# -*- coding: utf-8 -*-
"""
This module offers timezone implementations subclassing the abstract
:py:`datetime.tzinfo` type. There are classes to handle tzfile format files
(usually are in :file:`/etc/localtime`, :file:`/usr/share/zoneinfo`, etc), TZ
environment string (in all known formats), given ranges (with help from
relative deltas), local machine timezone, fixed offset timezone, and UTC
timezone.
"""
import datetime
import struct
import time
import sys
import os

from six import string_types, PY3

try:
    from dateutil.tzwin import tzwin, tzwinlocal
except ImportError:
    tzwin = tzwinlocal = None

relativedelta = None
parser = None
rrule = None

__all__ = ["tzutc", "tzoffset", "tzlocal", "tzfile", "tzrange",
           "tzstr", "tzical", "tzwin", "tzwinlocal", "gettz"]


def tzname_in_python2(namefunc):
    """Change unicode output into bytestrings in Python 2

    tzname() API changed in Python 3. It used to return bytes, but was changed
    to unicode strings
    """
    def adjust_encoding(*args, **kwargs):
        name = namefunc(*args, **kwargs)
        if name is not None and not PY3:
            name = name.encode()

        return name

    return adjust_encoding

ZERO = datetime.timedelta(0)
EPOCHORDINAL = datetime.datetime.utcfromtimestamp(0).toordinal()


class tzutc(datetime.tzinfo):

    def utcoffset(self, dt):
        return ZERO

    def dst(self, dt):
        return ZERO

    @tzname_in_python2
    def tzname(self, dt):
        return "UTC"

    def __eq__(self, other):
        return (isinstance(other, tzutc) or
                (isinstance(other, tzoffset) and other._offset == ZERO))

    def __ne__(self, other):
        return not self.__eq__(other)

    def __repr__(self):
        return "%s()" % self.__class__.__name__

    __reduce__ = object.__reduce__


class tzoffset(datetime.tzinfo):

    def __init__(self, name, offset):
        self._name = name
        self._offset = datetime.timedelta(seconds=offset)

    def utcoffset(self, dt):
        return self._offset

    def dst(self, dt):
        return ZERO

    @tzname_in_python2
    def tzname(self, dt):
        return self._name

    def __eq__(self, other):
        return (isinstance(other, tzoffset) and
                self._offset == other._offset)

    def __ne__(self, other):
        return not self.__eq__(other)

    def __repr__(self):
        return "%s(%s, %s)" % (self.__class__.__name__,
                               repr(self._name),
                               self._offset.days*86400+self._offset.seconds)

    __reduce__ = object.__reduce__


class tzlocal(datetime.tzinfo):

    _std_offset = datetime.timedelta(seconds=-time.timezone)
    if time.daylight:
        _dst_offset = datetime.timedelta(seconds=-time.altzone)
    else:
        _dst_offset = _std_offset

    def utcoffset(self, dt):
        if self._isdst(dt):
            return self._dst_offset
        else:
            return self._std_offset

    def dst(self, dt):
        if self._isdst(dt):
            return self._dst_offset-self._std_offset
        else:
            return ZERO

    @tzname_in_python2
    def tzname(self, dt):
        return time.tzname[self._isdst(dt)]

    def _isdst(self, dt):
        # We can't use mktime here. It is unstable when deciding if
        # the hour near to a change is DST or not.
        #
        # timestamp = time.mktime((dt.year, dt.month, dt.day, dt.hour,
        #                         dt.minute, dt.second, dt.weekday(), 0, -1))
        # return time.localtime(timestamp).tm_isdst
        #
        # The code above yields the following result:
        #
        # >>> import tz, datetime
        # >>> t = tz.tzlocal()
        # >>> datetime.datetime(2003,2,15,23,tzinfo=t).tzname()
        # 'BRDT'
        # >>> datetime.datetime(2003,2,16,0,tzinfo=t).tzname()
        # 'BRST'
        # >>> datetime.datetime(2003,2,15,23,tzinfo=t).tzname()
        # 'BRST'
        # >>> datetime.datetime(2003,2,15,22,tzinfo=t).tzname()
        # 'BRDT'
        # >>> datetime.datetime(2003,2,15,23,tzinfo=t).tzname()
        # 'BRDT'
        #
        # Here is a more stable implementation:
        #
        timestamp = ((dt.toordinal() - EPOCHORDINAL) * 86400
                     + dt.hour * 3600
                     + dt.minute * 60
                     + dt.second)
        return time.localtime(timestamp+time.timezone).tm_isdst

