feat: add voice ducking

src/bot/voice-ducking.ts

@@ -0,0 +1,183 @@
+export interface VoiceDuckingSettings {
+  enabled: boolean;
+  volumePercent: number;
+}
+
+export interface VoiceDuckingGainTarget {
+  setDuckingGain(gain: number, rampMs?: number): void;
+}
+
+export interface VoiceDuckingTiming {
+  attackMs: number;
+  holdMs: number;
+  releaseMs: number;
+}
+
+export const DEFAULT_VOICE_DUCKING_TIMING: Readonly<VoiceDuckingTiming> = {
+  attackMs: 50,
+  holdMs: 700,
+  releaseMs: 500,
+};
+
+interface VoiceDuckingControllerOptions {
+  timing?: Partial<VoiceDuckingTiming>;
+  now?: () => number;
+}
+
+function nonNegativeFinite(value: number | undefined, fallback: number): number {
+  return typeof value === "number" && Number.isFinite(value)
+    ? Math.max(0, value)
+    : fallback;
+}
+
+function normalizeSettings(settings: VoiceDuckingSettings): VoiceDuckingSettings {
+  return {
+    enabled: settings.enabled === true,
+    volumePercent:
+      typeof settings.volumePercent === "number" && Number.isFinite(settings.volumePercent)
+        ? Math.max(0, Math.min(100, settings.volumePercent))
+        : 30,
+  };
+}
+
+/**
+ * Converts the stream of incoming TeamSpeak voice packets into a stable
+ * ducking envelope. TeamSpeak's full-client protocol exposes voice packets,
+ * but not an explicit "stopped talking" event, so a speaker remains active
+ * for a short hold period after their most recent packet.
+ *
+ * Only one timeout is live at a time. Repeated ~20 ms voice packets update a
+ * deadline in the map instead of constantly destroying/recreating timers.
+ */
+export class VoiceDuckingController {
+  private settings: VoiceDuckingSettings;
+  private readonly timing: VoiceDuckingTiming;
+  private readonly now: () => number;
+  private readonly activeUntil = new Map<number, number>();
+  private expiryTimer: ReturnType<typeof setTimeout> | null = null;
+  private timerDueAt = Number.POSITIVE_INFINITY;
+  private timerGeneration = 0;
+  private ducking = false;
+
+  constructor(
+    private readonly target: VoiceDuckingGainTarget,
+    initialSettings: VoiceDuckingSettings,
+    options: VoiceDuckingControllerOptions = {},
+  ) {
+    this.settings = normalizeSettings(initialSettings);
+    this.timing = {
+      attackMs: nonNegativeFinite(options.timing?.attackMs, DEFAULT_VOICE_DUCKING_TIMING.attackMs),
+      holdMs: nonNegativeFinite(options.timing?.holdMs, DEFAULT_VOICE_DUCKING_TIMING.holdMs),
+      releaseMs: nonNegativeFinite(options.timing?.releaseMs, DEFAULT_VOICE_DUCKING_TIMING.releaseMs),
+    };
+    this.now = options.now ?? (() => performance.now());
+  }
+
+  handleVoiceActivity(clientId: number): void {
+    if (!this.settings.enabled || !Number.isInteger(clientId) || clientId <= 0) return;
+
+    const now = this.now();
+    this.activeUntil.set(clientId, now + this.timing.holdMs);
+
+    if (!this.ducking) {
+      this.ducking = true;
+      this.target.setDuckingGain(this.settings.volumePercent / 100, this.timing.attackMs);
+    }
+
+    this.scheduleNextSweep(now);
+  }
+
+  removeSpeaker(clientId: number): void {
+    if (!this.activeUntil.delete(clientId)) return;
+    if (this.activeUntil.size === 0) {
+      this.cancelTimer();
+      this.release();
+    }
+  }
+
+  updateSettings(settings: VoiceDuckingSettings): void {
+    const previous = this.settings;
+    this.settings = normalizeSettings(settings);
+
+    if (!this.settings.enabled) {
+      this.activeUntil.clear();
+      this.cancelTimer();
+      this.release();
+      return;
+    }
+
+    if (
+      previous.volumePercent !== this.settings.volumePercent &&
+      this.ducking
+    ) {
+      this.target.setDuckingGain(this.settings.volumePercent / 100, this.timing.attackMs);
+    }
+  }
+
+  /** Clear all activity. Disconnects use an immediate reset; disabling the
+   * feature uses updateSettings(), which returns smoothly over releaseMs. */
+  reset(immediate = true): void {
+    this.activeUntil.clear();
+    this.cancelTimer();
+    this.ducking = false;
+    this.target.setDuckingGain(1, immediate ? 0 : this.timing.releaseMs);
+  }
+
+  isDucking(): boolean {
+    return this.ducking;
+  }
+
+  activeSpeakerCount(): number {
+    return this.activeUntil.size;
+  }
+
+  private scheduleNextSweep(now = this.now()): void {
+    if (this.activeUntil.size === 0) return;
+
+    let nextDueAt = Number.POSITIVE_INFINITY;
+    for (const deadline of this.activeUntil.values()) {
+      if (deadline < nextDueAt) nextDueAt = deadline;
+    }
+
+    // Keeping an earlier timer is intentional. When it fires it will observe
+    // the refreshed deadline and schedule the remaining delay, avoiding timer
+    // churn on every incoming packet.
+    if (this.expiryTimer && this.timerDueAt <= nextDueAt) return;
+
+    this.cancelTimer();
+    const generation = ++this.timerGeneration;
+    this.timerDueAt = nextDueAt;
+    this.expiryTimer = setTimeout(() => {
+      if (generation !== this.timerGeneration) return;
+      this.expiryTimer = null;
+      this.timerDueAt = Number.POSITIVE_INFINITY;
+      this.sweepExpiredSpeakers();
+    }, Math.max(0, nextDueAt - now));
+  }
+
+  private sweepExpiredSpeakers(): void {
+    const now = this.now();
+    for (const [clientId, deadline] of this.activeUntil) {
+      if (deadline <= now) this.activeUntil.delete(clientId);
+    }
+
+    if (this.activeUntil.size > 0) {
+      this.scheduleNextSweep(now);
+    } else {
+      this.release();
+    }
+  }
+
+  private release(): void {
+    if (!this.ducking) return;
+    this.ducking = false;
+    this.target.setDuckingGain(1, this.timing.releaseMs);
+  }
+
+  private cancelTimer(): void {
+    this.timerGeneration++;
+    if (this.expiryTimer) clearTimeout(this.expiryTimer);
+    this.expiryTimer = null;
+    this.timerDueAt = Number.POSITIVE_INFINITY;
+  }
+}