module Scrivito

  class ObjData
    MissingAttribute = Class.new

    internal_key_list = %w[
      last_changed
      modification
      permalink
      text_links
      conflicts
    ]

    INTERNAL_KEYS = Set.new(internal_key_list.map { |name| "_#{name}" } )

    internal_comparison_key_list = %w[
      path
      permalink
      widget_pool
    ]

    INTERNAL_COMPARISON_KEYS = Set.new(internal_comparison_key_list.map { |name| "_#{name}" })

    SPECIAL_KEYS = Set.new(%w[ body title blob ])

    ATTRIBUTE_DEFAULT_VALUES = {
      "string"        => "",
      "text"          => "",
      "html"          => "",
      "multienum"     => [],
      "linklist"      => [],
      "referencelist" => [],
      "widget"        => [],
      "enum"          => nil,
      "binary"        => nil,
      "date"          => nil,
      "reference"     => nil,
      "link"          => nil,
    }.freeze

    def value_of(attribute_name)
      value_and_type_of(attribute_name).first
    end

    def type_of(attribute_name)
      value_and_type_of(attribute_name).second
    end

    def unchecked_value_of(attribute_name)
      unchecked_value_and_type_of(attribute_name).first
    end

    def value_and_type_of(attribute_name)
      value_and_type = internal_value_and_type_of(attribute_name)

      if value_and_type.first.is_a?(MissingAttribute)
        raise ScrivitoError.new("Illegal attribute name #{attribute_name}")
      else
        value_and_type
      end
    end

    def unchecked_value_and_type_of(attribute_name)
      value_and_type = internal_value_and_type_of(attribute_name)

      if value_and_type.first.is_a?(MissingAttribute)
        [nil, nil]
      else
        value_and_type
      end
    end

    def all_custom_attributes
      @all_custom_attributes ||= all_attributes.select do |attribute|
        has_custom_attribute?(attribute)
      end
    end

    def raw_value_and_type_of(attribute_name)
      raise NotImplementedError, "implement in subclass"
    end

    def has_custom_attribute?(name)
      raise NotImplementedError, "implement in subclass"
    end

    def all_attributes
      raise NotImplementedError, "implement in subclass"
    end

    def ==(other)
      if other.kind_of?(ObjData)
        (all_attributes | other.all_attributes).each do |attr|
          attr = attr.to_s

          next if attr.start_with?('_') && !INTERNAL_COMPARISON_KEYS.include?(attr)

          if unchecked_value_of(attr) != other.unchecked_value_of(attr)
            return false
          end
        end

        return true
      end

      false
    end

    private

    def internal_value_and_type_of(attribute_name)
      value_and_type = raw_value_and_type_of(attribute_name)

      if value_and_type.blank?
        if INTERNAL_KEYS.include?(attribute_name) || SPECIAL_KEYS.include?(attribute_name)
          type = type_of_internal(attribute_name)
          [default_attribute_value(attribute_name), type]
        else
          [ObjData::MissingAttribute.new, nil]
        end
      else
        value, type = value_and_type
        if value.nil? && has_custom_attribute?(attribute_name)
          value = ATTRIBUTE_DEFAULT_VALUES[type]
        end

        [value, type]
      end
    end

    def type_of_internal(key)
      case key
      when "_permalink"
        "string"
      when "_text_links"
        "linklist"
      when "_last_changed"
        "date"
      when "title", "body"
        "html"
      when "blob"
        "binary"
      else
        nil
      end
    end

    def default_attribute_value(attribute_name)
      case attribute_name
      when "_text_links"
        []
      else
        nil
      end
    end

  end

end