filterer.rb

module Rbac
  class Filterer
    # This list is used to detemine whether RBAC, based on assigned tags, should be applied for a class in a search that is based on the class.
    # Classes should be added to this list ONLY after:
    # 1. Tagging has been enabled in the UI
    # 2. Class contains acts_as_miq_taggable
    CLASSES_THAT_PARTICIPATE_IN_RBAC = %w(
      Authentication
      AvailabilityZone
      CloudNetwork
      CloudSubnet
      CloudTenant
      CloudVolume
      ConfigurationProfile
      ConfigurationScriptBase
      ConfigurationScriptSource
      ConfiguredSystem
      Container
      ContainerBuild
      ContainerGroup
      ContainerImage
      ContainerImageRegistry
      ContainerNode
      ContainerProject
      ContainerReplicator
      ContainerRoute
      ContainerService
      ContainerTemplate
      ContainerVolume
      EmsCluster
      EmsFolder
      ExtManagementSystem
      Flavor
      FloatingIp
      Host
      HostAggregate
      LoadBalancer
      MiddlewareDatasource
      MiddlewareDeployment
      MiddlewareDomain
      MiddlewareMessaging
      MiddlewareServer
      MiddlewareServerGroup
      MiqRequest
      NetworkPort
      NetworkRouter
      OrchestrationStack
      OrchestrationTemplate
      ResourcePool
      SecurityGroup
      Service
      ServiceTemplate
      Storage
      VmOrTemplate
    )

    TAGGABLE_FILTER_CLASSES = CLASSES_THAT_PARTICIPATE_IN_RBAC - %w(EmsFolder) + %w(MiqGroup User Tenant)

    NETWORK_MODELS_FOR_BELONGSTO_FILTER = %w(
      CloudNetwork
      CloudSubnet
      FloatingIp
      LoadBalancer
      NetworkPort
      NetworkRouter
      SecurityGroup
    ).freeze

    BELONGSTO_FILTER_CLASSES = %w(
      EmsCluster
      EmsFolder
      ExtManagementSystem
      Host
      ResourcePool
      Storage
      VmOrTemplate
    ) + NETWORK_MODELS_FOR_BELONGSTO_FILTER

    # key: MiqUserRole#name - user's role
    # value:
    #   array - disallowed roles for the user's role
    DISALLOWED_ROLES_FOR_USER_ROLE = {
      'EvmRole-tenant_administrator' => %w(EvmRole-super_administrator EvmRole-administrator)
    }.freeze

    # key: descendant::klass
    # value:
    #   if it is a symbol/method_name:
    #     descendant.send(method_name) ==> klass
    #   if it is an array [klass_id, descendant_id]
    #     klass.where(klass_id => descendant.select(descendant_id))
    MATCH_VIA_DESCENDANT_RELATIONSHIPS = {
      "ConfiguredSystem::ConfigurationProfile" => [:id, :configuration_profile_id],
      "ConfiguredSystem::ExtManagementSystem"  => :ext_management_system,
      "VmOrTemplate::EmsCluster"               => [:id, :ems_cluster_id],
      "VmOrTemplate::EmsFolder"                => :parent_blue_folders,
      "VmOrTemplate::ExtManagementSystem"      => [:id, :ems_id],
      "VmOrTemplate::Host"                     => [:id, :host_id],
      "VmOrTemplate::ResourcePool"             => :resource_pool,
    }

    # These classes should accept any of the relationship_mixin methods including:
    #   :parent_ids
    #   :ancestor_ids
    #   :child_ids
    #   :sibling_ids
    #   :descendant_ids
    #   ...
    TENANT_ACCESS_STRATEGY = {
      'CloudSnapshot'          => :descendant_ids,
      'CloudTenant'            => :descendant_ids,
      'CloudVolume'            => :descendant_ids,
      'ExtManagementSystem'    => :ancestor_ids,
      'MiqAeNamespace'         => :ancestor_ids,
      'MiqGroup'               => :descendant_ids,
      'MiqRequest'             => :descendant_ids,
      'MiqRequestTask'         => nil, # tenant only
      'MiqTemplate'            => :ancestor_ids,
      'Provider'               => :ancestor_ids,
      'Service'                => :descendant_ids,
      'ServiceTemplate'        => :ancestor_ids,
      'ServiceTemplateCatalog' => :ancestor_ids,
      'Tenant'                 => :descendant_ids,
      'User'                   => :descendant_ids,
      'Vm'                     => :descendant_ids
    }