    def __eq__(self, other):
        if not isinstance(other, tzlocal):
            return False
        return (self._std_offset == other._std_offset and
                self._dst_offset == other._dst_offset)
        return True

    def __ne__(self, other):
        return not self.__eq__(other)

    def __repr__(self):
        return "%s()" % self.__class__.__name__

    __reduce__ = object.__reduce__


class _ttinfo(object):
    __slots__ = ["offset", "delta", "isdst", "abbr", "isstd", "isgmt"]

    def __init__(self):
        for attr in self.__slots__:
            setattr(self, attr, None)

    def __repr__(self):
        l = []
        for attr in self.__slots__:
            value = getattr(self, attr)
            if value is not None:
                l.append("%s=%s" % (attr, repr(value)))
        return "%s(%s)" % (self.__class__.__name__, ", ".join(l))

    def __eq__(self, other):
        if not isinstance(other, _ttinfo):
            return False
        return (self.offset == other.offset and
                self.delta == other.delta and
                self.isdst == other.isdst and
                self.abbr == other.abbr and
                self.isstd == other.isstd and
                self.isgmt == other.isgmt)

    def __ne__(self, other):
        return not self.__eq__(other)

    def __getstate__(self):
        state = {}
        for name in self.__slots__:
            state[name] = getattr(self, name, None)
        return state

    def __setstate__(self, state):
        for name in self.__slots__:
            if name in state:
                setattr(self, name, state[name])


class tzfile(datetime.tzinfo):

    # http://www.twinsun.com/tz/tz-link.htm
    # ftp://ftp.iana.org/tz/tz*.tar.gz

    def __init__(self, fileobj, filename=None):
        file_opened_here = False
        if isinstance(fileobj, string_types):
            self._filename = fileobj
            fileobj = open(fileobj, 'rb')
            file_opened_here = True
        elif filename is not None:
            self._filename = filename
        elif hasattr(fileobj, "name"):
            self._filename = fileobj.name
        else:
            self._filename = repr(fileobj)

        # From tzfile(5):
        #
        # The time zone information files used by tzset(3)
        # begin with the magic characters "TZif" to identify
        # them as time zone information files, followed by
        # sixteen bytes reserved for future use, followed by
        # six four-byte values of type long, written in a
        # ``standard'' byte order (the high-order  byte
        # of the value is written first).
        try:
            if fileobj.read(4).decode() != "TZif":
                raise ValueError("magic not found")

            fileobj.read(16)

            (
                # The number of UTC/local indicators stored in the file.
                ttisgmtcnt,

                # The number of standard/wall indicators stored in the file.
                ttisstdcnt,

                # The number of leap seconds for which data is
                # stored in the file.
                leapcnt,

                # The number of "transition times" for which data
                # is stored in the file.
                timecnt,

                # The number of "local time types" for which data
                # is stored in the file (must not be zero).
                typecnt,

                # The  number  of  characters  of "time zone
                # abbreviation strings" stored in the file.
                charcnt,

            ) = struct.unpack(">6l", fileobj.read(24))

            # The above header is followed by tzh_timecnt four-byte
            # values  of  type long,  sorted  in ascending order.
            # These values are written in ``standard'' byte order.
            # Each is used as a transition time (as  returned  by
            # time(2)) at which the rules for computing local time
            # change.

            if timecnt:
                self._trans_list = struct.unpack(">%dl" % timecnt,
                                                 fileobj.read(timecnt*4))
            else:
                self._trans_list = []

            # Next come tzh_timecnt one-byte values of type unsigned
            # char; each one tells which of the different types of
            # ``local time'' types described in the file is associated
            # with the same-indexed transition time. These values
            # serve as indices into an array of ttinfo structures that
            # appears next in the file.

            if timecnt:
                self._trans_idx = struct.unpack(">%dB" % timecnt,
                                                fileobj.read(timecnt))
            else:
                self._trans_idx = []

