Parse response_body and flesh out attributes

lib/MailchimpMarketing/api_error.rb

@@ -10,6 +10,8 @@
 
 =end
 
+require 'json'
+
 module MailchimpMarketing
   class ApiError < StandardError
     attr_reader :status, :type, :title, :detail, :instance, :errors
@@ -21,20 +23,42 @@ class ApiError < StandardError
     #   ApiError.new("message")
     #   ApiError.new(:status => 500, :response_headers => {}, :response_body => "")
     #   ApiError.new(:status => 404, :message => "Not Found")
-    def initialize(arg = nil)
-      if arg.is_a? Hash
-        if arg.key?(:message) || arg.key?('message')
-          super(arg[:message] || arg['message'])
-        else
-          super arg
-        end
+    def initialize(arguments = nil)
+      @arguments = arguments
+      return super(@arguments) unless @arguments.is_a?(Hash)
+
+      @arguments.transform_keys!(&:to_sym)
+
+      expand_response_body_into_arguments
+
+      super(@arguments[:title] || @arguments[:message])
+
+      @arguments.each do |key, value|
+        instance_variable_set("@#{key}", value)
+      end
+    end
+
+    private
+
+    def expand_response_body_into_arguments
+      @arguments.merge!(parsed_response_body) unless parsed_response_body.nil?
+    end
 
-        arg.each do |k, v|
-          instance_variable_set "@#{k}", v
+    def parsed_response_body
+      @parsed_response_body ||= begin
+        parsed_response_body = JSON.parse(@arguments[:response_body]).transform_keys(&:to_sym)
+
+        if parsed_response_body[:errors].is_a?(Array)
+          parsed_response_body[:errors].map do |error|
+            error.transform_keys!(&:to_sym)
+          end
         end
-      else
-        super arg
+
+        parsed_response_body
+      rescue
+        nil
       end
     end
+
   end
 end