#!/usr/bin/env python
"""
Copyright 2009-2020 VMware, Inc.  All rights reserved. -- VMware Confidential

This module is for ISO 8601 parsing
"""
__author__ = 'VMware, Inc'

import re
import time
from datetime import datetime, timedelta, tzinfo

import six

# Regular expression to parse a subset of ISO 8601 format
_dtExpr = re.compile(
    # XMLSchema datetime. Mandatory to have - and :
    # See: http://www.w3.org/TR/xmlschema-2/#isoformats
    # Note: python datetime cannot handle the following:
    #       - leap second, ie. 0-60 seconds (not 0-59)
    #       - BC (negative years)
    # year [-]0000..9999
    r'(?P<year>-?\d{4})'
    # month 01..12
    r'(-(?P<month>(0[1-9]|1[0-2]))'
    # day 01..31
    r'(-(?P<day>(0[1-9]|[1-2]\d|3[01])))?)?'
    # time separator 'T'
    r'(T'
    # hour 00..24
    r'(?P<hour>([01]\d|2[0-4]))'
    # minute 00..59
    r'((:(?P<minute>[0-5]\d))'
    # seconds 00..60 (leap second ok)
    r'(:(?P<second>([0-5]\d|60))'
    # microsecond. max 16 digits
    # - Should not allows trailing zeros. But python isoformat() put zeros
    #   after microseconds. Oh well, allows trailing zeros, quite harmless
    r'(\.(?P<microsecond>\d{1,16}))?)?)?'
    # UTC 'Z', or...
    r'((?P<tzutc>Z)'
    # tz [+-]00..13:0..59|14:00
    r'|((?P<tzhr>[+-](([0]\d)|(1[0-3])|(?P<tzlimit>)14))'
    r'(:(?P<tzmin>(?(tzlimit)00|([0-5]\d))))?))?'
    r')?$')

# Default date time val. Key should match the tags in _dtExpr
_dtExprKeyDefValMap = {
    'year': None,
    'month': 1,
    'day': 1,
    'hour': 0,
    'minute': 0,
    'second': 0,
    'microsecond': 0
}


class TZInfo(tzinfo):
    """ Timezone info class """

    timedelta0 = timedelta(hours=0)
    timedelta1 = timedelta(hours=1)

    def __init__(self, tzname='UTC', utcOffset=None, dst=None):
        self._tzname = tzname
        if not utcOffset:
            utcOffset = self.timedelta0
        self._utcOffset = utcOffset
        if not dst:
            dst = None
        self._dst = dst

    def utcoffset(self, dt):
        return self._utcOffset + self.dst(dt)

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

    def dst(self, dt):
        ret = self.timedelta0
        if self._dst:
            if self._dst[0] <= dt.replace(tzinfo=None) < self._dst[1]:
                ret = self.timedelta1
        return ret


class TZManager:
    """ Time zone manager """
    _tzInfos = {}

    @staticmethod
    def GetTZInfo(tzname='UTC', utcOffset=None, dst=None):
        """ Get / Add timezone info """
        key = (tzname, utcOffset, dst)
        tzInfo = TZManager._tzInfos.get(key)
        if not tzInfo:
            tzInfo = TZInfo(tzname, utcOffset, dst)
            TZManager._tzInfos[key] = tzInfo
        return tzInfo


def ParseISO8601(datetimeStr):
    """
    Parse ISO 8601 date time from string.
    Returns datetime if ok, None otherwise
    Note: Allows YYYY / YYYY-MM, but truncate YYYY -> YYYY-01-01,
                                              YYYY-MM -> YYYY-MM-01
    Truncate microsecond to most significant 6 digits
    """
    datetimeVal = None
    match = _dtExpr.match(datetimeStr)
    if match:
        try:
            dt = {}
            for key, defaultVal in six.iteritems(_dtExprKeyDefValMap):
                val = match.group(key)
                if val:
                    if key == 'microsecond':
                        val = val[:6] + '0' * (6 - len(val))
                    dt[key] = int(val)
                elif defaultVal:
                    dt[key] = defaultVal

            # Orig. XMLSchema don't allow all zeros year. But newer draft is ok
            # if dt['year'] == 0:
            #   # Year cannot be all zeros
            #   raise Exception('Year cannot be all zeros')

