collection_helper.rb

module CollectionHelper
  #...
  
  # This does a shitload of magic. It handles sort, order, filter, page and search.
  #
  def self.filter_scope(scope, params = {})
    unpermitted_params = []
    params = params.with_indifferent_access

    params[:sort]  ||= 'id'
    params[:order] ||= 'asc'

    params.keys.each do |key|
      relation, column = key.to_s.split('.')
      value = params[key].dup
      negate = value[0] == '!'
      value.slice!(0) if negate
      value = [nil, ''] if value.blank? || value == '!'

      if column.nil?
        column   = relation
        relation = scope.table_name
      end

      table = relation.pluralize

      if scope.connection.table_exists?(table) && scope.connection.column_exists?(table, column)
        if table != scope.table_name
          if scope.reflect_on_association(relation)
            scope = scope.joins(relation.to_sym)
          else
            unpermitted_params << key
          end
        end

        if negate
          scope = scope.where.not("#{table}.#{column}" => value)
        else
          scope = scope.where("#{table}.#{column}" => value)
        end
      end
    end

    if params.include?(:q) or params.include?(:sort)
      sort = params[:sort] ? "#{params[:sort].try(:downcase)} #{params[:order].try(:downcase)}".strip : ''

      if scope.respond_to?(:search_for) && params[:q]
        scope = scope.search_for(params[:q])
      else
        unpermitted_params << 'q' if params[:q]
      end

      scope = scope.order(sort)
    end

    unless params[:page] == 'all' || !scope.respond_to?(:page)
      scope = scope.page(params[:page] || 1)
    end

    raise ActionController::UnpermittedParameters.new(unpermitted_params) if unpermitted_params.any?

    scope
  rescue ScopedSearch::QueryNotSupported => e
    raise ActionController::RoutingError.new(e.message)
  end
end