implement new SoundPlayer

- Add GreenPlayer as SoundPlayer replacement
- Standalone playback separate from an AudioPlayer
- Each GreenPlayer has their own VolumeEffect for fading out
- play() while already isPlaying fades out the last copy
- stop() fades the sound out
- stopImmediate() hard stops the sound

src/GreenPlayer.js

@@ -0,0 +1,166 @@
+const {EventEmitter} = require('events');
+
+const VolumeEffect = require('./effects/VolumeEffect');
+
+class SoundPlayer extends EventEmitter {
+    constructor (audioEngine, {id, buffer}) {
+        super();
+
+        this.id = id;
+
+        this.audioEngine = audioEngine;
+        this.buffer = buffer;
+
+        this.outputNode = null;
+        this.target = null;
+
+        this.initialized = false;
+        this.isPlaying = false;
+        this.playbackRate = 1;
+
+        this.onEnd = this.onEnd.bind(this);
+    }
+
+    onEnd () {
+        this.emit('stop');
+    }
+
+    initialize () {
+        this.outputNode = this.audioEngine.audioContext.createBufferSource();
+        this.outputNode.playbackRate.value = this.playbackRate;
+        this.outputNode.buffer = this.buffer;
+
+        this.outputNode.addEventListener('end', this.onEnd);
+
+        this.volumeEffect = new VolumeEffect(this.audioEngine, this, null);
+
+        this.initialized = true;
+
+        if (this.target !== null) {
+            this.connect(this.target);
+            this.setPlaybackRate(this.playbackRate);
+        }
+    }
+
+    connect (target) {
+        if (target === this.volumeEffect) {
+            this.outputNode.disconnect();
+            this.outputNode.connect(this.volumeEffect.getInputNode());
+            return;
+        }
+
+        this.target = target;
+
+        if (!this.initialized) {
+            return;
+        }
+
+        this.volumeEffect.connect(target);
+
+        return this;
+    }
+
+    dispose () {
+        if (!this.initialized) {
+            return;
+        }
+
+        this.stopImmediately();
+
+        this.volumeEffect.dispose();
+
+        this.outputNode.disconnect();
+        this.outputNode = null;
+
+        this.target = null;
+
+        this.initialized = false;
+    }
+
+    take () {
+        if (this.outputNode) {
+            this.outputNode.removeEventListener('end', this.onEnd);
+        }
+
+        const taken = new SoundPlayer(this.audioEngine, this);
+        taken.outputNode = this.outputNode;
+        if (this.volumeEffect !== null) {
+            taken.volumeEffect.set(this.volumeEffect.value);
+        }
+        if (this.target !== null) {
+            taken.connect(this.target);
+        }
+        taken.initialized = this.initialized;
+        taken.isPlaying = this.isPlaying;
+        taken.playbackRate = this.playbackRate;
+
+        if (this.isPlaying) {
+            this.emit('stop');
+            taken.emit('play');
+        }
+
+        this.outputNode = null;
+        if (this.volumeEffect !== null) {
+            this.volumeEffect.dispose();
+        }
+        this.volumeEffect = null;
+        this.target = null;
+        this.initialized = false;
+        this.isPlaying = false;
+    }
+
+    play () {
+        if (this.isPlaying) {
+            // Spawn a Player with the current buffer source, and play for a
+            // short period until its volume is 0 and release it to be
+            // eventually garbage collected.
+            this.take().stop();
+        }
+
+        if (!this.initialized) {
+            this.initialize();
+        }
+
+        this.volumeEffect.set(this.volumeEffect.DEFAULT_VALUE);
+        this.outputNode.start();
+
+        this.isPlaying = true;
+
+        this.emit('play');
+    }
+
+    stop () {
+        if (!this.isPlaying) {
+            return;
+        }
+
+        this.volumeEffect.set(0);
+        this.outputNode.stop(this.audioEngine.audioEngineoContext.currentTime + this.audioEngine.DECAY_TIME);
+
+        this.isPlaying = false;
+
+        this.emit('stop');
+    }
+
+    stopImmediately () {
+        if (!this.isPlaying) {
+            return;
+        }
+
+        this.outputNode.stop();
+
+        this.isPlaying = false;
+
+        this.emit('stop');
+    }
+
+    setPlaybackRate (value) {
+        this.playbackRate = value;
+
+        if (this.initialized) {
+            this.outputNode.playbackRate.value = value;
+        }
+    }
+}
+
+module.exports = SoundPlayer;