#
# Copyright (c) 2001 Bizar Software Pty Ltd (http://www.bizarsoftware.com.au/)
# This module is free software, and you may redistribute it and/or modify
# under the same terms as Python, so long as this copyright message and
# disclaimer are retained in their original form.
#
# IN NO EVENT SHALL BIZAR SOFTWARE PTY LTD BE LIABLE TO ANY PARTY FOR
# DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING
# OUT OF THE USE OF THIS CODE, EVEN IF THE AUTHOR HAS BEEN ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
#
# BIZAR SOFTWARE PTY LTD SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
# BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
# FOR A PARTICULAR PURPOSE.  THE CODE PROVIDED HEREUNDER IS ON AN "AS IS"
# BASIS, AND THERE IS NO OBLIGATION WHATSOEVER TO PROVIDE MAINTENANCE,
# SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

"""Date, time and time interval handling.
"""
from __future__ import print_function
__docformat__ = 'restructuredtext'

import calendar
import datetime
import re

from roundup.anypy.datetime_ import utcnow

try:
    import pytz
except ImportError:
    pytz = None

try:
    cmp
except NameError:
    # Python 3.
    def cmp(a, b):
        return (a > b) - (a < b)

from roundup import i18n
from roundup.anypy.strings import is_us

# no, I don't know why we must anchor the date RE when we only ever use it
# in a match()
date_re = re.compile(r'''^
    ((?P<y>\d\d\d\d)([/-](?P<m>\d\d?)([/-](?P<d>\d\d?))?)? # yyyy[-mm[-dd]]
    |(?P<a>\d\d?)[/-](?P<b>\d\d?))?              # or mm-dd
    (?P<n>[.T])?                                 # . or T
    (((?P<H>\d?\d):(?P<M>\d\d))?(:(?P<S>\d\d?(\.\d+)?))?)?  # hh:mm:ss
    (?:(?P<tz>\s?[+-]\d{4})|(?P<o>[\d\smywd\-+]+))? # time-zone offset, offset
$''', re.VERBOSE)
serialised_date_re = re.compile(r'''
    (\d{4})(\d\d)(\d\d)(\d\d)(\d\d)(\d\d?(\.\d+)?)
''', re.VERBOSE)

_timedelta0 = datetime.timedelta(0)

# load UTC tzinfo
if pytz:
    UTC = pytz.utc
else:
    # fallback implementation from Python Library Reference

    class _UTC(datetime.tzinfo):

        """Universal Coordinated Time zoneinfo"""

        def utcoffset(self, dt):
            return _timedelta0

        def tzname(self, dt):
            return "UTC"

        def dst(self, dt):
            return _timedelta0

        def __repr__(self):
            return "<UTC>"

        # pytz adjustments interface
        # Note: pytz verifies that dt is naive datetime for localize()
        # and not naive datetime for normalize().
        # In this implementation, we don't care.

        def normalize(self, dt, is_dst=False):
            return dt.replace(tzinfo=self)

        def localize(self, dt, is_dst=False):
            return dt.replace(tzinfo=self)

    UTC = _UTC()


# integral hours offsets were available in Roundup versions prior to 1.1.3
# and still are supported as a fallback if pytz module is not installed
class SimpleTimezone(datetime.tzinfo):

    """Simple zoneinfo with fixed numeric offset and no daylight savings"""

    def __init__(self, offset=0, name=None):
        super(SimpleTimezone, self).__init__()
        self.offset = offset
        if name:
            self.name = name
        else:
            self.name = "Etc/GMT%+d" % self.offset

    def utcoffset(self, dt):
        return datetime.timedelta(hours=self.offset)

    def tzname(self, dt):
        return self.name

    def dst(self, dt):
        return _timedelta0

    def __repr__(self):
        return "<%s: %s>" % (self.__class__.__name__, self.name)

    # pytz adjustments interface

    def normalize(self, dt):
        return dt.replace(tzinfo=self)

    def localize(self, dt, is_dst=False):
        return dt.replace(tzinfo=self)


# simple timezones with fixed offset
_tzoffsets = dict(GMT=0, UCT=0, EST=5, MST=7, HST=10)


def get_timezone(tz):
    # if tz is None, return None (will result in naive datetimes)
    # XXX should we return UTC for None?
    if tz is None:
        return None
    # try integer offset first for backward compatibility
    try:
        utcoffset = int(tz)
    except (TypeError, ValueError):
        pass
    else:
        if utcoffset == 0:
            return UTC
        else:
            return SimpleTimezone(utcoffset)
    # tz is a timezone name
    if pytz:
        try:
            return pytz.timezone(tz)
        except pytz.exceptions.UnknownTimeZoneError:
            pass

    if tz == "UTC":
        return UTC
    elif tz in _tzoffsets:
        return SimpleTimezone(_tzoffsets[tz], tz)
    else:
        raise KeyError(tz)


def _utc_to_local(y,m,d,H,M,S,tz):
    TZ = get_timezone(tz)
    S = min(S, 59.999)
    frac = S - int(S)
    dt = datetime.datetime(y, m, d, H, M, int(S), tzinfo=UTC)
    y,m,d,H,M,S = dt.astimezone(TZ).timetuple()[:6]
    S = S + frac
    return (y,m,d,H,M,S)


def _local_to_utc(y,m,d,H,M,S,tz):
    TZ = get_timezone(tz)
    dt = datetime.datetime(y,m,d,H,M,int(S))
    y,m,d,H,M,S = TZ.localize(dt).utctimetuple()[:6]
    return (y,m,d,H,M,S)


def test_ini(t):
    """ Monkey-patch to make doctest think it's always time t:
    """
    u = Date.now
    d = datetime.datetime.strptime(t, '%Y-%m-%d.%H:%M:%S.%f')
    Date.now = lambda x: d
    return u


def test_fin(u):
    """ Undo monkey patch above
    """
    Date.now = u


class Date:
    '''
    As strings, date-and-time stamps are specified with the date in
    international standard format (yyyy-mm-dd) joined to the time
    (hh:mm:ss) by a period ("."). Dates in this form can be easily compared
    and are fairly readable when printed. An example of a valid stamp is
    "2000-06-24.13:03:59". We'll call this the "full date format". When
    Timestamp objects are printed as strings, they appear in the full date
    format with the time always given in UTC. The full date format is
    always exactly 19 characters long.

