# Copyright 2002 Ben Escoto
#
# This file is part of duplicity.
#
# Duplicity is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the
# Free Software Foundation; either version 3 of the License, or (at your
# option) any later version.
#
# Duplicity is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with duplicity; if not, write to the Free Software Foundation,
# Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

"""Provide time related exceptions and functions"""

import time, types, re
import globals


class TimeException(Exception): pass

_interval_conv_dict = {"s": 1, "m": 60, "h": 3600, "D": 86400,
					   "W": 7*86400, "M": 30*86400, "Y": 365*86400}
_integer_regexp = re.compile("^[0-9]+$")
_interval_regexp = re.compile("^([0-9]+)([smhDWMY])")
_genstr_date_regexp1 = re.compile("^(?P<year>[0-9]{4})[-/]"
					   "(?P<month>[0-9]{1,2})[-/](?P<day>[0-9]{1,2})$")
_genstr_date_regexp2 = re.compile("^(?P<month>[0-9]{1,2})[-/]"
					   "(?P<day>[0-9]{1,2})[-/](?P<year>[0-9]{4})$")
curtime = curtimestr = None
prevtime = prevtimestr = None
been_awake_since = None # stores last time sleep() was run

def setcurtime(time_in_secs = None):
	"""Sets the current time in curtime and curtimestr"""
	global curtime, curtimestr
	t = time_in_secs or long(time.time())
	assert type(t) in (types.LongType, types.IntType)
	curtime, curtimestr = t, timetostring(t)

def setprevtime(time_in_secs):
	"""Sets the previous time in prevtime and prevtimestr"""
	global prevtime, prevtimestr
	assert type(time_in_secs) in (types.LongType, types.IntType), prevtime
	prevtime, prevtimestr = time_in_secs, timetostring(time_in_secs)

def timetostring(timeinseconds):
	"""Return w3 datetime compliant listing of timeinseconds"""

	# We need to know if DST applies to append the correct offset. So
	#    1. Save the tuple returned by localtime.
	#    2. Pass the DST flag into gettzd
	lcltime = time.localtime(timeinseconds)
	return time.strftime("%Y-%m-%dT%H" + globals.time_separator +
						 "%M" + globals.time_separator + "%S",
						 lcltime) + gettzd(lcltime[-1])

def stringtotime(timestring):
	"""Return time in seconds from w3 timestring

	If there is an error parsing the string, or it doesn't look
	like a w3 datetime string, return None.

	"""
	try:
		date, daytime = timestring[:19].split("T")
		year, month, day = map(int, date.split("-"))
		hour, minute, second = map(int,
								   daytime.split(globals.time_separator))
		assert 1900 < year < 2100, year
		assert 1 <= month <= 12
		assert 1 <= day <= 31
		assert 0 <= hour <= 23
		assert 0 <= minute <= 59
		assert 0 <= second <= 61  # leap seconds
		# We want to return the time in units of seconds since the
		# epoch. Unfortunately the only functin that does this
		# works in terms of the current timezone and we have a
		# timezone offset in the string.
		timetuple = (year, month, day, hour, minute, second, -1, -1, 0)
		local_in_secs = time.mktime(timetuple)
		# mktime assumed that the tuple was a local time. Compensate
		# by subtracting the value for the current timezone.
		# We don't need to worry about DST here because we turned it
		# off in the tuple
		utc_in_secs = local_in_secs - time.timezone
		# Now apply the offset that we were given in the time string
		# This gives the correct number of seconds from the epoch
		# even when we're not in the same timezone that wrote the
		# string
		return long (utc_in_secs + tzdtoseconds(timestring[19:]))
	except (TypeError, ValueError, AssertionError): return None


def timetopretty(timeinseconds):
	"""Return pretty version of time"""
	return time.asctime(time.localtime(timeinseconds))

def stringtopretty(timestring):
	"""Return pretty version of time given w3 time string"""
	return timetopretty(stringtotime(timestring))

def inttopretty(seconds):
	"""Convert num of seconds to readable string like "2 hours"."""
	partlist = []
	hours, seconds = divmod(seconds, 3600)
	if hours > 1: partlist.append("%d hours" % hours)
	elif hours == 1: partlist.append("1 hour")

	minutes, seconds = divmod(seconds, 60)
	if minutes > 1: partlist.append("%d minutes" % minutes)
	elif minutes == 1: partlist.append("1 minute")

	if seconds == 1: partlist.append("1 second")
	elif not partlist or seconds > 1:
		if isinstance(seconds, int) or isinstance(seconds, long):
			partlist.append("%s seconds" % seconds)
		else: partlist.append("%.2f seconds" % seconds)
	return " ".join(partlist)

def intstringtoseconds(interval_string):
	"""Convert a string expressing an interval (e.g. "4D2s") to seconds"""
	def error():
		raise TimeException("""Bad interval string "%s"

