 +61,23 @@ vi.mock("@/lib/services/swf-to-nitro", () => ({
 			defaultdir: 0,
 			partcolors: { color: [] },
 		},
-	})),
-	extractIconFromSwf: vi.fn(() => Buffer.from("fake-icon")),
-	parseNitroBundle: vi.fn(() => ({ json: null })),
 	}));
+	const extractIconFromSwf = vi.fn((_buffer: Buffer, _classname: string) =>
+		Buffer.from("fake-icon"),
+	);
+	const parseNitroBundle = vi.fn(() => ({ json: null }));
+	return {
+		convertSwfToNitro,
+		extractIconFromSwf,
+		parseNitroBundle,
+		convertSwfToNitroAsync: vi.fn(async (buffer: Buffer, classname: string) =>
+			convertSwfToNitro(buffer, classname),
+		),
+		extractIconFromSwfAsync: vi.fn(async (buffer: Buffer, classname: string) =>
+			extractIconFromSwf(buffer, classname),
+		),
+	};
+});
 
 vi.mock("@/lib/services/habbo-furnidata-cache", () => ({
 	lookupOfficialHabboFurni: vi.fn(async () => null),

src/lib/services/swf/conversion-worker.ts

@@ -0,0 +1,55 @@
+import { parentPort } from "node:worker_threads";
+import { convertSwfToNitro, extractIconFromSwf } from "./index";
+
+export interface ConvertRequest {
+	id: number;
+	type: "convert";
+	buffer: Buffer;
+	classname: string;
+}
+
+export interface IconRequest {
+	id: number;
+	type: "icon";
+	buffer: Buffer;
+	classname: string;
+}
+
+export type WorkerRequest = ConvertRequest | IconRequest;
+
+export type WorkerResponse =
+	| {
+			id: number;
+			ok: true;
+			result?: import("./index").ConversionResult;
+			icon?: Buffer | null;
+	  }
+	| { id: number; ok: false; error: string };
+
+if (parentPort) {
+	parentPort.on("message", (msg: WorkerRequest) => {
+		try {
+			if (msg.type === "convert") {
+				const result = convertSwfToNitro(msg.buffer, msg.classname);
+				parentPort!.postMessage({
+					id: msg.id,
+					ok: true,
+					result,
+				} satisfies WorkerResponse);
+			} else {
+				const icon = extractIconFromSwf(msg.buffer, msg.classname);
+				parentPort!.postMessage({
+					id: msg.id,
+					ok: true,
+					icon: icon ?? null,
+				} satisfies WorkerResponse);
+			}
+		} catch (err) {
+			parentPort!.postMessage({
+				id: msg.id,
+				ok: false,
+				error: (err as Error).message,
+			} satisfies WorkerResponse);
+		}
+	});
+}

src/lib/services/swf/index.ts

@@ -50,6 +50,11 @@ export type {
 	ConversionResult,
 	FurniMetadata,
 } from "@/types/furni";
+// Worker-pool wrappers — run the CPU-heavy conversion off the main thread.
+export {
+	convertSwfToNitroAsync,
+	extractIconFromSwfAsync,
+} from "./conversion-pool";
 // Re-export public API from submodules
 export { createNitroBundle, parseNitroBundle } from "./nitro-builder";
 export { computeDefaultDir, extractPartColors } from "./xml-processor";