    For user input, some partial forms are also permitted: the whole time
    or just the seconds may be omitted; and the whole date may be omitted
    or just the year may be omitted. If the time is given, the time is
    interpreted in the user's local time zone. The Date constructor takes
    care of these conversions. In the following examples, suppose that yyyy
    is the current year, mm is the current month, and dd is the current day
    of the month; and suppose that the user is on Eastern Standard Time.

    Note that Date conversion from user inputs will use the local
    timezone, either from the database user (some database schemas have
    a timezone property for a user) or from a default in the roundup
    configuration. Roundup will store all times in UTC in the database
    but display the time to the user in their local timezone as
    configured. In the following examples the timezone correction for
    Eastern Standard Time (GMT-5, no DST) will be applied explicitly via
    an offset, but times are given in UTC in the output.

    Examples::


        make doctest think it's always 2000-06-26.00:34:02:
        >>> u = test_ini('2000-06-26.00:34:02.0')

        >>> Date("2000-04-17-0500")
        <Date 2000-04-17.05:00:00.000>
        >>> Date("01-25-0500")
        <Date 2000-01-25.05:00:00.000>
        >>> Date("2000-04-17.03:45-0500")
        <Date 2000-04-17.08:45:00.000>
        >>> Date("08-13.22:13-0500")
        <Date 2000-08-14.03:13:00.000>
        >>> Date("11-07.09:32:43-0500")
        <Date 2000-11-07.14:32:43.000>
        >>> Date("14:25-0500")
        <Date 2000-06-26.19:25:00.000>
        >>> Date("8:47:11-0500")
        <Date 2000-06-26.13:47:11.000>
        >>> Date("2003 -0500")
        <Date 2003-01-01.05:00:00.000>
        >>> Date("2003-06 -0500")
        <Date 2003-06-01.05:00:00.000>

        "." means "right now":
        >>> Date(".")
        <Date 2000-06-26.00:34:02.000>

        >>> test_fin(u)

    The Date class should understand simple date expressions of the form
    stamp + interval and stamp - interval. When adding or subtracting
    intervals involving months or years, the components are handled
    separately. For example, when evaluating "2000-06-25 + 1m 10d", we
    first add one month to get 2000-07-25, then add 10 days to get
    2000-08-04 (rather than trying to decide whether 1m 10d means 38 or 40
    or 41 days).  Example usage::

        make doctest think it's always 2000-06-26.00:34:02:
        >>> u = test_ini('2000-06-26.00:34:02.0')

        >>> Date(".")
        <Date 2000-06-26.00:34:02.000>
        >>> _.local(-5)
        <Date 2000-06-25.19:34:02.000>
        >>> Date(". + 2d")
        <Date 2000-06-28.00:34:02.000>
        >>> Date("1997-04-17", -5)
        <Date 1997-04-17.05:00:00.000>
        >>> Date("01-25", -5)
        <Date 2000-01-25.05:00:00.000>
        >>> Date("08-13.22:13", -5)
        <Date 2000-08-14.03:13:00.000>
        >>> Date("14:25", -5)
        <Date 2000-06-26.19:25:00.000>

    The date format 'yyyymmddHHMMSS' (year, month, day, hour,
    minute, second) is the serialisation format returned by the serialise()
    method, and is accepted as an argument on instatiation.

    In addition, a timezone specifier can be appended to the date format.
    The timezone specifier is a sign ("+" or "-") followed by a 4-digit
    number as in the RFC 2822 date format.
    The first two digits indicate the number of hours, while the last two
    digits indicate the number of minutes the time is offset from
    Coordinated Universal Time (UTC). The "+" or "-" sign indicate whether
    the time is ahead of (east of) or behind (west of) UTC. Note that a
    given timezone specifier *overrides* an offset given to the Date
    constructor.  Examples::

        >>> Date ("2000-08-14+0200")
        <Date 2000-08-13.22:00:00.000>
        >>> Date ("08-15.22:00+0200")
        <Date 2000-08-15.20:00:00.000>
        >>> Date ("08-15.22:47+0200")
        <Date 2000-08-15.20:47:00.000>
        >>> Date ("08-15.22:47+0200", offset = 5)
        <Date 2000-08-15.20:47:00.000>
        >>> Date ("08-15.22:47", offset = 5)
        <Date 2000-08-15.17:47:00.000>

    The date class handles basic arithmetic, but note that arithmetic
    cannot be combined with timezone offsets (see last example)::

        >>> x=test_ini('2004-04-06.22:04:20.766830')
        >>> d1=Date('.')
        >>> d1
        <Date 2004-04-06.22:04:20.767>
        >>> d2=Date('2003-07-01')
        >>> d2
        <Date 2003-07-01.00:00:00.000>
        >>> d1-d2
        <Interval + 280d 22:04:20>
        >>> i1=_
        >>> d2+i1
        <Date 2004-04-06.22:04:20.000>
        >>> d1-i1
        <Date 2003-07-01.00:00:00.000>

        >>> test_fin(u)
    '''

    __slots__ = ("year", "month", "day", "hour", "minute", "second",
                 "_", "ngettext", "translator")
    
    def __init__(self, spec='.', offset=0, add_granularity=False,
                 translator=i18n):
        """Construct a date given a specification and a time zone offset.

