Send out VHS upcoming event emails

remind.py

#!/usr/bin/env python
import urllib, datetime, re, StringIO, smtplib

def add_tag(event, tag, data):
    if tag in ('DTSTART', 'DTEND', 'CREATED', 'LAST-MODIFIED', 'DTSTAMP'):
        # parse a date string as a datetime object
        (date, sep, time) = data.partition('T')
        year, month, day = (int(s) for s in (date[0:4], date[4:6], date[6:]))
        hour, min, sec = (int(s) for s in (time[0:2], time[2:4], time[4:]))
        event[tag] = datetime.datetime(year, month, day, hour, min, sec)
    else:
        event[tag] = data

def parse_events(url):
    """
    Parse an ical URL for upcoming events

    url -- URL of the calendar to parse

    Returns a list of event dicts
    """

    linenum = 0
    events = list()
    fp = urllib.urlopen(url)

    while True:
        line = fp.readline().rstrip()
        linenum += 1

        if not line:
            break       # end of feed
        elif line != 'BEGIN:VEVENT':
            continue
        
        event = dict()
        last_tag = None

        # parse VEVENT
        while True:
            line = fp.readline().rstrip()
            linenum += 1

            if line == 'END:VEVENT':
                events.append(event)
                event = dict()
                break
            elif line.startswith(' '):
                if not last_tag:
                    raise Exception('Malformed .ics file, line %d' % linenum)
                event[last_tag] += line[1:]
            else:
                (tag, sep, data) = line.partition(':')

                # new event
                last_tag = tag
                add_tag(event, tag, data)

    # post-processing
    for event in events:
        description = event.get('DESCRIPTION')
        if description:
            event['DESCRIPTION'] = description.decode('string_escape')

    return events
                
def _event_dump(event):
    return '\n'.join(['%s : %s' % (k, v) for k,v in event.iteritems()])

def _date_format(date):
    return date.strftime('%A %d %B %Y')

def email_events(events, sender, recipient, mailhost='localhost'):
    """
    Send out a formatted email of events using an authorized SMTP host
    """

    sio = StringIO.StringIO()
    for event in events:
        sio.write('%s\n%s\n\n' % (event['SUMMARY'], _date_format(event['DTSTART']))) 
        sio.write('%s\n\n\n' % event['DESCRIPTION'])

    now = datetime.datetime.now()

    email_text = """\
From: %s
To: %s
Subject: Upcoming VHS events (%s)

A weekly reminder of upcoming Vancouver Hack Space events.


%s
""" % (sender,
       recipient,
       '%d/%d/%d' % (now.day, now.month, now.year), 
       sio.getvalue())

    server = smtplib.SMTP(mailhost)
    server.sendmail(sender, recipient, email_text)
    server.quit()

if __name__ == '__main__':
    events = parse_events('http://vancal.org/events.ics')

    # Find all events in the upcoming week
    upcoming = lambda event: 0 <= (event['DTSTART'] - datetime.datetime.now()).days <= 7
    upcoming_vhs = lambda event: upcoming(event) and event['SUMMARY'].startswith('VHS:')

    upcoming_vhs_events = [ e for e in events if upcoming_vhs(e) ]

    email_events(upcoming_vhs_events,
                 sender='Dan V. <dan@expandingbrain.com>',
                 recipient='VHS <vanhackspace@lists.uselessdegree.net>')