            # Each ttinfo structure is written as a four-byte value
            # for tt_gmtoff  of  type long,  in  a  standard  byte
            # order, followed  by a one-byte value for tt_isdst
            # and a one-byte  value  for  tt_abbrind.   In  each
            # structure, tt_gmtoff  gives  the  number  of
            # seconds to be added to UTC, tt_isdst tells whether
            # tm_isdst should be set by  localtime(3),  and
            # tt_abbrind serves  as an index into the array of
            # time zone abbreviation characters that follow the
            # ttinfo structure(s) in the file.

            ttinfo = []

            for i in range(typecnt):
                ttinfo.append(struct.unpack(">lbb", fileobj.read(6)))

            abbr = fileobj.read(charcnt).decode()

            # Then there are tzh_leapcnt pairs of four-byte
            # values, written in  standard byte  order;  the
            # first  value  of  each pair gives the time (as
            # returned by time(2)) at which a leap second
            # occurs;  the  second  gives the  total  number of
            # leap seconds to be applied after the given time.
            # The pairs of values are sorted in ascending order
            # by time.

            # Not used, for now
            # if leapcnt:
            #    leap = struct.unpack(">%dl" % (leapcnt*2),
            #                         fileobj.read(leapcnt*8))

            # Then there are tzh_ttisstdcnt standard/wall
            # indicators, each stored as a one-byte value;
            # they tell whether the transition times associated
            # with local time types were specified as standard
            # time or wall clock time, and are used when
            # a time zone file is used in handling POSIX-style
            # time zone environment variables.

            if ttisstdcnt:
                isstd = struct.unpack(">%db" % ttisstdcnt,
                                      fileobj.read(ttisstdcnt))

            # Finally, there are tzh_ttisgmtcnt UTC/local
            # indicators, each stored as a one-byte value;
            # they tell whether the transition times associated
            # with local time types were specified as UTC or
            # local time, and are used when a time zone file
            # is used in handling POSIX-style time zone envi-
            # ronment variables.

            if ttisgmtcnt:
                isgmt = struct.unpack(">%db" % ttisgmtcnt,
                                      fileobj.read(ttisgmtcnt))

            # ** Everything has been read **
        finally:
            if file_opened_here:
                fileobj.close()

        # Build ttinfo list
        self._ttinfo_list = []
        for i in range(typecnt):
            gmtoff, isdst, abbrind = ttinfo[i]
            # Round to full-minutes if that's not the case. Python's
            # datetime doesn't accept sub-minute timezones. Check
            # http://python.org/sf/1447945 for some information.
            gmtoff = (gmtoff+30)//60*60
            tti = _ttinfo()
            tti.offset = gmtoff
            tti.delta = datetime.timedelta(seconds=gmtoff)
            tti.isdst = isdst
            tti.abbr = abbr[abbrind:abbr.find('\x00', abbrind)]
            tti.isstd = (ttisstdcnt > i and isstd[i] != 0)
            tti.isgmt = (ttisgmtcnt > i and isgmt[i] != 0)
            self._ttinfo_list.append(tti)

        # Replace ttinfo indexes for ttinfo objects.
        trans_idx = []
        for idx in self._trans_idx:
            trans_idx.append(self._ttinfo_list[idx])
        self._trans_idx = tuple(trans_idx)

        # Set standard, dst, and before ttinfos. before will be
        # used when a given time is before any transitions,
        # and will be set to the first non-dst ttinfo, or to
        # the first dst, if all of them are dst.
        self._ttinfo_std = None
        self._ttinfo_dst = None
        self._ttinfo_before = None
        if self._ttinfo_list:
            if not self._trans_list:
                self._ttinfo_std = self._ttinfo_first = self._ttinfo_list[0]
            else:
                for i in range(timecnt-1, -1, -1):
                    tti = self._trans_idx[i]
                    if not self._ttinfo_std and not tti.isdst:
                        self._ttinfo_std = tti
                    elif not self._ttinfo_dst and tti.isdst:
                        self._ttinfo_dst = tti
                    if self._ttinfo_std and self._ttinfo_dst:
                        break
                else:
                    if self._ttinfo_dst and not self._ttinfo_std:
                        self._ttinfo_std = self._ttinfo_dst

                for tti in self._ttinfo_list:
                    if not tti.isdst:
                        self._ttinfo_before = tti
                        break
                else:
                    self._ttinfo_before = self._ttinfo_list[0]

