module ActiveAdmin::Filters::ResourceExtension

def add_filter(attribute, options = {})
  raise Disabled unless filters_enabled?
  (@filters ||= {})[attribute.to_sym] = options
end

def add_filters_sidebar_section
  self.sidebar_sections << filters_sidebar_section
end

def add_search_status_sidebar_section
  self.sidebar_sections << ActiveAdmin::Filters::ActiveSidebar.new
end

def current_filters=(bool)
  @current_filters_enabled = bool
end

def current_filters_enabled?
  @current_filters_enabled.nil? ? namespace.current_filters : @current_filters_enabled
end

def custom_ransack_filters
  if resource_class.respond_to?(:_ransackers)
    resource_class._ransackers.keys.map(&:to_sym)
  else
    []
  end
end

def default_association_filters
  if resource_class.respond_to?(:reflect_on_all_associations)
    poly, not_poly = resource_class.reflect_on_all_associations.partition { |r| r.macro == :belongs_to && r.options[:polymorphic] }
    # remove deeply nested associations
    not_poly.reject! { |r| r.chain.length > 2 }
    filters = poly.map(&:foreign_type) + not_poly.map(&:name)
    filters.map &:to_sym
  else
    []
  end
end

def default_filters
  result = []
  result.concat default_association_filters if namespace.include_default_association_filters
  result.concat content_columns
  result.concat custom_ransack_filters
  result
end

def filter_lookup
  filters = @filters.try(:dup) || {}
  if filters.empty? || preserve_default_filters?
    default_filters.each do |f|
      filters[f] ||= {}
    end
  end
  if @filters_to_remove
    @filters_to_remove.each &filters.method(:delete)
  end
  filters
end

def filters
  filters_enabled? ? filter_lookup : {}
end

def filters=(bool)
  @filters_enabled = bool
end

def filters_enabled?
  @filters_enabled.nil? ? namespace.filters : @filters_enabled
end

def filters_sidebar_section
  ActiveAdmin::SidebarSection.new :filters, only: :index, if: -> { active_admin_config.filters.any? } do
    active_admin_filters_form_for assigns[:search], active_admin_config.filters
  end
end

def initialize(*)
  super
  add_filters_sidebar_section
  add_search_status_sidebar_section
end

def preserve_default_filters!
  @preserve_default_filters = true
end

def preserve_default_filters?
  @preserve_default_filters == true
end

def remove_filter(*attributes)
  raise Disabled unless filters_enabled?
  attributes.each { |attribute| (@filters_to_remove ||= []) << attribute.to_sym }
end

def reset_filters!
  @filters = nil
  @filters_to_remove = nil
end