ADD: Telegram bot as notification provider

lib/notification/adapter/telegram.js

@@ -0,0 +1,35 @@
+const config = require('../../../conf/config.json');
+const TelegramBot = require('tg-yarl');
+
+const opts = { parse_mode: 'Markdown' };
+const bot = new TelegramBot(config.notification.telegram.token);
+
+
+/**
+ * sends new listings to telegram
+ * @param serviceName e.g immoscout
+ * @param newListings an array with newly found listings
+ * @returns {Promise<Void> | void}
+ */
+exports.send = (serviceName, newListings) => {
+    let message = `Service _${serviceName}_ found _${newListings.length}_ new listings:\n\n`;
+
+    message += newListings.map(o =>
+            `*${shorten(o.title.replace(/\*/g, ''), 45)}*\n` +
+            [o.address, o.price, o.size].join(' | ') + '\n' +
+            `[LINK](${o.link})\n\n`);
+
+    return bot.sendMessage(config.notification.telegram.chatId, message, opts);
+};
+
+/**
+ * each integration needs to implement this method
+ */
+exports.enabled = () => {
+    return config.notification.telegram.enabled;
+};
+
+
+function shorten (str, len = 30) {
+    return str.length > len ? str.substring(0, len) + '...' : str;
+}