Intervals are specified like 2Y (2 years) or 2h30m (2.5 hours).  The
allowed special characters are s, m, h, D, W, M, and Y.  See the man
page for more information.
""" % interval_string)
	if len(interval_string) < 2: error()

	total = 0
	while interval_string:
		match = _interval_regexp.match(interval_string)
		if not match: error()
		num, ext = int(match.group(1)), match.group(2)
		if not ext in _interval_conv_dict or num < 0: error()
		total += num*_interval_conv_dict[ext]
		interval_string = interval_string[match.end(0):]
	return total

def gettzd(dstflag):
	"""Return w3's timezone identification string.

	Expresed as [+/-]hh:mm.  For instance, PST is -08:00.  Zone is
	coincides with what localtime(), etc., use.

	"""
	# time.daylight doesn't help us. It's a flag that indicates that we
	# have a dst option for the current timezone. Compensate by allowing
	# the caller to pass a flag to indicate that DST applies. This flag
	# is in the same format as the last member of the tuple returned by
	# time.localtime()
	
	if dstflag > 0: offset = -1 * time.altzone/60
	else: offset = -1 * time.timezone/60
	if offset > 0: prefix = "+"
	elif offset < 0: prefix = "-"
	else: return "Z" # time is already in UTC

	hours, minutes = map(abs, divmod(offset, 60))
	assert 0 <= hours <= 23
	assert 0 <= minutes <= 59
	return "%s%02d%s%02d" % (prefix, hours, globals.time_separator, minutes)

def tzdtoseconds(tzd):
	"""Given w3 compliant TZD, return how far ahead UTC is"""
	if tzd == "Z": return 0
	assert len(tzd) == 6 # only accept forms like +08:00 for now
	assert (tzd[0] == "-" or tzd[0] == "+") and \
		   tzd[3] == globals.time_separator
	return -60 * (60 * int(tzd[:3]) + int(tzd[4:]))

def cmp(time1, time2):
	"""Compare time1 and time2 and return -1, 0, or 1"""
	if type(time1) is types.StringType:
		time1 = stringtotime(time1)
		assert time1 is not None
	if type(time2) is types.StringType:
		time2 = stringtotime(time2)
		assert time2 is not None

	if time1 < time2: return -1
	elif time1 == time2: return 0
	else: return 1


def sleep(sleep_ratio):
	"""Sleep for period to maintain given sleep_ratio

	On my system sleeping for periods less than 1/20th of a second
	doesn't seem to work very accurately, so accumulate at least that
	much time before sleeping.

	"""
	global been_awake_since
	if been_awake_since is None: # first running
		been_awake_since = time.time()
	else:
		elapsed_time = time.time() - been_awake_since
		sleep_time = elapsed_time * (sleep_ratio/(1-sleep_ratio))
		if sleep_time >= 0.05:
			time.sleep(sleep_time)
			been_awake_since = time.time()

def genstrtotime(timestr, override_curtime = None):
	"""Convert a generic time string to a time in seconds"""
	if override_curtime is None: override_curtime = curtime
	if timestr == "now": return override_curtime

	def error():
		raise TimeException("""Bad time string "%s"

The acceptible time strings are intervals (like "3D64s"), w3-datetime
strings, like "2002-04-26T04:22:01-07:00" (strings like
"2002-04-26T04:22:01" are also acceptable - rdiff-backup will use the
current time zone), or ordinary dates like 2/4/1997 or 2001-04-23
(various combinations are acceptable, but the month always precedes
the day).""" % timestr)

	# Test for straight integer
	if _integer_regexp.search(timestr): return int(timestr)

	# Test for w3-datetime format, possibly missing tzd
	# This is an ugly hack. We need to know if DST applies when doing
	# gettzd. However, we don't have the flag to pass. Assume that DST
	# doesn't apply and pass 0. Getting a reasonable default from
	# localtime() is a bad idea, since we transition to/from DST between
	# calls to this method on the same run
	
	t = stringtotime(timestr) or stringtotime(timestr+gettzd(0))
	if t: return t

	try: # test for an interval, like "2 days ago"
		return override_curtime - intstringtoseconds(timestr)
	except TimeException: pass

	# Now check for dates like 2001/3/23
	match = _genstr_date_regexp1.search(timestr) or \
			_genstr_date_regexp2.search(timestr)
	if not match: error()
	timestr = "%s-%02d-%02dT00:00:00%s" % (match.group('year'),
			     int(match.group('month')), int(match.group('day')), gettzd(0))
	t = stringtotime(timestr)
	if t: return t
	else: error()