    # Classes inherited from these classes or mixins are allowing ownership feature on the target model,
    # scope user_or_group_owned is required on target model
    OWNERSHIP_CLASSES = %w(
      OwnershipMixin
      MiqRequest
    ).freeze

    include Vmdb::Logging

    def self.search(*args)
      new.search(*args)
    end

    def self.filtered(*args)
      new.filtered(*args)
    end

    def self.filtered_object(*args)
      new.filtered_object(*args)
    end

    def self.accessible_tenant_ids_strategy(klass)
      TENANT_ACCESS_STRATEGY[klass.base_model.to_s]
    end

    # @param  options filtering options
    # @option options :targets       [nil|Array<Numeric|Object>|scope] Objects to be filtered
    #   - an nil entry uses the optional where_clause
    #   - Array<Numeric> list if ids. :class is required. results are returned as ids
    #   - Array<Object> list of objects. results are returned as objects
    # @option options :named_scope   [Symbol|Array<String,Integer>] support for using named scope in search
    #     Example one scope without args:     :named_scope => :in_my_region
    #     Example one scope with args:        :named_scope => [[:in_region, 1]]
    #     Example more scopes without args:   :named_scope => [:in_my_region, :active]
    #     Example more scopes some with args: :named_scope => [[:in_region, 1], :active, [:with_manager, "X"]]
    # @option options :conditions    [Hash|String|Array<String>]
    # @option options :where_clause  []
    # @option options :sub_filter
    # @option options :include_for_find [Array<Symbol>]
    # @option options :filter

    # @option options :user         [User]     (default: current_user)
    # @option options :userid       [String]   User#userid (not user_id)
    # @option options :miq_group    [MiqGroup] (default: current_user.current_group)
    # @option options :miq_group_id [Numeric]
    # @option options :match_via_descendants [Hash]
    # @option options :order        [Numeric] (default: no order)
    # @option options :limit        [Numeric] (default: no limit)
    # @option options :offset       [Numeric] (default: no offset)
    # @option options :apply_limit_in_sql [Boolean]
    # @option options :ext_options
    # @option options :skip_count   [Boolean] (default: false)
    # @return [Array<Array<Object>,Hash>] list of object and the associated search options
    #   Array<Object> list of object in the same order as input targets if possible
    # @option attrs :auth_count [Numeric]
    # @option attrs :user_filters
    # @option attrs apply_limit_in_sql
    # @option attrs target_ids_for_paging
    def search(options = {})
      if options.key?(:targets) && options[:targets].kind_of?(Array) && options[:targets].empty?
        return [], {:auth_count => 0}
      end
      # => empty inputs - normal find with optional where_clause
      # => list if ids - :class is required for this format.
      # => list of objects
      # results are returned in the same format as the targets. for empty targets, the default result format is a list of ids.
      targets           = options[:targets]
      scope             = options[:named_scope]

      klass             = to_class(options[:class])
      conditions        = options[:conditions]
      where_clause      = options[:where_clause]
      sub_filter        = options[:sub_filter]
      include_for_find  = options[:include_for_find]
      search_filter     = options[:filter]

      limit             = options[:limit]  || targets.try(:limit_value)
      offset            = options[:offset] || targets.try(:offset_value)
      order             = options[:order]  || targets.try(:order_values)

      user, miq_group, user_filters = get_user_info(options[:user],
                                                    options[:userid],
                                                    options[:miq_group],
                                                    options[:miq_group_id])
      tz                     = user.try(:get_timezone)
      attrs                  = {:user_filters => copy_hash(user_filters)}
      ids_clause             = nil
      target_ids             = nil

