From dbc7b184581950f0cbf96b1b353c6d5122e86551 Mon Sep 17 00:00:00 2001
From: fallenoak <git@fallenoak.me>
Date: Thu, 28 Dec 2023 16:45:56 -0600
Subject: [PATCH] feat: add SceneWorker (#12)

---
 src/lib/SceneWorker.ts | 80 ++++++++++++++++++++++++++++++++++++++++++
 src/lib/index.ts       |  1 +
 2 files changed, 81 insertions(+)
 create mode 100644 src/lib/SceneWorker.ts

diff --git a/src/lib/SceneWorker.ts b/src/lib/SceneWorker.ts
new file mode 100644
index 0000000..62da20b
--- /dev/null
+++ b/src/lib/SceneWorker.ts
@@ -0,0 +1,80 @@
+const workerMessageHandler = (event: MessageEvent) => {
+  const id: number = event.data.id;
+  const functionName: string = event.data.functionName;
+  const functionArgs: any[] = event.data.functionArgs;
+  const transfer: Transferable[] = [];
+
+  try {
+    const fn = self[functionName];
+    const result = fn(...functionArgs);
+
+    if (ArrayBuffer.isView(result)) {
+      transfer.push(result.buffer);
+    } else if (result instanceof ArrayBuffer) {
+      transfer.push(result);
+    }
+
+    self.postMessage({ id, result, success: true }, { transfer });
+  } catch (error) {
+    self.postMessage({ id, result: error, success: false });
+  }
+};
+
+const contextToInlineUrl = (context: Record<any, any>) => {
+  const initializer = [];
+  for (const [rawKey, rawValue] of Object.entries(context)) {
+    let key = `'${rawKey.toString()}'`;
+
+    let value = rawValue;
+    if (typeof rawValue === 'function') {
+      value = rawValue.toString();
+    } else if (typeof rawValue === 'string' || typeof rawValue === 'object') {
+      value = JSON.stringify(rawValue);
+    }
+
+    initializer.push(`self[${key}] = `, value, ';', '\n\n');
+  }
+
+  initializer.push(`self['onmessage'] = `, workerMessageHandler.toString(), ';', '\n');
+
+  const blob = new Blob(initializer, { type: 'text/javascript' });
+  return URL.createObjectURL(blob);
+};
+
+class SceneWorker {
+  #worker: Worker;
+  #pending = new Map<number, { resolve: (value: any) => void; reject: (reason: any) => void }>();
+  #nextId = 0;
+
+  constructor(name: string, context: Record<any, any>) {
+    this.#worker = new Worker(contextToInlineUrl(context), { name });
+
+    this.#worker.onmessage = (event: MessageEvent) => {
+      const id: number = event.data.id;
+      const pending = this.#pending.get(id);
+
+      if (event.data.success) {
+        pending.resolve(event.data.result);
+      } else {
+        pending.reject(event.data.result);
+      }
+
+      this.#pending.delete(id);
+    };
+  }
+
+  call(name: string, ...args: any[]): Promise<any> {
+    const id = this.#nextId++;
+
+    const promise = new Promise((resolve, reject) => {
+      this.#pending.set(id, { resolve, reject });
+    });
+
+    this.#worker.postMessage({ id, functionName: name, functionArgs: args });
+
+    return promise;
+  }
+}
+
+export default SceneWorker;
+export { SceneWorker };
diff --git a/src/lib/index.ts b/src/lib/index.ts
index 50f2b92..4b0728e 100644
--- a/src/lib/index.ts
+++ b/src/lib/index.ts
@@ -3,3 +3,4 @@ export * from './controls/OrbitControls.js';
 export * from './AssetManager.js';
 export * from './FormatManager.js';
 export * from './TextureManager.js';
+export * from './SceneWorker.js';