path: root/ext/mixed/js/audio.js

/*
 * Copyright (C) 2019-2020  Alex Yatskov <alex@foosoft.net>
 * Author: Alex Yatskov <alex@foosoft.net>
 *
 * 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 apiAudioGetUrl*/

class TextToSpeechAudio {
    constructor(text, voice) {
        this.text = text;
        this.voice = voice;
        this._utterance = null;
        this._volume = 1;
    }

    get currentTime() {
        return 0;
    }
    set currentTime(value) {
        // NOP
    }

    get volume() {
        return this._volume;
    }
    set volume(value) {
        this._volume = value;
        if (this._utterance !== null) {
            this._utterance.volume = value;
        }
    }

    play() {
        try {
            if (this._utterance === null) {
                this._utterance = new SpeechSynthesisUtterance(this.text || '');
                this._utterance.lang = 'ja-JP';
                this._utterance.volume = this._volume;
                this._utterance.voice = this.voice;
            }

            speechSynthesis.cancel();
            speechSynthesis.speak(this._utterance);
        } catch (e) {
            // NOP
        }
    }

    pause() {
        try {
            speechSynthesis.cancel();
        } catch (e) {
            // NOP
        }
    }

    static createFromUri(ttsUri) {
        const m = /^tts:[^#?]*\?([^#]*)/.exec(ttsUri);
        if (m === null) { return null; }

        const searchParameters = new URLSearchParams(m[1]);
        const text = searchParameters.get('text');
        let voice = searchParameters.get('voice');
        if (text === null || voice === null) { return null; }

        voice = audioGetTextToSpeechVoice(voice);
        if (voice === null) { return null; }

        return new TextToSpeechAudio(text, voice);
    }
}

class AudioSystem {
    constructor() {
        this._cache = new Map();
        this._cacheSizeMaximum = 32;

        if (typeof speechSynthesis !== 'undefined') {
            // speechSynthesis.getVoices() will not be populated unless some API call is made.
            speechSynthesis.addEventListener('voiceschanged', this._onVoicesChanged.bind(this));
        }
    }

    async getExpressionAudio(expression, sources, optionsContext, details) {
        const key = `${expression.expression}:${expression.reading}`;
        const cacheValue = this._cache.get(expression);
        if (typeof cacheValue !== 'undefined') {
            const {audio, uri, source} = cacheValue;
            return {audio, uri, source};
        }

        for (const source of sources) {
            const uri = await apiAudioGetUrl(expression, source, optionsContext);
            if (uri === null) { continue; }

            try {
                const audio = await this._createAudio(uri, details);
                this._cacheCheck();
                this._cache.set(key, {audio, uri, source});
                return {audio, uri, source};
            } catch (e) {
                // NOP
            }
        }

        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
    }

    async _createAudio(uri, details) {
        const ttsParameters = this._getTextToSpeechParameters(uri);
        if (ttsParameters !== null) {
            if (typeof details === 'object' && details !== null) {
                if (details.tts === false) {
                    throw new Error('Text-to-speech not permitted');
                }
            }
            return this.createTextToSpeechAudio(ttsParameters);
        }

        return await this._createAudioFromUrl(uri);
    }

    _createAudioFromUrl(url) {
        return new Promise((resolve, reject) => {
            const audio = new Audio(url);
            audio.addEventListener('loadeddata', () => {
                const duration = audio.duration;
                if (duration === 5.694694 || duration === 5.720718) {
                    // Hardcoded values for invalid audio
                    reject(new Error('Could not retrieve audio'));
                } else {
                    resolve(audio);
                }
            });
            audio.addEventListener('error', () => reject(audio.error));
        });
    }

    _getTextToSpeechVoiceFromVoiceUri(voiceUri) {
        try {
            for (const voice of speechSynthesis.getVoices()) {
                if (voice.voiceURI === voiceUri) {
                    return voice;
                }
            }
        } catch (e) {
            // NOP
        }
        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);
        }
    }
}


function audioGetFromUrl(url, willDownload) {
    const tts = TextToSpeechAudio.createFromUri(url);
    if (tts !== null) {
        if (willDownload) {
            throw new Error('AnkiConnect does not support downloading text-to-speech audio.');
        }
        return Promise.resolve(tts);
    }

    return new Promise((resolve, reject) => {
        const audio = new Audio(url);
        audio.addEventListener('loadeddata', () => {
            if (audio.duration === 5.694694 || audio.duration === 5.720718) {
                // Hardcoded values for invalid audio
                reject(new Error('Could not retrieve audio'));
            } else {
                resolve(audio);
            }
        });
        audio.addEventListener('error', () => reject(audio.error));
    });
}

async function audioGetFromSources(expression, sources, optionsContext, willDownload, cache=null) {
    const key = `${expression.expression}:${expression.reading}`;
    if (cache !== null) {
        const cacheValue = cache.get(expression);
        if (typeof cacheValue !== 'undefined') {
            return cacheValue;
        }
    }

    for (let i = 0, ii = sources.length; i < ii; ++i) {
        const source = sources[i];
        const url = await apiAudioGetUrl(expression, source, optionsContext);
        if (url === null) {
            continue;
        }

        try {
            let audio = await audioGetFromUrl(url, willDownload);
            if (willDownload) {
                // AnkiConnect handles downloading URLs into cards
                audio = null;
            }
            const result = {audio, url, source};
            if (cache !== null) {
                cache.set(key, result);
            }
            return result;
        } catch (e) {
            // NOP
        }
    }
    return {audio: null, url: null, source: null};
}

function audioGetTextToSpeechVoice(voiceURI) {
    try {
        for (const voice of speechSynthesis.getVoices()) {
            if (voice.voiceURI === voiceURI) {
                return voice;
            }
        }
    } catch (e) {
        // NOP
    }
    return null;
}

function audioPrepareTextToSpeech(options) {
    if (
        audioPrepareTextToSpeech.state ||
        !options.audio.textToSpeechVoice ||
        !(
            options.audio.sources.includes('text-to-speech') ||
            options.audio.sources.includes('text-to-speech-reading')
        )
    ) {
        // Text-to-speech not in use.
        return;
    }

    // Chrome needs this value called once before it will become populated.
    // The first call will return an empty list.
    audioPrepareTextToSpeech.state = true;
    try {
        speechSynthesis.getVoices();
    } catch (e) {
        // NOP
    }
}
audioPrepareTextToSpeech.state = false;