# encoding: UTF-8

module DryCrud
  # Provides functionality to nest controllers/resources.
  # If a controller is nested, the parent classes and namespaces
  # may be defined as an array in the +nesting+ class attribute.
  #
  # For example, a cities controller, nested in country and a admin
  # namespace, may define this attribute as follows:
  #   self.nesting = :admin, Country
  module Nestable
    extend ActiveSupport::Concern

    # Adds the :nesting class attribute and parent helper methods
    # to the including controller.
    included do
      class_attribute :nesting

      helper_method :parent, :parents

      alias_method_chain :path_args, :nesting
      alias_method_chain :model_scope, :nesting
    end

    private

    # Returns the direct parent ActiveRecord of the current request, if any.
    def parent
      parents.select { |p| p.is_a?(ActiveRecord::Base) }.last
    end

    # Returns the parent entries of the current request, if any.
    # These are ActiveRecords or namespace symbols, corresponding
    # to the defined nesting attribute.
    def parents
      @parents ||= Array(nesting).map do |p|
        if p.is_a?(Class) && p < ActiveRecord::Base
          parent_entry(p)
        else
          p
        end
      end
    end

    # Loads the parent entry for the given ActiveRecord class.
    # By default, performs a find with the class_name_id param.
    def parent_entry(clazz)
      set_model_ivar(clazz.find(params["#{clazz.name.underscore}_id"]))
    end

    # An array of objects used in url_for and related functions.
    def path_args_with_nesting(last)
      parents + [last]
    end

    # Uses the parent entry (if any) to constrain the model scope.
    def model_scope_with_nesting
      if parent.present?
        parent_scope
      else
        model_scope_without_nesting
      end
    end

    # The model scope for the current parent resource.
    def parent_scope
      parent.send(model_class.name.underscore.pluralize)
    end
  end
end