            # 24 is a special case.
            # It is actually represented as next day 00:00
            delta = None
            if dt.get('hour', 0) == 24:
                # Must be 24:00:00.0
                if (dt.get('minute', 0) == 0 and dt.get('second', 0) == 0
                        and dt.get('microsecond', 0) == 0):
                    dt['hour'] = 23
                    delta = timedelta(hours=1)
                else:
                    return None

            # Set tzinfo
            # TODO: dst
            tzInfo = None
            val = match.group('tzutc')
            if val:
                tzInfo = TZManager.GetTZInfo()
            else:
                val = match.group('tzhr')
                if val:
                    # tz hours offset
                    tzhr = int(val)
                    utcsign = val[0]

                    # tz minutes offset
                    tzmin = 0
                    val = match.group('tzmin')
                    if val:
                        tzmin = tzhr >= 0 and int(val) or -int(val)

                    # Better tzname (map UTC +-00:00 to UTC)
                    tzname = 'UTC'
                    if tzhr != 0 or tzmin != 0:
                        tzname += ' %s%02d:%02d' % (utcsign, abs(tzhr),
                                                    abs(tzmin))

                    tzInfo = TZManager.GetTZInfo(
                        tzname=tzname,
                        utcOffset=timedelta(hours=tzhr, minutes=tzmin))
            if tzInfo:
                dt['tzinfo'] = tzInfo

            datetimeVal = datetime(**dt)
            if delta:
                datetimeVal += delta
        except Exception:
            pass
    return datetimeVal


def ISO8601Format(dt):
    """
    Python datetime isoformat() has the following problems:
    - leave trailing 0 at the end of microseconds (violates XMLSchema rule)
    - tz print +00:00 instead of Z
    - Missing timezone offset for datetime without tzinfo
    """
    isoStr = dt.strftime('%Y-%m-%dT%H:%M:%S')
    if dt.microsecond:
        isoStr += ('.%06d' % dt.microsecond).rstrip('0')
    if dt.tzinfo:
        tz = dt.strftime('%z')
    else:
        utcOffset_minutes = -time.altzone / 60
        tz = "%+.2d%.2d" % (utcOffset_minutes / 60,
                            (abs(utcOffset_minutes) % 60))
    if tz == '+0000':
        return isoStr + 'Z'
    elif tz:
        return isoStr + tz[:3] + ':' + tz[3:]
    else:
        # Local offset is unknown
        return isoStr + '-00:00'


# Testing
if __name__ == '__main__':
    # Valid entries
    for testStr in [
            '1971',  # 1971-01-01
            '1971-11',  # 1971-11-01
            '1971-11-02',
            '1971-11-02T23',
            '1971-11-02T23Z',
            '1971-11-02T23:04',
            '1971-11-02T23:04Z',
            '1971-11-02T23:04:15',
            '1971-11-02T23:04:15Z',
            '1971-11-02T23:04:15.1',
            '1971-11-02T23:04:15.01',
            '1971-11-02T23:04:15.023456',
            '1971-11-02T23:04:15.103456Z',
            '1971-11-02T23:04:15.123456+11',
            '1971-11-02T23:04:15.123456-11',
            '1971-11-02T23:04:15.123456+11:30',
            '1971-11-02T23:04:15.123456-11:30',
            '1971-11-02T23:04:15.123456+00:00',  # Same as Z
            '1971-11-02T23:04:15.123456-00:00',  # Same as Z
            '1971-01-02T23:04:15+14',
            '1971-01-02T23:04:15+14:00',
            '1971-01-02T23:04:15-14',
            '1971-01-02T23:04:15-14:00',

            # Valid: Truncate microsec to 6 digits
            '1971-01-02T23:04:15.123456891+11',
            '1971-01-02T24',  # 24 is valid. It should represent the 00:00 the
            # next day
            '1971-01-02T24:00',
            '1971-01-02T24:00:00',
            '1971-01-02T24:00:00.0',

            # Should NOT be valid but python isoformat adding trailing zeros
            '1971-01-02T23:04:15.123430',  # Microseconds ends in zero
            '1971-01-02T23:04:15.0',  # Microseconds ends in zero

