Add webpage translation functionality

README.md

@@ -230,6 +230,30 @@ directly:
 -   `getDocumentStatus()` (or `isDocumentTranslationComplete()`), and
 -   `downloadDocument()`
 
+#### Translating webpages
+
+Webpages can be translated as well by calling `translateWebpage()`. It has the same signature as `translateDocument` except for the
+first parameter, which is the URL for the webpage you would like translated.
+
+```javascript
+// Translate the English DeepL wikipedia page into German:
+await translator.translateWebpage(
+    'https://en.wikipedia.org/wiki/DeepL_Translator',
+    'DeepLWiki.html',
+    'en',
+    'de'
+);
+```
+
+Like `translateDocument()`, `translateWebpage()` wraps multiple API calls: uploading, polling status until
+the translation is complete, and downloading. If your application needs to
+execute these steps individually, you can instead use the following functions
+directly:
+
+-   `uploadWebpage()`,
+-   `getDocumentStatus()` (or `isDocumentTranslationComplete()`), and
+-   `downloadDocument()`
+
 #### Document translation options
 
 -   `formality`: same as in [Text translation options](#text-translation-options).

src/client.ts

@@ -106,14 +106,16 @@ export class HttpClient {
         url: string,
         timeoutMs: number,
         responseAsStream: boolean,
+        isDeepL: boolean,
         options: SendRequestOptions,
     ): AxiosRequestConfig {
         const headers = Object.assign({}, this.headers, options.headers);
+        logDebug(`isDeepL: ${isDeepL}`);
 
         const axiosRequestConfig: AxiosRequestConfig = {
             url,
             method,
-            baseURL: this.serverUrl,
+            baseURL: isDeepL ? this.serverUrl : undefined,
             headers,
             responseType: responseAsStream ? 'stream' : 'text',
             timeout: timeoutMs,
@@ -147,19 +149,26 @@ export class HttpClient {
     /**
      * Makes API request retrying if necessary, and returns (as Promise) response.
      * @param method HTTP method, for example 'GET'
-     * @param url Path to endpoint, excluding base server URL.
+     * @param url Path to endpoint, excluding base server URL if DeepL API request, including base server URL if a webpage.
      * @param options Additional options controlling request.
      * @param responseAsStream Set to true if the return type is IncomingMessage.
-     * @return Fulfills with status code and response (as text or stream).
+     * @return Fulfills with status code, content type, and response (as text or stream).
      */
     async sendRequestWithBackoff<TContent extends string | IncomingMessage>(
         method: HttpMethod,
         url: string,
         options?: SendRequestOptions,
         responseAsStream = false,
-    ): Promise<{ statusCode: number; content: TContent }> {
+    ): Promise<{ statusCode: number; content: TContent; contentType?: string }> {
+        let isDeepLUrl: boolean;
+        try {
+            isDeepLUrl = !!new URL(url);
+        } catch {
+            isDeepLUrl = true;
+        }
+
         options = options === undefined ? {} : options;
-        logInfo(`Request to DeepL API ${method} ${url}`);
+        logInfo(`${isDeepLUrl ? 'Request to DeepL API' : 'Request to webpage'} ${method} ${url}`);
         logDebug(`Request details: ${options.data}`);
         const backoff = new BackoffTimer();
         let response, error;
@@ -170,8 +179,14 @@ export class HttpClient {
                 url,
                 timeoutMs,
                 responseAsStream,
+                isDeepLUrl,
                 options,
             );
+
+            if (!isDeepLUrl && axiosRequestConfig.headers) {
+                delete axiosRequestConfig.headers.Authorization;
+            }
+
             try {
                 response = await HttpClient.sendAxiosRequest<TContent>(axiosRequestConfig);
                 error = undefined;
@@ -199,8 +214,12 @@ export class HttpClient {
         }
 
         if (response !== undefined) {
-            const { statusCode, content } = response;
-            logInfo(`DeepL API response ${method} ${url} ${statusCode}`);
+            const { statusCode, content, contentType } = response;
+            logInfo(
+                `${
+                    isDeepLUrl ? 'DeepL API response' : 'Webpage response'
+                } ${method} ${url} ${statusCode}${!isDeepLUrl ? ` ${contentType}` : ''}`,
+            );
             if (!responseAsStream) {
                 logDebug('Response details:', { content: content });
             }
@@ -217,7 +236,7 @@ export class HttpClient {
      */
     private static async sendAxiosRequest<TContent extends string | IncomingMessage>(
         axiosRequestConfig: AxiosRequestConfig,
-    ): Promise<{ statusCode: number; content: TContent }> {
+    ): Promise<{ statusCode: number; content: TContent; contentType?: string }> {
         try {
             const response = await axios.request(axiosRequestConfig);
 
