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Diffstat (limited to 'browser/components/translation/GoogleTranslator.jsm')
| -rw-r--r-- | browser/components/translation/GoogleTranslator.jsm | 306 |
1 files changed, 306 insertions, 0 deletions
diff --git a/browser/components/translation/GoogleTranslator.jsm b/browser/components/translation/GoogleTranslator.jsm new file mode 100644 index 0000000000..dd5da98b8b --- /dev/null +++ b/browser/components/translation/GoogleTranslator.jsm @@ -0,0 +1,306 @@ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +"use strict"; + +var EXPORTED_SYMBOLS = ["GoogleTranslator"]; + +const { PromiseUtils } = ChromeUtils.importESModule( + "resource://gre/modules/PromiseUtils.sys.mjs" +); +const { httpRequest } = ChromeUtils.importESModule( + "resource://gre/modules/Http.sys.mjs" +); + +// The maximum amount of net data allowed per request on Google's API. +const MAX_REQUEST_DATA = 5000; // XXX This is the Bing value + +// The maximum number of chunks allowed to be translated in a single +// request. +const MAX_REQUEST_CHUNKS = 128; // Undocumented, but the de facto upper limit. + +// Self-imposed limit of 15 requests. This means that a page that would need +// to be broken in more than 15 requests won't be fully translated. +// The maximum amount of data that we will translate for a single page +// is MAX_REQUESTS * MAX_REQUEST_DATA. +const MAX_REQUESTS = 15; + +const URL = "https://translation.googleapis.com/language/translate/v2"; + +/** + * Translates a webpage using Google's Translation API. + * + * @param translationDocument The TranslationDocument object that represents + * the webpage to be translated + * @param sourceLanguage The source language of the document + * @param targetLanguage The target language for the translation + * + * @returns {Promise} A promise that will resolve when the translation + * task is finished. + */ +var GoogleTranslator = function ( + translationDocument, + sourceLanguage, + targetLanguage +) { + this.translationDocument = translationDocument; + this.sourceLanguage = sourceLanguage; + this.targetLanguage = targetLanguage; + this._pendingRequests = 0; + this._partialSuccess = false; + this._translatedCharacterCount = 0; +}; + +GoogleTranslator.prototype = { + /** + * Performs the translation, splitting the document into several chunks + * respecting the data limits of the API. + * + * @returns {Promise} A promise that will resolve when the translation + * task is finished. + */ + async translate() { + let currentIndex = 0; + this._onFinishedDeferred = PromiseUtils.defer(); + + // Let's split the document into various requests to be sent to + // Google's Translation API. + for (let requestCount = 0; requestCount < MAX_REQUESTS; requestCount++) { + // Generating the text for each request can be expensive, so + // let's take the opportunity of the chunkification process to + // allow for the event loop to attend other pending events + // before we continue. + await new Promise(resolve => Services.tm.dispatchToMainThread(resolve)); + + // Determine the data for the next request. + let request = this._generateNextTranslationRequest(currentIndex); + + // Create a real request to the server, and put it on the + // pending requests list. + let googleRequest = new GoogleRequest( + request.data, + this.sourceLanguage, + this.targetLanguage + ); + this._pendingRequests++; + googleRequest + .fireRequest() + .then(this._chunkCompleted.bind(this), this._chunkFailed.bind(this)); + + currentIndex = request.lastIndex; + if (request.finished) { + break; + } + } + + return this._onFinishedDeferred.promise; + }, + + /** + * Function called when a request sent to the server completed successfully. + * This function handles calling the function to parse the result and the + * function to resolve the promise returned by the public `translate()` + * method when there's no pending request left. + * + * @param request The GoogleRequest sent to the server. + */ + _chunkCompleted(googleRequest) { + if (this._parseChunkResult(googleRequest)) { + this._partialSuccess = true; + // Count the number of characters successfully translated. + this._translatedCharacterCount += googleRequest.characterCount; + } + + this._checkIfFinished(); + }, + + /** + * Function called when a request sent to the server has failed. + * This function handles deciding if the error is transient or means the + * service is unavailable (zero balance on the key or request credentials are + * not in an active state) and calling the function to resolve the promise + * returned by the public `translate()` method when there's no pending. + * request left. + * + * @param aError [optional] The XHR object of the request that failed. + */ + _chunkFailed(aError) { + this._checkIfFinished(); + }, + + /** + * Function called when a request sent to the server has