"""Internal event store service with CalDAV push sync."""
from __future__ import annotations

import asyncio
import logging
import uuid
from datetime import datetime, timedelta, timezone

from dateutil.rrule import rrulestr
from sqlalchemy import and_, or_, select

from fabledassistant.models import async_session
from fabledassistant.models.event import Event

logger = logging.getLogger(__name__)


async def create_event(
    user_id: int,
    title: str,
    start_dt: datetime,
    end_dt: datetime | None = None,
    all_day: bool = False,
    description: str = "",
    location: str = "",
    color: str = "",
    recurrence: str | None = None,
    project_id: int | None = None,
    reminder_minutes: int | None = None,
    # CalDAV-only fields (not stored in DB, forwarded to push)
    duration: int | None = None,
    attendees: list[str] | None = None,
    calendar_name: str | None = None,
) -> Event:
    """Create an event in the DB, then fire a CalDAV push task."""
    uid = str(uuid.uuid4())
    async with async_session() as session:
        event = Event(
            user_id=user_id,
            uid=uid,
            title=title,
            start_dt=start_dt,
            end_dt=end_dt,
            all_day=all_day,
            description=description,
            location=location,
            color=color,
            recurrence=recurrence,
            project_id=project_id,
            reminder_minutes=reminder_minutes,
        )
        session.add(event)
        await session.commit()
        await session.refresh(event)

    extra_fields = {
        "duration": duration,
        "reminder_minutes": reminder_minutes,
        "attendees": attendees,
        "calendar_name": calendar_name,
    }
    asyncio.create_task(_push_create(event, user_id, extra_fields))
    return event


async def get_event(user_id: int, event_id: int) -> Event | None:
    """Return event owned by user_id, or None."""
    async with async_session() as session:
        result = await session.execute(
            select(Event).where(Event.id == event_id, Event.user_id == user_id)
        )
        return result.scalar_one_or_none()


async def list_events(
    user_id: int,
    date_from: datetime,
    date_to: datetime,
) -> list[dict]:
    """List events for user_id that overlap [date_from, date_to].

    Recurring events (with an RRULE recurrence string) are expanded into
    individual occurrences within the range.  Non-recurring events are
    returned as-is.  All results are sorted by start time and returned as
    dicts (same shape as Event.to_dict()).
    """
    async with async_session() as session:
        # Match strategy:
        #   - Recurring events: fetch all, expand via rrule below.
        #   - Non-recurring with an end_dt: standard overlap — starts before
        #     date_to and ends after date_from.
        #   - Non-recurring with no end_dt: treat as a point event at
        #     start_dt, include only if start_dt falls within the window.
        #     (Previously this branch matched any event with a null end_dt,
        #     returning all past events as "happening today".)
        result = await session.execute(
            select(Event).where(
                Event.user_id == user_id,
                or_(
                    Event.recurrence.isnot(None),
                    and_(
                        Event.recurrence.is_(None),
                        Event.start_dt <= date_to,
                        or_(
                            Event.end_dt >= date_from,
                            and_(
                                Event.end_dt.is_(None),
                                Event.start_dt >= date_from,
                            ),
                        ),
                    ),
                ),
            ).order_by(Event.start_dt)
        )
        events = list(result.scalars().all())

    items: list[dict] = []
    for event in events:
        if not event.recurrence:
            items.append(event.to_dict())
            continue

        # Expand recurring event occurrences within [date_from, date_to]
        duration = (event.end_dt - event.start_dt) if event.end_dt else None
        try:
            rule = rrulestr(event.recurrence, dtstart=event.start_dt, ignoretz=False)
            occurrences = rule.between(date_from, date_to, inc=True)
        except Exception:
            logger.warning("Failed to expand RRULE for event %d: %r", event.id, event.recurrence)
            items.append(event.to_dict())
            continue

        base = event.to_dict()
        for occ in occurrences:
            # Ensure occurrence is UTC-aware
            if occ.tzinfo is None:
                occ = occ.replace(tzinfo=timezone.utc)
            occurrence_dict = dict(base)
            occurrence_dict["start_dt"] = occ.isoformat()
            if duration is not None:
                occurrence_dict["end_dt"] = (occ + duration).isoformat()
            items.append(occurrence_dict)

    items.sort(key=lambda x: x["start_dt"])
    return items


async def search_events(
    user_id: int,
    query: str,
    days_ahead: int = 90,
    include_past: bool = False,
) -> list[Event]:
    """Search events by keyword in title, description, or location."""
    now = datetime.now(timezone.utc)
    q = f"%{query}%"
    async with async_session() as session:
        where = [
            Event.user_id == user_id,
            or_(
                Event.title.ilike(q),
                Event.description.ilike(q),
                Event.location.ilike(q),
            ),
        ]
        if not include_past:
            date_to = now + timedelta(days=days_ahead)
            where.extend([Event.start_dt >= now, Event.start_dt <= date_to])
        result = await session.execute(
            select(Event).where(*where).order_by(Event.start_dt)
        )
        return result.scalars().all()


