module MakeRestful::Loaders
  extend ActiveSupport::Concern

  included do

    before_filter :verify_method!
    before_filter :verify_format!

    collection do
      if pagination && !params.has_key?(:all)
        paginated_collection = @resource.paginate page: params[:page], per_page: (params[:per_page] || pagination[:per_page] || 25)
        { resource_name.to_sym => paginated_collection,
          pagination: {
              current_page:   paginated_collection.current_page,
              per_page:       paginated_collection.per_page,
              total_entries:  paginated_collection.total_entries,
              total_pages:    paginated_collection.total_pages
          }
        }
      else
        @resource.all
      end
    end

    instance do
      if finder && @resource.respond_to?(:where)
        @resource.where(finder.to_sym => finder_value).first
      else
        @resource.find(finder_value)
      end
    end

  end

  private

  def load_resource
    if (@resource = resource_class)
      nested_in_resources = params.select{ |param| /_id$/ =~ param }
      @resource = @resource.where(nested_in_resources) if nested_in_resources.present?

    else
      @response = { error: 'error when loading resource' }
      @status = :failed_dependency
      render(load_template: false) and return

    end
  end

  def load_collection
    @collection = instance_eval(&collection_loader)

    unless @collection.present?
      @response = { error: 'no results found' }
      @status = :not_found
      render(load_template: false) and return
    end

    eval("@#{resource_name} = @collection")
  end

  def load_instance(opts={})
    finder = opts[:finder] || send(:finder)
    finder_value = params[finder]

    @instance = instance_eval(&instance_loader)
    eval "@#{instance_name} = @instance"

    unless @instance
      @response = { error: "Could not find record with #{finder}: #{finder_value}"  }
      @status = :not_found
      render(load_template: false) and return
    end

  end

  def verify_method!
    return if allowed_actions.allowed?(params[:action]) || !%w{GET POST PUT PATCH}.include?(request.method)
    @response = { error: "Method not allowed" }
    @status = :method_not_allowed
    render(load_template: false)
  end

  def verify_format!
    return if allowed_formats.allowed?(request.format.symbol)
    @response = { error: "Format:#{request.format} is unsupported" }
    @status = :unsupported_media_type
    render(load_template: false)
  end

  alias :verify_action! :verify_method!

end