@@ -227,7 +246,12 @@ export class HttpClient {
                     response.data = JSON.stringify(response.data);
                 }
             }
-            return { statusCode: response.status, content: response.data };
+
+            return {
+                statusCode: response.status,
+                content: response.data,
+                contentType: response.headers['content-type'],
+            };
         } catch (axios_error_raw) {
             const axiosError = axios_error_raw as AxiosError;
             const message: string = axiosError.message || '';

src/errors.ts

@@ -41,3 +41,5 @@ export class DocumentTranslationError extends DeepLError {
 export class GlossaryNotFoundError extends DeepLError {}
 
 export class DocumentNotReadyError extends DeepLError {}
+
+export class WebsiteDownloadError extends DeepLError {}

src/index.ts

@@ -11,6 +11,7 @@ import {
     GlossaryNotFoundError,
     QuotaExceededError,
     TooManyRequestsError,
+    WebsiteDownloadError,
 } from './errors';
 import { GlossaryEntries } from './glossaryEntries';
 import {
@@ -645,6 +646,37 @@ export class Translator {
         }
     }
 
+    /**
+     * Uploads the HTML of the specified webpage to DeepL to translate into given target language, waits for
+     * translation to complete, then downloads translated webpage to specified output path.
+     * @param webpageUrl String or URL containing the URL of the webpage to be translated.
+     * @param outputFile String containing file path to create translated document, or Stream or
+     *     FileHandle to write translated document content.
+     * @param sourceLang Language code of input document, or null to use auto-detection.
+     * @param targetLang Language code of language to translate into.
+     * @param options Optional DocumentTranslateOptions object containing additional options controlling translation.
+     * @return Fulfills with a DocumentStatus object for the completed translation. You can use the
+     *     billedCharacters property to check how many characters were billed for the document.
+     * @throws {Error} If no file exists at the input file path, or a file already exists at the output file path.
+     * @throws {DocumentTranslationError} If any error occurs during document upload, translation or
+     *     download. The `documentHandle` property of the error may be used to recover the document.
+     */
+    async translateWebpage(
+        webpageUrl: string | URL,
+        outputFile: string | fs.WriteStream | fs.promises.FileHandle,
+        sourceLang: SourceLanguageCode | null,
+        targetLang: TargetLanguageCode,
+        options?: DocumentTranslateOptions,
+    ): Promise<DocumentStatus> {
+        return this.translateDocument(
+            Buffer.from(await this.getContentFromWebpage(webpageUrl)),
+            outputFile,
+            sourceLang,
+            targetLang,
+            { filename: 'webpage.html', ...options },
+        );
+    }
+
     /**
      * Uploads specified document to DeepL to translate into target language, and returns handle associated with the document.
      * @param inputFile String containing file path, stream containing file data, or FileHandle.
@@ -709,6 +741,28 @@ export class Translator {
         }
     }
 
+    /**
+     * Uploads specified webpage HTML to DeepL to translate into target language, and returns handle associated with the document.
+     * @param webpageUrl String or URL containing the URL of the webpage to be translated.
+     * @param sourceLang Language code of input document, or null to use auto-detection.
+     * @param targetLang Language code of language to translate into.
+     * @param options Optional DocumentTranslateOptions object containing additional options controlling translation.
+     * @return Fulfills with DocumentHandle associated with the in-progress translation.
+     */
+    async uploadWebpage(
+        webpageUrl: string | URL,
+        sourceLang: SourceLanguageCode | null,
+        targetLang: TargetLanguageCode,
+        options?: DocumentTranslateOptions,
+    ): Promise<DocumentHandle> {
+        return this.uploadDocument(
+            Buffer.from(await this.getContentFromWebpage(webpageUrl)),
+            sourceLang,
+            targetLang,
+            { filename: 'webpage.html', ...options },
+        );
+    }
+
     /**
      * Retrieves the status of the document translation associated with the given document handle.
      * @param handle Document handle associated with document.
@@ -1003,6 +1057,18 @@ export class Translator {
         return libraryInfoString;
     }
 
+    private async getContentFromWebpage(webpageUrl: string | URL): Promise<string> {
+        const { statusCode, content, contentType } =
+            await this.httpClient.sendRequestWithBackoff<string>('GET', webpageUrl.toString());
+        await checkStatusCode(statusCode, content);
+
+        if (!contentType?.includes('text/html')) {
+            throw new WebsiteDownloadError('URL to translate must return HTML');
+        }
+
+        return content;
+    }
+
     /**
      * HttpClient implements all HTTP requests and retries.
      * @private