Audio system refactor (#858)

* Refactor AudioUriBuilder

* Add downloadAudio function

* Refactor AudioSystem

* Update API usage

* Rename file

* Update scripts

* Add prepare calls

9 files changed, 189 insertions, 208 deletions

diff --git a/ext/bg/background.html b/ext/bg/background.html
index 6750ea69..ba0710e6 100644
--- a/ext/bg/background.html
+++ b/ext/bg/background.html
@@ -22,13 +22,12 @@
         <script src="/mixed/js/environment.js"></script>
         <script src="/mixed/js/japanese.js"></script>
 
-        <script src="/mixed/js/audio-system.js"></script>
         <script src="/mixed/js/cache-map.js"></script>
         <script src="/mixed/js/dictionary-data-util.js"></script>
         <script src="/mixed/js/object-property-accessor.js"></script>
 
         <script src="/bg/js/anki.js"></script>
-        <script src="/bg/js/audio-uri-builder.js"></script>
+        <script src="/bg/js/audio-downloader.js"></script>
         <script src="/bg/js/clipboard-monitor.js"></script>
         <script src="/bg/js/clipboard-reader.js"></script>
         <script src="/bg/js/database.js"></script>
diff --git a/ext/bg/js/audio-uri-builder.js b/ext/bg/js/audio-downloader.js
index 78ea9caa..8dd5d10f 100644
--- a/ext/bg/js/audio-uri-builder.js
+++ b/ext/bg/js/audio-downloader.js
@@ -20,20 +20,54 @@
  * jp
  */
 
-class AudioUriBuilder {
+class AudioDownloader {
     constructor({requestBuilder}) {
         this._requestBuilder = requestBuilder;
-        this._getUrlHandlers = new Map([
-            ['jpod101', this._getUriJpod101.bind(this)],
-            ['jpod101-alternate', this._getUriJpod101Alternate.bind(this)],
-            ['jisho', this._getUriJisho.bind(this)],
-            ['text-to-speech', this._getUriTextToSpeech.bind(this)],
-            ['text-to-speech-reading', this._getUriTextToSpeechReading.bind(this)],
-            ['custom', this._getUriCustom.bind(this)]
+        this._getInfoHandlers = new Map([
+            ['jpod101', this._getInfoJpod101.bind(this)],
+            ['jpod101-alternate', this._getInfoJpod101Alternate.bind(this)],
+            ['jisho', this._getInfoJisho.bind(this)],
+            ['text-to-speech', this._getInfoTextToSpeech.bind(this)],
+            ['text-to-speech-reading', this._getInfoTextToSpeechReading.bind(this)],
+            ['custom', this._getInfoCustom.bind(this)]
         ]);
     }
 
-    normalizeUrl(url, baseUrl, basePath) {
+    async getInfo(source, expression, reading, details) {
+        const handler = this._getInfoHandlers.get(source);
+        if (typeof handler === 'function') {
+            try {
+                return await handler(expression, reading, details);
+            } catch (e) {
+                // NOP
+            }
+        }
+        return null;
+    }
+
+    async downloadAudio(sources, expression, reading, details) {
+        for (const source of sources) {
+            const info = await this.getInfo(source, expression, reading, details);
+            if (info === null) { continue; }
+
+            switch (info.type) {
+                case 'url':
+                    try {
+                        const {details: {url}} = info;
+                        return await this._downloadAudioFromUrl(url);
+                    } catch (e) {
+                        // NOP
+                    }
+                    break;
+            }
+        }
+
+        throw new Error('Could not download audio');
+    }
+
+    // Private
+
+    _normalizeUrl(url, baseUrl, basePath) {
         if (url) {
             if (url[0] === '/') {
                 if (url.length >= 2 && url[1] === '/') {
@@ -51,19 +85,7 @@ class AudioUriBuilder {
         return url;
     }
 
-    async getUri(source, expression, reading, details) {
-        const handler = this._getUrlHandlers.get(source);
-        if (typeof handler === 'function') {
-            try {
-                return await handler(expression, reading, details);
-            } catch (e) {
-                // NOP
-            }
-        }
-        return null;
-    }
-
-    async _getUriJpod101(expression, reading) {
+    async _getInfoJpod101(expression, reading) {
         let kana = reading;
         let kanji = expression;
 
