refactor validators similar ActiveModel::Validations format

lib/bookland.rb

@@ -1,5 +1,7 @@
 require 'bookland/identifier'
 require 'bookland/ean'
+require 'bookland/invalid_isbn'
 require 'bookland/isbn'
 require 'bookland/asin'
+require 'bookland/isbn10'
 require 'bookland/validators' if defined?(ActiveModel)

lib/bookland/identifier.rb

@@ -11,7 +11,7 @@ def self.calculate_checksum_digit(data_digits)
     attr :digits
 
     def initialize(raw)
-      @digits = raw.split('')
+      @digits = raw.gsub('-','').split('')
     end
 
     def data_digits

lib/bookland/invalid_isbn.rb

@@ -0,0 +1,4 @@
+module Bookland
+  class InvalidISBN < StandardError
+  end
+end

lib/bookland/isbn10.rb

@@ -0,0 +1,37 @@
+module Bookland
+  # The now-obsolete 10-digit ISBN.
+  class ISBN10 < Identifier
+    # Calculates the checksum for the 9-digit data_digits of an ISBN-10.
+    def self.calculate_checksum_digit(data_digits)
+      data_digits.map! &:to_i
+      weights = 10.downto(2).to_a
+      sum = data_digits.zip(weights).inject(0) { |a , (i, j)| a + i * j }
+      checksum = 11 - sum % 11
+
+      case checksum
+      when 0..9 then checksum.to_s
+      when 10 then 'X'
+      when 11 then '0'
+      end
+    end
+
+    # Converts the given ISBN-10 to an ISBN.
+    def self.to_isbn(raw)
+      new(raw).to_isbn
+    end
+
+    # Converts the ISBN-10 to an ISBN.
+    def to_isbn
+      raise InvalidISBN unless valid?
+
+      new_data_digits = [9, 7, 8] +  data_digits
+      new_checksum = ISBN.calculate_checksum_digit new_data_digits
+
+      (new_data_digits << new_checksum).join
+    end
+
+    def valid?
+      digits.size == 10 && super
+    end
+  end
+end

lib/bookland/validators.rb

@@ -1,16 +1,55 @@
-%w(ASIN EAN ISBN).each do |klass|
+%w(ASIN EAN).each do |klass|
   Object.class_eval <<-EOF
-    class #{klass.capitalize}Validator < ActiveModel::EachValidator
-      def validate_each(record, attribute, value)
-        unless Bookland::#{klass}.valid?(value)
-          message = "is not an #{klass}"
-          if options[:strict]
-            raise ActiveModel::StrictValidationFailed, "\#{value} \#{message}"
-          else
-            record.errors[attribute] << message
+    module ValidationExtensions
+      class #{klass.capitalize}Validator < ActiveModel::EachValidator
+        def initialize(options)
+          options[:message]     ||= "is not a valid #{klass} code"
+          options[:allow_nil]   ||= false
+          options[:allow_blank] ||= false
+          super(options)
+        end
+
+        def validate_each(record, attribute, value)
+          unless Bookland::#{klass}.valid?(value) || (value.nil? && options[:allow_nil]) || (value.blank? && options[:allow_blank])
+            record.errors.add(attribute, options[:message])
           end
         end
       end
+
+      module HelperMethods
+        def validates_#{klass.downcase}(*attr_names)
+          validates_with #{klass.capitalize}Validator, _merge_attributes(attr_names)
+        end        
+      end
     end
   EOF
 end
+
+module ValidationExtensions
+  class IsbnValidator < ActiveModel::EachValidator
+    def initialize(options)
+      options[:message]     ||= "is not a valid ISBN code"
+      options[:allow_nil]   ||= false
+      options[:allow_blank] ||= false
+      options[:compatible] ||= true
+      super(options)
+    end
+
+    def validate_each(record, attribute, value)
+      return if  (value.nil? && options[:allow_nil]) || (value.blank? && options[:allow_blank])
+      unless Bookland::ISBN.valid?(value) || (options[:compatible] && Bookland::ISBN10.valid?(value))
+        record.errors.add(attribute, options[:message])
+      end
+    end
+  end
+
+  module HelperMethods
+    def validates_isbn(*attr_names)
+      validates_with IsbnValidator, _merge_attributes(attr_names)
+    end        
+  end  
+end
+
+ActiveModel::Validations.send(:include, ValidationExtensions)
+ActiveModel::Validations::HelperMethods.send(:include, ValidationExtensions::HelperMethods)
+