"""Strptime-related classes and functions.

CLASSES:

    LocaleTime -- Discovers and stores locale-specific time information

    TimeRE -- Creates regexes for pattern matching a string of text containing

                time information

FUNCTIONS:

    _getlang -- Figure out what language is being used for the locale

    strptime -- Calculates the time struct represented by the passed-in string

"""

import time

import locale

import calendar

from re import compile as re_compile

from re import IGNORECASE

from re import escape as re_escape

from datetime import date as datetime_date

try:

    from thread import allocate_lock as _thread_allocate_lock

except:

    from dummy_thread import allocate_lock as _thread_allocate_lock

__author__ = "Brett Cannon"

__email__ = "brett@python.org"

__all__ = ['strptime']

def _getlang():

    # Figure out what the current language is set to.

    return locale.getlocale(locale.LC_TIME)

class LocaleTime(object):

    """Stores and handles locale-specific information related to time.

    ATTRIBUTES:

        f_weekday -- full weekday names (7-item list)

        a_weekday -- abbreviated weekday names (7-item list)

        f_month -- full month names (13-item list; dummy value in [0], which

                    is added by code)

        a_month -- abbreviated month names (13-item list, dummy value in

                    [0], which is added by code)

        am_pm -- AM/PM representation (2-item list)

        LC_date_time -- format string for date/time representation (string)

        LC_date -- format string for date representation (string)

        LC_time -- format string for time representation (string)

        timezone -- daylight- and non-daylight-savings timezone representation

                    (2-item list of sets)

        lang -- Language used by instance (2-item tuple)

    """

    def __init__(self):

        """Set all attributes.

        Order of methods called matters for dependency reasons.

        The locale language is set at the offset and then checked again before

        exiting.  This is to make sure that the attributes were not set with a

        mix of information from more than one locale.  This would most likely

        happen when using threads where one thread calls a locale-dependent

        function while another thread changes the locale while the function in

        the other thread is still running.  Proper coding would call for

        locks to prevent changing the locale while locale-dependent code is

        running.  The check here is done in case someone does not think about

        doing this.

        Only other possible issue is if someone changed the timezone and did

        not call tz.tzset .  That is an issue for the programmer, though,

        since changing the timezone is worthless without that call.

        """

        self.lang = _getlang()

        self.__calc_weekday()

        self.__calc_month()

        self.__calc_am_pm()

        self.__calc_timezone()

        self.__calc_date_time()

        if _getlang() != self.lang:

            raise ValueError("locale changed during initialization")

    def __pad(self, seq, front):

        # Add '' to seq to either the front (is True), else the back.

        seq = list(seq)

        if front:

            seq.insert(0, '')

        else:

            seq.append('')

        return seq

    def __calc_weekday(self):

        # Set self.a_weekday and self.f_weekday using the calendar

        # module.

        a_weekday = [calendar.day_abbr[i].lower() for i in range(7)]

        f_weekday = [calendar.day_name[i].lower() for i in range(7)]

        self.a_weekday = a_weekday

        self.f_weekday = f_weekday

    def __calc_month(self):

        # Set self.f_month and self.a_month using the calendar module.

        a_month = [calendar.month_abbr[i].lower() for i in range(13)]

        f_month = [calendar.month_name[i].lower() for i in range(13)]

        self.a_month = a_month

        self.f_month = f_month

    def __calc_am_pm(self):

        # Set self.am_pm by using time.strftime().

        # The magic date (1999,3,17,hour,44,55,2,76,0) is not really that

        # magical; just happened to have used it everywhere else where a

        # static date was needed.

        am_pm = []

        for hour in (01,22):

            time_tuple = time.struct_time((1999,3,17,hour,44,55,2,76,0))

            am_pm.append(time.strftime("%p", time_tuple).lower())

        self.am_pm = am_pm

    def __calc_date_time(self):

