# encoding: utf-8
module Mongoid #:nodoc:
  module Attributes
    def self.included(base)
      base.class_eval do
        include InstanceMethods
        extend ClassMethods
      end
    end
    module InstanceMethods
      # Process the provided attributes casting them to their proper values if a
      # field exists for them on the +Document+. This will be limited to only the
      # attributes provided in the suppied +Hash+ so that no extra nil values get
      # put into the document's attributes.
      def process(attrs = {})
        attrs.each_pair do |key, value|
          send("#{key}=", value) unless value.blank?
        end
      end

      # Read a value from the +Document+ attributes. If the value does not exist
      # it will return nil.
      #
      # Options:
      #
      # name: The name of the attribute to get.
      #
      # Example:
      #
      # <tt>person.read_attribute(:title)</tt>
      def read_attribute(name)
        fields[name].get(@attributes[name])
      end

      # Remove a value from the +Document+ attributes. If the value does not exist
      # it will fail gracefully.
      #
      # Options:
      #
      # name: The name of the attribute to remove.
      #
      # Example:
      #
      # <tt>person.remove_attribute(:title)</tt>
      def remove_attribute(name)
        @attributes.delete(name)
      end

      # Write a single attribute to the +Document+ attribute +Hash+. This will
      # also fire the before and after update callbacks, and perform any
      # necessary typecasting.
      #
      # Options:
      #
      # name: The name of the attribute to update.
      # value: The value to set for the attribute.
      #
      # Example:
      #
      # <tt>person.write_attribute(:title, "Mr.")</tt>
      #
      # This will also cause the observing +Document+ to notify it's parent if
      # there is any.
      def write_attribute(name, value)
        run_callbacks(:before_update)
        @attributes[name] = fields[name].set(value)
        run_callbacks(:after_update)
        notify
      end

      # Writes the supplied attributes +Hash+ to the +Document+. This will only
      # overwrite existing attributes if they are present in the new +Hash+, all
      # others will be preserved.
      #
      # Options:
      #
      # attrs: The +Hash+ of new attributes to set on the +Document+
      #
      # Example:
      #
      # <tt>person.write_attributes(:title => "Mr.")</tt>
      #
      # This will also cause the observing +Document+ to notify it's parent if
      # there is any.
      def write_attributes(attrs = nil)
        process(attrs || {})
        notify
      end

      protected
      # Used when supplying a :reject_if block as an option to
      # accepts_nested_attributes_for
      def reject(attributes, options)
        rejector = options[:reject_if]
        if rejector
          attributes.delete_if do |key, value|
            rejector.call(value)
          end
        end
      end
    end

    module ClassMethods
      # Defines attribute setters for the associations specified by the names.
      # This will work for a has one or has many association.
      #
      # Example:
      #
      #   class Person < Mongoid::Document
      #     has_one :name
      #     has_many :addresses
      #
      #     accepts_nested_attributes_for :name, :addresses
      #   end
      def accepts_nested_attributes_for(*args)
        associations = args.flatten
        options = associations.last.is_a?(Hash) ? associations.pop : {}
        associations.each do |name|
          define_method("#{name}_attributes=") do |attrs|
            reject(attrs, options)
            association = send(name)
            update(association, true)
            association.nested_build(attrs)
          end
        end
      end
    end
  end
end