      if targets.nil?
        scope = apply_scope(klass, scope)
        scope = apply_select(klass, scope, options[:extra_cols]) if options[:extra_cols]
      elsif targets.kind_of?(Array)
        if targets.first.kind_of?(Numeric)
          target_ids = targets
          # assume klass is passed in
        else
          target_ids  = targets.collect(&:id)
          klass       = targets.first.class
          klass       = base_class if !klass.respond_to?(:find) && (base_class = rbac_base_class(klass))
          klass       = safe_base_class(klass) if is_sti?(klass) # always scope to base class if model is STI
        end
        scope = apply_scope(klass, scope)
        scope = apply_select(klass, scope, options[:extra_cols]) if options[:extra_cols]

        ids_clause = ["#{klass.table_name}.id IN (?)", target_ids] if klass.respond_to?(:table_name)
      else # targets is a class_name, scope, class, or acts_as_ar_model class (VimPerformanceDaily in particular)
        targets = to_class(targets).all
        scope = apply_scope(targets, scope)

        unless klass.respond_to?(:find)
          klass = targets
          klass = klass.klass if klass.respond_to?(:klass)
          # working around MiqAeDomain not being in rbac_class
          klass = base_class if (base_class = rbac_base_class(klass))
        end
        scope = apply_select(klass, scope, options[:extra_cols]) if options[:extra_cols]
      end

      user_filters['match_via_descendants'] = to_class(options[:match_via_descendants])

      exp_sql, exp_includes, exp_attrs = search_filter.to_sql(tz) if search_filter && !klass.try(:instances_are_derived?)
      attrs[:apply_limit_in_sql] = (exp_attrs.nil? || exp_attrs[:supported_by_sql]) && user_filters["belongsto"].blank?
      skip_references            = skip_references?(options, attrs)

      # for belongs_to filters, scope_targets uses scope to make queries. want to remove limits for those.
      # if you note, the limits are put back into scope a few lines down from here
      scope = scope.except(:offset, :limit, :order)
      scope = scope_targets(klass, scope, user_filters, user, miq_group)
              .where(conditions).where(sub_filter).where(where_clause).where(exp_sql).where(ids_clause)
              .includes(include_for_find).includes(exp_includes)
              .order(order)

      scope = include_references(scope, klass, include_for_find, exp_includes, skip_references)
      scope = scope.limit(limit).offset(offset) if attrs[:apply_limit_in_sql]
      targets = scope

      unless options[:skip_counts]
        auth_count = attrs[:apply_limit_in_sql] && limit ? targets.except(:offset, :limit, :order).count(:all) : targets.length
      end

      if search_filter && targets && (!exp_attrs || !exp_attrs[:supported_by_sql])
        rejects     = targets.reject { |obj| matches_search_filters?(obj, search_filter, tz) }
        auth_count -= rejects.length unless options[:skip_counts]
        targets -= rejects
      end

      if limit && !attrs[:apply_limit_in_sql]
        attrs[:target_ids_for_paging] = targets.collect(&:id) # Save ids of targets, since we have then all, to avoid going back to SQL for the next page
        offset = offset.to_i
        targets = targets[offset...(offset + limit.to_i)]
      end

      # Preserve sort order of incoming target_ids
      if !target_ids.nil? && !order
        targets = targets.sort_by { |a| target_ids.index(a.id) }
      end

      attrs[:auth_count] = auth_count unless options[:skip_counts]

      return targets, attrs
    end

    def is_sti?(klass)
      klass.respond_to?(:finder_needs_type_condition?) ? klass.finder_needs_type_condition? : false
    end