@@ -80,10 +102,11 @@ class AudioUriBuilder {
             params.push(`kana=${encodeURIComponent(kana)}`);
         }
 
-        return `https://assets.languagepod101.com/dictionary/japanese/audiomp3.php?${params.join('&')}`;
+        const url = `https://assets.languagepod101.com/dictionary/japanese/audiomp3.php?${params.join('&')}`;
+        return {type: 'url', details: {url}};
     }
 
-    async _getUriJpod101Alternate(expression, reading) {
+    async _getInfoJpod101Alternate(expression, reading) {
         const fetchUrl = 'https://www.japanesepod101.com/learningcenter/reference/dictionary_post';
         const data = `post=dictionary_reference&match_type=exact&search_query=${encodeURIComponent(expression)}&vulgar=true`;
         const response = await this._requestBuilder.fetchAnonymous(fetchUrl, {
@@ -109,7 +132,7 @@ class AudioUriBuilder {
                 const source = dom.getElementByTagName('source', audio);
                 if (source === null) { continue; }
 
-                const url = dom.getAttribute(source, 'src');
+                let url = dom.getAttribute(source, 'src');
                 if (url === null) { continue; }
 
                 const htmlReadings = dom.getElementsByClassName('dc-vocab_kana');
@@ -117,7 +140,8 @@ class AudioUriBuilder {
 
                 const htmlReading = dom.getTextContent(htmlReadings[0]);
                 if (htmlReading && (!reading || reading === htmlReading)) {
-                    return this.normalizeUrl(url, 'https://www.japanesepod101.com', '/learningcenter/reference/');
+                    url = this._normalizeUrl(url, 'https://www.japanesepod101.com', '/learningcenter/reference/');
+                    return {type: 'url', details: {url}};
                 }
             } catch (e) {
                 // NOP
@@ -127,7 +151,7 @@ class AudioUriBuilder {
         throw new Error('Failed to find audio URL');
     }
 
-    async _getUriJisho(expression, reading) {
+    async _getInfoJisho(expression, reading) {
         const fetchUrl = `https://jisho.org/search/${expression}`;
         const response = await this._requestBuilder.fetchAnonymous(fetchUrl, {
             method: 'GET',
@@ -145,9 +169,10 @@ class AudioUriBuilder {
             if (audio !== null) {
                 const source = dom.getElementByTagName('source', audio);
                 if (source !== null) {
-                    const url = dom.getAttribute(source, 'src');
+                    let url = dom.getAttribute(source, 'src');
                     if (url !== null) {
-                        return this.normalizeUrl(url, 'https://jisho.org', '/search/');
+                        url = this._normalizeUrl(url, 'https://jisho.org', '/search/');
+                        return {type: 'url', details: {url}};
                     }
                 }
             }
@@ -158,25 +183,72 @@ class AudioUriBuilder {
         throw new Error('Failed to find audio URL');
     }
 
-    async _getUriTextToSpeech(expression, reading, {textToSpeechVoice}) {
+    async _getInfoTextToSpeech(expression, reading, {textToSpeechVoice}) {
         if (!textToSpeechVoice) {
             throw new Error('No voice');
         }
-        return `tts:?text=${encodeURIComponent(expression)}&voice=${encodeURIComponent(textToSpeechVoice)}`;
+        return {type: 'tts', details: {text: expression, voice: textToSpeechVoice}};
     }
 
-    async _getUriTextToSpeechReading(expression, reading, {textToSpeechVoice}) {
+    async _getInfoTextToSpeechReading(expression, reading, {textToSpeechVoice}) {
         if (!textToSpeechVoice) {
             throw new Error('No voice');
         }
-        return `tts:?text=${encodeURIComponent(reading || expression)}&voice=${encodeURIComponent(textToSpeechVoice)}`;
+        return {type: 'tts', details: {text: reading || expression, voice: textToSpeechVoice}};
     }
 