        # Now fix transition times to become relative to wall time.
        #
        # I'm not sure about this. In my tests, the tz source file
        # is setup to wall time, and in the binary file isstd and
        # isgmt are off, so it should be in wall time. OTOH, it's
        # always in gmt time. Let me know if you have comments
        # about this.
        laststdoffset = 0
        self._trans_list = list(self._trans_list)
        for i in range(len(self._trans_list)):
            tti = self._trans_idx[i]
            if not tti.isdst:
                # This is std time.
                self._trans_list[i] += tti.offset
                laststdoffset = tti.offset
            else:
                # This is dst time. Convert to std.
                self._trans_list[i] += laststdoffset
        self._trans_list = tuple(self._trans_list)

    def _find_ttinfo(self, dt, laststd=0):
        timestamp = ((dt.toordinal() - EPOCHORDINAL) * 86400
                     + dt.hour * 3600
                     + dt.minute * 60
                     + dt.second)
        idx = 0
        for trans in self._trans_list:
            if timestamp < trans:
                break
            idx += 1
        else:
            return self._ttinfo_std
        if idx == 0:
            return self._ttinfo_before
        if laststd:
            while idx > 0:
                tti = self._trans_idx[idx-1]
                if not tti.isdst:
                    return tti
                idx -= 1
            else:
                return self._ttinfo_std
        else:
            return self._trans_idx[idx-1]

    def utcoffset(self, dt):
        if not self._ttinfo_std:
            return ZERO
        return self._find_ttinfo(dt).delta

    def dst(self, dt):
        if not self._ttinfo_dst:
            return ZERO
        tti = self._find_ttinfo(dt)
        if not tti.isdst:
            return ZERO

        # The documentation says that utcoffset()-dst() must
        # be constant for every dt.
        return tti.delta-self._find_ttinfo(dt, laststd=1).delta

        # An alternative for that would be:
        #
        # return self._ttinfo_dst.offset-self._ttinfo_std.offset
        #
        # However, this class stores historical changes in the
        # dst offset, so I belive that this wouldn't be the right
        # way to implement this.

    @tzname_in_python2
    def tzname(self, dt):
        if not self._ttinfo_std:
            return None
        return self._find_ttinfo(dt).abbr

    def __eq__(self, other):
        if not isinstance(other, tzfile):
            return False
        return (self._trans_list == other._trans_list and
                self._trans_idx == other._trans_idx and
                self._ttinfo_list == other._ttinfo_list)

    def __ne__(self, other):
        return not self.__eq__(other)

    def __repr__(self):
        return "%s(%s)" % (self.__class__.__name__, repr(self._filename))

    def __reduce__(self):
        if not os.path.isfile(self._filename):
            raise ValueError("Unpickable %s class" % self.__class__.__name__)
        return (self.__class__, (self._filename,))


class tzrange(datetime.tzinfo):
    def __init__(self, stdabbr, stdoffset=None,
                 dstabbr=None, dstoffset=None,
                 start=None, end=None):
        global relativedelta
        if not relativedelta:
            from dateutil import relativedelta
        self._std_abbr = stdabbr
        self._dst_abbr = dstabbr
        if stdoffset is not None:
            self._std_offset = datetime.timedelta(seconds=stdoffset)
        else:
            self._std_offset = ZERO
        if dstoffset is not None:
            self._dst_offset = datetime.timedelta(seconds=dstoffset)
        elif dstabbr and stdoffset is not None:
            self._dst_offset = self._std_offset+datetime.timedelta(hours=+1)
        else:
            self._dst_offset = ZERO
        if dstabbr and start is None:
            self._start_delta = relativedelta.relativedelta(
                hours=+2, month=4, day=1, weekday=relativedelta.SU(+1))
        else:
            self._start_delta = start
        if dstabbr and end is None:
            self._end_delta = relativedelta.relativedelta(
                hours=+1, month=10, day=31, weekday=relativedelta.SU(-1))
        else:
            self._end_delta = end

    def utcoffset(self, dt):
        if self._isdst(dt):
            return self._dst_offset
        else:
            return self._std_offset

    def dst(self, dt):
        if self._isdst(dt):
            return self._dst_offset-self._std_offset
        else:
            return ZERO