        'spec'
           is a full date or a partial form, with an optional added or
           subtracted interval. Or a date 9-tuple.
        'offset'
           is the local time zone offset from GMT in hours.
        'translator'
           is i18n module or one of gettext translation classes.
           It must have attributes 'gettext' and 'ngettext',
           serving as translation functions.
        """
        self.setTranslator(translator)
        # Python 2.3+ datetime object
        # common case when reading from database: avoid double-conversion
        if isinstance(spec, datetime.datetime):
            if offset == 0:
                self.year, self.month, self.day, self.hour, self.minute, \
                    self.second = spec.timetuple()[:6]
            else:
                # FIXME: what is tz supposed to be? is it the trailing
                # tz on the spec? Is it the offset?
                tz = None
                TZ = get_timezone(tz)
                self.year, self.month, self.day, self.hour, self.minute, \
                    self.second = TZ.localize(spec).utctimetuple()[:6]
            self.second += spec.microsecond/1000000.
            return

        if isinstance(spec, type('')):
            self.set(spec, offset=offset, add_granularity=add_granularity)
            return
        elif hasattr(spec, 'tuple'):
            spec = spec.tuple()
        elif isinstance(spec, Date):
            spec = spec.get_tuple()
        try:
            y,m,d,H,M,S,x,x,x = spec
            S = min(S, 59.999)
            frac = S - int(S)
            self.year, self.month, self.day, self.hour, self.minute, \
                self.second = _local_to_utc(y, m, d, H, M, S, offset)
            # we lost the fractional part
            self.second = self.second + frac
            # making sure we match the precision of serialise()
            self.second = min(self.second, 59.999)
        except Exception:
            raise ValueError('Unknown spec %r' % (spec,))

    def now(self):
        """ To be able to override for testing
        """
        return utcnow()

    def set(self, spec, offset=0, date_re=date_re,
            serialised_re=serialised_date_re, add_granularity=False):
        ''' set the date to the value in spec
        '''

        m = serialised_re.match(spec)
        if m is not None:
            # we're serialised - easy!
            g = m.groups()
            (self.year, self.month, self.day, self.hour, self.minute) = \
                map(int, g[:5])
            self.second = float(g[5])
            return

        # not serialised data, try usual format
        m = date_re.match(spec)
        if m is None:
            raise ValueError(self._('Not a date spec: %r '
                '("yyyy-mm-dd", "mm-dd", "HH:MM", "HH:MM:SS" or '
                '"yyyy-mm-dd.HH:MM:SS.SSS")' % spec))

        info = m.groupdict()

        # If add_granularity is true, construct the maximum time given
        # the precision of the input.  For example, given the input
        # "12:15", construct "12:15:59".  Or, for "2008", construct
        # "2008-12-31.23:59:59".
        if add_granularity:
            for gran in 'SMHdmy':
                if info[gran] is not None:
                    if gran == 'S':
                        raise ValueError
                    elif gran == 'M':
                        add_granularity = Interval('00:01')
                    elif gran == 'H':
                        add_granularity = Interval('01:00')
                    else:
                        add_granularity = Interval('+1%s' % gran)
                    break
            else:
                raise ValueError(self._('Could not determine granularity'))

        # get the current date as our default
        dt = self.now()
        y,m,d,H,M,S,x,x,x = dt.timetuple()
        S += dt.microsecond/1000000.

        # whether we need to convert to UTC
        adjust = False

        if info['y'] is not None or info['a'] is not None:
            if info['y'] is not None:
                y = int(info['y'])
                m,d = (1,1)
                if info['m'] is not None:
                    m = int(info['m'])
                    if info['d'] is not None:
                        d = int(info['d'])
            if info['a'] is not None:
                m = int(info['a'])
                d = int(info['b'])
            H = 0
            M = S = 0
            adjust = True

        # override hour, minute, second parts
        if info['H'] is not None and info['M'] is not None:
            H = int(info['H'])
            M = int(info['M'])
            S = 0
            if info['S'] is not None:
                S = float(info['S'])
            adjust = True

        if info.get('tz', None):
            offset = 0

        # now handle the adjustment of hour
        frac = S - int(S)
        dt = datetime.datetime(y,m,d,H,M,int(S), int(frac * 1000000.))
        y, m, d, H, M, S, x, x, x = dt.timetuple()
        if adjust:
            y, m, d, H, M, S = _local_to_utc(y, m, d, H, M, S, offset)
        self.year, self.month, self.day, self.hour, self.minute, \
            self.second = y, m, d, H, M, S
        # we lost the fractional part along the way
        self.second += dt.microsecond/1000000.

        if info.get('o', None):
            try:
                self.applyInterval(Interval(info['o'], allowdate=0))
            except ValueError:
                raise ValueError(self._('%r not a date / time spec '
                    '"yyyy-mm-dd", "mm-dd", "HH:MM", "HH:MM:SS" or '
                    '"yyyy-mm-dd.HH:MM:SS.SSS"') % (spec,))

        if info.get('tz', None):
            tz = info['tz'].strip()
            sign = [-1, 1][tz[0] == '-']
            minute = int(tz[3:], 10)
            hour = int(tz[1:3], 10)
            self.applyInterval(Interval((0, 0, 0, hour, minute, 0), sign=sign))

