#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

"""Timestamp utilities.

For internal use only; no backwards-compatibility guarantees.
"""

# pytype: skip-file
# mypy: disallow-untyped-defs

import datetime
import time
from typing import Union
from typing import overload

import dateutil.parser
import pytz
from google.protobuf import duration_pb2
from google.protobuf import timestamp_pb2

from apache_beam.portability import common_urns

# types compatible with Timestamp.of()
TimestampTypes = Union[int, float, 'Timestamp']
# types compatible with Duration.of()
DurationTypes = Union[int, float, 'Duration']
TimestampDurationTypes = Union[int, float, 'Duration', 'Timestamp']


class Timestamp(object):
  """Represents a Unix second timestamp with microsecond granularity.

  Can be treated in common timestamp arithmetic operations as a numeric type.

  Internally stores a time interval as an int of microseconds. This strategy
  is necessary since floating point values lose precision when storing values,
  especially after arithmetic operations (for example, 10000000 % 0.1 evaluates
  to 0.0999999994448885).
  """
  def __init__(self, seconds=0, micros=0):
    # type: (Union[int, float], Union[int, float]) -> None
    if not isinstance(seconds, (int, float)):
      raise TypeError(
          'Cannot interpret %s %s as seconds.' % (seconds, type(seconds)))
    if not isinstance(micros, (int, float)):
      raise TypeError(
          'Cannot interpret %s %s as micros.' % (micros, type(micros)))
    self.micros = int(seconds * 1000000) + int(micros)

  @staticmethod
  def of(seconds):
    # type: (TimestampTypes) -> Timestamp

    """Return the Timestamp for the given number of seconds.

    If the input is already a Timestamp, the input itself will be returned.

    Args:
      seconds: Number of seconds as int, float, long, or Timestamp.

    Returns:
      Corresponding Timestamp object.
    """

    if not isinstance(seconds, (int, float, Timestamp)):
      raise TypeError(
          'Cannot interpret %s %s as Timestamp.' % (seconds, type(seconds)))
    if isinstance(seconds, Timestamp):
      return seconds
    return Timestamp(seconds)

  @staticmethod
  def now():
    # type: () -> Timestamp
    return Timestamp(seconds=time.time())

  @staticmethod
  def _epoch_datetime_utc():
    # type: () -> datetime.datetime
    return datetime.datetime.fromtimestamp(0, pytz.utc)

  @classmethod
  def from_utc_datetime(cls, dt):
    # type: (datetime.datetime) -> Timestamp

    """Create a ``Timestamp`` instance from a ``datetime.datetime`` object.

    Args:
      dt: A ``datetime.datetime`` object in UTC (offset-aware).
    """
    if dt.tzinfo != pytz.utc and dt.tzinfo != datetime.timezone.utc:
      raise ValueError('dt not in UTC: %s' % dt)
    duration = dt - cls._epoch_datetime_utc()
    return Timestamp(duration.total_seconds())

  @classmethod
  def from_rfc3339(cls, rfc3339):
    # type: (str) -> Timestamp

    """Create a ``Timestamp`` instance from an RFC 3339 compliant string.

    .. note::
      All timezones are implicitly converted to UTC.

    Args:
      rfc3339: String in RFC 3339 form.
    """
    try:
      dt = dateutil.parser.isoparse(rfc3339).astimezone(pytz.UTC)
    except ValueError as e:
      raise ValueError(
          "Could not parse RFC 3339 string '{}' due to error: '{}'.".format(
              rfc3339, e))
    return cls.from_utc_datetime(dt)

  def seconds(self) -> int:
    """Returns the timestamp in seconds."""
    return self.micros // 1000000

  def predecessor(self):
    # type: () -> Timestamp

    """Returns the largest timestamp smaller than self."""
    return Timestamp(micros=self.micros - 1)

  def __repr__(self):
    # type: () -> str
    micros = self.micros
    sign = ''
    if micros < 0:
      sign = '-'
      micros = -micros
    int_part = micros // 1000000
    frac_part = micros % 1000000
    if frac_part:
      return 'Timestamp(%s%d.%06d)' % (sign, int_part, frac_part)
    return 'Timestamp(%s%d)' % (sign, int_part)

  def to_utc_datetime(self):
    # type: () -> datetime.datetime
    # We can't easily construct a datetime object from microseconds, so we
    # create one at the epoch and add an appropriate timedelta interval.
    return self._epoch_datetime_utc().replace(tzinfo=None) + datetime.timedelta(
        microseconds=self.micros)

  def to_rfc3339(self):
    # type: () -> str
    # Append 'Z' for UTC timezone.
    return self.to_utc_datetime().isoformat() + 'Z'

  def to_proto(self):
    # type: () -> timestamp_pb2.Timestamp

    """Returns the `google.protobuf.timestamp_pb2` representation."""
    secs = self.micros // 1000000
    nanos = (self.micros % 1000000) * 1000
    return timestamp_pb2.Timestamp(seconds=secs, nanos=nanos)