    @tzname_in_python2
    def tzname(self, dt):
        if self._isdst(dt):
            return self._dst_abbr
        else:
            return self._std_abbr

    def _isdst(self, dt):
        if not self._start_delta:
            return False
        year = datetime.datetime(dt.year, 1, 1)
        start = year+self._start_delta
        end = year+self._end_delta
        dt = dt.replace(tzinfo=None)
        if start < end:
            return dt >= start and dt < end
        else:
            return dt >= start or dt < end

    def __eq__(self, other):
        if not isinstance(other, tzrange):
            return False
        return (self._std_abbr == other._std_abbr and
                self._dst_abbr == other._dst_abbr and
                self._std_offset == other._std_offset and
                self._dst_offset == other._dst_offset and
                self._start_delta == other._start_delta and
                self._end_delta == other._end_delta)

    def __ne__(self, other):
        return not self.__eq__(other)

    def __repr__(self):
        return "%s(...)" % self.__class__.__name__

    __reduce__ = object.__reduce__


class tzstr(tzrange):

    def __init__(self, s):
        global parser
        if not parser:
            from dateutil import parser
        self._s = s

        res = parser._parsetz(s)
        if res is None:
            raise ValueError("unknown string format")

        # Here we break the compatibility with the TZ variable handling.
        # GMT-3 actually *means* the timezone -3.
        if res.stdabbr in ("GMT", "UTC"):
            res.stdoffset *= -1

        # We must initialize it first, since _delta() needs
        # _std_offset and _dst_offset set. Use False in start/end
        # to avoid building it two times.
        tzrange.__init__(self, res.stdabbr, res.stdoffset,
                         res.dstabbr, res.dstoffset,
                         start=False, end=False)

        if not res.dstabbr:
            self._start_delta = None
            self._end_delta = None
        else:
            self._start_delta = self._delta(res.start)
            if self._start_delta:
                self._end_delta = self._delta(res.end, isend=1)

    def _delta(self, x, isend=0):
        kwargs = {}
        if x.month is not None:
            kwargs["month"] = x.month
            if x.weekday is not None:
                kwargs["weekday"] = relativedelta.weekday(x.weekday, x.week)
                if x.week > 0:
                    kwargs["day"] = 1
                else:
                    kwargs["day"] = 31
            elif x.day:
                kwargs["day"] = x.day
        elif x.yday is not None:
            kwargs["yearday"] = x.yday
        elif x.jyday is not None:
            kwargs["nlyearday"] = x.jyday
        if not kwargs:
            # Default is to start on first sunday of april, and end
            # on last sunday of october.
            if not isend:
                kwargs["month"] = 4
                kwargs["day"] = 1
                kwargs["weekday"] = relativedelta.SU(+1)
            else:
                kwargs["month"] = 10
                kwargs["day"] = 31
                kwargs["weekday"] = relativedelta.SU(-1)
        if x.time is not None:
            kwargs["seconds"] = x.time
        else:
            # Default is 2AM.
            kwargs["seconds"] = 7200
        if isend:
            # Convert to standard time, to follow the documented way
            # of working with the extra hour. See the documentation
            # of the tzinfo class.
            delta = self._dst_offset-self._std_offset
            kwargs["seconds"] -= delta.seconds+delta.days*86400
        return relativedelta.relativedelta(**kwargs)

    def __repr__(self):
        return "%s(%s)" % (self.__class__.__name__, repr(self._s))


class _tzicalvtzcomp(object):
    def __init__(self, tzoffsetfrom, tzoffsetto, isdst,
                 tzname=None, rrule=None):
        self.tzoffsetfrom = datetime.timedelta(seconds=tzoffsetfrom)
        self.tzoffsetto = datetime.timedelta(seconds=tzoffsetto)
        self.tzoffsetdiff = self.tzoffsetto-self.tzoffsetfrom
        self.isdst = isdst
        self.tzname = tzname
        self.rrule = rrule


class _tzicalvtz(datetime.tzinfo):
    def __init__(self, tzid, comps=[]):
        self._tzid = tzid
        self._comps = comps
        self._cachedate = []
        self._cachecomp = []