-    async _getUriCustom(expression, reading, {customSourceUrl}) {
+    async _getInfoCustom(expression, reading, {customSourceUrl}) {
         if (typeof customSourceUrl !== 'string') {
             throw new Error('No custom URL defined');
         }
         const data = {expression, reading};
-        return customSourceUrl.replace(/\{([^}]*)\}/g, (m0, m1) => (hasOwn(data, m1) ? `${data[m1]}` : m0));
+        const url = customSourceUrl.replace(/\{([^}]*)\}/g, (m0, m1) => (hasOwn(data, m1) ? `${data[m1]}` : m0));
+        return {type: 'url', details: {url}};
+    }
+
+    async _downloadAudioFromUrl(url) {
+        const response = await this._requestBuilder.fetchAnonymous(url, {
+            method: 'GET',
+            mode: 'cors',
+            cache: 'default',
+            credentials: 'omit',
+            redirect: 'follow',
+            referrerPolicy: 'no-referrer'
+        });
+
+        if (!response.ok) {
+            throw new Error(`Invalid response: ${response.status}`);
+        }
+
+        const arrayBuffer = await response.arrayBuffer();
+
+        if (!await this._isAudioBinaryValid(arrayBuffer)) {
+            throw new Error('Could not retrieve audio');
+        }
+
+        return this._arrayBufferToBase64(arrayBuffer);
+    }
+
+    async _isAudioBinaryValid(arrayBuffer) {
+        const digest = await this._arrayBufferDigest(arrayBuffer);
+        switch (digest) {
+            case 'ae6398b5a27bc8c0a771df6c907ade794be15518174773c58c7c7ddd17098906': // jpod101 invalid audio
+                return false;
+            default:
+                return true;
+        }
+    }
+
+    async _arrayBufferDigest(arrayBuffer) {
+        const hash = new Uint8Array(await crypto.subtle.digest('SHA-256', new Uint8Array(arrayBuffer)));
+        let digest = '';
+        for (const byte of hash) {
+            digest += byte.toString(16).padStart(2, '0');
+        }
+        return digest;
+    }
+
+    _arrayBufferToBase64(arrayBuffer) {
+        return btoa(String.fromCharCode(...new Uint8Array(arrayBuffer)));
     }
 }
diff --git a/ext/bg/js/backend.js b/ext/bg/js/backend.js
index 91188fdc..b9d85b84 100644
--- a/ext/bg/js/backend.js
+++ b/ext/bg/js/backend.js
@@ -17,8 +17,7 @@
 
 /* global
  * AnkiConnect
- * AudioSystem
- * AudioUriBuilder
+ * AudioDownloader
  * ClipboardMonitor
  * ClipboardReader
  * DictionaryDatabase
@@ -54,14 +53,9 @@ class Backend {
         this._profileConditionsUtil = new ProfileConditions();
         this._defaultAnkiFieldTemplates = null;
         this._requestBuilder = new RequestBuilder();
-        this._audioUriBuilder = new AudioUriBuilder({
+        this._audioDownloader = new AudioDownloader({
             requestBuilder: this._requestBuilder
         });
-        this._audioSystem = new AudioSystem({
-            audioUriBuilder: this._audioUriBuilder,
-            requestBuilder: this._requestBuilder,
-            useCache: false
-        });
         this._optionsUtil = new OptionsUtil();
 
