ability.rb

# frozen_string_literal: true

require_relative 'ability/rules.rb'
require_relative 'ability/actions.rb'
require_relative 'unauthorized_message_resolver.rb'
require_relative 'ability/strong_parameter_support'

module CanCan
  # This module is designed to be included into an Ability class. This will
  # provide the "can" methods for defining and checking abilities.
  #
  #   class Ability
  #     include CanCan::Ability
  #
  #     def initialize(user)
  #       if user.admin?
  #         can :manage, :all
  #       else
  #         can :read, :all
  #       end
  #     end
  #   end
  #
  module Ability
    include CanCan::Ability::Rules
    include CanCan::Ability::Actions
    include CanCan::UnauthorizedMessageResolver
    include StrongParameterSupport

    # Check if the user has permission to perform a given action on an object.
    #
    #   can? :destroy, @project
    #
    # You can also pass the class instead of an instance (if you don't have one handy).
    #
    #   can? :create, Project
    #
    # Nested resources can be passed through a hash, this way conditions which are
    # dependent upon the association will work when using a class.
    #
    #   can? :create, @category => Project
    #
    # You can also pass multiple objects to check. You only need to pass a hash
    # following the pattern { :any => [many subjects] }. The behaviour is check if
    # there is a permission on any of the given objects.
    #
    #   can? :create, {:any => [Project, Rule]}
    #
    #
    # Any additional arguments will be passed into the "can" block definition. This
    # can be used to pass more information about the user's request for example.
    #
    #   can? :create, Project, request.remote_ip
    #
    #   can :create, Project do |project, remote_ip|
    #     # ...
    #   end
    #
    # Not only can you use the can? method in the controller and view (see ControllerAdditions),
    # but you can also call it directly on an ability instance.
    #
    #   ability.can? :destroy, @project
    #
    # This makes testing a user's abilities very easy.
    #
    #   def test "user can only destroy projects which he owns"
    #     user = User.new
    #     ability = Ability.new(user)
    #     assert ability.can?(:destroy, Project.new(:user => user))
    #     assert ability.cannot?(:destroy, Project.new)
    #   end
    #
    # Also see the RSpec Matchers to aid in testing.
    def can?(action, subject, attribute = nil, *extra_args)
      match = extract_subjects(subject).lazy.map do |a_subject|
        relevant_rules_for_match(action, a_subject).detect do |rule|
          rule.matches_conditions?(action, a_subject, attribute, *extra_args) && rule.matches_attributes?(attribute)
        end
      end.reject(&:nil?).first
      match ? match.base_behavior : false
    end

    # Convenience method which works the same as "can?" but returns the opposite value.
    #
    #   cannot? :destroy, @project
    #
    def cannot?(*args)
      !can?(*args)
    end

    # Defines which abilities are allowed using two arguments. The first one is the action
    # you're setting the permission for, the second one is the class of object you're setting it on.
    #
    #   can :update, Article
    #
    # You can pass an array for either of these parameters to match any one.
    # Here the user has the ability to update or destroy both articles and comments.
    #
    #   can [:update, :destroy], [Article, Comment]
    #
    # You can pass :all to match any object and :manage to match any action. Here are some examples.
    #
    #   can :manage, :all
    #   can :update, :all
    #   can :manage, Project
    #
    # You can pass a hash of conditions as the third argument. Here the user can only see active projects which he owns.
    #
    #   can :read, Project, :active => true, :user_id => user.id
    #
    # See ActiveRecordAdditions#accessible_by for how to use this in database queries. These conditions
    # are also used for initial attributes when building a record in ControllerAdditions#load_resource.
    #
    # If the conditions hash does not give you enough control over defining abilities, you can use a block
    # along with any Ruby code you want.
    #
    #   can :update, Project do |project|
    #     project.groups.include?(user.group)
    #   end
    #
    # If the block returns true then the user has that :update ability for that project, otherwise he
    # will be denied access. The downside to using a block is that it cannot be used to generate
    # conditions for database queries.
    #
    # You can pass custom objects into this "can" method, this is usually done with a symbol
    # and is useful if a class isn't available to define permissions on.
    #
    #   can :read, :stats
    #   can? :read, :stats # => true
    #
    # IMPORTANT: Neither a hash of conditions nor a block will be used when checking permission on a class.
    #
    #   can :update, Project, :priority => 3
    #   can? :update, Project # => true
    #
    # If you pass no arguments to +can+, the action, class, and object will be passed to the block and the
    # block will always be executed. This allows you to override the full behavior if the permissions are
    # defined in an external source such as the database.
    #
    #   can do |action, object_class, object|
    #     # check the database and return true/false
    #   end
    #
    def can(action = nil, subject = nil, *attributes_and_conditions, &block)
      add_rule(Rule.new(true, action, subject, *attributes_and_conditions, &block))
    end

