"""Generate ICS calendar containing only one user's duties (for subscription link)."""

from datetime import datetime, timezone

from icalendar import Calendar, Event

from duty_teller.db.models import Duty
from duty_teller.utils.dates import parse_utc_iso

# Summary labels by event_type (duty | unavailable | vacation)
SUMMARY_BY_TYPE: dict[str, str] = {
    "duty": "Duty",
    "unavailable": "Unavailable",
    "vacation": "Vacation",
}


def build_personal_ics(duties_with_name: list[tuple[Duty, str]]) -> bytes:
    """Build a VCALENDAR (ICS) with one VEVENT per duty.

    Args:
        duties_with_name: List of (Duty, full_name). full_name is available for
            DESCRIPTION; SUMMARY is taken from event_type (duty/unavailable/vacation).

    Returns:
        ICS file content as bytes (UTF-8).
    """
    cal = Calendar()
    cal.add("prodid", "-//Duty Teller//Personal Calendar//EN")
    cal.add("version", "2.0")
    cal.add("calscale", "GREGORIAN")

    for duty, _full_name in duties_with_name:
        event = Event()
        start_dt = parse_utc_iso(duty.start_at)
        end_dt = parse_utc_iso(duty.end_at)
        # Ensure timezone-aware for icalendar
        if start_dt.tzinfo is None:
            start_dt = start_dt.replace(tzinfo=timezone.utc)
        if end_dt.tzinfo is None:
            end_dt = end_dt.replace(tzinfo=timezone.utc)
        event.add("dtstart", start_dt)
        event.add("dtend", end_dt)
        summary = SUMMARY_BY_TYPE.get(
            duty.event_type if duty.event_type else "duty", "Duty"
        )
        event.add("summary", summary)
        event.add("uid", f"duty-{duty.id}@duty-teller")
        event.add("dtstamp", datetime.now(timezone.utc))
        cal.add_component(event)

    return cal.to_ical()