        # adjust by added granularity
        if add_granularity:
            self.applyInterval(add_granularity)
            self.applyInterval(Interval('- 00:00:01'))

    def addInterval(self, interval):
        ''' Add the interval to this date, returning the date tuple
        '''
        # do the basic calc
        sign = interval.sign
        year = self.year + sign * interval.year
        month = self.month + sign * interval.month
        day = self.day + sign * interval.day
        hour = self.hour + sign * interval.hour
        minute = self.minute + sign * interval.minute
        # Intervals work on whole seconds
        second = int(self.second) + sign * interval.second

        # now cope with under- and over-flow
        # first do the time
        while (second < 0 or second > 59 or minute < 0 or minute > 59 or
                hour < 0 or hour > 23):
            if second < 0: minute -= 1; second += 60
            elif second > 59: minute += 1; second -= 60
            if minute < 0: hour -= 1; minute += 60
            elif minute > 59: hour += 1; minute -= 60
            if hour < 0: day -= 1; hour += 24
            elif hour > 23: day += 1; hour -= 24

        # fix up the month so we're within range
        while month < 1 or month > 12:
            if month < 1: year -= 1; month += 12
            if month > 12: year += 1; month -= 12

        # now do the days, now that we know what month we're in
        def get_mdays(year, month):
            if month == 2 and calendar.isleap(year): return 29
            else: return calendar.mdays[month]

        while month < 1 or month > 12 or day < 1 or \
              day > get_mdays(year, month):
            # now to day under/over
            if day < 1:
                # When going backwards, decrement month, then increment days
                month -= 1
                day += get_mdays(year, month)
            elif day > get_mdays(year, month):
                # When going forwards, decrement days, then increment month
                day -= get_mdays(year, month)
                month += 1

            # possibly fix up the month so we're within range
            while month < 1 or month > 12:
                if month < 1: year -= 1; month += 12; day += 31
                if month > 12: year += 1; month -= 12

        return (year, month, day, hour, minute, second, 0, 0, 0)

    def differenceDate(self, other):
        "Return the difference between this date and another date"
        return self - other

    def applyInterval(self, interval):
        ''' Apply the interval to this date
        '''
        self.year, self.month, self.day, self.hour, self.minute, \
            self.second, x, x, x = self.addInterval(interval)

    def __add__(self, interval):
        """Add an interval to this date to produce another date.
        """
        return Date(self.addInterval(interval), translator=self.translator)

    # deviates from spec to allow subtraction of dates as well
    def __sub__(self, other):
        """ Subtract:
             1. an interval from this date to produce another date.
             2. a date from this date to produce an interval.
        """
        if isinstance(other, Interval):
            other = Interval(other.get_tuple())
            other.sign *= -1
            return self.__add__(other)

        assert isinstance(other, Date), 'May only subtract Dates or Intervals'

        return self.dateDelta(other)

    def dateDelta(self, other):
        """ Produce an Interval of the difference between this date
            and another date. Only returns days:hours:minutes:seconds.
        """
        # Returning intervals larger than a day is almost
        # impossible - months, years, weeks, are all so imprecise.
        a = calendar.timegm((self.year, self.month, self.day, self.hour,
                             self.minute, self.second, 0, 0, 0))
        b = calendar.timegm((other.year, other.month, other.day,
                             other.hour, other.minute, other.second, 0, 0, 0))
        # intervals work in whole seconds
        diff = int(a - b)
        if diff > 0:
            sign = 1
        else:
            sign = -1
            diff = -diff
        S = diff % 60
        M = (diff//60) % 60
        H = (diff//(60*60)) % 24
        d = diff//(24*60*60)
        return Interval((0, 0, d, H, M, S), sign=sign,
                        translator=self.translator)

    def __cmp__(self, other, int_seconds=0):
        """Compare this date to another date."""
        if other is None:
            return 1
        for attr in ('year', 'month', 'day', 'hour', 'minute'):
            if not hasattr(other, attr):
                return 1
            r = cmp(getattr(self, attr), getattr(other, attr))
            if r: return r
        if not hasattr(other, 'second'):
            return 1
        if int_seconds:
            return cmp(int(self.second), int(other.second))
        return cmp(self.second, other.second)

    def __lt__(self, other):
        return self.__cmp__(other) < 0

    def __le__(self, other):
        return self.__cmp__(other) <= 0

    def __eq__(self, other):
        return self.__cmp__(other) == 0

    def __ne__(self, other):
        return self.__cmp__(other) != 0

    def __gt__(self, other):
        return self.__cmp__(other) > 0

    def __ge__(self, other):
        return self.__cmp__(other) >= 0

    def __str__(self):
        """Return this date as a string in the yyyy-mm-dd.hh:mm:ss format."""
        return self.formal()

    def formal(self, sep='.', sec='%02d'):
        f = '%%04d-%%02d-%%02d%s%%02d:%%02d:%s' % (sep, sec)
        return f % (self.year, self.month, self.day, self.hour, self.minute,
                    self.second)

    def isoformat(self):
        ''' Represent the date/time in isoformat standard

            Originally needed for xml output support using
            dicttoxml in the rest interface.
        '''
        f = '%%04d-%%02d-%%02d%s%%02d:%%02d:%s' % ("T", "%02.6d")
        return f % (self.year, self.month, self.day, self.hour, self.minute,
                    self.second)

    def pretty(self, format='%d %B %Y'):
        ''' print up the date date using a pretty format...