completed. + * This function handles resolving the promise + * returned by the public `translate()` method when all chunks are completed. + */ + _checkIfFinished() { + // Check if all pending requests have been + // completed and then resolves the promise. + // If at least one chunk was successful, the + // promise will be resolved positively which will + // display the "Success" state for the infobar. Otherwise, + // the "Error" state will appear. + if (--this._pendingRequests == 0) { + if (this._partialSuccess) { + this._onFinishedDeferred.resolve({ + characterCount: this._translatedCharacterCount, + }); + } else { + this._onFinishedDeferred.reject("failure"); + } + } + }, + + /** + * This function parses the result returned by Bing's Http.svc API, + * which is a XML file that contains a number of elements. To our + * particular interest, the only part of the response that matters + * are the <TranslatedText> nodes, which contains the resulting + * items that were sent to be translated. + * + * @param request The request sent to the server. + * @returns boolean True if parsing of this chunk was successful. + */ + _parseChunkResult(googleRequest) { + let results; + try { + let response = googleRequest.networkRequest.response; + results = JSON.parse(response).data.translations; + } catch (e) { + return false; + } + let len = results.length; + if (len != googleRequest.translationData.length) { + // This should never happen, but if the service returns a different number + // of items (from the number of items submitted), we can't use this chunk + // because all items would be paired incorrectly. + return false; + } + + let error = false; + for (let i = 0; i < len; i++) { + try { + let result = results[i].translatedText; + let root = googleRequest.translationData[i][0]; + if (root.isSimpleRoot && result.includes("&")) { + // If the result contains HTML entities, we need to convert them as + // simple roots expect a plain text result. + let doc = new DOMParser().parseFromString(result, "text/html"); + result = doc.body.firstChild.nodeValue; + } + root.parseResult(result); + } catch (e) { + error = true; + } + } + + return !error; + }, + + /** + * This function will determine what is the data to be used for + * the Nth request we are generating, based on the input params. + * + * @param startIndex What is the index, in the roots list, that the + * chunk should start. + */ + _generateNextTranslationRequest(startIndex) { + let currentDataSize = 0; + let currentChunks = 0; + let output = []; + let rootsList = this.translationDocument.roots; + + for (let i = startIndex; i < rootsList.length; i++) { + let root = rootsList[i]; + let text = this.translationDocument.generateTextForItem(root); + if (!text) { + continue; + } + + let newCurSize = currentDataSize + text.length; + let newChunks = currentChunks + 1; + + if (newCurSize > MAX_REQUEST_DATA || newChunks > MAX_REQUEST_CHUNKS) { + // If we've reached the API limits, let's stop accumulating data + // for this request and return. We return information useful for + // the caller to pass back on the next call, so that the function + // can keep working from where it stopped. + return { + data: output, + finished: false, + lastIndex: i, + }; + } + + currentDataSize = newCurSize; + currentChunks = newChunks; + output.push([root, text]); + } + + return { + data: output, + finished: true, + lastIndex: 0, + }; + }, +}; + +/** + * Represents a request (for 1 chunk) sent off to Google's service. + * + * @params translationData The data to be used for this translation, + * generated by the generateNextTranslationRequest... + * function. + * @param sourceLanguage The source language of the document. + * @param targetLanguage The target language for the translation. + * + */ +function GoogleRequest(translationData, sourceLanguage, targetLanguage) { + this.translationData = translationData; + this.sourceLanguage = sourceLanguage; + this.targetLanguage = targetLanguage; + this.characterCount = 0; +} + +GoogleRequest.prototype = { + /** + * Initiates the request + */ + fireRequest() { + let key = + Services.cpmm.sharedData.get("translationKey") || + Services.prefs.getStringPref("browser.translation.google.apiKey", ""); + if (!key) { + return Promise.reject("no API key"); + } + + // Prepare the request body. + let postData = [ + ["key", key], + ["source", this.sourceLanguage], + ["target", this.targetLanguage], + ]; + + for (let [, text] of this.translationData) { + postData.push(["q", text]); + this.characterCount += text.length; + } + + // Set up request options. + return new Promise((resolve, reject) => { + let options = { + onLoad: (responseText, xhr) => { + resolve(this); + }, + onError(e, responseText, xhr) { + reject(xhr); + }, + postData, + }; + + // Fire the request. + this.networkRequest = httpRequest(URL, options); + }); + }, +}; |