        # Set self.date_time, self.date, & self.time by using

        # time.strftime().

        # Use (1999,3,17,22,44,55,2,76,0) for magic date because the amount of

        # overloaded numbers is minimized.  The order in which searches for

        # values within the format string is very important; it eliminates

        # possible ambiguity for what something represents.

        time_tuple = time.struct_time((1999,3,17,22,44,55,2,76,0))

        date_time = [None, None, None]

        date_time[0] = time.strftime("%c", time_tuple).lower()

        date_time[1] = time.strftime("%x", time_tuple).lower()

        date_time[2] = time.strftime("%X", time_tuple).lower()

        replacement_pairs = [('%', '%%'), (self.f_weekday[2], '%A'),

                    (self.f_month[3], '%B'), (self.a_weekday[2], '%a'),

                    (self.a_month[3], '%b'), (self.am_pm[1], '%p'),

                    ('1999', '%Y'), ('99', '%y'), ('22', '%H'),

                    ('44', '%M'), ('55', '%S'), ('76', '%j'),

                    ('17', '%d'), ('03', '%m'), ('3', '%m'),

                    # '3' needed for when no leading zero.

                    ('2', '%w'), ('10', '%I')]

        replacement_pairs.extend([(tz, "%Z") for tz_values in self.timezone

                                                for tz in tz_values])

        for offset,directive in ((0,'%c'), (1,'%x'), (2,'%X')):

            current_format = date_time[offset]

            for old, new in replacement_pairs:

                # Must deal with possible lack of locale info

                # manifesting itself as the empty string (e.g., Swedish's

                # lack of AM/PM info) or a platform returning a tuple of empty

                # strings (e.g., MacOS 9 having timezone as ('','')).

                if old:

                    current_format = current_format.replace(old, new)

            # If %W is used, then Sunday, 2005-01-03 will fall on week 0 since

            # 2005-01-03 occurs before the first Monday of the year.  Otherwise

            # %U is used.

            time_tuple = time.struct_time((1999,1,3,1,1,1,6,3,0))

            if '00' in time.strftime(directive, time_tuple):

                U_W = '%W'

            else:

                U_W = '%U'

            date_time[offset] = current_format.replace('11', U_W)

        self.LC_date_time = date_time[0]

        self.LC_date = date_time[1]

        self.LC_time = date_time[2]

    def __calc_timezone(self):

        # Set self.timezone by using time.tzname.

        # Do not worry about possibility of time.tzname[0] == timetzname[1]

        # and time.daylight; handle that in strptime .

        try:

            time.tzset()

        except AttributeError:

            pass

        no_saving = frozenset(["utc", "gmt", time.tzname[0].lower()])

        if time.daylight:

            has_saving = frozenset([time.tzname[1].lower()])

        else:

            has_saving = frozenset()

        self.timezone = (no_saving, has_saving)

class TimeRE(dict):

    """Handle conversion from format directives to regexes."""

    def __init__(self, locale_time=None):

        """Create keys/values.

        Order of execution is important for dependency reasons.

        """

        if locale_time:

            self.locale_time = locale_time

        else:

            self.locale_time = LocaleTime()

        base = super(TimeRE, self)

        base.__init__({

            # The " \d" part of the regex is to make %c from ANSI C work

            'd': r"(?P<d>3[0-1]|[1-2]\d|0[1-9]|[1-9]| [1-9])",

            'H': r"(?P<H>2[0-3]|[0-1]\d|\d)",

            'I': r"(?P<I>1[0-2]|0[1-9]|[1-9])",

            'j': r"(?P<j>36[0-6]|3[0-5]\d|[1-2]\d\d|0[1-9]\d|00[1-9]|[1-9]\d|0[1-9]|[1-9])",

            'm': r"(?P<m>1[0-2]|0[1-9]|[1-9])",

            'M': r"(?P<M>[0-5]\d|\d)",

            'S': r"(?P<S>6[0-1]|[0-5]\d|\d)",

            'U': r"(?P<U>5[0-3]|[0-4]\d|\d)",

            'w': r"(?P<w>[0-6])",

            # W is set below by using 'U'

            'y': r"(?P<y>\d\d)",

            #XXX: Does 'Y' need to worry about having less or more than

            #     4 digits?

            'Y': r"(?P<Y>\d\d\d\d)",

            'A': self.__seqToRE(self.locale_time.f_weekday, 'A'),

            'a': self.__seqToRE(self.locale_time.a_weekday, 'a'),

            'B': self.__seqToRE(self.locale_time.f_month[1:], 'B'),

            'b': self.__seqToRE(self.locale_time.a_month[1:], 'b'),

            'p': self.__seqToRE(self.locale_time.am_pm, 'p'),

            'Z': self.__seqToRE((tz for tz_names in self.locale_time.timezone

                                        for tz in tz_names),

                                'Z'),

            '%': '%'})

        base.__setitem__('W', base.__getitem__('U').replace('U', 'W'))

        base.__setitem__('c', self.pattern(self.locale_time.LC_date_time))

        base.__setitem__('x', self.pattern(self.locale_time.LC_date))

        base.__setitem__('X', self.pattern(self.locale_time.LC_time))

    def __seqToRE(self, to_convert, directive):

        """Convert a list to a regex string for matching a directive.