         this._searchPopupTabId = null;
@@ -91,7 +85,8 @@ class Backend {
             ['injectAnkiNoteMedia',          {async: true,  contentScript: true,  handler: this._onApiInjectAnkiNoteMedia.bind(this)}],
             ['noteView',                     {async: true,  contentScript: true,  handler: this._onApiNoteView.bind(this)}],
             ['commandExec',                  {async: false, contentScript: true,  handler: this._onApiCommandExec.bind(this)}],
-            ['audioGetUri',                  {async: true,  contentScript: true,  handler: this._onApiAudioGetUri.bind(this)}],
+            ['getDefinitionAudioInfo',       {async: true,  contentScript: true,  handler: this._onApiGetDefinitionAudioInfo.bind(this)}],
+            ['downloadDefinitionAudio',      {async: true,  contentScript: true,  handler: this._onApiDownloadDefinitionAudio.bind(this)}],
             ['screenshotGet',                {async: true,  contentScript: true,  handler: this._onApiScreenshotGet.bind(this)}],
             ['sendMessageToFrame',           {async: false, contentScript: true,  handler: this._onApiSendMessageToFrame.bind(this)}],
             ['broadcastTab',                 {async: false, contentScript: true,  handler: this._onApiBroadcastTab.bind(this)}],
@@ -117,7 +112,6 @@ class Backend {
             ['setAllSettings',               {async: true,  contentScript: false, handler: this._onApiSetAllSettings.bind(this)}],
             ['getOrCreateSearchPopup',       {async: true,  contentScript: true,  handler: this._onApiGetOrCreateSearchPopup.bind(this)}],
             ['isTabSearchPopup',             {async: true,  contentScript: true,  handler: this._onApiIsTabSearchPopup.bind(this)}],
-            ['getDefinitionAudio',           {async: true,  contentScript: true,  handler: this._onApiGetDefinitionAudio.bind(this)}],
             ['triggerDatabaseUpdated',       {async: false, contentScript: true,  handler: this._onApiTriggerDatabaseUpdated.bind(this)}]
         ]);
         this._messageHandlersWithProgress = new Map([
@@ -479,8 +473,12 @@ class Backend {
         return this._runCommand(command, params);
     }
 
-    async _onApiAudioGetUri({source, expression, reading, details}) {
-        return await this._audioUriBuilder.getUri(source, expression, reading, details);
+    async _onApiGetDefinitionAudioInfo({source, expression, reading, details}) {
+        return await this._audioDownloader.getInfo(source, expression, reading, details);
+    }
+
+    async _onApiDownloadDefinitionAudio({sources, expression, reading, details}) {
+        return await this._downloadDefinitionAudio(sources, expression, reading, details);
     }
 
     _onApiScreenshotGet({options}, sender) {
@@ -728,10 +726,6 @@ class Backend {
         return (tab !== null);
     }
 
-    async _onApiGetDefinitionAudio({sources, expression, reading, details}) {
-        return this._getDefinitionAudio(sources, expression, reading, details);
-    }
-
     _onApiTriggerDatabaseUpdated({type, cause}) {
         this._triggerDatabaseUpdated(type, cause);
     }
@@ -1511,8 +1505,8 @@ class Backend {
         }
     }
 
-    async _getDefinitionAudio(sources, expression, reading, details) {
-        return await this._audioSystem.getDefinitionAudio(sources, expression, reading, details);
+    async _downloadDefinitionAudio(sources, expression, reading, details) {
+        return await this._audioDownloader.downloadAudio(sources, expression, reading, details);
     }
 
     async _injectAnkNoteMedia(ankiConnect, expression, reading, timestamp, audioDetails, screenshotDetails, clipboardImage) {
@@ -1548,7 +1542,7 @@ class Backend {
             fileName = this._replaceInvalidFileNameCharacters(fileName);
 
             const {sources, customSourceUrl} = details;
-            const {audio: data} = await this._getDefinitionAudio(
+            const data = await this._downloadDefinitionAudio(
                 sources,
                 expression,
                 reading,
diff --git a/ext/bg/js/settings/audio-controller.js b/ext/bg/js/settings/audio-controller.js
index d389acb5..bd7951f7 100644
--- a/ext/bg/js/settings/audio-controller.js
+++ b/ext/bg/js/settings/audio-controller.js
@@ -22,17 +22,16 @@
 class AudioController {
     constructor(settingsController) {
         this._settingsController = settingsController;
-        this._audioSystem = null;
+        this._audioSystem = new AudioSystem({
+            cacheSize: 0
+        });
         this._audioSourceContainer = null;
         this._audioSourceAddButton = null;
         this._audioSourceEntries = [];
     }
 
     async prepare() {
-        this._audioSystem = new AudioSystem({
-            audioUriBuilder: null,
-            useCache: true
-        });
+        this._audioSystem.prepare();
 
         this._audioSourceContainer = document.querySelector('.audio-source-list');
         this._audioSourceAddButton = document.querySelector('.audio-source-add');
diff --git a/ext/bg/search.html b/ext/bg/search.html
index ecc79968..8b787a18 100644
--- a/ext/bg/search.html
+++ b/ext/bg/search.html
@@ -75,6 +75,7 @@
         <script src="/mixed/js/api.js"></script>
         <script src="/mixed/js/japanese.js"></script>
 
