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"""

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    Miscellaneous things

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"""

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import datetime, calendar, pytz

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import os, errno

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from qmsk.web.urltree import URLType

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class URLChannelName (URLType) :

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    """

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        Handle LogChannel names in URLs. Deals with instances of LogChannel

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    """

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    def __init__ (self, channels) :

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        """

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            Use the given { name -> LogChannel } dict

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        """

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        self.channels = channels

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    def parse (self, chan_name) :

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        """

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            chan_name -> LogChannel

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        """

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        return self.channels[chan_name]

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    def build (self, chan) :

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        """

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            LogChannel -> chan_name

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        """

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        return chan.id

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class URLDateType (URLType) :

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    """

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        Handle dates in URLs as naive datetime objects (with indeterminate time info)

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    """

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    def __init__ (self, date_fmt) :

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        """

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            Format/parse dates using the given format

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        """

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        self.date_fmt = date_fmt

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    def parse (self, date_str) :

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        """

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            date_str -> naive datetime.datetime

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        """

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        return datetime.datetime.strptime(date_str, self.date_fmt)

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    def build (self, date) :

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        """

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            datetime.date -> date_str

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        """

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        return date.strftime(self.date_fmt)

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class URLTimestampType (URLType) :

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    """

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        Handles an integer UNIX timestamp as an UTC datetime

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    """

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    def parse (self, timestamp_str) :

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        """

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            timestamp_str -> pytz.utc datetime.datetime

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        """

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        return from_utc_timestamp(int(timestamp_str))

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    def build (self, dtz) :

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        """

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            pytz.utc datetime.datetime -> timestamp_str

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        """

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        return str(to_utc_timestamp(dtz))

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def from_utc_timestamp (timestamp) :

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    """

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        Converts a UNIX timestamp into a datetime.datetime

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    """

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    return datetime.datetime.utcfromtimestamp(timestamp).replace(tzinfo=pytz.utc)

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def to_utc_timestamp (dt) :

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    """

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        Converts a datetime.datetime into a UNIX timestamp

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    """

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    return calendar.timegm(dt.utctimetuple())

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def mtime (path, ignore_missing=False) :

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    """

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        Gets the mtime for the given path as an UTC datetime, or None, if the file doesn't exist and ignore_missing

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    """

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    try :

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        # stat

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        st = os.stat(path)

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    # trap IOError

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    except os.error, e :

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        # ENOENT?

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        if ignore_missing and e.errno == errno.ENOENT :

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            return None

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        else :

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            raise

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    else :

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        # decode

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        return from_utc_timestamp(st.st_mtime)

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class FixedOffsetTimezone (pytz._FixedOffset) :

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    """

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        A Fixed-offset timezone with no DST info, compatible with pytz.

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        This is based on pytz._FixedOffset, but overrides dst() to return timedelta(0)

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    """

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    def __init__ (self, minutes) :

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        """

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            Minutes is simply the offset from UTC in minutes, positive or negative, at most 24h.

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        """

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        pytz._FixedOffset.__init__(self, minutes)

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    def dst (self, dt) :

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        """

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            No DST info

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        """

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        return datetime.timedelta(0)

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