    # This is a very primitive way of determining whether we want to skip
    # adding references to the query.
    #
    # For now, basically it checks if the caller has not provided :extra_cols,
    # or if the MiqExpression can't apply the limit in SQL.  If both of those
    # are true, then we don't add `.references` to the scope.
    #
    # If still invalid, there is an EXPLAIN check in #include_references that
    # will make sure the query is valid and if not, will include the references
    # as done previously.
    def skip_references?(options, attrs)
      options[:extra_cols].blank? && !attrs[:apply_limit_in_sql]
    end

    def include_references(scope, klass, include_for_find, exp_includes, skip)
      if skip
        # If we are in a transaction, we don't want to polute that
        # transaction with a failed EXPLAIN.  We use a SQL SAVEPOINT (which is
        # created via `transaction(:requires_new => true)`) to prevent that
        # from being an issue (happens in tests with transactional fixtures)
        #
        # See https://stackoverflow.com/a/31146267/3574689
        valid_skip = MiqDatabase.transaction(:requires_new => true) do
          begin
            ActiveRecord::Base.connection.explain(scope.to_sql)
          rescue ActiveRecord::StatementInvalid => e
            unless Rails.env.production?
              warn "There was an issue with the Rbac filter without references!"
              warn "Consider trying to fix this edge case in Rbac::Filterer!  Error Below:"
              warn e.message
              warn e.backtrace
            end
            # returns nil
            raise ActiveRecord::Rollback
          end
        end
        # If the result of the transaction is non-nil, then the block was
        # successful and didn't trigger the ActiveRecord::Rollback, so we can
        # return the scope as is.
        return scope if valid_skip
      end

      ref_includes = Hash(include_for_find).merge(Hash(exp_includes))
      unless polymorphic_include?(klass, ref_includes)
        scope = scope.references(include_for_find).references(exp_includes)
      end
      scope
    end

    def polymorphic_include?(target_klass, includes)
      includes.keys.any? do |incld|
        reflection = target_klass.reflect_on_association(incld)
        reflection && reflection.polymorphic?
      end
    end

    def filtered(objects, options = {})
      Rbac.search(options.reverse_merge(:targets => objects, :skip_counts => true)).first
    end

    def filtered_object(object, options = {})
      filtered([object], options).first
    end

    private

    ##
    # Determine if permissions should be applied directly via klass
    # (klass directly participates in RBAC)
    #
    def apply_rbac_directly?(klass)
      CLASSES_THAT_PARTICIPATE_IN_RBAC.include?(safe_base_class(klass).name)
    end

    ##
    # Determine if permissions should be applied via an associated parent class of klass
    # If the klass is a metrics subclass, RBAC bases permissions checks on
    # the associated application model.  See #rbac_class method
    #
    def apply_rbac_through_association?(klass)
      klass != VimPerformanceDaily && (klass < MetricRollup || klass < Metric)
    end

    def rbac_base_class(klass)
      klass.base_class if klass.respond_to?(:base_class) && rbac_class(klass).nil? && rbac_class(klass.base_class)
    end

    def safe_base_class(klass)
      klass = klass.base_class if klass.respond_to?(:base_class)
      klass
    end

    def rbac_class(scope)
      klass = scope.respond_to?(:klass) ? scope.klass : scope
      return klass if apply_rbac_directly?(klass)
      if apply_rbac_through_association?(klass)
        # Strip "Performance" off class name, which is the associated model
        # of that metric.
        # e.g. HostPerformance => Host
        #      VmPerformance   => VmOrTemplate
        return klass.name[0..-12].constantize.base_class
      end
      nil
    end

    def pluck_ids(targets)
      targets.pluck(:id) if targets
    end

    def self_service_ownership_scope?(miq_group, klass)
      is_ownership_class = OWNERSHIP_CLASSES.any? { |allowed_ownership_klass| klass <= allowed_ownership_klass.safe_constantize }
      miq_group.present? && miq_group.self_service? && is_ownership_class && klass.respond_to?(:user_or_group_owned)
    end

    def self_service_ownership_scope(user, miq_group, klass)
      return nil unless self_service_ownership_scope?(miq_group, klass)

      # for limited_self_service, use user's resources, not user.current_group's resources
      # for reports (user = nil), still use miq_group
      miq_group = nil if user && miq_group.limited_self_service?

