module ActiveModel
  module Validations
    module ClassMethods
      ALL_RANGE_OPTIONS = [ :is, :within, :in, :minimum, :maximum ].freeze

      # Validates that the specified attribute matches the length restrictions supplied. Only one option can be used at a time:
      #
      #   class Person < ActiveRecord::Base
      #     validates_length_of :first_name, :maximum=>30
      #     validates_length_of :last_name, :maximum=>30, :message=>"less than 30 if you don't mind"
      #     validates_length_of :fax, :in => 7..32, :allow_nil => true
      #     validates_length_of :phone, :in => 7..32, :allow_blank => true
      #     validates_length_of :user_name, :within => 6..20, :too_long => "pick a shorter name", :too_short => "pick a longer name"
      #     validates_length_of :zip_code, :minimum => 5, :too_short => "please enter at least 5 characters"
      #     validates_length_of :smurf_leader, :is => 4, :message => "papa is spelled with 4 characters... don't play me."
      #     validates_length_of :essay, :minimum => 100, :too_short => "Your essay must be at least 100 words."), :tokenizer => lambda {|str| str.scan(/\w+/) }
      #   end
      #
      # Configuration options:
      # * <tt>:minimum</tt> - The minimum size of the attribute.
      # * <tt>:maximum</tt> - The maximum size of the attribute.
      # * <tt>:is</tt> - The exact size of the attribute.
      # * <tt>:within</tt> - A range specifying the minimum and maximum size of the attribute.
      # * <tt>:in</tt> - A synonym(or alias) for <tt>:within</tt>.
      # * <tt>:allow_nil</tt> - Attribute may be +nil+; skip validation.
      # * <tt>:allow_blank</tt> - Attribute may be blank; skip validation.
      # * <tt>:too_long</tt> - The error message if the attribute goes over the maximum (default is: "is too long (maximum is {{count}} characters)").
      # * <tt>:too_short</tt> - The error message if the attribute goes under the minimum (default is: "is too short (min is {{count}} characters)").
      # * <tt>:wrong_length</tt> - The error message if using the <tt>:is</tt> method and the attribute is the wrong size (default is: "is the wrong length (should be {{count}} characters)").
      # * <tt>:message</tt> - The error message to use for a <tt>:minimum</tt>, <tt>:maximum</tt>, or <tt>:is</tt> violation.  An alias of the appropriate <tt>too_long</tt>/<tt>too_short</tt>/<tt>wrong_length</tt> message.
      # * <tt>:on</tt> - Specifies when this validation is active (default is <tt>:save</tt>, other options <tt>:create</tt>, <tt>:update</tt>).
      # * <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.
      # * <tt>:tokenizer</tt> - Specifies how to split up the attribute string. (e.g. <tt>:tokenizer => lambda {|str| str.scan(/\w+/)}</tt> to
      #   count words as in above example.)
      #   Defaults to <tt>lambda{ |value| value.split(//) }</tt> which counts individual characters.
      def validates_length_of(*attrs)
        # Merge given options with defaults.
        options = { :tokenizer => lambda {|value| value.split(//)} }
        options.update(attrs.extract_options!.symbolize_keys)

        # Ensure that one and only one range option is specified.
        range_options = ALL_RANGE_OPTIONS & options.keys
        case range_options.size
        when 0
          raise ArgumentError, 'Range unspecified.  Specify the :within, :maximum, :minimum, or :is option.'
        when 1
          # Valid number of options; do nothing.
        else
          raise ArgumentError, 'Too many range options specified.  Choose only one.'
        end

        # Get range option and value.
        option = range_options.first
        option_value = options[range_options.first]
        key = {:is => :wrong_length, :minimum => :too_short, :maximum => :too_long}[option]
        custom_message = options[:message] || options[key]

        case option
        when :within, :in
          raise ArgumentError, ":#{option} must be a Range" unless option_value.is_a?(Range)

          validates_each(attrs, options) do |record, attr, value|
            value = options[:tokenizer].call(value) if value.kind_of?(String)

            min, max = option_value.begin, option_value.end
            max = max - 1 if option_value.exclude_end?

            if value.nil? || value.size < min
              record.errors.add(attr, :too_short, :default => custom_message || options[:too_short], :count => min)
            elsif value.size > max
              record.errors.add(attr, :too_long, :default => custom_message || options[:too_long], :count => max)
            end
          end
        when :is, :minimum, :maximum
          raise ArgumentError, ":#{option} must be a nonnegative Integer" unless option_value.is_a?(Integer) and option_value >= 0

          # Declare different validations per option.
          validity_checks = { :is => "==", :minimum => ">=", :maximum => "<=" }

          validates_each(attrs, options) do |record, attr, value|
            value = options[:tokenizer].call(value) if value.kind_of?(String)

            valid_value = if option == :maximum
              value.nil? || value.size.send(validity_checks[option], option_value)
            else
              value && value.size.send(validity_checks[option], option_value)
            end

            record.errors.add(attr, key, :default => custom_message, :count => option_value) unless valid_value
          end
        end
      end

      alias_method :validates_size_of, :validates_length_of
    end
  end
end