Add ability to regex postbacks

lib/BootBot.js

@@ -35,6 +35,7 @@ class BootBot extends EventEmitter {
     this.webhook = this.webhook.charAt(0) !== '/' ? `/${this.webhook}` : this.webhook;
     this.app.use(this.webhook, bodyParser.json({ verify: this._verifyRequestSignature.bind(this) }));
     this._hearMap = [];
+    this._postbackMap = [];
     this._conversations = [];
   }
 
@@ -457,6 +458,12 @@ class BootBot extends EventEmitter {
     return this;
   }
 
+  postback(keywords, callback) {
+    keywords = Array.isArray(keywords) ? keywords : [keywords];
+    keywords.forEach(keyword => this._postbackMap.push({ keyword, callback }));
+    return this;
+  }
+
   /**
    * Modules are simple functions that you can use to organize your code in different files and folders.
    * @param {Function} factory Called immediatly and receives the bot instance as its only parameter.
@@ -573,7 +580,30 @@ class BootBot extends EventEmitter {
   _handlePostbackEvent(event) {
     if (this._handleConversationResponse('postback', event)) { return; }
     const payload = event.postback.payload;
-    if (payload) {
+    const senderId = event.sender.id;
+      if (payload) {
+        let captured = false;
+
+        this._postbackMap.forEach(postback => {
+            if (typeof postback.keyword === 'string' && postback.keyword.toLowerCase() === payload.toLowerCase()) {
+                const res = postback.callback.apply(this, [event, new Chat(this, senderId), {
+                    keyword: postback.keyword,
+                    captured
+                }]);
+                captured = true;
+                return res;
+            } else if (postback.keyword instanceof RegExp && postback.keyword.test(payload)) {
+                const res = postback.callback.apply(this, [event, new Chat(this, senderId), {
+                    keyword: postback.keyword,
+                    match: payload.match(postback.keyword),
+                    captured
+                }]);
+                captured = true;
+                return res;
+            }
+        });
+      if (captured) return;
+
       this._handleEvent(`postback:${payload}`, event);
     }
     this._handleEvent('postback', event);