            Note that if the day is zero, and the day appears first in the
            format, then the day number will be removed from output.
        '''
        dt = datetime.datetime(self.year, self.month, self.day, self.hour,
            self.minute, int(self.second),
            int((self.second - int(self.second)) * 1000000.))
        str = dt.strftime(format)

        # handle zero day by removing it
        if format.startswith('%d') and str[0] == '0':
            return ' ' + str[1:]
        return str

    def __repr__(self):
        return '<Date %s>' % self.formal(sec='%06.3f')

    def local(self, offset):
        """ Return this date as yyyy-mm-dd.hh:mm:ss in a local time zone.
            The offset is a pytz tz offset if pytz is installed.
        """
        y,m,d,H,M,S = _utc_to_local(self.year, self.month, self.day,
                   self.hour, self.minute, self.second, offset)
        return Date((y,m,d,H,M,S,0,0,0), translator=self.translator)

    def __deepcopy__(self, memo):
        return Date((self.year, self.month, self.day, self.hour,
            self.minute, self.second, 0, 0, 0), translator=self.translator)

    def get_tuple(self):
        return (self.year, self.month, self.day, self.hour, self.minute,
                self.second, 0, 0, 0)

    def serialise(self):
        """ Return serialised string for self's datetime.

        Uses '%06.3f' as format for self.second, which therefor
        must be <=59.999 to work. Otherwise it will be rounded
        to 60.000.

        """
        return '%04d%02d%02d%02d%02d%06.3f' % (self.year, self.month,
            self.day, self.hour, self.minute, self.second)

    def timestamp(self):
        ''' return a UNIX timestamp for this date '''
        frac = self.second - int(self.second)
        ts = calendar.timegm((self.year, self.month, self.day, self.hour,
                              self.minute, self.second, 0, 0, 0))
        # we lose the fractional part
        return ts + frac

    def setTranslator(self, translator):
        """Replace the translation engine

        'translator'
           is i18n module or one of gettext translation classes.
           It must have attributes 'gettext' and 'ngettext',
           serving as translation functions.
        """
        self.translator = translator
        self._ = translator.gettext
        self.ngettext = translator.ngettext

    def fromtimestamp(cls, ts):
        """Create a date object from a timestamp.

        The timestamp may be outside the gmtime year-range of
        1902-2038.
        """
        usec = int((ts - int(ts)) * 1000000.)
        delta = datetime.timedelta(seconds=int(ts), microseconds=usec)
        return cls(datetime.datetime(1970, 1, 1) + delta)
    fromtimestamp = classmethod(fromtimestamp)


class Interval:
    '''
    Date intervals are specified using the suffixes "y", "m", and "d". The
    suffix "w" (for "week") means 7 days. Time intervals are specified in
    hh:mm:ss format (the seconds may be omitted, but the hours and minutes
    may not).

      "3y" means three years
      "2y 1m" means two years and one month
      "1m 25d" means one month and 25 days
      "2w 3d" means two weeks and three days
      "1d 2:50" means one day, two hours, and 50 minutes
      "14:00" means 14 hours
      "0:04:33" means four minutes and 33 seconds

    Example usage:
        make doctest think it's always 2000-06-26.00:34:02:
        >>> u = test_ini('2000-06-26.00:34:02.0')

        >>> Interval("  3w  1  d  2:00")
        <Interval + 22d 2:00>
        >>> Date(". + 2d") + Interval("- 3w")
        <Date 2000-06-07.00:34:02.000>
        >>> Interval('1:59:59') + Interval('00:00:01')
        <Interval + 2:00>
        >>> Interval('2:00') + Interval('- 00:00:01')
        <Interval + 1:59:59>
        >>> Interval('1y')/2
        <Interval + 6m>
        >>> Interval('1:00')/2
        <Interval + 0:30>

        [number of days between 2000-06-26.00:34:02 and 2003-03-18
        >>> Interval('2003-03-18')
        <Interval - 995d>

        [number of days between 2000-06-26.00:34:02 and 2003-03-14
        >>> Interval('-4d 2003-03-18')
        <Interval - 991d>

        >>> test_fin(u)

    Interval arithmetic is handled in a couple of special ways, trying
    to cater for the most common cases. Fundamentally, Intervals which
    have both date and time parts will result in strange results in
    arithmetic - because of the impossibility of handling day->month->year
    over- and under-flows. Intervals may also be divided by some number.

    Intervals are added to Dates in order of:
       seconds, minutes, hours, years, months, days

    Calculations involving months (eg '+2m') have no effect on days - only
    days (or over/underflow from hours/mins/secs) will do that, and
    days-per-month and leap years are accounted for. Leap seconds are not.

    The interval format 'syyyymmddHHMMSS' (sign, year, month, day, hour,
    minute, second) is the serialisation format returned by the serialise()
    method, and is accepted as an argument on instatiation.

    TODO: more examples, showing the order of addition operation
    '''
    def __init__(self, spec, sign=1, allowdate=1, add_granularity=False,
                 translator=i18n):
        """Construct an interval given a specification."""
        self.setTranslator(translator)
        try:
            # Python 2.
            arith_types = (int, float, long)
        except NameError:
            # Python 3.
            arith_types = (int, float)
        if isinstance(spec, arith_types):
            self.from_seconds(spec)
        elif is_us(spec):
            self.set(spec, allowdate=allowdate,
                     add_granularity=add_granularity)
        elif isinstance(spec, Interval):
            (self.sign, self.year, self.month, self.day, self.hour,
                self.minute, self.second) = spec.get_tuple()
        else:
            if len(spec) == 7:
                self.sign, self.year, self.month, self.day, self.hour, \
                    self.minute, self.second = spec
                self.second = int(self.second)
            else:
                # old, buggy spec form
                self.sign = sign
                self.year, self.month, self.day, self.hour, self.minute, \
                    self.second = spec
                self.second = int(self.second)

    def __deepcopy__(self, memo):
        return Interval((self.sign, self.year, self.month, self.day,
            self.hour, self.minute, self.second), translator=self.translator)

