1 files changed, 94 insertions, 0 deletions
diff --git a/ext/js/media/audio-system.js b/ext/js/media/audio-system.js
new file mode 100644
index 00000000..cf63511f
--- /dev/null
+++ b/ext/js/media/audio-system.js
@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2019-2021  Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/* global
+ * TextToSpeechAudio
+ */
+
+class AudioSystem {
+    constructor() {
+        this._fallbackAudio = null;
+    }
+
+    prepare() {
+        // speechSynthesis.getVoices() will not be populated unless some API call is made.
+        if (typeof speechSynthesis === 'undefined') { return; }
+
+        const eventListeners = new EventListenerCollection();
+        const onVoicesChanged = () => { eventListeners.removeAllEventListeners(); };
+        eventListeners.addEventListener(speechSynthesis, 'voiceschanged', onVoicesChanged, false);
+    }
+
+    getFallbackAudio() {
+        if (this._fallbackAudio === null) {
+            this._fallbackAudio = new Audio('/data/audio/button.mp3');
+        }
+        return this._fallbackAudio;
+    }
+
+    createAudio(url, source) {
+        return new Promise((resolve, reject) => {
+            const audio = new Audio(url);
+            audio.addEventListener('loadeddata', () => {
+                if (!this._isAudioValid(audio, source)) {
+                    reject(new Error('Could not retrieve audio'));
+                } else {
+                    resolve(audio);
+                }
+            });
+            audio.addEventListener('error', () => reject(audio.error));
+        });
+    }
+
+    createTextToSpeechAudio(text, voiceUri) {
+        const voice = this._getTextToSpeechVoiceFromVoiceUri(voiceUri);
+        if (voice === null) {
+            throw new Error('Invalid text-to-speech voice');
+        }
+        return new TextToSpeechAudio(text, voice);
+    }
+
+    // Private
+
+    _isAudioValid(audio, source) {
+        switch (source) {
+            case 'jpod101':
+            {
+                const duration = audio.duration;
+                return (
+                    duration !== 5.694694 && // Invalid audio (Chrome)
+                    duration !== 5.720718 // Invalid audio (Firefox)
+                );
+            }
+            default:
+                return true;
+        }
+    }
+
+    _getTextToSpeechVoiceFromVoiceUri(voiceUri) {
+        try {
+            for (const voice of speechSynthesis.getVoices()) {
+                if (voice.voiceURI === voiceUri) {
+                    return voice;
+                }
+            }
+        } catch (e) {
+            // NOP
+        }
+        return null;
+    }
+}