"""Booking validation service."""
from datetime import datetime

from sqlalchemy import and_
from sqlalchemy.orm import Session

from app.models.booking import Booking
from app.models.settings import Settings
from app.models.space import Space
from app.utils.timezone import convert_from_utc, convert_to_utc


def validate_booking_rules(
    db: Session,
    space_id: int,
    user_id: int,
    start_datetime: datetime,
    end_datetime: datetime,
    exclude_booking_id: int | None = None,
    user_timezone: str = "UTC",
) -> list[str]:
    """
    Validate booking against global and per-space settings rules.

    Args:
        db: Database session
        space_id: ID of the space to book
        user_id: ID of the user making the booking
        start_datetime: Booking start time (UTC)
        end_datetime: Booking end time (UTC)
        exclude_booking_id: Optional booking ID to exclude from overlap check
                           (used when re-validating an existing booking)
        user_timezone: User's IANA timezone (e.g., "Europe/Bucharest")

    Returns:
        List of validation error messages (empty list = validation OK)
    """
    errors = []

    # Fetch global settings (create default if not exists)
    settings = db.query(Settings).filter(Settings.id == 1).first()
    if not settings:
        settings = Settings(
            id=1,
            min_duration_minutes=30,
            max_duration_minutes=480,
            working_hours_start=8,
            working_hours_end=20,
            max_bookings_per_day_per_user=3,
            min_hours_before_cancel=2,
        )
        db.add(settings)
        db.commit()
        db.refresh(settings)

    # Fetch space and get per-space settings (with fallback to global)
    space = db.query(Space).filter(Space.id == space_id).first()
    wh_start = (
        space.working_hours_start
        if space and space.working_hours_start is not None
        else settings.working_hours_start
    )
    wh_end = (
        space.working_hours_end
        if space and space.working_hours_end is not None
        else settings.working_hours_end
    )
    min_dur = (
        space.min_duration_minutes
        if space and space.min_duration_minutes is not None
        else settings.min_duration_minutes
    )
    max_dur = (
        space.max_duration_minutes
        if space and space.max_duration_minutes is not None
        else settings.max_duration_minutes
    )

    # Convert UTC times to user timezone for validation
    local_start = convert_from_utc(start_datetime, user_timezone)
    local_end = convert_from_utc(end_datetime, user_timezone)

    # a) Validate duration in range
    duration_minutes = (end_datetime - start_datetime).total_seconds() / 60
    if duration_minutes < min_dur or duration_minutes > max_dur:
        errors.append(
            f"Durata rezervării trebuie să fie între {min_dur} și {max_dur} minute"
        )

    # b) Validate working hours (in user's local time)
    if local_start.hour < wh_start or local_end.hour > wh_end:
        errors.append(
            f"Rezervările sunt permise doar între {wh_start}:00 și {wh_end}:00"
        )

    # c) Check for overlapping bookings
    query = db.query(Booking).filter(
        Booking.space_id == space_id,
        Booking.status.in_(["approved", "pending"]),
        and_(
            Booking.start_datetime < end_datetime,
            Booking.end_datetime > start_datetime,
        ),
    )

    # Exclude current booking if re-validating
    if exclude_booking_id is not None:
        query = query.filter(Booking.id != exclude_booking_id)

    overlapping_bookings = query.first()
    if overlapping_bookings:
        errors.append("Spațiul este deja rezervat în acest interval")

    # d) Check max bookings per day per user (using local date)
    booking_date_local = local_start.date()
    local_start_of_day = datetime.combine(booking_date_local, datetime.min.time())
    local_end_of_day = datetime.combine(booking_date_local, datetime.max.time())

    # Convert local day boundaries to UTC
    start_of_day_utc = convert_to_utc(local_start_of_day, user_timezone)
    end_of_day_utc = convert_to_utc(local_end_of_day, user_timezone)

    user_bookings_count = (
        db.query(Booking)
        .filter(
            Booking.user_id == user_id,
            Booking.status.in_(["approved", "pending"]),
            Booking.start_datetime >= start_of_day_utc,
            Booking.start_datetime <= end_of_day_utc,
        )
        .count()
    )

    if user_bookings_count >= settings.max_bookings_per_day_per_user:
        errors.append(
            f"Ai atins limita de {settings.max_bookings_per_day_per_user} rezervări pe zi"
        )

    return errors