    def set(self, spec, allowdate=1, interval_re=re.compile(r'''
            \s*(?P<s>[-+])?         # + or -
            \s*((?P<y>\d+\s*)y)?    # year
            \s*((?P<m>\d+\s*)m)?    # month
            \s*((?P<w>\d+\s*)w)?    # week
            \s*((?P<d>\d+\s*)d)?    # day
            \s*(((?P<H>\d+):(?P<M>\d+))?(:(?P<S>\d+))?)?   # time
            \s*(?P<D>
                 (\d\d\d\d[/-])?(\d\d?)?[/-](\d\d?)?       # [yyyy-]mm-dd
                 \.?                                       # .
                 (\d?\d:\d\d)?(:\d\d)?                     # hh:mm:ss
               )?''', re.VERBOSE), serialised_re=re.compile(r'''
            (?P<s>[+-])?1?(?P<y>([ ]{3}\d|\d{4}))(?P<m>\d{2})(?P<d>\d{2})
            (?P<H>\d{2})(?P<M>\d{2})(?P<S>\d{2})''', re.VERBOSE),
            add_granularity=False):
        ''' set the date to the value in spec
        '''
        self.year = self.month = self.week = self.day = self.hour = \
            self.minute = self.second = 0
        self.sign = 1
        m = serialised_re.match(spec)
        if not m:
            m = interval_re.match(spec)
            if not m:
                raise ValueError(self._('Not an interval spec: "%s"'
                    ' ([+-] [#y] [#m] [#w] [#d] [[[H]H:MM]:SS] [date spec])'
                    % spec))
        else:
            allowdate = 0

        # pull out all the info specified
        info = m.groupdict()
        if add_granularity:
            for gran in 'SMHdwmy':
                if info[gran] is not None:
                    info[gran] = int(info[gran]) + (info['s'] == '-' and -1 or 1)
                    break

        valid = 0
        for group, attr in {'y': 'year', 'm': 'month', 'w': 'week', 'd': 'day',
                'H': 'hour', 'M': 'minute', 'S': 'second'}.items():
            if info.get(group, None) is not None:
                valid = 1
                setattr(self, attr, int(info[group]))

        # make sure it's valid
        if not valid and not info['D']:
            raise ValueError(self._('Not an interval spec: "%s"'
                ' ([+-] [#y] [#m] [#w] [#d] [[[H]H:MM]:SS])'
                % spec))

        if self.week:
            self.day = self.day + self.week*7

        if info['s'] is not None:
            self.sign = {'+': 1, '-': -1}[info['s']]

        # use a date spec if one is given
        if allowdate and info['D'] is not None:
            now = Date('.')
            date = Date(info['D'])
            # if no time part was specified, nuke it in the "now" date
            if not date.hour or date.minute or date.second:
                now.hour = now.minute = now.second = 0
            if date != now:
                y = now - (date + self)
                self.__init__(y.get_tuple())

    def __lt__(self, other):
        """Compare this interval to another interval."""

        if other is None:
            # we are always larger than None
            return False
        return self.as_seconds() < other.as_seconds()

    def __le__(self, other):
        """Compare this interval to another interval."""

        if other is None:
            # we are always larger than None
            return False
        return self.as_seconds() <= other.as_seconds()

    def __eq__(self, other):
        """Compare this interval to another interval."""

        if other is None:
            # we are always larger than None
            return False
        return self.as_seconds() == other.as_seconds()

    def __ne__(self, other):
        """Compare this interval to another interval."""

        if other is None:
            # we are always larger than None
            return True
        return self.as_seconds() != other.as_seconds()

    def __gt__(self, other):
        """Compare this interval to another interval."""

        if other is None:
            # we are always larger than None
            return True
        return self.as_seconds() > other.as_seconds()

    def __ge__(self, other):
        """Compare this interval to another interval."""

        if other is None:
            # we are always larger than None
            return True
        return self.as_seconds() >= other.as_seconds()

    def __str__(self):
        """Return this interval as a string."""
        l = []
        if self.year: l.append('%sy' % self.year)
        if self.month: l.append('%sm' % self.month)
        if self.day: l.append('%sd' % self.day)
        if self.second:
            l.append('%d:%02d:%02d' % (self.hour, self.minute, self.second))
        elif self.hour or self.minute:
            l.append('%d:%02d' % (self.hour, self.minute))
        if l:
            l.insert(0, {1: '+', -1: '-'}[self.sign])
        else:
            l.append('00:00')
        return ' '.join(l)

    def __add__(self, other):
        if isinstance(other, Date):
            # the other is a Date - produce a Date
            return Date(other.addInterval(self), translator=self.translator)
        elif isinstance(other, Interval):
            # add the other Interval to this one
            a = self.get_tuple()
            asgn = a[0]
            b = other.get_tuple()
            bsgn = b[0]
            i = [asgn*x + bsgn*y for x, y in zip(a[1:], b[1:])]
            i.insert(0, 1)
            i = fixTimeOverflow(i)
            return Interval(i, translator=self.translator)
        # nope, no idea what to do with this other...
        raise TypeError("Can't add %r" % other)

    def __sub__(self, other):
        if isinstance(other, Date):
            # the other is a Date - produce a Date
            interval = Interval(self.get_tuple())
            interval.sign *= -1
            return Date(other.addInterval(interval),
                        translator=self.translator)
        elif isinstance(other, Interval):
            # add the other Interval to this one
            a = self.get_tuple()
            asgn = a[0]
            b = other.get_tuple()
            bsgn = b[0]
            i = [asgn*x - bsgn*y for x, y in zip(a[1:], b[1:])]
            i.insert(0, 1)
            i = fixTimeOverflow(i)
            return Interval(i, translator=self.translator)
        # nope, no idea what to do with this other...
        raise TypeError("Can't add %r" % other)

    def __truediv__(self, other):
        """ Divide this interval by an int value.