    # Defines an ability which cannot be done. Accepts the same arguments as "can".
    #
    #   can :read, :all
    #   cannot :read, Comment
    #
    # A block can be passed just like "can", however if the logic is complex it is recommended
    # to use the "can" method.
    #
    #   cannot :read, Product do |product|
    #     product.invisible?
    #   end
    #
    def cannot(action = nil, subject = nil, *attributes_and_conditions, &block)
      add_rule(Rule.new(false, action, subject, *attributes_and_conditions, &block))
    end

    # User shouldn't specify targets with names of real actions or it will cause Seg fault
    def validate_target(target)
      error_message = "You can't specify target (#{target}) as alias because it is real action name"
      raise Error, error_message if aliased_actions.values.flatten.include? target
    end

    def model_adapter(model_class, action)
      adapter_class = ModelAdapters::AbstractAdapter.adapter_class(model_class)
      adapter_class.new(model_class, relevant_rules_for_query(action, model_class))
    end

    # See ControllerAdditions#authorize! for documentation.
    def authorize!(action, subject, *args)
      message = args.last.is_a?(Hash) && args.last.key?(:message) ? args.pop[:message] : nil
      if cannot?(action, subject, *args)
        message ||= unauthorized_message(action, subject)
        raise AccessDenied.new(message, action, subject, args)
      end
      subject
    end

    def attributes_for(action, subject)
      attributes = {}
      relevant_rules(action, subject).map do |rule|
        attributes.merge!(rule.attributes_from_conditions) if rule.base_behavior
      end
      attributes
    end

    def has_block?(action, subject)
      relevant_rules(action, subject).any?(&:only_block?)
    end

    def has_raw_sql?(action, subject)
      relevant_rules(action, subject).any?(&:only_raw_sql?)
    end

    # Copies all rules and aliased actions of the given +CanCan::Ability+ and adds them to +self+.
    #   class ReadAbility
    #     include CanCan::Ability
    #
    #     def initialize
    #       can :read, User
    #       alias_action :show, :index, to: :see
    #     end
    #   end
    #
    #   class WritingAbility
    #     include CanCan::Ability
    #
    #     def initialize
    #       can :edit, User
    #       alias_action :create, :update, to: :modify
    #     end
    #   end
    #
    #   read_ability = ReadAbility.new
    #   read_ability.can? :edit, User.new #=> false
    #   read_ability.merge(WritingAbility.new)
    #   read_ability.can? :edit, User.new #=> true
    #   read_ability.aliased_actions #=> [:see => [:show, :index], :modify => [:create, :update]]
    #
    # If there are collisions when merging the +aliased_actions+, the actions on +self+ will be
    # overwritten.
    #
    # class ReadAbility
    #   include CanCan::Ability
    #
    #   def initialize
    #     alias_action :show, :index, to: :see
    #   end
    # end
    #
    # class ShowAbility
    #   include CanCan::Ability
    #
    #   def initialize
    #     alias_action :show, to: :see
    #   end
    # end
    #
    # read_ability = ReadAbility.new
    # read_ability.merge(ShowAbility)
    # read_ability.aliased_actions #=> [:see => [:show]]
    def merge(ability)
      ability.rules.each do |rule|
        add_rule(rule.dup)
      end
      @aliased_actions = aliased_actions.merge(ability.aliased_actions)
      self
    end

    # Return a hash of permissions for the user in the format of:
    #   {
    #     can: can_hash,
    #     cannot: cannot_hash
    #   }
    #
    # Where can_hash and cannot_hash are formatted thusly:
    #   {
    #     action: { subject: [attributes] }
    #   }
    def permissions
      permissions_list = {
        can: Hash.new { |actions, k1| actions[k1] = Hash.new { |subjects, k2| subjects[k2] = [] } },
        cannot: Hash.new { |actions, k1| actions[k1] = Hash.new { |subjects, k2| subjects[k2] = [] } }
      }
      rules.each { |rule| extract_rule_in_permissions(permissions_list, rule) }
      permissions_list
    end

    def extract_rule_in_permissions(permissions_list, rule)
      expand_actions(rule.actions).each do |action|
        container = rule.base_behavior ? :can : :cannot
        rule.subjects.each do |subject|
          permissions_list[container][action][subject.to_s] += rule.attributes
        end
      end
    end

    private

    def unauthorized_message_keys(action, subject)
      subject = (subject.class == Class ? subject : subject.class).name.underscore unless subject.is_a? Symbol
      aliases = aliases_for_action(action)
      [subject, :all].product([*aliases, :manage]).map do |try_subject, try_action|
        :"#{try_action}.#{try_subject}"
      end
    end

    # It translates to an array the subject or the hash with multiple subjects given to can?.
    def extract_subjects(subject)
      if subject.is_a?(Hash) && subject.key?(:any)
        subject[:any]
      else
        [subject]
      end
    end

    def alternative_subjects(subject)
      subject = subject.class unless subject.is_a?(Module)
      [:all, *subject.ancestors, subject.class.to_s]
    end
  end
end