module ActiveModel
  module Type
    class DateTime < Value # :nodoc:
      include Helpers::TimeValue
      include Helpers::AcceptsMultiparameterTime.new(
        defaults: { 4 => 0, 5 => 0 }
      )

      def type
        :datetime
      end

      private

      def cast_value(value)
        return apply_seconds_precision(value) unless value.is_a?(::String)
        return if value.empty?

        fast_string_to_time(value) || fallback_string_to_time(value)
      end

      # '0.123456' -> 123456
      # '1.123456' -> 123456
      def microseconds(time)
        time[:sec_fraction] ? (time[:sec_fraction] * 1_000_000).to_i : 0
      end

      def fallback_string_to_time(string)
        time_hash = ::Date._parse(string)
        time_hash[:sec_fraction] = microseconds(time_hash)

        new_time(*time_hash.values_at(:year, :mon, :mday, :hour, :min, :sec, :sec_fraction, :offset))
      end

      def value_from_multiparameter_assignment(values_hash)
        missing_parameter = (1..3).detect { |key| !values_hash.key?(key) }
        if missing_parameter
          raise ArgumentError, missing_parameter
        end
        super
      end
    end
  end
end
