module Scrivito

# This class is for handling attributes: setting and accessing their values, providing
# default values, restricting the types of widgets that may be added to a +widgetlist+
# attribute, plus a couple of convenience methods.
# @api public
# @see http://scrivito.com/attribute-types Attributes and their type
#
module AttributeContent
  ATTRIBUTE_TYPES = %w[
    binary
    date
    enum
    html
    link
    linklist
    multienum
    reference
    referencelist
    string
    stringlist
    widgetlist
  ]

  COMPATIBLE_ATTRIBUTE_TYPES = [
    %w[enum string],
    %w[html string],
    %w[multienum stringlist],
    %w[string html],
  ]

  #
  # @api public
  #
  # Default attribute values.
  #
  DEFAULT_ATTRIBUTE_VALUES = {
    'binary'        => nil,
    'date'          => nil,
    'enum'          => nil,
    'html'          => '',
    'link'          => nil,
    'linklist'      => [],
    'multienum'     => [],
    'reference'     => nil,
    'referencelist' => [],
    'string'        => '',
    'stringlist'    => [],
    'widgetlist'    => [],
  }

  delegate :attribute_definitions, to: :class

  def has_attribute?(attribute_name)
    has_public_system_attribute?(attribute_name) || has_custom_attribute?(attribute_name)
  end

  def has_custom_attribute?(attribute_name)
    !!attribute_definitions[attribute_name]
  end

  def read_attribute(attribute_name)
    @attribute_cache.fetch(attribute_name) do
      @attribute_cache[attribute_name] = value_of_attribute(attribute_name)
    end
  end

  def type_of_attribute(attribute_name)
    type_of_system_attribute(attribute_name) || attribute_definitions[attribute_name].try(:type)
  end

  def respond_to?(method_id, include_private = false)
    has_custom_attribute?(method_id) || super
  end

  def method_missing(method_name, *args)
    attribute_name = method_name.to_s
    has_custom_attribute?(attribute_name) ? read_attribute(attribute_name) : super
  end

  #
  # Returns the value of an attribute specified by its name.
  # Passing an invalid key will not raise an error but return +nil+.
  #
  # @api public
  # @param [Symbol, String] attribute_name the name of the attribute.
  # @return the value of the attribute if it's defined or +nil+ otherwise.
  #
  def [](attribute_name)
    attribute_name = attribute_name.to_s
    read_attribute(attribute_name) if has_attribute?(attribute_name)
  end

  #
  # Hook method that lets you control the widget classes that are made available for adding
  # instances of them to this page or widget. Override it to allow only specific classes
  # or none at all.
  # Must return either +NilClass+, or +Array+.
  #
  # If +nil+ is returned (default), all widget classes will be available for this page
  # or widget.
  #
  # If an +Array+ is returned, it is expected to include the permitted classes.
  # Their order is preserved as they are offered to the user via the widget browser.
  #
  # @api public
  # @param [String] field_name Name of the widget attribute.
  # @return [nil, Array<Class>]
  # @see http://scrivito.com/limiting-widget-and-page-types Limiting available widget and page types
  #
  def valid_widget_classes_for(field_name)
  end

  def valid_widget_ruby_classes_for(field)
    computed_classes = self.class.assert_classes(valid_widget_classes_for(field),
        '#valid_widget_classes_for')

    ruby_classes = computed_classes || Scrivito.models.widgets.to_a

    ruby_classes.select { |ruby_class| ruby_class.valid_inside_container?(self.class) }
  end


  def modification_for_attribute(attribute_name, revision=Workspace.current.base_revision)
    return Modification::UNMODIFIED unless revision

    if new?(revision)
      Modification::NEW
    elsif deleted?(revision)
      Modification::DELETED
    else
      cms_data_in_revision = cms_data_for_revision(revision)

      if cms_data_in_revision
        other_value = cms_data_in_revision.value_of(attribute_name.to_s)
        if data_from_cms.value_of(attribute_name.to_s) == other_value
          Modification::UNMODIFIED
        else
          Modification::EDITED
        end
      else # I am deleted in both revisions!
        Modification::UNMODIFIED
      end
    end
  end

