module AbAdmin
  module Concerns
    module Fileuploads
      def self.included(base)
        base.send :extend, SingletonMethods
      end

      module SingletonMethods
        # Join ActiveRecord object with uploaded file
        # Usage:
        #
        #   class Article < ActiveRecord::Base
        #     has_one :picture, as: :assetable, dependent: :destroy
        #
        #     fileuploads :picture
        #   end
        #
        #
        def fileuploads(*args)
          class_attribute :fileuploads_columns, instance_writer: false
          self.fileuploads_columns = args

          unless self.is_a?(ClassMethods)
            include InstanceMethods
            extend ClassMethods

            attr_accessible :fileupload_guid
            after_create :fileuploads_update, if: :fileupload_changed?
          end
        end
      end

      module ClassMethods
        # Update reflection klass by guid
        def fileupload_update(record_id, guid, method)
          fileupload_scope(method, guid).update_all(assetable_id: record_id, guid: nil)
        end

        # Find asset(s) by guid
        def fileupload_find(method, guid)
          query = fileupload_scope(method, guid)
          fileupload_multiple?(method) ? query.to_a : query.first
        end

        def fileupload_scope(method, guid)
          assoc = reflect_on_association(method.to_sym)
          assoc_scope = assoc.scope ? assoc.klass.instance_exec(&assoc.scope) : assoc.klass
          assoc_scope.where(guid: guid, assetable_type: base_class.name.to_s)
        end

        # Find class by reflection
        def fileupload_klass(method)
          reflect_on_association(method.to_sym).klass
        end

        def fileupload_multiple?(method)
          reflect_on_association(method.to_sym).try(:collection?)
        end
      end

      module InstanceMethods
        def fileupload_guid
          @fileupload_guid ||= AbAdmin.friendly_token
        end

        def fileupload_guid=(value)
          @fileupload_changed = true unless value.blank?
          @fileupload_guid = value.blank? ? nil : value
        end

        def fileupload_changed?
          @fileupload_changed === true
        end

        def fileupload_multiple?(method)
          self.class.fileupload_multiple?(method)
        end

        # Find or build new asset object
        def fileupload_asset(method)
          if fileuploads_columns.include?(method.to_sym)
            asset = new_record? ? self.class.fileupload_find(method, fileupload_guid) : send(method)
            asset ||= send("build_#{method}") if respond_to?("build_#{method}")
            asset
          end
        end

        def fileuploads_columns
          self.class.fileuploads_columns
        end

        protected

        def fileuploads_update
          fileuploads_columns.each do |method|
            self.class.fileupload_update(id, fileupload_guid, method)
          end
        end
      end
    end
  end
end