  @staticmethod
  def from_proto(timestamp_proto):
    # type: (timestamp_pb2.Timestamp) -> Timestamp

    """Creates a Timestamp from a `google.protobuf.timestamp_pb2`.

    Note that the google has a sub-second resolution of nanoseconds whereas this
    class has a resolution of microsends. This class will truncate the
    nanosecond resolution down to the microsecond.
    """

    if timestamp_proto.nanos % 1000 != 0:
      # TODO(BEAM-8738): Better define timestamps.
      raise ValueError(
          "Cannot convert from nanoseconds to microseconds " +
          "because this loses precision. Please make sure that " +
          "this is the correct behavior you want and manually " +
          "truncate the precision to the nearest microseconds. " +
          "See [BEAM-8738] for more information.")

    return Timestamp(
        seconds=timestamp_proto.seconds, micros=timestamp_proto.nanos // 1000)

  def __float__(self):
    # type: () -> float
    # Note that the returned value may have lost precision.
    return self.micros / 1000000

  def __int__(self):
    # type: () -> int
    # Note that the returned value may have lost precision.
    return self.micros // 1000000

  def __eq__(self, other):
    # type: (object) -> bool
    # Allow comparisons between Duration and Timestamp values.
    if isinstance(other, (Duration, Timestamp)):
      return self.micros == other.micros
    elif isinstance(other, (int, float)):
      return self.micros == Timestamp.of(other).micros
    else:
      # Support equality with other types
      return NotImplemented

  def __lt__(self, other):
    # type: (TimestampDurationTypes) -> bool
    # Allow comparisons between Duration and Timestamp values.
    if not isinstance(other, Duration):
      other = Timestamp.of(other)
    return self.micros < other.micros

  def __gt__(self, other):
    # type: (TimestampDurationTypes) -> bool
    return not (self < other or self == other)

  def __le__(self, other):
    # type: (TimestampDurationTypes) -> bool
    return self < other or self == other

  def __ge__(self, other):
    # type: (TimestampDurationTypes) -> bool
    return not self < other

  def __hash__(self):
    # type: () -> int
    return hash(self.micros)

  def __add__(self, other):
    # type: (DurationTypes) -> Timestamp
    other = Duration.of(other)
    return Timestamp(micros=self.micros + other.micros)

  def __radd__(self, other):
    # type: (DurationTypes) -> Timestamp
    return self + other

  @overload
  def __sub__(self, other):
    # type: (DurationTypes) -> Timestamp
    pass

  @overload
  def __sub__(self, other):
    # type: (Timestamp) -> Duration
    pass

  def __sub__(self, other):
    # type: (Union[DurationTypes, Timestamp]) -> Union[Timestamp, Duration]
    if isinstance(other, Timestamp):
      return Duration(micros=self.micros - other.micros)
    other = Duration.of(other)
    return Timestamp(micros=self.micros - other.micros)

  def __mod__(self, other):
    # type: (DurationTypes) -> Duration
    other = Duration.of(other)
    return Duration(micros=self.micros % other.micros)


MIN_TIMESTAMP = Timestamp(
    micros=int(common_urns.constants.MIN_TIMESTAMP_MILLIS.constant) * 1000)
MAX_TIMESTAMP = Timestamp(
    micros=int(common_urns.constants.MAX_TIMESTAMP_MILLIS.constant) * 1000)


class Duration(object):
  """Represents a second duration with microsecond granularity.

  Can be treated in common arithmetic operations as a numeric type.

  Internally stores a time interval as an int of microseconds. This strategy
  is necessary since floating point values lose precision when storing values,
  especially after arithmetic operations (for example, 10000000 % 0.1 evaluates
  to 0.0999999994448885).
  """
  def __init__(self, seconds=0, micros=0):
    # type: (Union[int, float], Union[int, float]) -> None
    self.micros = int(seconds * 1000000) + int(micros)

  @staticmethod
  def of(seconds):
    # type: (DurationTypes) -> Duration

    """Return the Duration for the given number of seconds since Unix epoch.

