module Scrivito
  # This class represents a CMS attribute. Attributes can be created, updated, deleted and all
  # attribute properties can be read. Attributes are part of an
  # {Scrivito::ObjClass} and therefore each attribute belongs to exactly
  # one {Scrivito::ObjClass}. Most of the operations interact with the currently
  # selected {Scrivito::Workspace}. Operations like +create+, +destroy+
  # and +update+ need to be performed in the "rtc" workspace.
  #
  # @api public
  class Attribute
    include ModelIdentity

    # Initializes a new attribute.
    #
    # @api public
    #
    # This allows you to set the different properties of an attribute by
    # providing a Hash with the property names as keys and the values you want to set as values.
    #
    # @example Create a new attribute with name "locale" and type "string".
    #   Attribute.new(name: 'locale', type: :string)
    #
    # @example Create a new "enum" attribute named "category" and provide values.
    #   Attribute.new(name: 'category', type: :enum, values: %w(tech social))
    #
    # @param [Hash] properties
    # @option properties [String] :name The name of the attribute.
    # @option properties [String] :type The type of the attribute, can be +string+, +text+, +html+, +linklist+, +link+, +reference+, +referencelist+, +date+, +binary+, +widget+, +enum+ or +multienum+.
    # @option properties [Array<String>] :values Possible values if the type is either +enum+ or +multienum+.
    #
    # @return [Scrivito::Attribute]
    # @raise [Scrivito::ScrivitoError] Raised when no +properties+ are provided.
    def initialize(properties)
      raise ScrivitoError, 'Please provide a hash of Attribute properties.' unless properties

      update_instance_properties(properties)
    end

    # Returns the name of this attribute.
    # @api public
    # @return [String]
    def name
      @name
    end

    # Returns the type of this attribute. The type is either +string+, +text+, +html+, +linklist+,
    # +link+, +reference+, +referencelist+, +date+, +binary+, +widget+, +enum+ or +multienum+.
    # @api public
    # @return [String]
    def type
      @type
    end

    # Returns the values of this attribute, if it is of type +enum+ or +multienum+.
    # @api public
    # @return [Array<String>] values
    def values
      @values
    end

    # Returns the obj class this attribute belongs to.
    # @api public
    # @return [Scrivito::ObjClass]
    attr_reader :obj_class

    # Returns a unique identifier of this attribute. An attribute is unique by
    # its +name+ and its +obj_class+. Implements the {Scrivito::ModelIdentity} interface.
    # @return [Array]
    def id
      [name, obj_class]
    end

    # Binds this attribute to an obj class.
    # @return [Scrivito::ObjClass]
    attr_writer :obj_class

    # Updates this attribute and persists the changes
    # in the CMS on its obj class. The +obj_class+ and +name+ of this attribute can not be updated.
    #
    # @api public
    #
    # See {Attribute#initialize} for a detailed overview of what properties are allowed
    # and how to set them.
    #
    # @example Change the +type+ of the "locale" attribute to "string".
    #   attribute = ObjClass.find('Homepage').attributes['locale']
    #   attribute.update(type: :string)
    #
    # @example Adding the value "sports" to the +enum+ attribute "category" on the "Homepage" obj class.
    #   attribute = ObjClass.find('Homepage').attributes['category']
    #   attribute.update(values: attribute.values << 'sports')
    #
    # @param [Hash] properties
    #
    # @return [nil]
    # @raise [Scrivito::ScrivitoError] Raised when trying to change the +name+ or +obj_class+ property.
    def update(properties)
      properties = properties.with_indifferent_access

      if properties.has_key?(:name)
        raise ScrivitoError, "#{self.class} does not support changing its 'name'. Please remove" \
          " the key from the properties."
      end

      properties = to_cms_rest_api.merge(properties)
      update_instance_properties(properties)
      obj_class.update(attributes: obj_class.attributes.to_a)

      nil
    end

    # Destroys this attribute and persists the change in the CMS.
    #
    # @api public
    #
    # @example Remove the "locale" attribute from the "Homepage" obj class.
    #   ObjClass.find('Homepage').attributes['locale'].destroy
    #
    # @return [nil]
    def destroy
      obj_class.attributes.delete(self)
      obj_class.update(attributes: obj_class.attributes.to_a)

      nil
    end

    # Returns this attribute in the CMS REST API format.
    #
    # @return [Hash]
    def to_cms_rest_api
      data = {
        name: name,
        type: type,
      }

      if %w(enum multienum).include?(type)
        data[:values] = values
      end

      data
    end

    private

    # Updates the instance properties of this attribute with +properties+
    # given in the CMS REST API format.
    #
    # @param [Hash] properties
    # @return [void]
    def update_instance_properties(properties)
      properties = properties.with_indifferent_access

      @name = properties[:name].to_s
      @type = properties[:type].to_s
      @values = (properties[:values] || []).map(&:to_s)
    end
  end
end