  #
  # Returns the object class name of this CMS object.
  # @api public
  # @return [String]
  #
  def obj_class_name
    data_from_cms.value_of('_obj_class')
  end

  def find_attribute_containing_widget(widget_id)
    attribute_definitions.each do |attribute_definition|
      if attribute_definition.widgetlist?
        widgetlist_name = attribute_definition.name
        widgetlist_value = data_from_cms.value_of(widgetlist_name)
        return widgetlist_name if widgetlist_value && widgetlist_value.include?(widget_id)
      end
    end
    nil
  end

  def referenced_widgets
    widgets = []

    data_from_cms.attribute_names.each do |attr_name|
      if data_from_cms.type_of(attr_name) == "widgetlist"
        value = data_from_cms.value_of(attr_name) || []
        widgets_in_value = value.map { |widget_id| widget_from_pool(widget_id) }
        widgets += widgets_in_value
      end
    end

    widgets
  end

  def contained_widgets
    referenced = referenced_widgets
    referenced + referenced.map { |widget| widget.contained_widgets }.flatten
  end

  def update_data(data)
    self.data_from_cms = data
    @attribute_cache = {}
  end

  def to_show_view_path
    to_view_path('show')
  end

  def to_details_view_path
    to_view_path('details')
  end

  def data_from_cms
    if @data_from_cms.respond_to?(:call)
      @data_from_cms = @data_from_cms.call
    else
      @data_from_cms
    end
  end

  #
  # Returns a hash to be used for the JSON serialization.
  # @api public
  # @note Override it in subclasses to fit your needs.
  # @param [Hash] options
  # @return [Hash]
  # @see http://api.rubyonrails.org/classes/ActiveModel/Serializers/JSON.html
  #
  def as_json(options = nil)
    {id: id}
  end

  private

  attr_writer :data_from_cms

  def value_of_attribute(attribute_name)
    return obj_class if attribute_name == '_obj_class'
    return value_of_system_attribute(attribute_name) if has_system_attribute?(attribute_name)

    if attribute_definition = attribute_definitions[attribute_name]
      if has_compatible_type_in_backend?(attribute_definition)
        deserialize_attribute_value(attribute_definition)
      else
        default_attribute_value(attribute_definition)
      end
    end
  end

  def has_compatible_type_in_backend?(attribute_definition)
    attribute_name, attribute_type = attribute_definition.name, attribute_definition.type
    attribute_type_from_backend = data_from_cms.type_of(attribute_name)
    attribute_type == attribute_type_from_backend ||
      COMPATIBLE_ATTRIBUTE_TYPES.include?([attribute_type, attribute_type_from_backend])
  end

  def deserialize_attribute_value(attribute_definition)
    serialized_attribute_value = data_from_cms.value_of(attribute_definition.name)
    attribute_deserializer.deserialize(serialized_attribute_value, attribute_definition)
  end

  def attribute_deserializer
    @attribute_deserializer ||= AttributeDeserializer.new(self, workspace)
  end

  def default_attribute_value(attribute_definition)
    if attribute_value = DEFAULT_ATTRIBUTE_VALUES[attribute_definition.type]
      attribute_value.dup
    end
  end

  def to_view_path(view_name)
    "#{obj_class_name.underscore}/#{view_name}"
  end

  #
  # @api public
  #
  module ClassMethods
    #
    # Instantiate an {BasicObj Obj} or {BasicWidget Widget} instance from +obj_data+.
    # If a subclass of +Obj+ or +Widget+ with the same name as the +_obj_class+ property exists,
    # the instantiated +Obj+ or +Widget+ will be an instance of that subclass.
    #
    def instantiate(obj_data)
      obj_class = obj_data.value_of('_obj_class')

      instance = type_computer.compute_type(obj_class).allocate
      instance.update_data(obj_data)

      instance
    end

    def prepare_attributes_for_instantiation(attributes)
      attributes.with_indifferent_access.tap do |attributes|
        prepare_obj_class_attribute(attributes) unless special_class?
      end
    end

    def extract_obj_class_from_attributes(attributes)
      if special_class? && (obj_class_name = attributes[:_obj_class] || attributes['_obj_class'])
        type_computer.compute_type_without_fallback(obj_class_name)
      end
    end

