import os
import msal
import requests
import json
from datetime import datetime
from dateutil import parser
from dateutil.tz import UTC

# Read Azure app credentials from environment variables
client_id = os.getenv('AZURE_CLIENT_ID')
tenant_id = os.getenv('AZURE_TENANT_ID')

if not client_id or not tenant_id:
    raise ValueError("Please set the AZURE_CLIENT_ID and AZURE_TENANT_ID environment variables.")

# Token cache
cache = msal.SerializableTokenCache()
cache_file = 'token_cache.bin'

if os.path.exists(cache_file):
    cache.deserialize(open(cache_file, 'r').read())

# Authentication
authority = f'https://login.microsoftonline.com/{tenant_id}'
scopes = ['https://graph.microsoft.com/Calendars.Read']

app = msal.PublicClientApplication(client_id, authority=authority, token_cache=cache)
accounts = app.get_accounts()

if accounts:
    token_response = app.acquire_token_silent(scopes, account=accounts[0])
else:
    flow = app.initiate_device_flow(scopes=scopes)
    if 'user_code' not in flow:
        raise Exception("Failed to create device flow")
    print(flow['message'])
    token_response = app.acquire_token_by_device_flow(flow)

if 'access_token' not in token_response:
    raise Exception("Failed to acquire token")

# Save token cache
with open(cache_file, 'w') as f:
    f.write(cache.serialize())

access_token = token_response['access_token']

# Fetch events with pagination and expand recurring events
headers = {'Authorization': f'Bearer {access_token}'}
events_url = 'https://graph.microsoft.com/v1.0/me/events?$top=100&$expand=instances'
events = []
print("Fetching events...")
while events_url:
    response = requests.get(events_url, headers=headers)
    response_data = response.json()
    events.extend(response_data.get('value', []))
    print(f"Fetched {len(events)} events so far...", end='\r')
    events_url = response_data.get('@odata.nextLink')

# Save events to a file in iCalendar format
output_file = f'output_ics/outlook_events_latest.ics'
print(f"Saving events to {output_file}...")
with open(output_file, 'w') as f:
    f.write("BEGIN:VCALENDAR\nVERSION:2.0\n")
    for event in events:
        if 'start' in event and 'end' in event:
            start = parser.isoparse(event['start']['dateTime'])
            end = parser.isoparse(event['end']['dateTime'])
            f.write(f"BEGIN:VEVENT\nSUMMARY:{event['subject']}\n")
            f.write(f"DTSTART:{start.strftime('%Y%m%dT%H%M%S')}\n")
            f.write(f"DTEND:{end.strftime('%Y%m%dT%H%M%S')}\n")
            if 'recurrence' in event and event['recurrence']:  # Check if 'recurrence' exists and is not None
                for rule in event['recurrence']:
                    if rule.startswith('RRULE'):
                        rule_parts = rule.split(';')
                        new_rule_parts = []
                        for part in rule_parts:
                            if part.startswith('UNTIL='):
                                until_value = part.split('=')[1]
                                until_date = parser.isoparse(until_value)
                                if start.tzinfo is not None and until_date.tzinfo is None:
                                    until_date = until_date.replace(tzinfo=UTC)
                                new_rule_parts.append(f"UNTIL={until_date.strftime('%Y%m%dT%H%M%SZ')}")
                            else:
                                new_rule_parts.append(part)
                        rule = ';'.join(new_rule_parts)
                    f.write(f"{rule}\n")
            f.write("END:VEVENT\n")
    f.write("END:VCALENDAR\n")