element-call/src/lotus/lotusMutedSpeech.ts

/*
Copyright 2026 Lotus Guild

SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
Please see LICENSE in the repository root for full details.
*/

import {
  type Observable,
  distinctUntilChanged,
  map,
  scan,
  startWith,
} from "rxjs";

import { type CallViewModel } from "../state/CallViewModel/CallViewModel";
import { type LocalMicSample, observeLocalMicSample$ } from "./lotusMicLevel";

/**
 * [lotus #37] "Talking while muted" detection for the LOCAL participant.
 *
 * While the mic is muted LiveKit keeps the capture alive and merely disables
 * the published MediaStreamTrack, so VAD/`speaking` is false and nothing
 * tells the user they are talking into a muted mic. This taps a CLONE of the
 * published track (the post-processor track when the in-source denoiser is
 * active, so keyboard noise doesn't count), samples RMS at ~10 Hz and emits a
 * debounced boolean. Local-only —
 * the flag rides `io.lotus.call_state` to the host and never reaches other
 * participants.
 */

export const MUTED_SPEECH_RMS = 0.015; // ≈ −36 dBFS; normal speech into a headset is 0.05–0.3
const ON_SAMPLES = 3; // 300 ms of voice before we say "talking"
const OFF_SAMPLES = 8; // 800 ms of quiet before we drop it

/** Pure hysteresis gate over successive RMS samples (unit-tested). */
export class MutedSpeechGate {
  private above = 0;

  private below = 0;

  private on = false;

  public constructor(private readonly threshold = MUTED_SPEECH_RMS) {}

  public push(rms: number): boolean {
    if (rms >= this.threshold) {
      this.above += 1;
      this.below = 0;
      if (!this.on && this.above >= ON_SAMPLES) this.on = true;
    } else {
      this.below += 1;
      this.above = 0;
      if (this.on && this.below >= OFF_SAMPLES) this.on = false;
    }
    return this.on;
  }

  public get value(): boolean {
    return this.on;
  }
}

/**
 * Emits while the local mic is muted and voice is detected on it. Emits
 * `false` whenever the mic is unmuted, unpublished or the connection changes.
 * [lotus #146] Fed by the shared local mic sampler (lotusMicLevel.ts), which
 * also drives the host's mic level meter while unmuted.
 */
export function observeSpeakingWhileMuted$(
  vm: CallViewModel,
): Observable<boolean> {
  return observeLocalMicSample$(vm).pipe(
    scan((gate: MutedSpeechGate | null, sample: LocalMicSample | null) => {
      if (!sample?.muted) return null;
      const g = gate ?? new MutedSpeechGate();
      g.push(sample.rms);
      return g;
    }, null),
    map((gate) => gate?.value ?? false),
    startWith(false),
    distinctUntilChanged(),
  );
}