    #
    # Defines an attribute.
    #
    # @api public
    #
    # For the purpose of persisting model data in the CMS, the attributes of the model need
    # to be defined. When defining an attribute, you specify the name under which Scrivito
    # should persist its value as well as the type of content it is meant to contain, and,
    # for the +enum+ and +multienum+ types, the selectable values.
    #
    # Attributes are inherited. If, for example, the +Page+ model defines a +title+ attribute
    # of the +string+ type, the +SpecialPage+ model, which inherits from +Page+, is also equipped
    # with +title+. Inherited attributes can be overridden, i.e. you may redefine +title+ in
    # +SpecialPage+ if you want its type to be +html+, for example.
    #
    # @param [Symbol, String] name name of the attribute.
    # @param [Symbol, String] type type of the attribute. Scrivito supports the following types:
    #   +string+, +stringlist+, +html+, +enum+, +multienum+, +widgetlist+, +reference+,
    #   +referencelist+, +link+, +linklist+, and +binary+.
    # @param [Hash] options definition options.
    #
    # @option options [Symbol, String] :values selectable values for +enum+ and +multienum+ attributes.
    #   If no values are provided for attributes of these types, the resulting array of selectable
    #   values is empty.
    # @option options [Symbol, String] :default custom default value.
    #   See {Scrivito::AttributeContent::DEFAULT_ATTRIBUTE_VALUES} for factory defaults.
    #   See {Scrivito::AttributeContent::ClassMethods#default_for} for more advanced defaults.
    #
    # @return nil
    # @raise [Scrivito::ScrivitoError] if the +type+ is unknown
    # @see Scrivito::AttributeContent::DEFAULT_ATTRIBUTE_VALUES
    # @see Scrivito::AttributeContent::ClassMethods#default_for
    #
    # @example Defining attributes:
    #   class Page < ::Obj
    #     attribute :my_string, :string
    #     attribute 'my_html', 'my_html'
    #     attribute :my_enum, :enum, values: %w[a b c], default: 'a'
    #     attribute :my_multienum, :multienum
    #   end
    #
    #   Page.attribute_definitions
    #   #=> #<Scrivito::AttributeDefinitionCollection>
    #
    #   Page.attribute_definitions[:my_string]
    #   #=> #<Scrivito::AttributeDefinition>
    #
    #   Page.attribute_definitions[:my_string].type
    #   #=> "string"
    #
    #   Page.attribute_definitions[:my_html].type
    #   #=> "html"
    #
    #   Page.attribute_definitions[:my_enum].type
    #   #=> "enum"
    #   Page.attribute_definitions[:my_enum].values
    #   #=> ["a", "b", "c"]
    #
    #   Page.attribute_definitions[:my_multienum].type
    #   #=> "multienum"
    #   Page.attribute_definitions[:my_multienum].values
    #   #=> []
    #
    # @example Inheriting attributes:
    #   class Page < ::Obj
    #     attribute :title, :string
    #   end
    #
    #   class SpecialPage < Page
    #   end
    #
    #   SpecialPage.attribute_definitions[:title].type
    #   #=> "string"
    #
    # @example Overriding inherited attributes:
    #   class Page < ::Obj
    #     attribute :title, :string
    #   end
    #
    #   class SpecialPage < Page
    #     attribute :title, :html
    #   end
    #
    #   Page.attribute_definitions[:title].type
    #   #=> "string"
    #
    #   SpecialPage.attribute_definitions[:title].type
    #   #=> "html"
    #
    # @see http://scrivito.com/default-attribute-values Specifying default attribute values
    #
    def attribute(name, type, options = {})
      name, type, options = name.to_s, type.to_s, options
      assert_valid_attribute_name(name)
      assert_valid_attribute_type(type)
      default = options.delete(:default) || options.delete('default')
      if default
        assert_valid_attribute_default(name, type, default)
        default_for(name) { default }
      end
      own_attribute_definitions[name] = AttributeDefinition.new(name, type, options)
      nil
    end

