module ActiveModel
  module Validations
    module ClassMethods
      ALL_NUMERICALITY_CHECKS = { :greater_than => '>', :greater_than_or_equal_to => '>=',
                                  :equal_to => '==', :less_than => '<', :less_than_or_equal_to => '<=',
                                  :odd => 'odd?', :even => 'even?' }.freeze

      # Validates whether the value of the specified attribute is numeric by trying to convert it to
      # a float with Kernel.Float (if <tt>only_integer</tt> is false) or applying it to the regular expression
      # <tt>/\A[\+\-]?\d+\Z/</tt> (if <tt>only_integer</tt> is set to true).
      #
      #   class Person < ActiveRecord::Base
      #     validates_numericality_of :value, :on => :create
      #   end
      #
      # Configuration options:
      # * <tt>:message</tt> - A custom error message (default is: "is not a number").
      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
      # * <tt>:only_integer</tt> - Specifies whether the value has to be an integer, e.g. an integral value (default is +false+).
      # * <tt>:allow_nil</tt> - Skip validation if attribute is +nil+ (default is +false+). Notice that for fixnum and float columns empty strings are converted to +nil+.
      # * <tt>:greater_than</tt> - Specifies the value must be greater than the supplied value.
      # * <tt>:greater_than_or_equal_to</tt> - Specifies the value must be greater than or equal the supplied value.
      # * <tt>:equal_to</tt> - Specifies the value must be equal to the supplied value.
      # * <tt>:less_than</tt> - Specifies the value must be less than the supplied value.
      # * <tt>:less_than_or_equal_to</tt> - Specifies the value must be less than or equal the supplied value.
      # * <tt>:odd</tt> - Specifies the value must be an odd number.
      # * <tt>:even</tt> - Specifies the value must be an even number.
      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
      #   not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>).  The
      #   method, proc or string should return or evaluate to a true or false value.
      #
      # The following checks can also be supplied with a proc or a symbol which corresponds to a method:
      # * <tt>:greater_than</tt>
      # * <tt>:greater_than_or_equal_to</tt>
      # * <tt>:equal_to</tt>
      # * <tt>:less_than</tt>
      # * <tt>:less_than_or_equal_to</tt>
      #
      #   class Person < ActiveRecord::Base
      #     validates_numericality_of :width, :less_than => Proc.new { |person| person.height }
      #     validates_numericality_of :width, :greater_than => :minimum_weight
      #   end
      #
      #

      def validates_numericality_of(*attr_names)
        configuration = { :only_integer => false, :allow_nil => false }
        configuration.update(attr_names.extract_options!)

        numericality_options = ALL_NUMERICALITY_CHECKS.keys & configuration.keys

        (numericality_options - [ :odd, :even ]).each do |option|
          value = configuration[option]
          raise ArgumentError, ":#{option} must be a number, a symbol or a proc" unless value.is_a?(Numeric) || value.is_a?(Proc) || value.is_a?(Symbol)
        end

        validates_each(attr_names,configuration) do |record, attr_name, value|
          before_type_cast = "#{attr_name}_before_type_cast"

          if record.respond_to?(before_type_cast.to_sym)
            raw_value = record.send("#{attr_name}_before_type_cast") || value
          else
            raw_value = value
          end

          next if configuration[:allow_nil] and raw_value.nil?

          if configuration[:only_integer]
            unless raw_value.to_s =~ /\A[+-]?\d+\Z/
              record.errors.add(attr_name, :not_a_number, :value => raw_value, :default => configuration[:message])
              next
            end
            raw_value = raw_value.to_i
          else
            begin
              raw_value = Kernel.Float(raw_value)
            rescue ArgumentError, TypeError
              record.errors.add(attr_name, :not_a_number, :value => raw_value, :default => configuration[:message])
              next
            end
          end

          numericality_options.each do |option|
            case option
            when :odd, :even
              unless raw_value.to_i.method(ALL_NUMERICALITY_CHECKS[option])[]
                record.errors.add(attr_name, option, :value => raw_value, :default => configuration[:message])
              end
            else
              configuration[option] = configuration[option].call(record)        if configuration[option].is_a? Proc
              configuration[option] = record.method(configuration[option]).call if configuration[option].is_a? Symbol
              
              unless raw_value.method(ALL_NUMERICALITY_CHECKS[option])[configuration[option]]
                record.errors.add(attr_name, option, :default => configuration[:message], :value => raw_value, :count => configuration[option])
              end
            end
          end
        end
      end
    end
  end
end