            Can't divide years and months sensibly in the _same_
            calculation as days/time, so raise an error in that situation.
        """
        try:
            other = float(other)
        except TypeError:
            raise ValueError("Can only divide Intervals by numbers")

        y, m, d, H, M, S = (self.year, self.month, self.day,
                            self.hour, self.minute, self.second)
        if y or m:
            if d or H or M or S:
                raise ValueError("Can't divide Interval with date and time")
            months = self.year*12 + self.month
            months *= self.sign

            months = int(months/other)

            sign = months < 0 and -1 or 1
            m = months % 12
            y = months // 12
            return Interval((sign, y, m, 0, 0, 0, 0),
                            translator=self.translator)

        else:
            # handle a day/time division
            seconds = S + M*60 + H*60*60 + d*60*60*24
            seconds *= self.sign

            seconds = int(seconds/other)

            sign = seconds < 0 and -1 or 1
            seconds *= sign
            S = seconds % 60
            seconds //= 60
            M = seconds % 60
            seconds //= 60
            H = seconds % 24
            d = seconds // 24
            return Interval((sign, 0, 0, d, H, M, S),
                            translator=self.translator)
    # Python 2 compatibility:
    __div__ = __truediv__

    def __repr__(self):
        return '<Interval %s>' % self.__str__()

    def pretty(self):
        ''' print up the date date using one of these nice formats..
        '''
        _quarters = self.minute // 15
        if self.year:
            s = self.ngettext("%(number)s year", "%(number)s years",
                              self.year) % {'number': self.year}
        elif self.month or self.day > 28:
            _months = max(1, int(((self.month * 30) + self.day) / 30))
            s = self.ngettext("%(number)s month", "%(number)s months",
                              _months) % {'number': _months}
        elif self.day > 7:
            _weeks = int(self.day / 7)
            s = self.ngettext("%(number)s week", "%(number)s weeks",
                              _weeks) % {'number': _weeks}
        elif self.day > 1:
            # Note: singular form is not used
            s = self.ngettext('%(number)s day', '%(number)s days',
                              self.day) % {'number': self.day}
        elif self.day == 1 or self.hour > 12:
            if self.sign > 0:
                return self._('tomorrow')
            else:
                return self._('yesterday')
        elif self.hour > 1:
            # Note: singular form is not used
            s = self.ngettext('%(number)s hour', '%(number)s hours',
                              self.hour) % {'number': self.hour}
        elif self.hour == 1:
            if self.minute < 15:
                s = self._('an hour')
            elif _quarters == 2:
                s = self._('1 1/2 hours')
            else:
                s = self.ngettext('1 %(number)s/4 hours',
                                  '1 %(number)s/4 hours',
                                  _quarters) % {'number': _quarters}
        elif self.minute < 1:
            if self.sign > 0:
                return self._('in a moment')
            else:
                return self._('just now')
        elif self.minute == 1:
            # Note: used in expressions "in 1 minute" or "1 minute ago"
            s = self._('1 minute')
        elif self.minute < 15:
            # Note: used in expressions "in 2 minutes" or "2 minutes ago"
            s = self.ngettext('%(number)s minute', '%(number)s minutes',
                              self.minute) % {'number': self.minute}
        elif _quarters == 2:
            s = self._('1/2 an hour')
        else:
            s = self.ngettext('%(number)s/4 hour', '%(number)s/4 hours',
                              _quarters) % {'number': _quarters}
        # XXX this is internationally broken
        if self.sign < 0:
            s = self._('%s ago') % s
        else:
            s = self._('in %s') % s
        return s

    def get_tuple(self):
        return (self.sign, self.year, self.month, self.day, self.hour,
                self.minute, self.second)

    def serialise(self):
        sign = self.sign > 0 and '+' or '-'
        return '%s%04d%02d%02d%02d%02d%02d' % (sign, self.year, self.month,
            self.day, self.hour, self.minute, self.second)

    def isoformat(self):
        '''Represent interval as an ISO 8061 duration (absolute value)

           Originally needed for xml output support using
           dicttoxml in the rest interface.
        '''
        return 'P%04dY%02dM%02dDT%02dH%02dM%02dS' % (self.year, self.month,
            self.day, self.hour, self.minute, self.second)

    def as_seconds(self):
        '''Calculate the Interval as a number of seconds.

        Months are counted as 30 days, years as 365 days. Returns a Long
        int.
        '''
        n = self.year * 365
        n = n + self.month * 30
        n = n + self.day
        n = n * 24
        n = n + self.hour
        n = n * 60
        n = n + self.minute
        n = n * 60
        n = n + self.second
        return n * self.sign

    def from_seconds(self, val):
        '''Figure my second, minute, hour and day values using a seconds
        value.
        '''
        val = int(val)
        if val < 0:
            self.sign = -1
            val = -val
        else:
            self.sign = 1
        self.second = val % 60
        val = val // 60
        self.minute = val % 60
        val = val // 60
        self.hour = val % 24
        val = val // 24
        self.day = val
        self.month = self.year = 0

    def setTranslator(self, translator):
        """Replace the translation engine

        'translator'
           is i18n module or one of gettext translation classes.
           It must have attributes 'gettext' and 'ngettext',
           serving as translation functions.
        """
        self.translator = translator
        self._ = translator.gettext
        self.ngettext = translator.ngettext


def fixTimeOverflow(time):
    """ Handle the overflow in the time portion (H, M, S) of "time":
            (sign, y,m,d,H,M,S)

        Overflow and underflow will at most affect the _days_ portion of
        the date. We do not overflow days to months as we don't know _how_
        to, generally.
    """
    # XXX we could conceivably use this function for handling regular dates
    # XXX too - we just need to interrogate the month/year for the day
    # XXX overflow...

    sign, y, m, d, H, M, S = time
    seconds = sign * (S + M*60 + H*60*60 + d*60*60*24)
    if seconds:
        sign = seconds < 0 and -1 or 1
        seconds *= sign
        S = seconds % 60
        seconds //= 60
        M = seconds % 60
        seconds //= 60
        H = seconds % 24
        d = seconds // 24
    else:
        months = y*12 + m
        sign = months < 0 and -1 or 1
        months *= sign
        m = months % 12
        y = months//12

    return (sign, y, m, d, H, M, S)


class Range:
    """Represents range between two values
    Ranges can be created using one of theese two alternative syntaxes:

    1. Native english syntax::

            [[From] <value>][ To <value>]

       Keywords "From" and "To" are case insensitive. Keyword "From" is
       optional.

