"""Compatibility layer for Office 365 and Exchange Server iCalendar files.

This module provides a context manager that can allow invalid calendar files
to be parsed.
"""

import contextlib
from collections.abc import Generator
import logging
import re

from . import dtstart_until_compat, same_day_dtend_compat, timezone_compat


_LOGGER = logging.getLogger(__name__)

# Capture group that extracts the PRODID from the ics content.
_PRODID_RE = r"PRODID:(?P<prodid>.*[^\\r\\n]+)"

_EXCHANGE_PRODID = "Microsoft Exchange Server"
_GOOGLE_PRODID = "Google Inc//Google Calendar"


def _get_prodid(ics: str) -> str | None:
    """Extract the PRODID from the iCalendar content."""
    match = re.search(_PRODID_RE, ics)
    if match:
        _LOGGER.debug("Extracted PRODID: %s", match)
        return match.group("prodid")
    return None


@contextlib.contextmanager
def enable_compat_mode(ics: str) -> Generator[str]:
    """Enable compatibility mode to fix known broken calendar content."""
    # Always enable same-day DTEND compatibility for all calendars
    # This is a common issue across many calendar providers
    with same_day_dtend_compat.enable_same_day_dtend_compat():
        # Check if the PRODID is from Microsoft Exchange Server
        prodid = _get_prodid(ics)

        if prodid and _EXCHANGE_PRODID in prodid:
            _LOGGER.debug("Enabling compatibility mode for Microsoft Exchange Server")
            # Enable compatibility mode for Microsoft Exchange Server
            with (
                timezone_compat.enable_allow_invalid_timezones(),
                timezone_compat.enable_extended_timezones(),
            ):
                yield ics
        elif prodid and _GOOGLE_PRODID in prodid:
            _LOGGER.debug("Enabling compatibility mode for Google Calendar")
            # Google Calendar historically generates RRULE UNTIL as DATE when
            # DTSTART is DATE-TIME, violating RFC 5545 section 3.3.10.
            with dtstart_until_compat.enable_dtstart_until_compat():
                yield ics
        else:
            yield ics