# modules/calendar/service.py
from sqlalchemy.orm import Session
from sqlalchemy import or_ # Import or_
from datetime import datetime
from modules.calendar.models import CalendarEvent
from core.exceptions import not_found_exception
from modules.calendar.schemas import CalendarEventCreate, CalendarEventUpdate # Import schemas

def create_calendar_event(db: Session, user_id: int, event_data: CalendarEventCreate):
    # Ensure tags is None if not provided or empty list, matching model
    tags_to_store = event_data.tags if event_data.tags else None
    event = CalendarEvent(
        **event_data.model_dump(exclude={'tags'}), # Use model_dump and exclude tags initially
        tags=tags_to_store, # Set tags separately
        user_id=user_id
    )
    db.add(event)
    db.commit()
    db.refresh(event)
    return event

def get_calendar_events(db: Session, user_id: int, start: datetime | None, end: datetime | None):
    query = db.query(CalendarEvent).filter(CalendarEvent.user_id == user_id)

    # If start and end dates are provided, filter for events overlapping the range.
    # An event overlaps if: event_start < query_end AND (event_end IS NULL OR event_end > query_start)
    if start and end:
        query = query.filter(
            CalendarEvent.start < end, # Event starts before the query window ends
            or_(
                CalendarEvent.end == None, # Event has no end date (considered single point in time at start)
                CalendarEvent.end > start   # Event ends after the query window starts
            )
        )
    # If only start is provided, filter events starting on or after start
    elif start:
        query = query.filter(CalendarEvent.start >= start)
    # If only end is provided, filter events ending on or before end (or starting before end if no end date)
    elif end:
         query = query.filter(
            or_(
                CalendarEvent.end <= end,
                (CalendarEvent.end == None and CalendarEvent.start < end)
            )
        )

    return query.order_by(CalendarEvent.start).all() # Order by start time

def get_calendar_event_by_id(db: Session, user_id: int, event_id: int):
    event = db.query(CalendarEvent).filter(
        CalendarEvent.id == event_id,
        CalendarEvent.user_id == user_id
    ).first()
    if not event:
        raise not_found_exception()
    return event

def update_calendar_event(db: Session, user_id: int, event_id: int, event_data: CalendarEventUpdate):
    event = get_calendar_event_by_id(db, user_id, event_id) # Reuse get_by_id for check
    # Use model_dump with exclude_unset=True to only update provided fields
    update_data = event_data.model_dump(exclude_unset=True)

    for key, value in update_data.items():
        # Ensure tags is handled correctly (set to None if empty list provided)
        if key == 'tags' and isinstance(value, list) and not value:
            setattr(event, key, None)
        else:
            setattr(event, key, value)

    db.commit()
    db.refresh(event)
    return event

def delete_calendar_event(db: Session, user_id: int, event_id: int):
    event = get_calendar_event_by_id(db, user_id, event_id) # Reuse get_by_id for check
    db.delete(event)
    db.commit()