path: root/ext/js/background/offscreen-proxy.js

/*
 * Copyright (C) 2023-2024  Yomitan Authors
 * Copyright (C) 2016-2022  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/>.
 */

import {ExtensionError} from '../core/extension-error.js';
import {isObjectNotArray} from '../core/object-utilities.js';
import {base64ToArrayBuffer} from '../data/array-buffer-util.js';

/**
 * This class is responsible for creating and communicating with an offscreen document.
 * This offscreen document is used to solve two issues:
 *
 * - Provide clipboard access for the `ClipboardReader` class in the context of a MV3 extension.
 *   The background service workers doesn't have access a webpage to read the clipboard from,
 *   so it must be done in the offscreen page.
 *
 * - Provide a longer lifetime for the dictionary database. The background service worker can be
 *   terminated by the web browser, which means that when it restarts, it has to go through its
 *   initialization process again. This initialization process can take a non-trivial amount of
 *   time, which is primarily caused by the startup of the IndexedDB database, especially when a
 *   large amount of dictionary data is installed.
 *
 *   The offscreen document stays alive longer, potentially forever, which may be an artifact of
 *   the clipboard access it requests in the `reasons` parameter. Therefore, this initialization
 *   process should only take place once, or at the very least, less frequently than the service
 *   worker.
 *
 *   The long lifetime of the offscreen document is not guaranteed by the spec, which could
 *   result in this code functioning poorly in the future if a web browser vendor changes the
 *   APIs or the implementation substantially, and this is even referenced on the Chrome
 *   developer website.
 * @see https://developer.chrome.com/blog/Offscreen-Documents-in-Manifest-v3
 * @see https://developer.chrome.com/docs/extensions/reference/api/offscreen
 */
export class OffscreenProxy {
    /**
     * @param {import('../extension/web-extension.js').WebExtension} webExtension
     */
    constructor(webExtension) {
        /** @type {import('../extension/web-extension.js').WebExtension} */
        this._webExtension = webExtension;
        /** @type {?Promise<void>} */
        this._creatingOffscreen = null;
    }

    /**
     * @see https://developer.chrome.com/docs/extensions/reference/offscreen/
     */
    async prepare() {
        if (await this._hasOffscreenDocument()) {
            return;
        }
        if (this._creatingOffscreen) {
            await this._creatingOffscreen;
            return;
        }

        this._creatingOffscreen = chrome.offscreen.createDocument({
            url: 'offscreen.html',
            reasons: [
                /** @type {chrome.offscreen.Reason} */ ('CLIPBOARD')
            ],
            justification: 'Access to the clipboard'
        });
        await this._creatingOffscreen;
        this._creatingOffscreen = null;
    }

    /**
     * @returns {Promise<boolean>}
     */
    async _hasOffscreenDocument() {
        const offscreenUrl = chrome.runtime.getURL('offscreen.html');
        if (!chrome.runtime.getContexts) { // Chrome version below 116
            // Clients: https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerGlobalScope/clients
            // @ts-expect-error - Types not set up for service workers yet
            const matchedClients = await clients.matchAll();
            // @ts-expect-error - Types not set up for service workers yet
            return await matchedClients.some((client) => client.url === offscreenUrl);
        }

        const contexts = await chrome.runtime.getContexts({
            contextTypes: [
                /** @type {chrome.runtime.ContextType} */ ('OFFSCREEN_DOCUMENT')
            ],
            documentUrls: [offscreenUrl]
        });
        return contexts.length > 0;
    }

    /**
     * @template {import('offscreen').ApiNames} TMessageType
     * @param {import('offscreen').ApiMessage<TMessageType>} message
     * @returns {Promise<import('offscreen').ApiReturn<TMessageType>>}
     */
    async sendMessagePromise(message) {
        const response = await this._webExtension.sendMessagePromise(message);
        return this._getMessageResponseResult(/** @type {import('core').Response<import('offscreen').ApiReturn<TMessageType>>} */ (response));
    }

    /**
     * @template [TReturn=unknown]
     * @param {import('core').Response<TReturn>} response
     * @returns {TReturn}
     * @throws {Error}
     */
    _getMessageResponseResult(response) {
        const runtimeError = chrome.runtime.lastError;
        if (typeof runtimeError !== 'undefined') {
            throw new Error(runtimeError.message);
        }
        if (!isObjectNotArray(response)) {
            throw new Error('Offscreen document did not respond');
        }
        const responseError = response.error;
        if (responseError) {
            throw ExtensionError.deserialize(responseError);
        }
        return response.result;
    }
}

export class DictionaryDatabaseProxy {
    /**
     * @param {OffscreenProxy} offscreen
     */
    constructor(offscreen) {
        /** @type {OffscreenProxy} */
        this._offscreen = offscreen;
    }