      # Get the list of objects that are owned by the user or their LDAP group
      klass.user_or_group_owned(user, miq_group).except(:order)
    end

    def calc_filtered_ids(scope, user_filters, user, miq_group, scope_tenant_filter)
      klass = scope.respond_to?(:klass) ? scope.klass : scope
      expression = miq_group.try(:entitlement).try(:filter_expression)
      expression.set_tagged_target(klass) if expression
      u_filtered_ids = pluck_ids(self_service_ownership_scope(user, miq_group, klass))
      b_filtered_ids = get_belongsto_filter_object_ids(klass, user_filters['belongsto'])
      m_filtered_ids = pluck_ids(get_managed_filter_object_ids(scope, expression || user_filters['managed']))
      d_filtered_ids = pluck_ids(matches_via_descendants(rbac_class(klass), user_filters['match_via_descendants'],
                                                         :user => user, :miq_group => miq_group))

      combine_filtered_ids(u_filtered_ids, b_filtered_ids, m_filtered_ids, d_filtered_ids, scope_tenant_filter.try(:ids))
    end

    #
    # Algorithm: b_intersection_m = (b_filtered_ids INTERSECTION m_filtered_ids)
    #            d_union_b_and_m  = d_filtered_ids UNION b_intersection_m
    #            filter           = d_union_b_and_m INTERSECTION tenant_filter_ids INTERSECTION u_filtered_ids
    #
    # a nil as input for any field means it DOES NOT apply the operation(INTERSECTION, UNION)
    # a nil as output means there is not filter
    #
    # @param u_filtered_ids [nil|Array<Integer>] self service user owned objects
    # @param b_filtered_ids [nil|Array<Integer>] objects that belong to parent
    # @param m_filtered_ids [nil|Array<Integer>] managed filter object ids
    # @param d_filtered_ids [nil|Array<Integer>] ids from descendants
    # @param tenant_filter_ids [nil|Array<Integer>] ids
    # @return nil if filters do not apply
    # @return [Array<Integer>] target ids for filter

    def combine_filtered_ids(u_filtered_ids, b_filtered_ids, m_filtered_ids, d_filtered_ids, tenant_filter_ids)
      intersection = ->(operand1, operand2, operand3 = nil) { [operand1, operand2, operand3].compact.reduce(&:&) }
      union        = ->(operand1, operand2) { [operand1, operand2].compact.reduce(&:|) }

      b_intersection_m         = intersection.call(b_filtered_ids, m_filtered_ids)
      d_union_b_intersection_m = union.call(d_filtered_ids, b_intersection_m)

      intersection.call(d_union_b_intersection_m, tenant_filter_ids, u_filtered_ids)
    end

    # @param parent_class [Class] Class of parent (e.g. Host)
    # @param klass [Class] Class of child node (e.g. Vm)
    # @param scope [] scope for active records (e.g. Vm.archived)
    # @param filtered_ids [nil|Array<Integer>] ids for the parent class (e.g. [1,2,3] for host)
    # @return [Array<Array<Object>,Integer,Integer] targets, authorized count
    def scope_by_parent_ids(parent_class, scope, filtered_ids)
      if filtered_ids
        if (reflection = scope.reflections[parent_class.name.underscore])
          scope.where(reflection.foreign_key.to_sym => filtered_ids)
        else
          scope.where(:resource_type => parent_class.name, :resource_id => filtered_ids)
        end
      else
        scope
      end
    end

    def scope_by_ids(scope, filtered_ids)
      if filtered_ids
        scope.where(:id => filtered_ids)
      else
        scope
      end
    end

    def get_belongsto_filter_object_ids(klass, filter)
      return nil if !BELONGSTO_FILTER_CLASSES.include?(safe_base_class(klass).name) || filter.blank?
      get_belongsto_matches(filter, rbac_class(klass)).collect(&:id)
    end

    def get_managed_filter_object_ids(scope, filter)
      return scope.where(filter.to_sql.first) if filter.kind_of?(MiqExpression)
      klass = scope.respond_to?(:klass) ? scope.klass : scope
      return nil if !TAGGABLE_FILTER_CLASSES.include?(safe_base_class(klass).name) || filter.blank?
      scope.find_tags_by_grouping(filter, :ns => '*').reorder(nil)
    end

