Addons support

src/Workspace.ts

@@ -1,13 +1,29 @@
+import * as engine from "./index.js";
+import * as stateMachine from "@mixery/state-machine";
 import { LiveNote } from "./midi/Note.js";
+import { Addon } from "./addons/Addon.js";
+import { ExternalAddonLoader } from "./addons/ExternalAddonLoader.js";
 
 export class Workspace {
+    addonRequires = new Map<string, any>();
+    addons: Addon[] = [];
+
     public constructor(
         public readonly audioContext: BaseAudioContext
-    ) {}
+    ) {
+        this.addonRequires.set("@mixery/engine", engine);
+        this.addonRequires.set("@mixery/state-machine", stateMachine);
+    }
 
     private _lastNoteId = 0;
 
     public autoNoteId(note: LiveNote) {
         note.id = this._lastNoteId++;
     }
+
+    async loadAddonFromUrl(url: string) {
+        let addon = await ExternalAddonLoader.loadFromUrl(this, url);
+        this.addons.push(addon);
+        return addon;
+    }
 }

src/addons/Addon.ts

@@ -8,6 +8,11 @@ export interface AddonInfo {
     description?: string;
 }
 
+export interface AddonMetadata extends AddonInfo {
+    id: string;
+    main: string;
+}
+
 export type AddonFactory = (addon: Addon) => any;
 
 export class Addon {

src/addons/ExternalAddonLoader.ts

@@ -0,0 +1,46 @@
+import { Addon, AddonMetadata } from "../addons/Addon.js";
+import { Workspace } from "../Workspace.js";
+
+export class ExternalAddonLoader {
+    metadata: AddonMetadata;
+    addon: Addon;
+
+    constructor(
+        public readonly workspace: Workspace
+    ) {}
+
+    static async loadFromUrl(workspace: Workspace, url: string) {
+        // Security risk: Loading addons from URLs allows scripts to have access to your
+        // data (projects, presets, etc) that is stored inside Mixery.
+
+        if (url.endsWith("/")) url = url.substring(0, url.length - 1);
+        const metadata: AddonMetadata = await (await fetch(`${url}/addon.metadata.json`)).json();
+        const script = await (await fetch(`${url}/${metadata.main}`)).text();
+        const loader = new ExternalAddonLoader(workspace);
+
+        loader.metadata = metadata;
+        loader.createAddonInstance();
+        loader.runScript(script);
+        return loader.addon;
+    }
+
+    require(name: string) {
+        let module = this.workspace.addonRequires.get(name);
+        if (!module) throw new Error(`Can't find module ${name} (Have you registered your module using Workspace#addonRequires.set() yet?).`);
+        return module;
+    }
+
+    createAddonInstance() {
+        this.addon = new Addon(this.metadata.id, this.metadata);
+    }
+
+    runScript(script: string) {
+        let func = new Function("require", "id", "metadata", "addon", script);
+        func(
+            (name: string) => this.require(name),
+            this.metadata.id,
+            this.metadata,
+            this.addon
+        );
+    }
+}

src/test.workspace.ts

@@ -78,4 +78,7 @@ function render() {
     ctx.stroke();
     ctx.closePath();
 }
-window.requestAnimationFrame(render);
+window.requestAnimationFrame(render);
+
+// Expose some methods
+globalThis.loadAddonFromUrl = (url: string) => workspace.loadAddonFromUrl(url);