            # Should be valid but python datetime don't support it
            # '2005-12-31T23:59:60Z', # Leap second
            # '-0001', # BC 1
    ]:
        dt = ParseISO8601(testStr)
        if dt is None:
            print('Failed to parse (%s)' % testStr)
            assert (False)

        # Make sure we can translate back
        isoformat = ISO8601Format(dt)
        dt1 = ParseISO8601(isoformat)
        if dt.tzinfo is None:
            dt = dt.replace(tzinfo=dt1.tzinfo)
        if dt1 != dt:
            print('ParseISO8601 -> ISO8601Format -> ParseISO8601 failed (%s)' %
                  testStr)
            assert (False)

        # Make sure we can parse python isoformat()
        dt2 = ParseISO8601(dt.isoformat())
        if dt2 is None:
            print('ParseISO8601("%s".isoformat()) failed' % testStr)
            assert (False)

        print(testStr, '->', dt, isoformat)

    # Basic form
    for testStr in [
            '197111',  # 1971-11-01
            '19711102',
            '19711102T23',
            '19711102T23Z',
            '19711102T2304',
            '19711102T2304Z',
            '19711102T230415',
            '19711102T230415Z',
            '19711102T230415.123456',
            '19711102T230415.123456Z',
            '19711102T230415.123456+11',
            '19711102T230415.123456-11',
            '19711102T230415.123456+1130',
            '19711102T230415.123456-1130',
    ]:
        # Reject for now
        dt = ParseISO8601(testStr)
        if dt is not None:
            print('ParseISO8601 (%s) should fail, but it did not' % testStr)
            assert (False)
        # print testStr, '->', dt
        # assert(dt != None)

    # Invalid entries
    for testStr in [
            # Xml schema reject year 0
            '0000',  # 0 years are not allowed
            '+0001',  # Leading + is not allowed
            '',  # Empty datetime str
            '09',  # Years must be at least 4 digits
            '1971-01-02T',  # T not follow by time
            '1971-01-02TZ',  # T not follow by time
            '1971-01-02T+10',  # T not follow by time
            '1971-01-02T-10',  # T not follow by time
            '1971-01-02T23:',  # extra :
            '1971-01-02T23:04:',  # extra :
            '1971-01-02T23:0d',  # 0d
            '1971-01-02T23:04:15.',  # Dot not follows by microsec
            '1971-01-02+12',  # time without T
            '1971Z',  # Z without T
            '1971-01-02T23:04:15.123456Z+11',  # Z follows by +
            '1971-01-02T23:04:15.123456Z-11',  # Z follows by -
            '1971-01-02T23:04:15.123456+:30',  # extra :
            '1971-01-02T23:04:15.123456+30:',  # extra :
            # Too many microseconds digits
            '1971-01-02T23:04:15.01234567890123456789',

            # Python isoformat leave trailing zeros in microseconds
            # Relax regular expression to accept it
            # '1971-01-02T23:04:15.123430', # Microseconds ends in zero
            # '1971-01-02T23:04:15.0', # Microseconds ends in zero

            # Timezone must be between +14 / -14
            '1971-01-02T23:04:15+15',
            '1971-01-02T23:04:15-15',
            '1971-01-02T23:04:15+14:01',
            '1971-01-02T23:04:15-14:01',

            # Mix basic form with extended format
            '197101-02T23:04:15.123456',
            '19710102T23:04:15.123456',
            '19710102T230415.123456+11:30',
            '1971-01-02T230415.123456',
            '1971-01-02T23:04:15.123456+1130',

            # Error captured by datetime class
            '1971-00-02',  # Less than 1 month
            '1971-13-02',  # Larger than 12 months
            '1971-01-00',  # Less than 1 day
            '1971-11-32',  # Larger than 30 days for Nov
            '1971-12-32',  # Larger than 31 days
            '1971-01-02T24:01',  # Larger than 23 hr
            '1971-01-02T23:61',  # Larger than 60 min
            '1971-01-02T23:60:61',  # Larger than 61 sec
    ]:
        dt = ParseISO8601(testStr)
        if dt is not None:
            print('ParseISO8601 (%s) should fail, but it did not' % testStr)
            assert (False)
