module ActiveRecord
  module Scoping
    module Default
      extend ActiveSupport::Concern

      included do
        # Stores the default scope for the class.
        class_attribute :default_scopes, instance_writer: false, instance_predicate: false
        class_attribute :default_scope_override, instance_writer: false, instance_predicate: false

        self.default_scopes = []
        self.default_scope_override = nil
      end

      module ClassMethods
        # Returns a scope for the model without the previously set scopes.
        #
        #   class Post < ActiveRecord::Base
        #     def self.default_scope
        #       where(published: true)
        #     end
        #   end
        #
        #   Post.all                                  # Fires "SELECT * FROM posts WHERE published = true"
        #   Post.unscoped.all                         # Fires "SELECT * FROM posts"
        #   Post.where(published: false).unscoped.all # Fires "SELECT * FROM posts"
        #
        # This method also accepts a block. All queries inside the block will
        # not use the previously set scopes.
        #
        #   Post.unscoped {
        #     Post.limit(10) # Fires "SELECT * FROM posts LIMIT 10"
        #   }
        def unscoped
          block_given? ? relation.scoping { yield } : relation
        end

        # Are there attributes associated with this scope?
        def scope_attributes? # :nodoc:
          super || default_scopes.any? || respond_to?(:default_scope)
        end

        def before_remove_const #:nodoc:
          self.current_scope = nil
        end

        private

          # Use this macro in your model to set a default scope for all operations on
          # the model.
          #
          #   class Article < ActiveRecord::Base
          #     default_scope { where(published: true) }
          #   end
          #
          #   Article.all # => SELECT * FROM articles WHERE published = true
          #
          # The #default_scope is also applied while creating/building a record.
          # It is not applied while updating a record.
          #
          #   Article.new.published    # => true
          #   Article.create.published # => true
          #
          # (You can also pass any object which responds to +call+ to the
          # +default_scope+ macro, and it will be called when building the
          # default scope.)
          #
          # If you use multiple #default_scope declarations in your model then
          # they will be merged together:
          #
          #   class Article < ActiveRecord::Base
          #     default_scope { where(published: true) }
          #     default_scope { where(rating: 'G') }
          #   end
          #
          #   Article.all # => SELECT * FROM articles WHERE published = true AND rating = 'G'
          #
          # This is also the case with inheritance and module includes where the
          # parent or module defines a #default_scope and the child or including
          # class defines a second one.
          #
          # If you need to do more complex things with a default scope, you can
          # alternatively define it as a class method:
          #
          #   class Article < ActiveRecord::Base
          #     def self.default_scope
          #       # Should return a scope, you can call 'super' here etc.
          #     end
          #   end
          def default_scope(scope = nil) # :doc:
            scope = Proc.new if block_given?

            if scope.is_a?(Relation) || !scope.respond_to?(:call)
              raise ArgumentError,
                "Support for calling #default_scope without a block is removed. For example instead " \
                "of `default_scope where(color: 'red')`, please use " \
                "`default_scope { where(color: 'red') }`. (Alternatively you can just redefine " \
                "self.default_scope.)"
            end

            self.default_scopes += [scope]
          end

          def build_default_scope(base_rel = nil)
            return if abstract_class?

            if default_scope_override.nil?
              self.default_scope_override = !Base.is_a?(method(:default_scope).owner)
            end

            if default_scope_override
              # The user has defined their own default scope method, so call that
              evaluate_default_scope { default_scope }
            elsif default_scopes.any?
              base_rel ||= relation
              evaluate_default_scope do
                default_scopes.inject(base_rel) do |default_scope, scope|
                  scope = scope.respond_to?(:to_proc) ? scope : scope.method(:call)
                  default_scope.merge(base_rel.instance_exec(&scope))
                end
              end
            end
          end

          def ignore_default_scope?
            ScopeRegistry.value_for(:ignore_default_scope, base_class)
          end

          def ignore_default_scope=(ignore)
            ScopeRegistry.set_value_for(:ignore_default_scope, base_class, ignore)
          end

          # The ignore_default_scope flag is used to prevent an infinite recursion
          # situation where a default scope references a scope which has a default
          # scope which references a scope...
          def evaluate_default_scope
            return if ignore_default_scope?

            begin
              self.ignore_default_scope = true
              yield
            ensure
              self.ignore_default_scope = false
            end
          end
      end
    end
  end
end
