Handle basic state machine of recordings

src/components/views/voice_messages/PlaybackWaveform.tsx

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+/*
+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 {IRecordingUpdate, VoiceRecording} from "../../../voice/VoiceRecording";
+import {replaceableComponent} from "../../../utils/replaceableComponent";
+import {arrayFastResample, arraySeed, arrayTrimFill} from "../../../utils/arrays";
+import {percentageOf} from "../../../utils/numbers";
+import Waveform from "./Waveform";
+import {DOWNSAMPLE_TARGET, IRecordingWaveformProps, IRecordingWaveformState} from "./IRecordingWaveformStateProps";
+
+/**
+ * A waveform which shows the waveform of a previously recorded recording
+ */
+@replaceableComponent("views.voice_messages.LiveRecordingWaveform")
+export default class PlaybackWaveform extends React.PureComponent<IRecordingWaveformProps, IRecordingWaveformState> {
+    public constructor(props) {
+        super(props);
+
+        // Like the live recording waveform
+        const bars = arrayFastResample(this.props.recorder.finalWaveform, DOWNSAMPLE_TARGET);
+        const seed = arraySeed(0, DOWNSAMPLE_TARGET);
+        const heights = arrayTrimFill(bars, DOWNSAMPLE_TARGET, seed).map(b => percentageOf(b, 0, 0.5));
+        this.state = {heights};
+    }
+
+    public render() {
+        return <Waveform relHeights={this.state.heights} />;
+    }
+}