+        <script src="/mixed/js/cache-map.js"></script>
         <script src="/mixed/js/document-util.js"></script>
         <script src="/fg/js/dom-text-scanner.js"></script>
         <script src="/fg/js/source.js"></script>
diff --git a/ext/fg/float.html b/ext/fg/float.html
index 2c64a777..2c15f0d2 100644
--- a/ext/fg/float.html
+++ b/ext/fg/float.html
@@ -50,6 +50,7 @@
         <script src="/mixed/js/api.js"></script>
         <script src="/mixed/js/japanese.js"></script>
 
+        <script src="/mixed/js/cache-map.js"></script>
         <script src="/mixed/js/document-util.js"></script>
         <script src="/fg/js/dom-text-scanner.js"></script>
         <script src="/fg/js/source.js"></script>
diff --git a/ext/mixed/js/api.js b/ext/mixed/js/api.js
index 1973ca22..f7711cbd 100644
--- a/ext/mixed/js/api.js
+++ b/ext/mixed/js/api.js
@@ -85,8 +85,12 @@ const api = (() => {
             return this._invoke('noteView', {noteId});
         }
 
-        audioGetUri(source, expression, reading, details) {
-            return this._invoke('audioGetUri', {source, expression, reading, details});
+        getDefinitionAudioInfo(source, expression, reading, details) {
+            return this._invoke('getDefinitionAudioInfo', {source, expression, reading, details});
+        }
+
+        downloadDefinitionAudio(sources, expression, reading, details) {
+            return this._invoke('downloadDefinitionAudio', {sources, expression, reading, details});
         }
 
         commandExec(command, params) {
@@ -189,10 +193,6 @@ const api = (() => {
             return this._invoke('isTabSearchPopup', {tabId});
         }
 
-        getDefinitionAudio(sources, expression, reading, details) {
-            return this._invoke('getDefinitionAudio', {sources, expression, reading, details});
-        }
-
         triggerDatabaseUpdated(type, cause) {
             return this._invoke('triggerDatabaseUpdated', {type, cause});
         }
diff --git a/ext/mixed/js/audio-system.js b/ext/mixed/js/audio-system.js
index a8226820..89302ada 100644
--- a/ext/mixed/js/audio-system.js
+++ b/ext/mixed/js/audio-system.js
@@ -16,101 +16,72 @@
  */
 
 /* global
+ * CacheMap
  * TextToSpeechAudio
  */
 
 class AudioSystem {
-    constructor({audioUriBuilder, requestBuilder=null, useCache}) {
-        this._cache = useCache ? new Map() : null;
-        this._cacheSizeMaximum = 32;
-        this._audioUriBuilder = audioUriBuilder;
-        this._requestBuilder = requestBuilder;
+    constructor({getAudioInfo, cacheSize=32}) {
+        this._cache = new CacheMap(cacheSize);
+        this._getAudioInfo = getAudioInfo;
+    }
 
-        if (typeof speechSynthesis !== 'undefined') {
-            // speechSynthesis.getVoices() will not be populated unless some API call is made.
-            speechSynthesis.addEventListener('voiceschanged', this._onVoicesChanged.bind(this));
-        }
+    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);
     }
 
-    async getDefinitionAudio(sources, expression, reading, details) {
-        const key = `${expression}:${reading}`;
-        const hasCache = (this._cache !== null && !details.disableCache);
+    async createDefinitionAudio(sources, expression, reading, details) {
+        const key = [expression, reading];
 