    def _find_comp(self, dt):
        if len(self._comps) == 1:
            return self._comps[0]
        dt = dt.replace(tzinfo=None)
        try:
            return self._cachecomp[self._cachedate.index(dt)]
        except ValueError:
            pass
        lastcomp = None
        lastcompdt = None
        for comp in self._comps:
            if not comp.isdst:
                # Handle the extra hour in DST -> STD
                compdt = comp.rrule.before(dt-comp.tzoffsetdiff, inc=True)
            else:
                compdt = comp.rrule.before(dt, inc=True)
            if compdt and (not lastcompdt or lastcompdt < compdt):
                lastcompdt = compdt
                lastcomp = comp
        if not lastcomp:
            # RFC says nothing about what to do when a given
            # time is before the first onset date. We'll look for the
            # first standard component, or the first component, if
            # none is found.
            for comp in self._comps:
                if not comp.isdst:
                    lastcomp = comp
                    break
            else:
                lastcomp = comp[0]
        self._cachedate.insert(0, dt)
        self._cachecomp.insert(0, lastcomp)
        if len(self._cachedate) > 10:
            self._cachedate.pop()
            self._cachecomp.pop()
        return lastcomp

    def utcoffset(self, dt):
        return self._find_comp(dt).tzoffsetto

    def dst(self, dt):
        comp = self._find_comp(dt)
        if comp.isdst:
            return comp.tzoffsetdiff
        else:
            return ZERO

    @tzname_in_python2
    def tzname(self, dt):
        return self._find_comp(dt).tzname

    def __repr__(self):
        return "<tzicalvtz %s>" % repr(self._tzid)

    __reduce__ = object.__reduce__


class tzical(object):
    def __init__(self, fileobj):
        global rrule
        if not rrule:
            from dateutil import rrule

        if isinstance(fileobj, string_types):
            self._s = fileobj
            # ical should be encoded in UTF-8 with CRLF
            fileobj = open(fileobj, 'r')
        elif hasattr(fileobj, "name"):
            self._s = fileobj.name
        else:
            self._s = repr(fileobj)

        self._vtz = {}

        self._parse_rfc(fileobj.read())

    def keys(self):
        return list(self._vtz.keys())

    def get(self, tzid=None):
        if tzid is None:
            keys = list(self._vtz.keys())
            if len(keys) == 0:
                raise ValueError("no timezones defined")
            elif len(keys) > 1:
                raise ValueError("more than one timezone available")
            tzid = keys[0]
        return self._vtz.get(tzid)

    def _parse_offset(self, s):
        s = s.strip()
        if not s:
            raise ValueError("empty offset")
        if s[0] in ('+', '-'):
            signal = (-1, +1)[s[0] == '+']
            s = s[1:]
        else:
            signal = +1
        if len(s) == 4:
            return (int(s[:2])*3600+int(s[2:])*60)*signal
        elif len(s) == 6:
            return (int(s[:2])*3600+int(s[2:4])*60+int(s[4:]))*signal
        else:
            raise ValueError("invalid offset: "+s)

    def _parse_rfc(self, s):
        lines = s.splitlines()
        if not lines:
            raise ValueError("empty string")

        # Unfold
        i = 0
        while i < len(lines):
            line = lines[i].rstrip()
            if not line:
                del lines[i]
            elif i > 0 and line[0] == " ":
                lines[i-1] += line[1:]
                del lines[i]
            else:
                i += 1