    def scope_to_tenant(scope, user, miq_group)
      klass = scope.respond_to?(:klass) ? scope.klass : scope
      user_or_group = user || miq_group
      tenant_id_clause = klass.tenant_id_clause(user_or_group)
      tenant_id_clause ? scope.where(tenant_id_clause) : scope
    end

    def scope_to_cloud_tenant(scope, user, miq_group)
      klass = scope.respond_to?(:klass) ? scope.klass : scope
      user_or_group = user || miq_group
      tenant_id_clause = klass.tenant_id_clause(user_or_group)
      klass.tenant_joins_clause(scope).where(tenant_id_clause)
    end

    def scope_for_user_role_group(klass, scope, miq_group, user, managed_filters)
      user_or_group = miq_group || user

      if user_or_group.try!(:self_service?) && MiqUserRole != klass
        scope.where(:id => klass == User ? user.id : miq_group.id)
      else
        if user_or_group.disallowed_roles
          scope = scope.with_allowed_roles_for(user_or_group)
        end

        if MiqUserRole != klass
          filtered_ids = pluck_ids(get_managed_filter_object_ids(scope, managed_filters))
          scope = scope.with_current_user_groups(user)
        end

        scope_by_ids(scope, filtered_ids)
      end
    end

    ##
    # Main scoping method
    #
    def scope_targets(klass, scope, rbac_filters, user, miq_group)
      # Results are scoped by tenant if the TenancyMixin is included in the class,
      # with a few manual exceptions (User, Tenant). Note that the classes in
      # TENANT_ACCESS_STRATEGY are a consolidated list of them.
      if klass.respond_to?(:scope_by_tenant?) && klass.scope_by_tenant?
        scope = scope_to_tenant(scope, user, miq_group)
      elsif klass.respond_to?(:scope_by_cloud_tenant?) && klass.scope_by_cloud_tenant?
        scope = scope_to_cloud_tenant(scope, user, miq_group)
      end

      if apply_rbac_directly?(klass)
        filtered_ids = calc_filtered_ids(scope, rbac_filters, user, miq_group, nil)
        scope_by_ids(scope, filtered_ids)
      elsif apply_rbac_through_association?(klass)
        # if subclasses of MetricRollup or Metric, use the associated
        # model to derive permissions from
        associated_class = rbac_class(scope)

        if associated_class.try(:scope_by_tenant?)
          scope_tenant_filter = scope_to_tenant(associated_class, user, miq_group)
        end

        filtered_ids = calc_filtered_ids(associated_class, rbac_filters, user, miq_group, scope_tenant_filter)
        scope_by_parent_ids(associated_class, scope, filtered_ids)
      elsif [MiqUserRole, MiqGroup, User].include?(klass)
        scope_for_user_role_group(klass, scope, miq_group, user, rbac_filters['managed'])
      elsif klass == Tenant
        filtered_ids = pluck_ids(get_managed_filter_object_ids(scope, rbac_filters['managed']))
        scope_by_ids(scope, filtered_ids)
      else
        scope
      end
    end

    def get_user_info(user, userid, miq_group, miq_group_id)
      user, miq_group = lookup_user_group(user, userid, miq_group, miq_group_id)
      [user, miq_group, lookup_user_filters(user || miq_group)]
    end

    def lookup_user_group(user, userid, miq_group, miq_group_id)
      user ||= (userid && User.find_by_userid(userid)) || User.current_user
      miq_group_id ||= miq_group.try!(:id)
      return [user, user.current_group] if user && user.current_group_id.to_s == miq_group_id.to_s

      if user
        if miq_group_id && (detected_group = user.miq_groups.detect { |g| g.id.to_s == miq_group_id.to_s })
          user.current_group = detected_group
        elsif miq_group_id && user.super_admin_user?
          user.current_group = miq_group || MiqGroup.find_by(:id => miq_group_id)
        end
      else
        miq_group ||= miq_group_id && MiqGroup.find_by(:id => miq_group_id)
      end
      [user, user.try(:current_group) || miq_group]
    end

