Move field obfuscation into own class

[MAILPOET-1014]

lib/Form/Util/FieldNameObfuscator.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace MailPoet\Form\Util;
+
+class FieldNameObfuscator {
+
+  const OBFUSCATED_FIELD_PREFIX = 'form_field_';
+
+  public function obfuscate($name) {
+    return FieldNameObfuscator::OBFUSCATED_FIELD_PREFIX.base64_encode($name);
+  }
+
+  public function deobfuscate($name) {
+    $prefixLength = strlen(FieldNameObfuscator::OBFUSCATED_FIELD_PREFIX);
+    return base64_decode(substr($name, $prefixLength));
+  }
+
+  public function deobfuscateFormPayload($data) {
+    $result = array();
+    foreach($data as $key => $value) {
+      $result[$this->deobfuscateField($key)] = $value;
+    }
+    return $result;
+  }
+
+  private function deobfuscateField($name) {
+    if($this->wasFieldObfuscated($name)) {
+      return $this->deobfuscate($name);
+    } else {
+      return $name;
+    }
+  }
+
+  private function wasFieldObfuscated($name) {
+    return strpos($name, FieldNameObfuscator::OBFUSCATED_FIELD_PREFIX) === 0;
+  }
+
+}