Small Script to Filter iCal Events by Date

icalfilt.py

# /// script
# requires-python = ">=3.13"
# dependencies = [
#     "icalendar>=7.2.2",
#     "requests>=2.34.2"
# ]
# ///

from argparse import ArgumentParser, Namespace
from contextlib import AbstractContextManager, nullcontext
import datetime as dt
from io import StringIO
from pathlib import Path
from sys import stdin, stdout
from zoneinfo import ZoneInfo

import icalendar
import requests


def opener(uri: str) -> AbstractContextManager:
    if uri == "-":
        return nullcontext(stdin)
    url = requests.utils.urlparse(uri)
    if url.scheme in ("http", "https"):
        return StringIO(requests.get(uri).content.decode())
    elif url.scheme == "file":
        return Path.from_uri(uri).open("rt")
    else:
        return Path(uri).open("rt")


def ensure_datetime(input: dt.date | dt.datetime) -> dt.datetime:
    return (
        input
        if isinstance(input, dt.datetime)
        else dt.datetime.combine(input, time=dt.time(tzinfo=ZoneInfo("UTC")))
    )


def update_zones(options: Namespace):
    z = (
        ZoneInfo(options.timezone)
        if options.timezone
        else dt.datetime.now().astimezone().tzinfo
    )
    if options.start_after:
        options.start_after = options.start_after.replace(tzinfo=z)
    if options.start_before:
        options.start_before = options.start_before.replace(tzinfo=z)


def main(options: Namespace) -> None:
    update_zones(options)
    with opener(options.SOURCE) as input:
        cal: icalendar.Calendar = icalendar.Calendar.from_ical(input.read())
        filtered: icalendar.Calendar = icalendar.Calendar.new()
        for event in cal.events:
            if (
                options.start_after
                and ensure_datetime(event.start) < options.start_after
            ):
                continue
            if (
                options.start_before
                and ensure_datetime(event.start) > options.start_before
            ):
                continue
            filtered.add_component(event)
        stdout.write(filtered.to_ical().decode("UTF8"))


if __name__ == "__main__":
    parser = ArgumentParser(description="A script to filter iCalendar events")
    parser.add_argument("SOURCE", type=str, help="Source (a file or URL)")
    parser.add_argument(
        "-a",
        "--start-after",
        type=dt.datetime.fromisoformat,
        default=None,
        help="Include only events with start dates after the specified value (ISO 8601 format)",
    )
    parser.add_argument(
        "-b",
        "--start-before",
        type=dt.datetime.fromisoformat,
        default=None,
        help="Include only events with start dates before the specified value (ISO 8601 format)",
    )
    parser.add_argument(
        "-z",
        "--timezone",
        type=str,
        default=None,
        help="Timezone to use for date comparisons, defaults to local",
    )
    main(parser.parse_args())