    #
    # Sets the default value of an attribute.
    #
    # @api public
    #
    # If {Scrivito::BasicObj.create Obj.create} or {Scrivito::BasicWidget.new Widget.new} are called
    # without providing a value for a specific custom attribute, the +block+ is called, and its
    # return value is used as the initial value of this attribute.
    #
    # The +block+ is called with two parameters.
    #
    # The first parameter is an +ActiveSupport::HashWithIndifferentAccess+ containing the attributes
    # that were passed to {Scrivito::BasicObj.create Obj.create} or
    # {Scrivito::BasicWidget.new Widget.new}.
    #
    # The second parameter is a +Hash+ containing the context that was handed over to
    # {Scrivito::BasicObj.create Obj.create} or {Scrivito::BasicWidget.new Widget.new}. If the
    # current visitor is a {Scrivito::User}, this user can be accessed by means of the
    # +:scrivito_user+ key contained in the provided context.
    #
    # @param [Symbol, String] attribute_name the name of the attribute.
    # @param [Proc] block that returns the default value.
    # @raise [Scrivito::ScrivitoError] if no block is present
    # @return nil
    #
    # @see Scrivito::BasicObj.create
    # @see Scrivito::BasicWidget.new
    # @see Scrivito::Configuration.editing_auth
    #
    # @example Setting a simple default:
    #   class MyPage < Obj
    #     attribute :title, :string
    #     default_for(:title) { 'Spam' }
    #   end
    #
    #   my_page = MyPage.create
    #   my_page.title # => 'Spam'
    #
    # @example A default depending on the given attributes:
    #   class MyPage < Obj
    #     attribute :title, :string
    #
    #     default_for :title do |attributes|
    #       if (path = attributes[:_path]) && path.starts_with('/de')
    #         'Hier den Titel eingeben'
    #       else
    #         'Your title here'
    #       end
    #     end
    #   end
    #
    #   my_page = MyPage.create(_path: '/en/test')
    #   my_page.title # => 'Your title here'
    #
    #   my_page = MyPage.create(_path: '/de/test')
    #   my_page.title # => 'Hier den Titel eingeben'
    #
    # @example A more complex default, depending on the given attributes and the current user:
    #   class MyPage < Obj
    #     attribute :title, :string
    #
    #     default_for :title do |attributes, context|
    #       if use_german_title?(context[:scrivito_user], attributes[:_path])
    #         'Hier den Titel eingeben'
    #       else
    #         'Your title here'
    #       end
    #     end
    #
    #     private
    #
    #     #
    #     # Assuming there is a +MyUser+ model equipped with a +preferences+ method which
    #     # returns the preferences of the current user.
    #     # The +email+ of a +MyUser+ is the +id+ of the corresponding +Scrivito::User+ as set in
    #     # +Scrivito::Configuration.editing_auth+.
    #     #
    #     def use_german_title?(scrivito_user, path)
    #       scrivito_user && MyUser.find_by(email: scrivito_user.id).preferences[:locale] == 'de' ||
    #         path && path.starts_with?('/de')
    #     end
    #   end
    #
    #   alice = Scrivito::User.define('alice@scrivito.com')
    #   alice.preferences[:locale] # => 'en'
    #
    #   my_page = MyPage.create({_path: '/de/test'}, alice)
    #   my_page.title # => 'Your title here'
    #
    #   bob = Scrivito::User.define('bob@scrivito.com')
    #   bob.preferences[:locale] # => 'de'
    #
    #   my_page = MyPage.create({_path: '/en/test'}, bob)
    #   my_page.title # => 'Hier den Titel eingeben'
    #
    # @see http://scrivito.com/default-attribute-values Specifying default attribute values
    #
    def default_for(attribute_name, &block)
      attribute_name = attribute_name.to_s
      raise ScrivitoError, 'No block given' unless block_given?
      attribute_defaults[attribute_name] = block
      nil
    end

