module Scrivito
  # @api beta
  class User < Struct.new(:id, :abilities, :description_proc, :suggest_users_proc, :restriction_set)
    class << self
      # Defines a new user.
      # @api beta
      # @param [String] id the unique, unalterable id of the user.
      #   The user id is used to associate the user with the corresponding CMS resources.
      #   It will be persisted in the CMS.
      # @raise [Scrivito::ScrivitoError] if id is blank
      # @raise [Scrivito::ScrivitoError] if id is more than 64 characters long
      # @yieldparam [Scrivito::UserDefinition] user object to define abilities on
      # @see Scrivito::UserDefinition#can
      # @see Scrivito::UserDefinition#description
      # @example
      #   Scrivito::User.define('alice') do |user|
      #     user.can(:publish_workspace) { true }
      #   end
      #
      #   Scrivito::User.define('bob') do |user|
      #     user.description { 'Bob Doe' }
      #     user.can(:publish_workspace) { true }
      #   end
      def define(id, &block)
        assert_valid_id(id)
        user_definition = UserDefinition.new(id)
        yield user_definition
        user_definition.user
      end

      def anonymous_admin
        User.new(
          id: nil,
          abilities: Hash.new(-> {true}).with_indifferent_access,
          description_proc: nil,
          suggest_users_proc: nil
        )
      end

      def find(id)
        if Configuration.find_user_proc
          user = Scrivito::Configuration.find_user_proc.call(id)
          assert_valid_user(user)
          user
        end
      end

      private

      def assert_valid_id(id)
        raise ScrivitoError.new('User id can not be blank') if id.blank?
        raise ScrivitoError.new('User id is too long (max length 64)') if id.length > 64
      end

      def assert_valid_user(user)
        unless user.is_a?(User) || user.nil?
          raise ScrivitoError.new("Expected an instance of #{self} or nil, but got #{user.inspect}")
        end
      end
    end

    def initialize(options)
      super(*options.values_at(:id, :abilities, :description_proc,
        :suggest_users_proc, :restriction_set))
    end

    def able_to?(ability_name)
      !!abilities[ability_name].call
    end

    # Verfies if the User is able to publish changes to a certain {BasicObj Obj}
    #
    # @api beta
    # @param [BasicObj] obj the obj that should be published
    # @return [Boolean] true if the user is allowed to publish otherwise false
    def can_publish?(obj)
      restriction_messages_for(obj).empty?
    end

    # Checks if the User is able to publish changes and returns the message
    # specified in a {UserDefinition#restrict_obj_publish} callback if they are not
    # If the user can publish the obj an empty array is returned
    #
    # @api beta
    # @param [BasicObj] obj the obj that should be published
    # @return [Array<String>] Hints why the user can't publish
    def restriction_messages_for(obj)
      return [] if able_to?(UserDefinition::ADMINISTRATE_CMS_ABILITY)

      if obj.modification == Modification::EDITED
        base_revision_obj = obj.in_revision(obj.revision.workspace.base_revision)

        restriction_set.restriction_messages_for(obj) |
          restriction_set.restriction_messages_for(base_revision_obj)
      else
        restriction_set.restriction_messages_for(obj)
      end
    end

    def description
      @description ||= calculate_description
    end

    def suggest_users(input)
      suggest_users_proc ? suggest_users_proc.call(input) : []
    end

    private

    def calculate_description
      description_proc ? description_proc.call : id
    end
  end
end