async def update_event(user_id: int, event_id: int, **fields) -> Event | None:
    """Partial update. Returns updated event or None if not found."""
    async with async_session() as session:
        result = await session.execute(
            select(Event).where(Event.id == event_id, Event.user_id == user_id)
        )
        event = result.scalar_one_or_none()
        if event is None:
            return None
        old_title = event.title  # capture before mutation for CalDAV lookup
        allowed = {"title", "start_dt", "end_dt", "all_day", "description",
                   "location", "color", "recurrence", "project_id", "reminder_minutes"}
        # Nullable fields that callers can explicitly set to None to clear
        nullable = {"end_dt", "recurrence", "project_id", "reminder_minutes"}
        for key, value in fields.items():
            if key in allowed and (value is not None or key in nullable):
                setattr(event, key, value)
        await session.commit()
        await session.refresh(event)

    asyncio.create_task(_push_update(event, user_id, old_title=old_title))
    return event


async def delete_event(user_id: int, event_id: int) -> None:
    """Delete event. Fires CalDAV delete push if caldav_uid is set."""
    async with async_session() as session:
        result = await session.execute(
            select(Event).where(Event.id == event_id, Event.user_id == user_id)
        )
        event = result.scalar_one_or_none()
        if event is None:
            return
        caldav_uid = event.caldav_uid
        event_title = event.title  # needed to find the event on CalDAV by title
        await session.delete(event)
        await session.commit()

    if caldav_uid:
        asyncio.create_task(_push_delete(caldav_uid, event_title, user_id))


async def find_events_by_query(user_id: int, query: str) -> list[Event]:
    """ILIKE search on title — used by AI update/delete tools.

    Returns upcoming events first (start_dt >= now), falling back to
    past events so the AI operates on the most relevant match.
    """
    q = f"%{query}%"
    now = datetime.now(timezone.utc)
    async with async_session() as session:
        # Prefer events at or after now; fall back to past events
        upcoming = (await session.execute(
            select(Event).where(
                Event.user_id == user_id,
                Event.title.ilike(q),
                Event.start_dt >= now,
            ).order_by(Event.start_dt)
        )).scalars().all()
        if upcoming:
            return list(upcoming)
        past = (await session.execute(
            select(Event).where(
                Event.user_id == user_id,
                Event.title.ilike(q),
                Event.start_dt < now,
            ).order_by(Event.start_dt.desc())
        )).scalars().all()
        return list(past)


# ---------------------------------------------------------------------------
# CalDAV push helpers (fire-and-forget)
# ---------------------------------------------------------------------------

async def _push_create(event: Event, user_id: int, extra: dict) -> None:
    try:
        from fabledassistant.services.caldav import (
            create_event as caldav_create,
            is_caldav_configured,
        )
        if not await is_caldav_configured(user_id):
            return
        await caldav_create(
            user_id=user_id,
            title=event.title,
            start=event.start_dt.isoformat(),
            end=event.end_dt.isoformat() if event.end_dt else None,
            description=event.description or None,
            location=event.location or None,
            all_day=event.all_day,
            recurrence=event.recurrence,
            uid=event.uid,
            duration=extra.get("duration"),
            reminder_minutes=extra.get("reminder_minutes"),
            attendees=extra.get("attendees"),
            calendar_name=extra.get("calendar_name"),
        )
        # Mark as synced
        async with async_session() as session:
            result = await session.execute(
                select(Event).where(Event.id == event.id)
            )
            ev = result.scalar_one_or_none()
            if ev:
                ev.caldav_uid = event.uid
                await session.commit()
    except Exception:
        logger.warning("CalDAV push (create) failed for event %d", event.id, exc_info=True)


async def _push_update(event: Event, user_id: int, old_title: str = "") -> None:
    """Push an update to CalDAV. Uses old_title to locate the event by its pre-rename SUMMARY."""
    if not event.caldav_uid:
        return
    try:
        from fabledassistant.services.caldav import (
            update_event as caldav_update,
            is_caldav_configured,
        )
        if not await is_caldav_configured(user_id):
            return
        # Use old_title so CalDAV can find the event even if the title was changed
        query_title = old_title or event.title
        await caldav_update(
            user_id=user_id,
            query=query_title,
            title=event.title,
            start=event.start_dt.isoformat(),
            end=event.end_dt.isoformat() if event.end_dt else None,
            description=event.description or None,
            location=event.location or None,
        )
    except Exception:
        logger.warning("CalDAV push (update) failed for event %d", event.id, exc_info=True)


async def _push_delete(caldav_uid: str, event_title: str, user_id: int) -> None:
    """Push a delete to CalDAV. Uses event_title to locate the event by SUMMARY."""
    try:
        from fabledassistant.services.caldav import (
            delete_event as caldav_delete,
            is_caldav_configured,
        )
        if not await is_caldav_configured(user_id):
            return
        await caldav_delete(user_id=user_id, query=event_title)
    except Exception:
        logger.warning("CalDAV push (delete) failed for uid %s", caldav_uid, exc_info=True)