    2. "Geek" syntax::

          [<value>][; <value>]

    Either first or second <value> can be omitted in both syntaxes.

    Examples (consider local time is Sat Mar  8 22:07:48 EET 2003)::

        make doctest think it's always 2000-06-26.00:34:02:
        >>> u = test_ini('2003-03-08.20:07:48.0')

        >>> Range("from 2-12 to 4-2", Date)
        <Range from 2003-02-12.00:00:00 to 2003-04-02.00:00:00>

        >>> Range("18:00 to +2m", Date)
        <Range from 2003-03-08.18:00:00 to 2003-05-08.20:07:48>

        >>> Range("tO +3d", Date)
        <Range from None to 2003-03-11.20:07:48>

        >>> Range("12:00 to", Date)
        <Range from 2003-03-08.12:00:00 to None>

        >>> Range("12:00;", Date)
        <Range from 2003-03-08.12:00:00 to None>

        >>> Range("2002-11-10; 2002-12-12", Date)
        <Range from 2002-11-10.00:00:00 to 2002-12-12.00:00:00>

        >>> Range("; 20:00 +1d", Date)
        <Range from None to 2003-03-09.20:00:00>

        >>> Range("from 2003-02-16", Date)
        <Range from 2003-02-16.00:00:00 to None>

        >>> Range("2003-02-16;", Date)
        <Range from 2003-02-16.00:00:00 to None>

        Granularity tests:

        >>> Range("12:00", Date)
        <Range from 2003-03-08.12:00:00 to 2003-03-08.12:00:59>

        >>> Range("2003-03-08", Date)
        <Range from 2003-03-08.00:00:00 to 2003-03-08.23:59:59>

        >>> test_fin(u)

        Range of Interval tests

        >>> Range ("from 0:50 to 2:00", Interval)
        <Range from + 0:50 to + 2:00>
        >>> Range ("from 0:50 to 1d 2:00", Interval)
        <Range from + 0:50 to + 1d 2:00>
        >>> Range ("from 5:50", Interval)
        <Range from + 5:50 to None>
        >>> Range ("to 0:05", Interval)
        <Range from None to + 0:05>

    """
    def __init__(self, spec, Type, allow_granularity=True, **params):
        """Initializes Range of type <Type> from given <spec> string.

        Sets two properties - from_value and to_value. None assigned to any of
        this properties means "infinitum" (-infinitum to from_value and
        +infinitum to to_value)

        The Type parameter here should be class itself (e.g. Date), not a
        class instance.
        """
        self.range_type = Type
        re_range = r'^(?:from)?(.+?)?to(.+?)?$'
        re_range_no_to = r'^from(.+)(.)?$'
        re_geek_range = r'^(.+?)?;(.+?)?$'
        # Check which syntax to use
        if ';' in spec:
            # Geek
            m = re.search(re_geek_range, spec.strip())
        else:
            # Native english
            m = re.search(re_range, spec.strip(), re.IGNORECASE)
            if not m:
                m = re.search(re_range_no_to, spec.strip(), re.IGNORECASE)
        if m:
            self.from_value, self.to_value = m.groups()
            if self.from_value:
                self.from_value = Type(self.from_value.strip(), **params)
            if self.to_value:
                self.to_value = Type(self.to_value.strip(), **params)
        else:
            if allow_granularity:
                self.from_value = Type(spec, **params)
                self.to_value = Type(spec, add_granularity=True, **params)
            else:
                raise ValueError("Invalid range")

    def __str__(self):
        return "from %s to %s" % (self.from_value, self.to_value)

    def __repr__(self):
        return "<Range %s>" % self.__str__()


def test_range():
    rspecs = ("from 2-12 to 4-2", "from 18:00 TO +2m", "12:00;", "tO +3d",
        "2002-11-10; 2002-12-12", "; 20:00 +1d", '2002-10-12')
    rispecs = ('from -1w 2d 4:32 to 4d', '-2w 1d')
    for rspec in rspecs:
        print('>>> Range("%s")' % rspec)
        print(repr(Range(rspec, Date)))
        print()
    for rspec in rispecs:
        print('>>> Range("%s")' % rspec)
        print(repr(Range(rspec, Interval)))
        print()


def test():
    intervals = ("  3w  1  d  2:00", " + 2d", "3w")
    for interval in intervals:
        print('>>> Interval("%s")' % interval)
        print(repr(Interval(interval)))

    dates = (".", "2000-06-25.19:34:02", ". + 2d", "1997-04-17", "01-25",
             "08-13.22:13", "14:25", '2002-12')
    for date in dates:
        print('>>> Date("%s")' % date)
        print(repr(Date(date)))

    sums = ((". + 2d", "3w"), (".", "  3w  1  d  2:00"))
    for date, interval in sums:
        print('>>> Date("%s") + Interval("%s")' % (date, interval))
        print(repr(Date(date) + Interval(interval)))


if __name__ == '__main__':
    test()

# vim: set filetype=python sts=4 sw=4 et si :