Add Google TTS Provider

Adds a Google Translate TTS Provider, allowing users to use TTS without
an API key from an existing provider.

Author: philhawthorne

README.md

@@ -365,6 +365,7 @@ Experimental support for TTS. Today the following providers are available:
 * voicerss
 * Microsoft Cognitive Services (Bing Text to Speech API)
 * AWS Polly
+* Google
 
 It will use the one you configure in settings.json. If you define settings for multiple TTS services, it will not be guaranteed which one it will choose!
 
@@ -539,6 +540,70 @@ This is the current list of voice names and their corresponding language and acc
 | Welsh | cy-GB | Female | Gwyneth |
 | Welsh | English | en-GB-WLS | Male | Geraint |
 
+#### Google
+
+Does not require any API keys. Please note that Google has been known in the past to change the requirements for its Text-to-Speech API, and this may stop working in the future.
+
+The following language codes are supported
+
+| Language code | Language |
+| ------------- | -------- |
+| af | Afrikaans |
+| sq | Albanian |
+| ar | Arabic |
+| hy | Armenian |
+| bn | Bengali |
+| ca | Catalan |
+| zh | Chinese |
+| zh-cn | Chinese (Mandarin/China) |
+| zh-tw | Chinese (Mandarin/Taiwan) |
+| zh-yue | Chinese (Cantonese) |
+| hr | Croatian |
+| cs | Czech |
+| da | Danish |
+| nl | Dutch |
+| en | English |
+| en-au | English (Australia) |
+| en-gb | English (Great Britain) |
+| en-us | English (United States) |
+| eo | Esperanto |
+| fi | Finnish |
+| fr | Franch |
+| de | German |
+| el | Greek |
+| hi | Hindi |
+| hu | Hungarian |
+| is | Icelandic |
+| id | Indonesian |
+| it | Italian |
+| ja | Japanese |
+| ko | Korean |
+| la | Latin |
+| lv | Latvian |
+| mk | Macedonian |
+| no | Norwegian |
+| pl | Polish |
+| pt | Portuguese |
+| pt-br | Portuguese (Brazil) |
+| ro | Romanian |
+| ru | Russian |
+| sr | Serbian |
+| sk | Slovak |
+| es | Spanish |
+| es-es | Spanish (Spain) |
+| es-us | Spanish (United States) |
+| sw | Swahili |
+| sv | Swedish |
+| ta | Tamil |
+| th | Thai |
+| tr | Turkish |
+| vi | Vietnamese |
+| cy | Welsh |
+
+Action is:
+
+	/[Room name]/say/[phrase][/[language_code]][/[announce volume]]
+	/sayall/[phrase][/[language_code]][/[announce volume]]
 
 Line-in
 -------

lib/tts-providers/google.js

@@ -0,0 +1,48 @@
+'use strict';
+const crypto = require('crypto');
+const fs = require('fs');
+const http = require('http');
+const path = require('path');
+const settings = require('../../settings');
+
+function google(phrase, language) {
+  // Use Google tts translation service to create a mp3 file
+  const ttsRequestUrl = 'http://translate.google.com/translate_tts?client=tw-ob&tl=' + language + '&q=' + phrase;
+  
+  // Construct a filesystem neutral filename
+  const phraseHash = crypto.createHash('sha1').update(phrase).digest('hex');
+  const filename = `google-${phraseHash}-${language}.mp3`;
+  const filepath = path.resolve(settings.webroot, 'tts', filename);
+  
+  const expectedUri = `/tts/${filename}`;
+  try {
+    fs.accessSync(filepath, fs.R_OK);
+    return Promise.resolve(expectedUri);
+  } catch (err) {
+    console.log(`announce file for phrase "${phrase}" does not seem to exist, downloading`);
+  }
+
+  return new Promise((resolve, reject) => {
+    var file = fs.createWriteStream(filepath);
+    var options = {"headers": {"User-Agent": "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/47.0.2526.106 Safari/537.36"}, "host": "translate.google.com", "path": "/translate_tts?client=tw-ob&tl=" + language + "&q=" + encodeURIComponent(phrase) }
+    var callback = function (response) {
+      if (response.statusCode < 300 && response.statusCode >= 200) {
+        response.pipe(file);
+        file.on('finish', function () {
+          file.end();
+          resolve(expectedUri);
+        });
+      } else {
+        reject(new Error(`Download from google TTS failed with status ${response.statusCode}, ${response.message}`));
+        
+      }
+    }
+    
+    http.request(options, callback).on('error', function (err) {
+      fs.unlink(dest);
+      reject(err);
+    }).end();
+  });
+}
+
+module.exports = google;