-        if (hasCache) {
-            const cacheValue = this._cache.get(key);
-            if (typeof cacheValue !== 'undefined') {
-                const {audio, uri, source} = cacheValue;
-                const index = sources.indexOf(source);
-                if (index >= 0) {
-                    return {audio, uri, index};
-                }
+        const cacheValue = this._cache.get(key);
+        if (typeof cacheValue !== 'undefined') {
+            const {audio, source} = cacheValue;
+            const index = sources.indexOf(source);
+            if (index >= 0) {
+                return {audio, index};
             }
         }
 
         for (let i = 0, ii = sources.length; i < ii; ++i) {
             const source = sources[i];
-            const uri = await this._getAudioUri(source, expression, reading, details);
-            if (uri === null) { continue; }
+            const info = await this._getAudioInfo(source, expression, reading, details);
+            if (info === null) { continue; }
 
+            let audio;
             try {
-                const audio = (
-                    details.binary ?
-                    await this._createAudioBinary(uri) :
-                    await this._createAudio(uri)
-                );
-                if (hasCache) {
-                    this._cacheCheck();
-                    this._cache.set(key, {audio, uri, source});
+                switch (info.type) {
+                    case 'url':
+                        {
+                            const {details: {url}} = info;
+                            audio = await this.createAudio(url);
+                        }
+                        break;
+                    case 'tts':
+                        {
+                            const {details: {text, voice}} = info;
+                            audio = this.createTextToSpeechAudio(text, voice);
+                        }
+                        break;
+                    default:
+                        throw new Error(`Unsupported type: ${info.type}`);
                 }
-                return {audio, uri, index: i};
             } catch (e) {
-                // NOP
+                continue;
             }
-        }
-
-        throw new Error('Could not create audio');
-    }
-
-    createTextToSpeechAudio(text, voiceUri) {
-        const voice = this._getTextToSpeechVoiceFromVoiceUri(voiceUri);
-        if (voice === null) {
-            throw new Error('Invalid text-to-speech voice');
-        }
-        return new TextToSpeechAudio(text, voice);
-    }
-
-    _onVoicesChanged() {
-        // NOP
-    }
-
-    _getAudioUri(source, expression, reading, details) {
-        return (
-            this._audioUriBuilder !== null ?
-            this._audioUriBuilder.getUri(source, expression, reading, details) :
-            null
-        );
-    }
-
-    async _createAudio(uri) {
-        const ttsParameters = this._getTextToSpeechParameters(uri);
-        if (ttsParameters !== null) {
-            const {text, voiceUri} = ttsParameters;
-            return this.createTextToSpeechAudio(text, voiceUri);
-        }
-
-        return await this._createAudioFromUrl(uri);
-    }
 
-    async _createAudioBinary(uri) {
-        const ttsParameters = this._getTextToSpeechParameters(uri);
-        if (ttsParameters !== null) {
-            throw new Error('Cannot create audio from text-to-speech');
+            this._cache.set(key, {audio, source});
+            return {audio, index: i};
         }
 
-        return await this._createAudioBinaryFromUrl(uri);
+        throw new Error('Could not create audio');
     }
 
-    _createAudioFromUrl(url) {
+    createAudio(url) {
         return new Promise((resolve, reject) => {
             const audio = new Audio(url);
             audio.addEventListener('loadeddata', () => {
@@ -124,27 +95,15 @@ class AudioSystem {
         });
     }
 
-    async _createAudioBinaryFromUrl(url) {
-        const response = await this._requestBuilder.fetchAnonymous(url, {
-            method: 'GET',
-            mode: 'cors',
-            cache: 'default',
-            credentials: 'omit',
-            redirect: 'follow',
-            referrerPolicy: 'no-referrer'
-        });
-        const arrayBuffer = await response.arrayBuffer();
-
-        if (!await this._isAudioBinaryValid(arrayBuffer)) {
-            throw new Error('Could not retrieve audio');
+    createTextToSpeechAudio(text, voiceUri) {
+        const voice = this._getTextToSpeechVoiceFromVoiceUri(voiceUri);
+        if (voice === null) {
+            throw new Error('Invalid text-to-speech voice');
         }
-
-        return this._arrayBufferToBase64(arrayBuffer);
+        return new TextToSpeechAudio(text, voice);
     }
 
