module Martyr
  module Runtime
    class FutureFactValue

      attr_reader :fact_record, :level, :fact_key_value, :key_supported
      delegate :dimension_bus, to: :fact_record

      # @param fact_record [Fact]
      # @param level [BaseLevelDefinition] the level that needs to be fetched
      # @param key_supported [Boolean] if true, this means the fact has direct association with the level, and the
      #   value simply needs to be fetched from the dimension. fact_key_value must be provided when true.
      # @param fact_key_value [String, Integer] only relevant if key_supported is true.
      def initialize(fact_record, level, key_supported:, fact_key_value: nil)
        @level = level
        @fact_record = fact_record
        @fact_key_value = fact_key_value.try(:to_i)
        @key_supported = key_supported
      end

      def inspect
        value_loaded? ? @value.inspect : '?'
      end

      def value
        return @value if value_loaded?
        if key_supported
          @active_record = dimension_bus.fetch_supported_query_level_record(level.id, fact_key_value)
          @value = level.record_value(@active_record)
        else
          value = dimension_bus.fetch_unsupported_level_value(level.id, fact_record)
          if level.degenerate?
            @value = value
          else
            @active_record = value
            @value = level.record_value(@active_record)
          end
        end
        @value_loaded = true
        @value
      end

      def active_record
        value unless value_loaded?
        @active_record
      end

      def value_loaded?
        !!@value_loaded
      end

      protected

      def ==(other)
        value == other.value and fact_key_value == other.fact_key_value
      end
    end
  end
end