    # for reports, user is currently nil, so use the group filter
    # the user.get_filters delegates to user.current_group anyway
    def lookup_user_filters(miq_group)
      filters = miq_group.try!(:get_filters).try!(:dup) || {}
      filters["managed"] ||= []
      filters["belongsto"] ||= []
      filters
    end

    # @param klass [Class] base_class found in CLASSES_THAT_PARTICIPATE_IN_RBAC
    # @option options :user [User]
    # @option options :miq_group [MiqGroup]
    def matches_via_descendants(klass, descendant_klass, options)
      if descendant_klass && (method_name = lookup_method_for_descendant_class(klass, descendant_klass))
        descendants = filtered(descendant_klass, options)
        if method_name.kind_of?(Array)
          klass_id, descendant_id = method_name
          klass.where(klass_id => descendants.select(descendant_id)).distinct
        else
          MiqPreloader.preload(descendants, method_name)
          descendants.flat_map { |object| object.send(method_name) }.grep(klass).uniq
        end
      end
    end

    def lookup_method_for_descendant_class(klass, descendant_klass)
      key = "#{descendant_klass.base_class}::#{klass.base_class}"
      MATCH_VIA_DESCENDANT_RELATIONSHIPS[key].tap do |method_name|
        _log.warn("could not find method name for #{key}") if method_name.nil?
      end
    end

    def to_class(klass)
      klass.kind_of?(String) || klass.kind_of?(Symbol) ? klass.to_s.constantize : klass
    end

    def send_scope(klass, scope)
      scope_name = Array.wrap(scope).first
      if scope_name.nil?
        klass
      elsif klass.nil? || !klass.respond_to?(scope_name)
        class_name = klass.nil? ? "Object" : klass.name
        raise _("Named scope '%{scope_name}' is not defined for class '%{class_name}'") % {:scope_name => scope_name,
                                                                                           :class_name => class_name}
      else
        klass.send(*scope)
      end
    end

    def apply_scope(klass, scope)
      klass = klass.all
      if scope.kind_of?(Array)
        scope.inject(klass) { |k, s| send_scope(k, s) }
      else
        send_scope(klass, scope)
      end
    end

    def apply_select(klass, scope, extra_cols)
      scope.select(scope.select_values.blank? ? klass.arel_table[Arel.star] : nil).select(extra_cols)
    end

    def get_belongsto_matches(blist, klass)
      return get_belongsto_matches_for_host(blist) if klass <= Host
      return get_belongsto_matches_for_storage(blist) if klass == Storage
      association_name = klass.base_model.to_s.tableize

      blist.flat_map do |bfilter|
        vcmeta_list = MiqFilter.belongsto2object_list(bfilter)
        next [] if vcmeta_list.empty?
        # typically, this is the only one we want:
        vcmeta = vcmeta_list.last

        if ([ExtManagementSystem, Host].any? { |x| vcmeta.kind_of?(x) } && klass <= VmOrTemplate) ||
           (vcmeta.kind_of?(ManageIQ::Providers::NetworkManager)        && NETWORK_MODELS_FOR_BELONGSTO_FILTER.any? { |association_class| klass <= association_class.safe_constantize })
          vcmeta.send(association_name).to_a
        else
          vcmeta_list.grep(klass) + vcmeta.descendants.grep(klass)
        end
      end.uniq
    end

    def get_belongsto_matches_for_host(blist)
      clusters = []
      hosts = []
      blist.each do |bfilter|
        vcmeta = MiqFilter.belongsto2object(bfilter)
        next unless vcmeta

        subtree  = vcmeta.subtree
        clusters += subtree.grep(EmsCluster)
        hosts    += subtree.grep(Host)
      end
      MiqPreloader.preload_and_map(clusters, :hosts) + hosts
    end

    def get_belongsto_matches_for_storage(blist)
      sources = blist.map do |bfilter|
        MiqFilter.belongsto2object_list(bfilter).reverse.detect { |v| v.respond_to?(:storages) }
      end.select(&:present?)
      MiqPreloader.preload_and_map(sources, :storages)
    end

    def matches_search_filters?(obj, filter, tz)
      filter.nil? || filter.lenient_evaluate(obj, tz)
    end
  end
end