Add sound effect for call joined / left (#2794)

* Add renderer for call joined / left

* lint

* Add new sounds

* Updates sounds in renderer

* lint

* move import

* pad sounds with silence

* lint

* tidy

* Drop autoplay since we now subscribe correctly.

* Comitting test files I am going to be going to lunch so will tidy up in a little while.

* finish up tests

* Add support for multiple channels per sound.

* lint

src/room/CallEventAudioRenderer.tsx

@@ -0,0 +1,117 @@
+/*
+Copyright 2024 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only
+Please see LICENSE in the repository root for full details.
+*/
+
+import { ReactNode, useEffect, useRef } from "react";
+import { filter } from "rxjs";
+
+import {
+  soundEffectVolumeSetting as effectSoundVolumeSetting,
+  useSetting,
+} from "../settings/settings";
+import { CallViewModel } from "../state/CallViewModel";
+import enterCallSoundMp3 from "../sound/join_call.mp3";
+import enterCallSoundOgg from "../sound/join_call.ogg";
+import leftCallSoundMp3 from "../sound/left_call.mp3";
+import leftCallSoundOgg from "../sound/left_call.ogg";
+
+// Do not play any sounds if the participant count has exceeded this
+// number.
+export const MAX_PARTICIPANT_COUNT_FOR_SOUND = 8;
+export const CONCURRENT_AUDIO_CHANNELS = 2;
+
+export function CallEventAudioRenderer({
+  vm,
+}: {
+  vm: CallViewModel;
+}): ReactNode {
+  const [effectSoundVolume] = useSetting(effectSoundVolumeSetting);
+  const callEntered = useRef<(HTMLAudioElement | null)[]>([]);
+  const callLeft = useRef<(HTMLAudioElement | null)[]>([]);
+
+  useEffect(() => {
+    if (effectSoundVolume === 0) {
+      return;
+    }
+    const joinSub = vm.memberChanges
+      .pipe(
+        filter(
+          ({ joined, ids }) =>
+            ids.length <= MAX_PARTICIPANT_COUNT_FOR_SOUND && joined.length > 0,
+        ),
+      )
+      .subscribe(({ joined }) => {
+        const availablePlayer = callEntered.current.find((v) => v?.paused);
+        void availablePlayer?.play();
+      });
+
+    const leftSub = vm.memberChanges
+      .pipe(
+        filter(
+          ({ ids, left }) =>
+            ids.length <= MAX_PARTICIPANT_COUNT_FOR_SOUND && left.length > 0,
+        ),
+      )
+      .subscribe(() => {
+        const availablePlayer = callLeft.current.find((v) => v?.paused);
+        void availablePlayer?.play();
+      });
+
+    return (): void => {
+      joinSub.unsubscribe();
+      leftSub.unsubscribe();
+    };
+  }, [effectSoundVolume, callEntered, callLeft, vm]);
+
+  // Set volume.
+  useEffect(() => {
+    callEntered.current.forEach((a) => {
+      if (a) {
+        a.volume = effectSoundVolume;
+      }
+    });
+    callLeft.current.forEach((a) => {
+      if (a) {
+        a.volume = effectSoundVolume;
+      }
+    });
+  }, [callEntered, callLeft, effectSoundVolume]);
+
+  // Do not render any audio elements if playback is disabled. Will save
+  // audio file fetches.
+  if (effectSoundVolume === 0) {
+    return null;
+  }
+
+  return (
+    // Will play as soon as it's mounted, which is what we want as this will
+    // play when the call is entered.
+    <>
+      {Array.from({ length: CONCURRENT_AUDIO_CHANNELS }).map((_, index) => (
+        <audio
+          key={index}
+          ref={(r) => (callEntered.current[index] = r)}
+          preload="auto"
+          hidden
+        >
+          <source src={enterCallSoundOgg} type="audio/ogg; codecs=vorbis" />
+          <source src={enterCallSoundMp3} type="audio/mpeg" />
+        </audio>
+      ))}
+      {Array.from({ length: CONCURRENT_AUDIO_CHANNELS }).map((_, index) => (
+        <audio
+          key={index}
+          ref={(r) => (callLeft.current[index] = r)}
+          preload="auto"
+          hidden
+        >
+          <source src={leftCallSoundOgg} type="audio/ogg; codecs=vorbis" />
+          <source src={leftCallSoundMp3} type="audio/mpeg" />
+        </audio>
+      ))}
+    </>
+  );
+}