import workletUrl from "./worklet.ts?worker&url";
import type { AudioMessage } from "./worklet";

/** The browser side of the sound: an AudioContext running the synthesizer
 * worklet, fed the engine's register writes frame by frame. Browsers start
 * audio only from a user gesture, so `unlock` runs from the first press. */
export class AudioOutput {
  private context?: AudioContext;
  private node?: AudioWorkletNode;
  private gain = 1;
  private failed = false;

  /** Create or resume the context; call from a user gesture. */
  unlock() {
    if (this.failed) return;
    try {
      if (!this.context) {
        const Context =
          window.AudioContext ??
          (window as unknown as { webkitAudioContext?: typeof AudioContext }).webkitAudioContext;
        if (!Context || !("audioWorklet" in Context.prototype)) {
          this.failed = true;
          return;
        }
        const context = new Context({ latencyHint: "interactive" });
        this.context = context;
        void context.audioWorklet
          .addModule(workletUrl)
          .then(() => {
            const node = new AudioWorkletNode(context, "crystal-audio", {
              numberOfInputs: 0,
              outputChannelCount: [2],
            });
            node.connect(context.destination);
            this.node = node;
            this.post({ kind: "gain", value: this.gain });
          })
          .catch(() => {
            this.failed = true;
          });
      }
      if (this.context.state !== "running") void this.context.resume().catch(() => {});
    } catch {
      this.failed = true;
    }
  }
  /** Whether sound is playing (unlocked, loaded and running). */
  get running() {
    return !!this.node && this.context?.state === "running";
  }
  /** Frames of register writes, in order. */
  send(frames: number[][]) {
    if (!frames.length || !this.running) return;
    this.post({ kind: "frames", frames });
  }
  setGain(value: number) {
    this.gain = value;
    this.post({ kind: "gain", value });
  }
  /** Pause: silence at once and drop the queued frames. */
  suspend() {
    this.post({ kind: "reset" });
    if (this.context?.state === "running") void this.context.suspend().catch(() => {});
  }
  resume() {
    if (this.context && this.context.state !== "running") void this.context.resume().catch(() => {});
  }
  dispose() {
    this.node?.disconnect();
    void this.context?.close().catch(() => {});
    this.node = undefined;
    this.context = undefined;
  }
  private post(message: AudioMessage) {
    this.node?.port.postMessage(message);
  }
}