src/telegram: Emit 'info' on stream from TelegramBot#getFileStream()

doc/api.md

@@ -846,7 +846,11 @@ which returns just path to file on remote server (you will have to manually buil
 
 ### telegramBot.getFileStream(fileId, [options]) ⇒ <code>stream.Readable</code>
 Return a readable stream for file.
+
 `fileStream.path` is the specified file ID i.e. `fileId`.
+`fileStream` emits event `info` passing a single argument i.e.
+`info` with the interface `{ uri }` where `uri` is the URI of the
+file on Telegram servers.
 
 This method is a sugar extension of the [getFileLink](#TelegramBot+getFileLink) method,
 which returns the full URI to the file on remote server.

src/telegram.js

@@ -1324,7 +1324,11 @@ class TelegramBot extends EventEmitter {
 
   /**
    * Return a readable stream for file.
+   *
    * `fileStream.path` is the specified file ID i.e. `fileId`.
+   * `fileStream` emits event `info` passing a single argument i.e.
+   * `info` with the interface `{ uri }` where `uri` is the URI of the
+   * file on Telegram servers.
    *
    * This method is a sugar extension of the [getFileLink](#TelegramBot+getFileLink) method,
    * which returns the full URI to the file on remote server.
@@ -1338,6 +1342,9 @@ class TelegramBot extends EventEmitter {
     fileStream.path = fileId;
     this.getFileLink(fileId, form)
       .then((fileURI) => {
+        fileStream.emit('info', {
+          uri: fileURI,
+        });
         pump(streamedRequest({ uri: fileURI }), fileStream);
       })
       .catch((error) => {

test/telegram.js

@@ -1160,7 +1160,7 @@ describe('TelegramBot', function telegramSuite() {
       return bot.getFileLink(FILE_ID)
         .then(fileURI => {
           assert.ok(is.string(fileURI));
-          assert.ok(/https?:\/\/.*\/file\/bot.*\/.*/.test(fileURI));
+          assert.ok(utils.isTelegramFileURI(fileURI));
         });
     });
   });
@@ -1174,12 +1174,16 @@ describe('TelegramBot', function telegramSuite() {
       const fileStream = bot.getFileStream(FILE_ID);
       assert.ok(fileStream instanceof stream.Readable);
       assert.equal(fileStream.path, FILE_ID);
+      fileStream.on('info', (info) => {
+        assert.ok(info);
+        assert.ok(utils.isTelegramFileURI(info.uri), `${info.uri} is not a file URI`);
         fileStream.pipe(concat(function readFile(buffer) {
           buffer.equals(fs.readFileSync(FILE_PATH)); // sync :(
           return done();
         }));
       });
     });
+  });
 
   describe('#downloadFile', function downloadFileSuite() {
     const downloadPath = os.tmpdir();

test/utils.js

@@ -30,6 +30,13 @@ exports = module.exports = {
    * @return {Promise}
    */
   isPollingMockServer,
+  /**
+   * Return true if the string is a URI to a file
+   * on Telegram servers.
+   * @param  {String} uri
+   * @return {Boolean}
+   */
+  isTelegramFileURI,
   /**
    * Send a message to the webhook at the specified port and path.
    * @param  {Number} port
@@ -217,3 +224,8 @@ function handleRatelimit(bot, methodName, suite) {
   };
   return bot;
 }
+
+
+function isTelegramFileURI(uri) {
+  return /https?:\/\/.*\/file\/bot.*\/.*/.test(uri);
+}