Basic functionality is here with a crappy ai generated frontend.

src/spotify.ts

@@ -0,0 +1,82 @@
+import { buildCommand, type Command, type BaseCommand, parseCommand } from "./commandBuilder.ts";
+
+type GetSong = () => string | null;
+export type Song = {
+  name: string;
+  uri: string;
+  artists: string[];
+  album: {
+    name: string;
+    coverUrl: string | undefined;
+  };
+};
+
+export class SpotifyWS {
+  public ws: WebSocket;
+  private queryList: {
+    [x: string]: (value: Song[] | PromiseLike<Song[]>) => void;
+  } = {};
+
+  constructor(ws: WebSocket) {
+    this.ws = ws;
+
+    this.onMessage = this.onMessage.bind(this);
+    this.onClose = this.onClose.bind(this);
+    this.ws.addEventListener("message", this.onMessage);
+    this.ws.addEventListener("close", this.onClose);
+  }
+
+  public search(query: string): Promise<Song[]> {
+    return new Promise<Song[]>((resolve, reject) => {
+      if (this.ws.readyState != this.ws.OPEN) reject("WS Isn't connected.");
+
+      const id = crypto.randomUUID();
+      this.send(buildCommand("search", { query, id }));
+      this.queryList[id] = resolve;
+
+      setTimeout(() => {
+        reject("Timeout.");
+        delete this.queryList[id];
+      }, 3000);
+    });
+  }
+
+  public sendSong(uri?: string) {
+    const song = uri ?? playerManager.getNext()?.uri;
+    if (!song) return;
+
+    this.send(buildCommand("next_song", { song }));
+  }
+
+  private send(data: string) {
+    if (this.ws.readyState != this.ws.OPEN) return;
+    this.ws.send(data);
+  }
+
+  private onClose() {
+    globalThis.spotify = undefined;
+  }
+  private onMessage(msg: MessageEvent<string>) {
+    const text = msg.data;
+    const parsed = parseCommand(text);
+
+    if (parsed === null) return;
+
+    switch (parsed.c) {
+      case "next_song":
+        this.sendSong();
+        break;
+
+      case "search": {
+        if (!parsed.d || !parsed.d.id || !parsed.d.results) break;
+        const cmd = parsed as Command<{id: string, results: Song[]}>
+
+        const { id, results } = cmd.d;
+        if (!(id in this.queryList)) break;
+
+        this.queryList[id](results);
+        break;
+      }
+    }
+  }
+}