-    _arrayBufferToBase64(arrayBuffer) {
-        return btoa(String.fromCharCode(...new Uint8Array(arrayBuffer)));
-    }
+    // Private
 
     _isAudioValid(audio) {
         const duration = audio.duration;
@@ -154,16 +113,6 @@ class AudioSystem {
         );
     }
 
-    async _isAudioBinaryValid(arrayBuffer) {
-        const digest = await AudioSystem.arrayBufferDigest(arrayBuffer);
-        switch (digest) {
-            case 'ae6398b5a27bc8c0a771df6c907ade794be15518174773c58c7c7ddd17098906': // jpod101 invalid audio
-                return false;
-            default:
-                return true;
-        }
-    }
-
     _getTextToSpeechVoiceFromVoiceUri(voiceUri) {
         try {
             for (const voice of speechSynthesis.getVoices()) {
@@ -176,38 +125,4 @@ class AudioSystem {
         }
         return null;
     }
-
-    _getTextToSpeechParameters(uri) {
-        const m = /^tts:[^#?]*\?([^#]*)/.exec(uri);
-        if (m === null) { return null; }
-
-        const searchParameters = new URLSearchParams(m[1]);
-        const text = searchParameters.get('text');
-        const voiceUri = searchParameters.get('voice');
-        return (text !== null && voiceUri !== null ? {text, voiceUri} : null);
-    }
-
-    _cacheCheck() {
-        const removeCount = this._cache.size - this._cacheSizeMaximum;
-        if (removeCount <= 0) { return; }
-
-        const removeKeys = [];
-        for (const key of this._cache.keys()) {
-            removeKeys.push(key);
-            if (removeKeys.length >= removeCount) { break; }
-        }
-
-        for (const key of removeKeys) {
-            this._cache.delete(key);
-        }
-    }
-
-    static async arrayBufferDigest(arrayBuffer) {
-        const hash = new Uint8Array(await crypto.subtle.digest('SHA-256', new Uint8Array(arrayBuffer)));
-        let digest = '';
-        for (const byte of hash) {
-            digest += byte.toString(16).padStart(2, '0');
-        }
-        return digest;
-    }
 }
diff --git a/ext/mixed/js/display.js b/ext/mixed/js/display.js
index a62e0212..689fa7e4 100644
--- a/ext/mixed/js/display.js
+++ b/ext/mixed/js/display.js
@@ -43,12 +43,7 @@ class Display extends EventDispatcher {
         this._audioPlaying = null;
         this._audioFallback = null;
         this._audioSystem = new AudioSystem({
-            audioUriBuilder: {
-                getUri: async (source, expression, reading, details) => {
-                    return await api.audioGetUri(source, expression, reading, details);
-                }
-            },
-            useCache: true
+            getAudioInfo: this._getAudioInfo.bind(this)
         });
         this._styleNode = null;
         this._eventListeners = new EventListenerCollection();
@@ -165,6 +160,7 @@ class Display extends EventDispatcher {
     }
 
     async prepare() {
+        this._audioSystem.prepare();
         this._updateMode();
         this._setInteractive(true);
         await this._displayGenerator.prepare();
@@ -1096,7 +1092,7 @@ class Display extends EventDispatcher {
             try {
                 const {sources, textToSpeechVoice, customSourceUrl} = this._options.audio;
                 let index;
-                ({audio, index} = await this._audioSystem.getDefinitionAudio(sources, expression, reading, {textToSpeechVoice, customSourceUrl}));
+                ({audio, index} = await this._audioSystem.createDefinitionAudio(sources, expression, reading, {textToSpeechVoice, customSourceUrl}));
                 info = `From source ${1 + index}: ${sources[index]}`;
             } catch (e) {
                 if (this._audioFallback === null) {
@@ -1419,4 +1415,8 @@ class Display extends EventDispatcher {
             modeOptions
         });
     }
+
+    async _getAudioInfo(source, expression, reading, details) {
+        return await api.getDefinitionAudioInfo(source, expression, reading, details);
+    }
 }