class Fluent::TimeParser

def parse(value)
  unless value.is_a?(String)
    raise TimeParseError, "value must be string: #{value}"
  end
  if @cache1_key == value
    return @cache1_time
  elsif @cache2_key == value
    return @cache2_time
  else
    begin
      time = @parse.call(value)
    rescue => e
      raise TimeParseError, "invalid time format: value = #{value}, error_class = #{e.class.name}, error = #{e.message}"
    end
    @cache1_key = @cache2_key
    @cache1_time = @cache2_time
    @cache2_key = value
    @cache2_time = time
    return time
  end
end