defmodule Google.Protobuf.Timestamp do
  @moduledoc """
  A Timestamp represents a point in time independent of any time zone or local
  calendar, encoded as a count of seconds and fractions of seconds at
  nanosecond resolution. The count is relative to an epoch at UTC midnight on
  January 1, 1970, in the proleptic Gregorian calendar which extends the
  Gregorian calendar backwards to year one.

  All minutes are 60 seconds long. Leap seconds are "smeared" so that no leap
  second table is needed for interpretation, using a [24-hour linear
  smear](https://developers.google.com/time/smear).

  The range is from 0001-01-01T00:00:00Z to 9999-12-31T23:59:59.999999999Z. By
  restricting to that range, we ensure that we can convert to and from [RFC
  3339](https://www.ietf.org/rfc/rfc3339.txt) date strings.

  # Examples

  Example 1: Compute Timestamp from POSIX `time()`.

      Timestamp timestamp;
      timestamp.set_seconds(time(NULL));
      timestamp.set_nanos(0);

  Example 2: Compute Timestamp from POSIX `gettimeofday()`.

      struct timeval tv;
      gettimeofday(&tv, NULL);

      Timestamp timestamp;
      timestamp.set_seconds(tv.tv_sec);
      timestamp.set_nanos(tv.tv_usec * 1000);

  Example 3: Compute Timestamp from Win32 `GetSystemTimeAsFileTime()`.

      FILETIME ft;
      GetSystemTimeAsFileTime(&ft);
      UINT64 ticks = (((UINT64)ft.dwHighDateTime) << 32) | ft.dwLowDateTime;

      // A Windows tick is 100 nanoseconds. Windows epoch 1601-01-01T00:00:00Z
      // is 11644473600 seconds before Unix epoch 1970-01-01T00:00:00Z.
      Timestamp timestamp;
      timestamp.set_seconds((INT64) ((ticks / 10000000) - 11644473600LL));
      timestamp.set_nanos((INT32) ((ticks % 10000000) * 100));

  Example 4: Compute Timestamp from Java `System.currentTimeMillis()`.

      long millis = System.currentTimeMillis();

      Timestamp timestamp = Timestamp.newBuilder().setSeconds(millis / 1000)
          .setNanos((int) ((millis % 1000) * 1000000)).build();

  Example 5: Compute Timestamp from Java `Instant.now()`.

      Instant now = Instant.now();

      Timestamp timestamp =
          Timestamp.newBuilder().setSeconds(now.getEpochSecond())
              .setNanos(now.getNano()).build();

  Example 6: Compute Timestamp from current time in Python.

      timestamp = Timestamp()
      timestamp.GetCurrentTime()

  # JSON Mapping

  In JSON format, the Timestamp type is encoded as a string in the
  [RFC 3339](https://www.ietf.org/rfc/rfc3339.txt) format. That is, the
  format is "{year}-{month}-{day}T{hour}:{min}:{sec}[.{frac_sec}]Z"
  where {year} is always expressed using four digits while {month}, {day},
  {hour}, {min}, and {sec} are zero-padded to two digits each. The fractional
  seconds, which can go up to 9 digits (i.e. up to 1 nanosecond resolution),
  are optional. The "Z" suffix indicates the timezone ("UTC"); the timezone
  is required. A proto3 JSON serializer should always use UTC (as indicated by
  "Z") when printing the Timestamp type and a proto3 JSON parser should be
  able to accept both UTC and other timezones (as indicated by an offset).

  For example, "2017-01-15T01:30:15.01Z" encodes 15.01 seconds past
  01:30 UTC on January 15, 2017.

  In JavaScript, one can convert a Date object to this format using the
  standard
  [toISOString()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toISOString)
  method. In Python, a standard `datetime.datetime` object can be converted
  to this format using
  [`strftime`](https://docs.python.org/2/library/time.html#time.strftime) with
  the time format spec '%Y-%m-%dT%H:%M:%S.%fZ'. Likewise, in Java, one can use
  the Joda Time's [`ISODateTimeFormat.dateTime()`](
  http://joda-time.sourceforge.net/apidocs/org/joda/time/format/ISODateTimeFormat.html#dateTime()
  ) to obtain a formatter capable of generating timestamps in this format.
  """

  use Protobuf, protoc_gen_elixir_version: "0.14.1", syntax: :proto3

  def descriptor do
    # credo:disable-for-next-line
    %Google.Protobuf.DescriptorProto{
      name: "Timestamp",
      field: [
        %Google.Protobuf.FieldDescriptorProto{
          name: "seconds",
          extendee: nil,
          number: 1,
          label: :LABEL_OPTIONAL,
          type: :TYPE_INT64,
          type_name: nil,
          default_value: nil,
          options: nil,
          oneof_index: nil,
          json_name: "seconds",
          proto3_optional: nil,
          __unknown_fields__: []
        },
        %Google.Protobuf.FieldDescriptorProto{
          name: "nanos",
          extendee: nil,
          number: 2,
          label: :LABEL_OPTIONAL,
          type: :TYPE_INT32,
          type_name: nil,
          default_value: nil,
          options: nil,
          oneof_index: nil,
          json_name: "nanos",
          proto3_optional: nil,
          __unknown_fields__: []
        }
      ],
      nested_type: [],
      enum_type: [],
      extension_range: [],
      extension: [],
      options: nil,
      oneof_decl: [],
      reserved_range: [],
      reserved_name: [],
      __unknown_fields__: []
    }
  end

  field :seconds, 1, type: :int64
  field :nanos, 2, type: :int32
end
