"""Unified RPKI date/time handling, based on the standard Python datetime module.

Module name chosen to sidestep a nightmare of import-related errors
that occur with the more obvious module names.

$Id$

Copyright (C) 2007--2008  American Registry for Internet Numbers ("ARIN")

Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND ARIN DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS.  IN NO EVENT SHALL ARIN BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.
"""

import datetime as pydatetime
import re

def now():
  """Get current timestamp."""
  return datetime.utcnow()

class datetime(pydatetime.datetime):
  """RPKI extensions to standard datetime.datetime class.  All work
  here is in UTC, so we use naive datetime objects.
  """

  def totimestamp(self):
    """Convert to seconds from epoch (like time.time()).  Conversion
    method is a bit silly, but avoids time module timezone whackiness.
    """
    return int(self.strftime("%s"))

  @classmethod
  def fromUTCTime(cls, x):
    """Convert from ASN.1 UTCTime."""
    return cls.strptime(x, "%y%m%d%H%M%SZ")

  def toUTCTime(self):
    """Convert to ASN.1 UTCTime."""
    return self.strftime("%y%m%d%H%M%SZ")

  @classmethod
  def fromGeneralizedTime(cls, x):
    """Convert from ASN.1 GeneralizedTime."""
    return cls.strptime(x, "%Y%m%d%H%M%SZ")

  def toGeneralizedTime(self):
    """Convert to ASN.1 GeneralizedTime."""
    return self.strftime("%Y%m%d%H%M%SZ")

  @classmethod
  def fromASN1tuple(cls, x):
    """Convert from ASN.1 tuple representation."""
    assert isinstance(x, tuple) and len(x) == 2 and x[0] in ("utcTime", "generalTime")
    if x[0] == "utcTime":
      return cls.fromUTCTime(x[1])
    else:
      return cls.fromGeneralizedTime(x[1])

  ## @var PKIX_threshhold
  # Threshold specified in RFC 3280 for switchover from UTCTime to GeneralizedTime.

  PKIX_threshhold = pydatetime.datetime(2050, 1, 1)

  def toASN1tuple(self):
    """Convert to ASN.1 tuple representation."""
    if self < self.PKIX_threshhold:
      return "utcTime", self.toUTCTime()
    else:
      return "generalTime", self.toGeneralizedTime()

  @classmethod
  def fromXMLtime(cls, x):
    """Convert from XML time representation."""
    if x is None:
      return None
    else:
      return cls.strptime(x, "%Y-%m-%dT%H:%M:%SZ")

  def toXMLtime(self):
    """Convert to XML time representation."""
    return self.strftime("%Y-%m-%dT%H:%M:%SZ")

  def __str__(self):
    return self.toXMLtime()

  @classmethod
  def fromdatetime(cls, x):
    """Convert a datetime.datetime object into this subclass.
    This is whacky due to the weird constructors for datetime.
    """
    return cls.combine(x.date(), x.time())

  def __add__(self, other):
    """Force correct class for timedelta results."""
    return self.fromdatetime(pydatetime.datetime.__add__(self, other))
  
  def __sub__(self, other):
    """Force correct class for timedelta results."""
    return self.fromdatetime(pydatetime.datetime.__sub__(self, other))
  
  @classmethod
  def from_sql(cls, x):
    """Convert from SQL storage format."""
    return cls.fromdatetime(x)

  def to_sql(self):
    """Convert to SQL storage format.

    There's something whacky going on in the MySQLdb module, it throws
    range errors when storing a derived type into a DATETIME column.
    Investigate some day, but for now brute force this by copying the
    relevant fields into a datetime.datetime for MySQLdb's
    consumption.

    """
    return pydatetime.datetime(year = self.year, month = self.month, day = self.day,
                               hour = self.hour, minute = self.minute, second = self.second,
                               microsecond = 0, tzinfo = None)

  def later(self, other):
    """Return the later of two timestamps."""
    return other if other > self else self

  def earlier(self, other):
    """Return the earlier of two timestamps."""
    return other if other < self else self

class timedelta(pydatetime.timedelta):
  """Timedelta with text parsing.  This accepts two input formats:

  - A simple integer, indicating a number of seconds.

  - A string of the form "wD xH yM zS" where w, x, y, and z are integers
    and D, H, M, and S indicate days, hours, minutes, and seconds.
    All of the fields are optional, but at least one must be specified.
    Eg, "3D4H" means "three days plus four hours".
  """

  ## @var regexp
  # Hideously ugly regular expression to parse the complex text form.
  # Tags are intended for use with re.MatchObject.groupdict() and map
  # directly to the keywords expected by the timedelta constructor.

  regexp = re.compile("\\s*".join(("^",
                                   "(?:(?P<days>\\d+)D)?",
                                   "(?:(?P<hours>\\d+)H)?",
                                   "(?:(?P<minutes>\\d+)M)?",
                                   "(?:(?P<seconds>\\d+)S)?",
                                   "$")),
                      re.I)

  @classmethod
  def parse(cls, arg):
    """Parse text into a timedelta object."""
    if not isinstance(arg, str):
      return cls(seconds = arg)
    elif arg.isdigit():
      return cls(seconds = int(arg))
    else:
      match = cls.regexp.match(arg)
      if match:
        return cls(**dict((k, int(v)) for (k, v) in match.groupdict().items() if v is not None))
      else:
        raise RuntimeError, "Couldn't parse timedelta %s" % repr(arg)


  def convert_to_seconds(self):
    """Convert a timedelta interval to seconds."""
    return self.days * 24 * 60 * 60 + self.seconds

if __name__ == "__main__":

  def test(t):
    print
    print "str:                ", t
    print "repr:               ", repr(t)
    print "seconds since epoch:", t.strftime("%s")
    print "UTCTime:            ", t.toUTCTime()
    print "GeneralizedTime:    ", t.toGeneralizedTime()
    print "ASN1tuple:          ", t.toASN1tuple()
    print "XMLtime:            ", t.toXMLtime()
    print

  print
  print "Testing time conversion routines"
  test(now())
  test(now() + timedelta(days = 30))
  test(now() + timedelta.parse("3d5s"))
  timedelta.parse(" 3d 5s ")