        Want possible matching values to be from longest to shortest.  This

        prevents the possibility of a match occuring for a value that also

        a substring of a larger value that should have matched (e.g., 'abc'

        matching when 'abcdef' should have been the match).

        """

        to_convert = sorted(to_convert, key=len, reverse=True)

        for value in to_convert:

            if value != '':

                break

        else:

            return ''

        regex = '|'.join(re_escape(stuff) for stuff in to_convert)

        regex = '(?P<%s>%s' % (directive, regex)

        return '%s)' % regex

    def pattern(self, format):

        """Return regex pattern for the format string.

        Need to make sure that any characters that might be interpreted as

        regex syntax are escaped.

        """

        processed_format = ''

        # The sub() call escapes all characters that might be misconstrued

        # as regex syntax.  Cannot use re.escape since we have to deal with

        # format directives (%m, etc.).

        regex_chars = re_compile(r"([\\.^$*+?\(\){}\[\]|])")

        format = regex_chars.sub(r"\\\1", format)

        whitespace_replacement = re_compile('\s+')

        format = whitespace_replacement.sub('\s+', format)

        while '%' in format:

            directive_index = format.index('%')+1

            processed_format = "%s%s%s" % (processed_format,

                                           format[:directive_index-1],

                                           self[format[directive_index]])

            format = format[directive_index+1:]

        return "%s%s" % (processed_format, format)

    def compile(self, format):

        """Return a compiled re object for the format string."""

        return re_compile(self.pattern(format), IGNORECASE)

_cache_lock = _thread_allocate_lock()

# DO NOT modify _TimeRE_cache or _regex_cache without acquiring the cache lock

# first!

_TimeRE_cache = TimeRE()

_CACHE_MAX_SIZE = 5 # Max number of regexes stored in _regex_cache

_regex_cache = {}

def _calc_julian_from_U_or_W(year, week_of_year, day_of_week, week_starts_Mon):

    """Calculate the Julian day based on the year, week of the year, and day of

    the week, with week_start_day representing whether the week of the year

    assumes the week starts on Sunday or Monday (6 or 0)."""

    first_weekday = datetime_date(year, 1, 1).weekday()

    # If we are dealing with the %U directive (week starts on Sunday), it's

    # easier to just shift the view to Sunday being the first day of the

    # week.

    if not week_starts_Mon:

        first_weekday = (first_weekday + 1) % 7

        day_of_week = (day_of_week + 1) % 7

    # Need to watch out for a week 0 (when the first day of the year is not

    # the same as that specified by %U or %W).

    week_0_length = (7 - first_weekday) % 7

    if week_of_year == 0:

        return 1 + day_of_week - first_weekday

    else:

        days_to_week = week_0_length + (7 * (week_of_year - 1))

        return 1 + days_to_week + day_of_week

def strptime(data_string, format="%a %b %d %H:%M:%S %Y"):

    """Return a time struct based on the input string and the format string."""

    global _TimeRE_cache, _regex_cache

    _cache_lock.acquire()

    try:

        if _getlang() != _TimeRE_cache.locale_time.lang:

            _TimeRE_cache = TimeRE()

            _regex_cache.clear()

        if len(_regex_cache) > _CACHE_MAX_SIZE:

            _regex_cache.clear()

        locale_time = _TimeRE_cache.locale_time

        format_regex = _regex_cache.get(format)

        if not format_regex:

            try:

                format_regex = _TimeRE_cache.compile(format)

            # KeyError raised when a bad format is found; can be specified as

            # \\, in which case it was a stray % but with a space after it

            except KeyError, err:

                bad_directive = err.args[0]

                if bad_directive == "\\":

                    bad_directive = "%"

                del err

                raise ValueError("'%s' is a bad directive in format '%s'" %

                                    (bad_directive, format))

            # IndexError only occurs when the format string is "%"

            except IndexError:

                raise ValueError("stray %% in format '%s'" % format)

            _regex_cache[format] = format_regex

    finally:

