module Granite
  module Form
    module Model
      module Attributes
        class Base
          attr_reader :type_definition
          delegate :type, :reflection, :owner, :enum, to: :type_definition
          delegate :name, :readonly, to: :reflection

          def initialize(type_definition)
            @type_definition = type_definition
            @origin = :default
          end

          def write_value(value, origin: :user)
            reset
            @origin = origin
            @value_cache = value
          end

          def write(value)
            return if readonly?
            write_value value
          end

          def reset
            remove_variable(:value, :value_before_type_cast)
          end

          def read
            @value_cache
          end

          def read_before_type_cast
            @value_cache
          end

          def came_from_user?
            @origin == :user
          end

          def came_from_default?
            @origin == :default
          end

          def value_present?
            !read.nil? && !(read.respond_to?(:empty?) && read.empty?)
          end

          def query
            !(read.respond_to?(:zero?) ? read.zero? : read.blank?)
          end

          def readonly?
            !!owner.evaluate(readonly)
          end

          def inspect_attribute
            value = case read
            when Date, Time, DateTime
              %("#{read.to_formatted_s(:db)}")
            else
              inspection = read.inspect
              inspection.size > 100 ? inspection.truncate(50) : inspection
            end
            "#{name}: #{value}"
          end

          def pollute
            pollute = owner.class.dirty? && !owner.send(:attribute_changed?, name)

            if pollute
              previous_value = owner.__send__(name)
              owner.send("#{name}_will_change!")

              result = yield

              owner.__send__(:clear_attribute_changes, [name]) if owner.__send__(name) == previous_value

              if previous_value != read || (
                read.respond_to?(:changed?) &&
                  read.changed?
              )
                owner.send(:set_attribute_was, name, previous_value)
              end
              result
            else
              yield
            end
          end

        private

          def remove_variable(*names)
            names.flatten.each do |name|
              name = :"@#{name}"
              remove_instance_variable(name) if instance_variable_defined?(name)
            end
          end

          def variable_cache(name)
            name = :"@#{name}"
            if instance_variable_defined?(name)
              instance_variable_get(name)
            else
              instance_variable_set(name, yield)
            end
          end
        end
      end
    end
  end
end