i guess this works 🤷

.gitignore

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+__pycache__
+config.ini

LICENSE

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+Copyright 2021 Jan Koppe
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.txt

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+# durchsage
+
+Daemon that will follow a pretalx conference schedule.json ("fahrplan") and make announcements ("durchsage") on a MQTT topic when an event starts. 

durchsage.py

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+#!/usr/bin/env python3
+import argparse
+from apscheduler.schedulers.blocking import BlockingScheduler
+from apscheduler.triggers.cron import CronTrigger
+import configparser
+import datetime
+import dateutil.parser
+import json
+import logging
+import multiprocessing
+import re
+import requests
+import signal
+import sys
+from typing import Tuple
+from paho.mqtt import publish as mqtt_publish
+
+config = configparser.ConfigParser()
+
+l = logging.getLogger(__name__)
+lh = logging.StreamHandler(sys.stdout)
+lh.setFormatter(logging.Formatter("[%(levelname)s]: %(message)s"))
+l.addHandler(lh)
+
+
+s = BlockingScheduler()
+
+manager = multiprocessing.Manager()
+versions = manager.dict()
+
+
+def signal_handler(sig, frame):
+    l.info("shutting down")
+    s.shutdown()
+    sys.exit(0)
+
+
+def mqtt_send(topic: str, msg: str) -> None:
+
+    username = config.get('mqtt', 'username', fallback=None)
+    password = config.get('mqtt', 'password', fallback=None)
+
+    auth = {
+        'username': username,
+        'password': password,
+    } if username is not None and password is not None else None
+
+    tls = {
+        'ca_certs': config.get('mqtt', 'ca_certs', fallback='/etc/ssl/certs/ca-certificates.crt'),
+        'insecure': not config.getboolean('mqtt', 'tls_verify', fallback=True)
+    } if config.getboolean('mqtt', 'tls', fallback=False) else None
+
+    mqtt_publish.single(
+        topic=topic,
+        payload=msg,
+        hostname=config.get('mqtt', 'host', fallback='localhost'),
+        port=config.getint('mqtt', 'port', fallback=1883),
+        tls=tls,
+        auth=auth,
+    )
+
+
+def event_is_in_future(event: dict) -> bool:
+    date = dateutil.parser.isoparse(event['date'])
+    now = datetime.datetime.now(date.tzinfo)
+
+    return date > now
+
+
+def fetch_schedule_json(url: str) -> dict:
+    """
+    Fetches the schedule as JSON from the provided url and returns it as a dict.
+    """
+    ua = {
+        'User-Agent': 'fahrplan durchsage (github.com/chaoswest-tv/durchsage)',
+    }
+    try:
+        r = requests.get(url, timeout=10, headers=ua)
+        r.raise_for_status()
+    except (requests.exceptions.HTTPError,
+            requests.exceptions.ConnectionError,
+            requests.exceptions.Timeout,
+            requests.exceptions.RequestException) as e:
+        l.error("error fetching the schedule.json: %s" % str(e))
+        raise e
+
+    try:
+        d = r.json()
+    except json.decoder.JSONDecodeError as e:
+        l.error("error parsing returned json: %s" % str(e))
+        raise e
+
+    return d
+
+
+def parse_schedule(data: dict) -> Tuple[list, str]:
+    """
+    Parses the schedule dict to find all future events and the schedule version.
+    """
+    version = data['schedule']['version']
+    events = []
+
+    # extract all events across all days and rooms
+    for day in data['schedule']['conference']['days']:
+        for room in day['rooms']:
+            events.extend(day['rooms'][room])
+
+    # filter out events that are not in the future
+    events = list(filter(event_is_in_future, events))
+
+    return events, version
+
+
+def update_event_jobs(fahrplan: str) -> None:
+    """
+    Loads the current schedule from the configured url. If the schedule version changes,
+    removes all pending event jobs and adds all events from the fetched schedule as new jobs.
+
+    This routine will be periodically executed by a cron trigger.
+    """
+
+    l.debug("%s - updating schedule. local state has version '%s'." %
+            (fahrplan, versions.get(fahrplan, None)))
+
+    fc = config["fahrplan:%s" % fahrplan]
+    pre_announce_mins = fc.getint('pre_announce', fallback=0)
+
+    try:
+        d = fetch_schedule_json(fc.get('url'))
+        events, version = parse_schedule(d)
+    except Exception as _:
+        l.error("%s - updating the schedule failed." % fahrplan)
+        return
+
+    # if the version did not change we don't need to do anything.
+    if versions.get(fahrplan, None) == version:
+        return
+
+    # remove all old scheduled events
+    for job in [x for x in s.get_jobs() if x.name.startswith("%s_event_" % fahrplan)]:
+        job.remove()
+
+    # add all new events to scheduler
+    for event in events:
+        date = dateutil.parser.isoparse(event['date'])
+        s.add_job(announce_event, args=[fahrplan, event], trigger='date',
+                  run_date=date, name="%s_event_%s" % (fahrplan, event['guid']))
+        l.debug("announcing %s at %s" % (event['guid'], date))
+
+        if pre_announce_mins != 0:
+            pre_date = date - datetime.timedelta(minutes=pre_announce_mins)
+            s.add_job(announce_event, args=[fahrplan, event, True], trigger='date',
+                      run_date=pre_date, name="%s_event_pre_%s" % (fahrplan, event['guid']))
+            l.debug("pre-announcing %s at %s" % (event['guid'], pre_date))
+
+    versions[fahrplan] = version
+    l.info("%s - imported schedule version '%s' with %d upcoming events." %
+           (fahrplan, versions[fahrplan], len(events)))
+    mqtt_send('fahrplan/%s/version' % fahrplan, versions[fahrplan])
+
+
+def announce_event(fahrplan: str, event: dict, pre: bool = False) -> None:
+    """
+    Takes an event dict and announces it by sending it onto the configured MQTT topic.
+    """
+    l.info("[%s] announcing event %s" % (fahrplan, event['guid']))
+
+    sub_topic = 'soon' if pre else 'now'
+    msg = json.dumps(event)
+    mqtt_send("fahrplan/%s/%s" % (fahrplan, sub_topic), msg)
+
+
+if __name__ == "__main__":
+    signal.signal(signal.SIGINT, signal_handler)
+
+    parser = argparse.ArgumentParser(description='fahrplan durchsage daemon')
+    parser.add_argument('-c', '--config', help='path to config file',
+                        type=str, default='config.ini', required=False)
+    parser.add_argument(
+        '-v', '--verbose', help='increase verbosity level', action='count', default=0)
+    args = parser.parse_args()
+
+    # set logging verbosity
+    loglevel = max(logging.WARNING - (10 * args.verbose), 10)
+    l.setLevel(loglevel)
+
+    # import configuration file
+    config.read(args.config)
+
+    # find all fahrplan sections from configfile.
+    sections = [section.lstrip('fahrplan:') for section in config.sections(
+    ) if section.startswith('fahrplan:')]
+
+    for fahrplan in sections:
+        fc = config["fahrplan:%s" % fahrplan]
+        # names need to start with letter or number, and can contain letters, numbers, dashes - or underscores _
+        if re.fullmatch('^[a-z0-9][a-z0-9\-\_]*$', fahrplan) is None:
+            l.error(
+                "config section [fahrplan:%s] has invalid name. will skip section." % fahrplan)
+            continue
+
+        if fc.get('url', fallback=None) is None:
+            l.error(
+                "config section [fahrplan:%s] is missing 'url'. will skip section." % fahrplan)
+            continue
+
+        cron = CronTrigger.from_crontab(fc.get('cron', fallback='*/5 * * * *'))
+        s.add_job(update_event_jobs, args=[
+                  fahrplan], name="update_event_jobs_%s" % fahrplan, trigger=cron)
+        update_event_jobs(fahrplan)
+
+    # hand over to scheduler, this will block until scheduler is shut down
+    s.start()

example.ini

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+[mqtt]
+host = 127.0.0.1
+port = 8883
+tls = yes
+tls_verify = yes
+username = hans
+password = wurst
+
+[fahrplan:example]
+# the url is required.
+url = https://pretalx.example.com/example-conference/schedule/export/schedule.json
+
+# optional: refresh/pull the fahrplan according to this crontab expression
+# defaults to every 5 minutes.
+cron = * * * * *
+
+# optional: give an advance notice x minutes before the talk starts on the 'soon' topic
+# defaults to no advance notice
+pre_announce = 1

requirements.txt

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+apscheduler
+requests
+paho-mqtt