        _cache_lock.release()

    found = format_regex.match(data_string)

    if not found:

        raise ValueError("time data did not match format:  data=%s  fmt=%s" %

                         (data_string, format))

    if len(data_string) != found.end():

        raise ValueError("unconverted data remains: %s" %

                          data_string[found.end():])

    year = 1900

    month = day = 1

    hour = minute = second = 0

    tz = -1

    # Default to -1 to signify that values not known; not critical to have,

    # though

    week_of_year = -1

    week_of_year_start = -1

    # weekday and julian defaulted to -1 so as to signal need to calculate

    # values

    weekday = julian = -1

    found_dict = found.groupdict()

    for group_key in found_dict.iterkeys():

        # Directives not explicitly handled below:

        #   c, x, X

        #      handled by making out of other directives

        #   U, W

        #      worthless without day of the week

        if group_key == 'y':

            year = int(found_dict['y'])

            # Open Group specification for strptime() states that a %y

            #value in the range of [00, 68] is in the century 2000, while

            #[69,99] is in the century 1900

            if year <= 68:

                year += 2000

            else:

                year += 1900

        elif group_key == 'Y':

            year = int(found_dict['Y'])

        elif group_key == 'm':

            month = int(found_dict['m'])

        elif group_key == 'B':

            month = locale_time.f_month.index(found_dict['B'].lower())

        elif group_key == 'b':

            month = locale_time.a_month.index(found_dict['b'].lower())

        elif group_key == 'd':

            day = int(found_dict['d'])

        elif group_key == 'H':

            hour = int(found_dict['H'])

        elif group_key == 'I':

            hour = int(found_dict['I'])

            ampm = found_dict.get('p', '').lower()

            # If there was no AM/PM indicator, we'll treat this like AM

            if ampm in ('', locale_time.am_pm[0]):

                # We're in AM so the hour is correct unless we're

                # looking at 12 midnight.

                # 12 midnight == 12 AM == hour 0

                if hour == 12:

                    hour = 0

            elif ampm == locale_time.am_pm[1]:

                # We're in PM so we need to add 12 to the hour unless

                # we're looking at 12 noon.

                # 12 noon == 12 PM == hour 12

                if hour != 12:

                    hour += 12

        elif group_key == 'M':

            minute = int(found_dict['M'])

        elif group_key == 'S':

            second = int(found_dict['S'])

        elif group_key == 'A':

            weekday = locale_time.f_weekday.index(found_dict['A'].lower())

        elif group_key == 'a':

            weekday = locale_time.a_weekday.index(found_dict['a'].lower())

        elif group_key == 'w':

            weekday = int(found_dict['w'])

            if weekday == 0:

                weekday = 6

            else:

                weekday -= 1

        elif group_key == 'j':

            julian = int(found_dict['j'])

        elif group_key in ('U', 'W'):

            week_of_year = int(found_dict[group_key])

            if group_key == 'U':

                # U starts week on Sunday.

                week_of_year_start = 6

            else:

                # W starts week on Monday.

                week_of_year_start = 0

        elif group_key == 'Z':

            # Since -1 is default value only need to worry about setting tz if

            # it can be something other than -1.

            found_zone = found_dict['Z'].lower()

            for value, tz_values in enumerate(locale_time.timezone):

                if found_zone in tz_values:

                    # Deal with bad locale setup where timezone names are the

                    # same and yet time.daylight is true; too ambiguous to

                    # be able to tell what timezone has daylight savings

                    if (time.tzname[0] == time.tzname[1] and

                       time.daylight and found_zone not in ("utc", "gmt")):

                        break

                    else:

                        tz = value

                        break

    # If we know the week of the year and what day of that week, we can figure

    # out the Julian day of the year.

    if julian == -1 and week_of_year != -1 and weekday != -1:

        week_starts_Mon = True if week_of_year_start == 0 else False

        julian = _calc_julian_from_U_or_W(year, week_of_year, weekday,

                                            week_starts_Mon)

    # Cannot pre-calculate datetime_date() since can change in Julian

    # calculation and thus could have different value for the day of the week

    # calculation.

    if julian == -1:

        # Need to add 1 to result since first day of the year is 1, not 0.

        julian = datetime_date(year, month, day).toordinal() - \

                  datetime_date(year, 1, 1).toordinal() + 1

    else:  # Assume that if they bothered to include Julian day it will

           # be accurate.

        datetime_result = datetime_date.fromordinal((julian - 1) + datetime_date(year, 1, 1).toordinal())

        year = datetime_result.year

        month = datetime_result.month

        day = datetime_result.day

    if weekday == -1:

        weekday = datetime_date(year, month, day).weekday()

    return time.struct_time((year, month, day,

                             hour, minute, second,

                             weekday, julian, tz))