Initial Commit

packages/media/audio/audio-controllers/src/sequencer/sequencer.ts

@@ -0,0 +1,83 @@
+import type { TransportLike, TransportTime } from "@suaveplan/audio-transport";
+import { getControllerOtel } from "../base/otel.js";
+import type { SequencerOptions, StepCallback } from "./sequencer.types.js";
+
+/**
+ * Transport-synced step sequencer. Every step fires through
+ * `Transport.scheduleRepeat`; no `setInterval`/`setTimeout`/`Date.now`
+ * appears anywhere on the timing path.
+ */
+export class Sequencer {
+    private readonly transport: TransportLike;
+    private readonly stepDuration: TransportTime;
+    private steps: boolean[] = [];
+    private readonly stepListeners = new Map<number, Set<StepCallback>>();
+    private repeatId: number | undefined;
+    private cursor = 0;
+    private bpm = 120;
+
+    constructor(options: SequencerOptions) {
+        this.transport = options.transport;
+        this.stepDuration = options.stepDuration ?? "16n";
+    }
+
+    public setTempo(bpm: number): void {
+        this.bpm = bpm;
+        this.transport.bpm.setValueAtTime(bpm, 0);
+    }
+
+    public getTempo(): number {
+        return this.bpm;
+    }
+
+    public setSteps(steps: ReadonlyArray<boolean>): void {
+        this.steps = steps.slice();
+    }
+
+    public setStep(index: number, active: boolean): void {
+        while (this.steps.length <= index) this.steps.push(false);
+        this.steps[index] = active;
+    }
+
+    public getSteps(): ReadonlyArray<boolean> {
+        return this.steps.slice();
+    }
+
+    public start(): void {
+        if (this.repeatId !== undefined) return;
+        this.repeatId = this.transport.scheduleRepeat(
+            (time) => this.tick(time),
+            this.stepDuration
+        );
+    }
+
+    public stop(): void {
+        if (this.repeatId === undefined) return;
+        this.transport.cancel(this.repeatId);
+        this.repeatId = undefined;
+    }
+
+    public reset(): void {
+        this.cursor = 0;
+    }
+
+    public onStep(index: number, callback: StepCallback): () => void {
+        const bucket = this.stepListeners.get(index) ?? new Set<StepCallback>();
+        bucket.add(callback);
+        this.stepListeners.set(index, bucket);
+        return () => bucket.delete(callback);
+    }
+
+    private tick(time: number): void {
+        const otel = getControllerOtel();
+        otel.sequencerSteps.add(1);
+        const idx = this.cursor % Math.max(this.steps.length, 1);
+        if (this.steps[idx]) {
+            const bucket = this.stepListeners.get(idx);
+            if (bucket) {
+                for (const fn of bucket) fn(time);
+            }
+        }
+        this.cursor = (this.cursor + 1) % Math.max(this.steps.length, 1);
+    }
+}