    # @api public
    #
    # Short description of a CMS object or widget type for the UI. The description is displayed
    # when adding new pages or widgets, for example. As a general rule, it is used whenever no
    # widget or object instance is available. If there is, the +BasicObj#description_for_editor+
    # and, respectively, +BasicWidget#description_for_editor+ instance methods are used instead.
    #
    # This method can be overridden to customize the description displayed to editors.
    #
    # @return [String] the +Class+ name
    def description_for_editor
      name
    end

    #
    # Returns the attribute definitions.
    #
    # @api public
    # @see Scrivito::AttributeContent.attribute
    # @return [Scrivito::AttributeDefinitionCollection]
    #
    def attribute_definitions
      AttributeDefinitionCollection.new(all_attribute_definitions)
    end

    # For testing purposes only.
    def reset_attribute_defaults!
      @attribute_defaults = nil
    end

    def build_attributes_with_defaults(attributes = {}, context = {})
      attributes_with_indifferent_access = attributes.with_indifferent_access
      attributes_with_defaults = attributes_with_indifferent_access.dup

      attribute_definitions.each do |attribute_definition|
        attribute_name = attribute_definition.name
        attribute_default = attribute_defaults[attribute_name]
        if !attributes_with_indifferent_access.has_key?(attribute_name) && attribute_default
          attributes_with_defaults[attribute_name] =
            attribute_default.call(attributes_with_indifferent_access, context)
        end
      end

      if superclass.respond_to?(:build_attributes_with_defaults)
        attributes_with_defaults.merge!(
          superclass.build_attributes_with_defaults(attributes_with_defaults, context))
      end

      attributes_with_defaults
    end

    # @api public
    #
    # This method prevents UI users from creating +Objs+ or +Widgets+ of the given type.
    # It does not prevent adding such objects programatically.
    #
    # By default, +hide_from_editor+ is +false+.
    #
    # @example Hiding error pages:
    #   class ErrorPage < Obj
    #     hide_from_editor
    #   end
    #
    # @example Hiding admin widgets:
    #   class AdminWidget < Widget
    #     hide_from_editor
    #   end
    def hide_from_editor
      @hide_from_editor = true
    end

    def hide_from_editor?
      !!@hide_from_editor
    end

    def special_class?
      type_computer.special_class?(self)
    end

    def assert_classes(classes_expected, callback_method_name)
      if (classes_expected || []).any?{ |a| !a.is_a?(Class) }
        raise "Overridden method #{callback_method_name} must return actual classes!"
      end

      classes_expected
    end

    protected

    def assert_valid_attribute_name(name)
      if name.starts_with?('_')
        raise ScrivitoError,
          "Invalid attribute name '#{name}'. Only system attributes can start with an underscore."
      end
    end

    def assert_valid_attribute_type(type)
      raise ScrivitoError, "Unknown attribute type '#{type}'" unless ATTRIBUTE_TYPES.include?(type)
    end

    def assert_valid_attribute_default(name, type, default)
      inlined_default_allowed = ['string', 'stringlist', 'enum', 'multienum', 'html']
      unless inlined_default_allowed.include?(type)
        raise ScrivitoError, "Attribute '#{name}': " \
            "Inline defaults for '#{type}' attributes are not supported. " \
            "Please use 'default_for(:#{name})' for '#{type}' attributes instead."
      end
    end

    def all_attribute_definitions
      if superclass.respond_to?(:all_attribute_definitions, true)
        superclass.all_attribute_definitions.merge(own_attribute_definitions)
      else
        own_attribute_definitions
      end
    end

    def own_attribute_definitions
      @own_attribute_definitions ||= {}
    end

    private

    def prepare_obj_class_attribute(attributes)
      if obj_class = attributes['_obj_class']
        assert_valid_obj_class(obj_class)
      else
        attributes.merge!('_obj_class' => to_s)
      end
    end

    def assert_valid_obj_class(obj_class)
      unless obj_class == to_s
        raise ScrivitoError, "Cannot set _obj_class to #{obj_class.inspect} when creating #{self}"
      end
    end

    def attribute_defaults
      @attribute_defaults ||= {}
    end
  end
end

end