playground: most of the logic for both frontend and backend is implemented, some bugs remain

frontend/tools/pyodide-worker.ts

@@ -1,27 +1,33 @@
-import {loadPyodide, version} from "pyodide";
+import {loadPyodide, type PyodideInterface} from "pyodide";
 
-let pyodideReadyPromise = loadPyodide({
-    indexURL: `https://cdn.jsdelivr.net/pyodide/v${version}/full/`, // FIXME: Local deployment?
-    packages: ["micropip", "sqlite3"], // Preloaded faster here...
-    stdout: (msg) => self.postMessage({stdout: msg}),
-    stderr: (msg) => self.postMessage({stderr: msg}),
+let myLoadPyodide = (initOpts: Parameters<typeof loadPyodide>[0]) => loadPyodide({
+    ...initOpts,
+    stdout: (msg) => self.postMessage({stdout: msg + "\n"}), // Add newline for better readability
+    stderr: (msg) => self.postMessage({stderr: msg + "\n"}), // Add newline for better readability
     stdin: () => {
         console.warn("Input requested by Python code, but stdin is not supported in this playground.");
         return "";
     },
 });
 
-self.onmessage = async (event) => {
+let pyodideReadyPromise: Promise<PyodideInterface> | null = null;
+
+self.onmessage = async (event: MessageEvent<any>) => {
+    if (!pyodideReadyPromise) { // First message is always the init message
+        // If we haven't loaded Pyodide yet, do so now.
+        // This is a singleton, so we only load it once.
+        pyodideReadyPromise = myLoadPyodide(event.data as Parameters<typeof loadPyodide>[0]);
+        return;
+    }
+    // All other messages are code to run.
+    let code = event.data as string;
     // make sure loading is done
     const pyodide = await pyodideReadyPromise;
-    const {id, code} = event.data;
     // Now load any packages we need, run the code, and send the result back.
     await pyodide.loadPackagesFromImports(code);
     try {
-        // Execute the python code in this context
-        const result = await pyodide.runPythonAsync(code);
-        self.postMessage({result, id});
+        self.postMessage({result: await pyodide.runPythonAsync(code)});
     } catch (error: any) {
-        self.postMessage({error: error.message, id});
+        self.postMessage({error: error.message});
     }
 };