        tzid = None
        comps = []
        invtz = False
        comptype = None
        for line in lines:
            if not line:
                continue
            name, value = line.split(':', 1)
            parms = name.split(';')
            if not parms:
                raise ValueError("empty property name")
            name = parms[0].upper()
            parms = parms[1:]
            if invtz:
                if name == "BEGIN":
                    if value in ("STANDARD", "DAYLIGHT"):
                        # Process component
                        pass
                    else:
                        raise ValueError("unknown component: "+value)
                    comptype = value
                    founddtstart = False
                    tzoffsetfrom = None
                    tzoffsetto = None
                    rrulelines = []
                    tzname = None
                elif name == "END":
                    if value == "VTIMEZONE":
                        if comptype:
                            raise ValueError("component not closed: "+comptype)
                        if not tzid:
                            raise ValueError("mandatory TZID not found")
                        if not comps:
                            raise ValueError(
                                "at least one component is needed")
                        # Process vtimezone
                        self._vtz[tzid] = _tzicalvtz(tzid, comps)
                        invtz = False
                    elif value == comptype:
                        if not founddtstart:
                            raise ValueError("mandatory DTSTART not found")
                        if tzoffsetfrom is None:
                            raise ValueError(
                                "mandatory TZOFFSETFROM not found")
                        if tzoffsetto is None:
                            raise ValueError(
                                "mandatory TZOFFSETFROM not found")
                        # Process component
                        rr = None
                        if rrulelines:
                            rr = rrule.rrulestr("\n".join(rrulelines),
                                                compatible=True,
                                                ignoretz=True,
                                                cache=True)
                        comp = _tzicalvtzcomp(tzoffsetfrom, tzoffsetto,
                                              (comptype == "DAYLIGHT"),
                                              tzname, rr)
                        comps.append(comp)
                        comptype = None
                    else:
                        raise ValueError("invalid component end: "+value)
                elif comptype:
                    if name == "DTSTART":
                        rrulelines.append(line)
                        founddtstart = True
                    elif name in ("RRULE", "RDATE", "EXRULE", "EXDATE"):
                        rrulelines.append(line)
                    elif name == "TZOFFSETFROM":
                        if parms:
                            raise ValueError(
                                "unsupported %s parm: %s " % (name, parms[0]))
                        tzoffsetfrom = self._parse_offset(value)
                    elif name == "TZOFFSETTO":
                        if parms:
                            raise ValueError(
                                "unsupported TZOFFSETTO parm: "+parms[0])
                        tzoffsetto = self._parse_offset(value)
                    elif name == "TZNAME":
                        if parms:
                            raise ValueError(
                                "unsupported TZNAME parm: "+parms[0])
                        tzname = value
                    elif name == "COMMENT":
                        pass
                    else:
                        raise ValueError("unsupported property: "+name)
                else:
                    if name == "TZID":
                        if parms:
                            raise ValueError(
                                "unsupported TZID parm: "+parms[0])
                        tzid = value
                    elif name in ("TZURL", "LAST-MODIFIED", "COMMENT"):
                        pass
                    else:
                        raise ValueError("unsupported property: "+name)
            elif name == "BEGIN" and value == "VTIMEZONE":
                tzid = None
                comps = []
                invtz = True

    def __repr__(self):
        return "%s(%s)" % (self.__class__.__name__, repr(self._s))

if sys.platform != "win32":
    TZFILES = ["/etc/localtime", "localtime"]
    TZPATHS = ["/usr/share/zoneinfo", "/usr/lib/zoneinfo", "/etc/zoneinfo"]
else:
    TZFILES = []
    TZPATHS = []


def gettz(name=None):
    tz = None
    if not name:
        try:
            name = os.environ["TZ"]
        except KeyError:
            pass
    if name is None or name == ":":
        for filepath in TZFILES:
            if not os.path.isabs(filepath):
                filename = filepath
                for path in TZPATHS:
                    filepath = os.path.join(path, filename)
                    if os.path.isfile(filepath):
                        break
                else:
                    continue
            if os.path.isfile(filepath):
                try:
                    tz = tzfile(filepath)
                    break
                except (IOError, OSError, ValueError):
                    pass
        else:
            tz = tzlocal()
    else:
        if name.startswith(":"):
            name = name[:-1]
        if os.path.isabs(name):
            if os.path.isfile(name):
                tz = tzfile(name)
            else:
                tz = None
        else:
            for path in TZPATHS:
                filepath = os.path.join(path, name)
                if not os.path.isfile(filepath):
                    filepath = filepath.replace(' ', '_')
                    if not os.path.isfile(filepath):
                        continue
                try:
                    tz = tzfile(filepath)
                    break
                except (IOError, OSError, ValueError):
                    pass
            else:
                tz = None
                if tzwin is not None:
                    try:
                        tz = tzwin(name)
                    except WindowsError:
                        tz = None
                if not tz:
                    from dateutil.zoneinfo import gettz
                    tz = gettz(name)
                if not tz:
                    for c in name:
                        # name must have at least one offset to be a tzstr
                        if c in "0123456789":
                            try:
                                tz = tzstr(name)
                            except ValueError:
                                pass
                            break
                    else:
                        if name in ("GMT", "UTC"):
                            tz = tzutc()
                        elif name in time.tzname:
                            tz = tzlocal()
    return tz

# vim:ts=4:sw=4:et