# File: strptime.py

import re
import string

MONTHS = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug",
          "Sep", "Oct", "Nov", "Dec"]

SPEC = {
    # map formatting code to a regular expression fragment
    "%a": "(?P<weekday>[a-z]+)",
    "%A": "(?P<weekday>[a-z]+)",
    "%b": "(?P<month>[a-z]+)",
    "%B": "(?P<month>[a-z]+)",
    "%C": "(?P<century>\d\d?)",
    "%d": "(?P<day>\d\d?)",
    "%D": "(?P<month>\d\d?)/(?P<day>\d\d?)/(?P<year>\d\d)",
    "%e": "(?P<day>\d\d?)",
    "%h": "(?P<month>[a-z]+)",
    "%H": "(?P<hour>\d\d?)",
    "%I": "(?P<hour12>\d\d?)",
    "%j": "(?P<yearday>\d\d?\d?)",
    "%m": "(?P<month>\d\d?)",
    "%M": "(?P<minute>\d\d?)",
    "%p": "(?P<ampm12>am|pm)",
    "%R": "(?P<hour>\d\d?):(?P<minute>\d\d?)",
    "%S": "(?P<second>\d\d?)",
    "%T": "(?P<hour>\d\d?):(?P<minute>\d\d?):(?P<second>\d\d?)",
    "%U": "(?P<week>\d\d)",
    "%w": "(?P<weekday>\d)",
    "%W": "(?P<weekday>\d\d)",
    "%y": "(?P<year>\d\d)",
    "%Y": "(?P<year>\d\d\d\d)",
    "%%": "%"
}

class TimeParser:
    def __init__(self, format):
        # convert strptime format string to regular expression
        format = string.join(re.split("(?:\s|%t|%n)+", format))
        pattern = []
        try:
            for spec in re.findall("%\w|%%|.", format):
                if spec[0] == "%":
                    spec = SPEC[spec]
                pattern.append(spec)
        except KeyError:
            raise ValueError, "unknown specificer: %s" % spec
        self.pattern = re.compile("(?i)" + string.join(pattern, ""))
    def match(self, daytime):
        # match time string
        match = self.pattern.match(daytime)
        if not match:
            raise ValueError, "format mismatch"
        get = match.groupdict().get
        tm = [0] * 9
        # extract date elements
        y = get("year")
        if y:
            y = int(y)
            if y < 68:
                y = 2000 + y
            elif y < 100:
                y = 1900 + y
            tm[0] = y
        m = get("month")
        if m:
            if m in MONTHS:
                m = MONTHS.index(m) + 1
            tm[1] = int(m)
        d = get("day")
        if d: tm[2] = int(d)
        # extract time elements
        h = get("hour")
        if h:
            tm[3] = int(h)
        else:
            h = get("hour12")
            if h:
                h = int(h)
                if string.lower(get("ampm12", "")) == "pm":
                    h = h + 12
                tm[3] = h
        m = get("minute")
        if m: tm[4] = int(m)
        s = get("second")
        if s: tm[5] = int(s)
        # ignore weekday/yearday for now
        return tuple(tm)

def strptime(string, format="%a %b %d %H:%M:%S %Y"):
    return TimeParser(format).match(string)

if __name__ == "__main__":
    # try it out
    import time
    print strptime("2000-12-20 01:02:03", "%Y-%m-%d %H:%M:%S")
    print strptime(time.ctime(time.time()))

## (2000, 12, 20, 1, 2, 3, 0, 0, 0)
## (2000, 11, 15, 12, 30, 45, 0, 0, 0)