Add honeypot field for spambot

[MAILPOET-1014]

lib/Form/Block/Base.php

@@ -104,7 +104,7 @@ abstract class Base {
     if((int)$block['id'] > 0) {
       return 'cf_'.$block['id'];
     } else {
-      return $block['id'];
+      return 'form_field_'.base64_encode($block['id']);//obfuscate field name for spambots
     }
   }
 

lib/Form/Renderer.php

@@ -15,6 +15,7 @@ class Renderer {
     $styles = new Util\Styles(static::getStyles($form));
 
     $html = '<style type="text/css">';
+    $html .= '.mailpoet_hp_email_label{position: absolute;left: -999em;}';// move honeypot field out of the sight
     $html .= $styles->render($prefix);
     $html .= '</style>';
 
@@ -38,7 +39,8 @@ class Renderer {
   }
 
   static function renderBlocks($blocks = array()) {
-    $html = '';
+    // this is a honeypot for spambots
+    $html = '<label class="mailpoet_hp_email_label">Please leave this field empty<input type="email" name="data[email]"></label>';
     foreach($blocks as $key => $block) {
       $html .= static::renderBlock($block)."\n";
     }