    /**
     * @returns {Promise<void>}
     */
    async prepare() {
        await this._offscreen.sendMessagePromise({action: 'databasePrepareOffscreen'});
    }

    /**
     * @returns {Promise<import('dictionary-importer').Summary[]>}
     */
    async getDictionaryInfo() {
        return this._offscreen.sendMessagePromise({action: 'getDictionaryInfoOffscreen'});
    }

    /**
     * @returns {Promise<boolean>}
     */
    async purge() {
        return await this._offscreen.sendMessagePromise({action: 'databasePurgeOffscreen'});
    }

    /**
     * @param {import('dictionary-database').MediaRequest[]} targets
     * @returns {Promise<import('dictionary-database').Media[]>}
     */
    async getMedia(targets) {
        const serializedMedia = /** @type {import('dictionary-database').Media<string>[]} */ (await this._offscreen.sendMessagePromise({action: 'databaseGetMediaOffscreen', params: {targets}}));
        return serializedMedia.map((m) => ({...m, content: base64ToArrayBuffer(m.content)}));
    }
}

export class TranslatorProxy {
    /**
     * @param {OffscreenProxy} offscreen
     */
    constructor(offscreen) {
        /** @type {OffscreenProxy} */
        this._offscreen = offscreen;
    }

    /**
     * @param {import('language-transformer').LanguageTransformDescriptor[]} descriptors
     */
    async prepare(descriptors) {
        await this._offscreen.sendMessagePromise({action: 'translatorPrepareOffscreen', params: {descriptors}});
    }

    /**
     * @param {string} text
     * @param {import('translation').FindKanjiOptions} options
     * @returns {Promise<import('dictionary').KanjiDictionaryEntry[]>}
     */
    async findKanji(text, options) {
        const enabledDictionaryMapList = [...options.enabledDictionaryMap];
        /** @type {import('offscreen').FindKanjiOptionsOffscreen} */
        const modifiedOptions = {
            ...options,
            enabledDictionaryMap: enabledDictionaryMapList
        };
        return this._offscreen.sendMessagePromise({action: 'findKanjiOffscreen', params: {text, options: modifiedOptions}});
    }

    /**
     * @param {import('translator').FindTermsMode} mode
     * @param {string} text
     * @param {import('translation').FindTermsOptions} options
     * @returns {Promise<import('translator').FindTermsResult>}
     */
    async findTerms(mode, text, options) {
        const {enabledDictionaryMap, excludeDictionaryDefinitions, textReplacements} = options;
        const enabledDictionaryMapList = [...enabledDictionaryMap];
        const excludeDictionaryDefinitionsList = excludeDictionaryDefinitions ? [...excludeDictionaryDefinitions] : null;
        const textReplacementsSerialized = textReplacements.map((group) => {
            return group !== null ? group.map((opt) => ({...opt, pattern: opt.pattern.toString()})) : null;
        });
        /** @type {import('offscreen').FindTermsOptionsOffscreen} */
        const modifiedOptions = {
            ...options,
            enabledDictionaryMap: enabledDictionaryMapList,
            excludeDictionaryDefinitions: excludeDictionaryDefinitionsList,
            textReplacements: textReplacementsSerialized
        };
        return this._offscreen.sendMessagePromise({action: 'findTermsOffscreen', params: {mode, text, options: modifiedOptions}});
    }

    /**
     * @param {import('translator').TermReadingList} termReadingList
     * @param {string[]} dictionaries
     * @returns {Promise<import('translator').TermFrequencySimple[]>}
     */
    async getTermFrequencies(termReadingList, dictionaries) {
        return this._offscreen.sendMessagePromise({action: 'getTermFrequenciesOffscreen', params: {termReadingList, dictionaries}});
    }

    /** */
    async clearDatabaseCaches() {
        await this._offscreen.sendMessagePromise({action: 'clearDatabaseCachesOffscreen'});
    }
}

export class ClipboardReaderProxy {
    /**
     * @param {OffscreenProxy} offscreen
     */
    constructor(offscreen) {
        /** @type {?import('environment').Browser} */
        this._browser = null;
        /** @type {OffscreenProxy} */
        this._offscreen = offscreen;
    }

    /** @type {?import('environment').Browser} */
    get browser() { return this._browser; }
    set browser(value) {
        if (this._browser === value) { return; }
        this._browser = value;
        void this._offscreen.sendMessagePromise({action: 'clipboardSetBrowserOffscreen', params: {value}});
    }

    /**
     * @param {boolean} useRichText
     * @returns {Promise<string>}
     */
    async getText(useRichText) {
        return await this._offscreen.sendMessagePromise({action: 'clipboardGetTextOffscreen', params: {useRichText}});
    }

    /**
     * @returns {Promise<?string>}
     */
    async getImage() {
        return await this._offscreen.sendMessagePromise({action: 'clipboardGetImageOffscreen'});
    }
}