    If the input is already a Duration, the input itself will be returned.

    Args:
      seconds: Number of seconds as int, float or Duration.

    Returns:
      Corresponding Duration object.
    """

    if isinstance(seconds, Timestamp):
      raise TypeError('Cannot interpret %s as Duration.' % seconds)
    if isinstance(seconds, Duration):
      return seconds
    return Duration(seconds)

  def to_proto(self):
    # type: () -> duration_pb2.Duration

    """Returns the `google.protobuf.duration_pb2` representation."""
    secs = self.micros // 1000000
    nanos = (self.micros % 1000000) * 1000
    return duration_pb2.Duration(seconds=secs, nanos=nanos)

  @staticmethod
  def from_proto(duration_proto):
    # type: (duration_pb2.Duration) -> Duration

    """Creates a Duration from a `google.protobuf.duration_pb2`.

    Note that the google has a sub-second resolution of nanoseconds whereas this
    class has a resolution of microsends. This class will truncate the
    nanosecond resolution down to the microsecond.
    """

    if duration_proto.nanos % 1000 != 0:
      # TODO(BEAM-8738): Better define durations.
      raise ValueError(
          "Cannot convert from nanoseconds to microseconds " +
          "because this loses precision. Please make sure that " +
          "this is the correct behavior you want and manually " +
          "truncate the precision to the nearest microseconds. " +
          "See [BEAM-8738] for more information.")

    return Duration(
        seconds=duration_proto.seconds, micros=duration_proto.nanos // 1000)

  def __repr__(self):
    # type: () -> str
    micros = self.micros
    sign = ''
    if micros < 0:
      sign = '-'
      micros = -micros
    int_part = micros // 1000000
    frac_part = micros % 1000000
    if frac_part:
      return 'Duration(%s%d.%06d)' % (sign, int_part, frac_part)
    return 'Duration(%s%d)' % (sign, int_part)

  def __float__(self):
    # type: () -> float
    # Note that the returned value may have lost precision.
    return self.micros / 1000000

  def __eq__(self, other):
    # type: (object) -> bool
    # Allow comparisons between Duration and Timestamp values.
    if isinstance(other, (Duration, Timestamp)):
      return self.micros == other.micros
    elif isinstance(other, (int, float)):
      return self.micros == Duration.of(other).micros
    else:
      # Support equality with other types
      return NotImplemented

  def __lt__(self, other):
    # type: (TimestampDurationTypes) -> bool
    # Allow comparisons between Duration and Timestamp values.
    if not isinstance(other, Timestamp):
      other = Duration.of(other)
    return self.micros < other.micros

  def __gt__(self, other):
    # type: (TimestampDurationTypes) -> bool
    return not (self < other or self == other)

  def __le__(self, other):
    # type: (TimestampDurationTypes) -> bool
    return self < other or self == other

  def __ge__(self, other):
    # type: (TimestampDurationTypes) -> bool
    return not self < other

  def __hash__(self):
    # type: () -> int
    return hash(self.micros)

  def __neg__(self):
    # type: () -> Duration
    return Duration(micros=-self.micros)

  def __add__(self, other):
    # type: (DurationTypes) -> Duration
    if isinstance(other, Timestamp):
      # defer to Timestamp.__add__
      return NotImplemented
    other = Duration.of(other)
    return Duration(micros=self.micros + other.micros)

  def __radd__(self, other):
    # type: (DurationTypes) -> Duration
    return self + other

  def __sub__(self, other):
    # type: (DurationTypes) -> Duration
    other = Duration.of(other)
    return Duration(micros=self.micros - other.micros)

  def __rsub__(self, other):
    # type: (DurationTypes) -> Duration
    return -(self - other)

  def __mul__(self, other):
    # type: (DurationTypes) -> Duration
    other = Duration.of(other)
    return Duration(micros=self.micros * other.micros // 1000000)

  def __rmul__(self, other):
    # type: (DurationTypes) -> Duration
    return self * other

  def __mod__(self, other):
    # type: (DurationTypes) -> Duration
    other = Duration.of(other)
    return Duration(micros=self.micros % other.micros)


# The minimum granularity / interval expressible in a Timestamp / Duration
# object.
TIME_GRANULARITY = Duration(micros=1)
