"""Extract ICS calendar data from emails."""

import email
import logging
from dataclasses import dataclass
from email.message import Message

import icalendar

log = logging.getLogger(__name__)


@dataclass
class CalendarEvent:
    method: str  # REQUEST, REPLY, CANCEL, PUBLISH
    vevent: icalendar.cal.Event
    uid: str


def process_email(raw_bytes: bytes) -> list[CalendarEvent]:
    """Parse a raw email and extract calendar events from ICS content.

    Looks for:
    - text/calendar MIME parts (iMIP inline)
    - application/ics attachments
    - Attachments with .ics extension
    """
    msg = email.message_from_bytes(raw_bytes)
    subject = msg.get("Subject", "(no subject)")
    log.debug("Processing email: %s", subject)

    events: list[CalendarEvent] = []

    for part in msg.walk():
        content_type = part.get_content_type()
        filename = part.get_filename() or ""

        is_calendar = content_type in ("text/calendar", "application/ics")
        is_ics_attachment = filename.lower().endswith(".ics")

        if not (is_calendar or is_ics_attachment):
            continue

        payload = part.get_payload(decode=True)
        if not payload:
            continue

        try:
            cal = icalendar.Calendar.from_ical(payload)
        except Exception:
            log.warning("Failed to parse ICS from email: %s", subject, exc_info=True)
            continue

        method = str(cal.get("METHOD", "PUBLISH")).upper()

        for component in cal.walk():
            if component.name != "VEVENT":
                continue
            uid = str(component.get("UID", ""))
            if not uid:
                log.warning("VEVENT without UID in email: %s", subject)
                continue
            events.append(CalendarEvent(method=method, vevent=component, uid=uid))

    if events:
        log.info("Found %d calendar event(s) in email: %s", len(events), subject)
    else:
        log.debug("No calendar content in email: %s", subject)

    return events