Move playback to its own set of classes

This all started with a bug where the clock wouldn't update appropriately, and ended with a whole refactoring to support later playback in the timeline.

Playback and recording instances are now independent, and this applies to the <Playback* /> components as well. Instead of those playback components taking a recording, they take a playback instance which has all the information the components need.

The clock was incredibly difficult to do because of the audio context's time tracking and the source's inability to say where it is at in the buffer/in time. This means we have to track when we started playing the clip so we can capture the audio context's current time, which may be a few seconds by the first time the user hits play. We also track stops so we know when to reset that flag.

Waveform calculations have also been moved into the base component, deduplicating the math a bit.

src/components/views/voice_messages/PlaybackClock.tsx

@@ -0,0 +1,71 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import React from "react";
+import {replaceableComponent} from "../../../utils/replaceableComponent";
+import Clock from "./Clock";
+import {Playback, PlaybackState} from "../../../voice/Playback";
+import {UPDATE_EVENT} from "../../../stores/AsyncStore";
+
+interface IProps {
+    playback: Playback;
+}
+
+interface IState {
+    seconds: number;
+    durationSeconds: number;
+    playbackPhase: PlaybackState;
+}
+
+/**
+ * A clock for a playback of a recording.
+ */
+@replaceableComponent("views.voice_messages.PlaybackClock")
+export default class PlaybackClock extends React.PureComponent<IProps, IState> {
+    public constructor(props) {
+        super(props);
+
+        this.state = {
+            seconds: this.props.playback.clockInfo.timeSeconds,
+            // we track the duration on state because we won't really know what the clip duration
+            // is until the first time update, and as a PureComponent we are trying to dedupe state
+            // updates as much as possible. This is just the easiest way to avoid a forceUpdate() or
+            // member property to track "did we get a duration".
+            durationSeconds: this.props.playback.clockInfo.durationSeconds,
+            playbackPhase: PlaybackState.Stopped, // assume not started, so full clock
+        };
+        this.props.playback.on(UPDATE_EVENT, this.onPlaybackUpdate);
+        this.props.playback.clockInfo.liveData.onUpdate(this.onTimeUpdate);
+    }
+
+    private onPlaybackUpdate = (ev: PlaybackState) => {
+        // Convert Decoding -> Stopped because we don't care about the distinction here
+        if (ev === PlaybackState.Decoding) ev = PlaybackState.Stopped;
+        this.setState({playbackPhase: ev});
+    };
+
+    private onTimeUpdate = (time: number[]) => {
+        this.setState({seconds: time[0], durationSeconds: time[1]});
+    };
+
+    public render() {
+        let seconds = this.state.seconds;
+        if (this.state.playbackPhase === PlaybackState.Stopped) {
+            seconds = this.state.durationSeconds;
+        }
+        return <Clock seconds={seconds} />;
+    }
+}