import os
from icalendar.cal import Calendar, Event
import requests
from flask import Flask
from datetime import date, datetime, timedelta, time
import zoneinfo

app = Flask(__name__)

user_name = (os.environ.get("NAME") or os.environ.get("USER") or "unknown").title()
tz = zoneinfo.ZoneInfo(os.environ.get("TZ") or "Europe/Berlin")

def fetch_calendar(calendar_url):
    return requests.get(calendar_url).content

def read_calendar_file(calendar_file):
    with open(calendar_file, 'rb') as f:
        return f.read()

def get_calendar():
    file = os.environ.get('CALENDAR_FILE')
    if file is not None:
        return read_calendar_file(file)
    else:
        calendar_url = os.environ.get("CALENDAR_URL")
        if calendar_url is None:
            raise ValueError("CALENDAR_URL not set.")
        return fetch_calendar(calendar_url)

def fixup_date(dt):
    if type(dt) == date:
        return datetime.combine(dt, time.min, tzinfo=tz)
    elif dt.tzinfo is None:
        return dt.replace(tzinfo=tz)
    else:
        return dt.astimezone(tz)

@app.route('/')
def index():
    start_date = datetime.combine(date.today(), time.min, tzinfo=tz)
    end_date = start_date + timedelta(days=30)

    output = Calendar()
    output.add('prodid', '-//Calendar Anonymiser//alin.ovh//')
    output.add('version', '2.0')

    # Parse with icalendar
    try:
        input = Calendar.from_ical(get_calendar())
        for component in input.walk():
            if component.name == "VEVENT":
                dtstart = fixup_date(component.get('dtstart').dt)
                dtend = fixup_date(component.get('dtend', component.get('dtstart')).dt)
                if dtstart >= start_date and dtend <= end_date:
                    ev = Event()
                    ev.add('summary', f'{user_name} Busy')
                    ev.DTSTART = dtstart
                    ev.DTEND = dtend
                    output.add_component(ev)
        return output.to_ical(), { "Content-Type": "text/plain" }
    except Exception as e:
        return f"Error parsing with icalendar: {str(e)}", 500

if __name__ == '__main__':
    app.run(debug=True)