"""Date range validation utilities for booking and availability."""

from datetime import date, timedelta

from fastapi import HTTPException

from shared_constants import MAX_ADVANCE_DAYS, MIN_ADVANCE_DAYS


def get_bookable_date_range() -> tuple[date, date]:
    """
    Get the valid date range for booking/availability.

    Returns:
        Tuple of (min_date, max_date) where:
        - min_date is MIN_ADVANCE_DAYS from today
        - max_date is MAX_ADVANCE_DAYS from today
    """
    today = date.today()
    min_date = today + timedelta(days=MIN_ADVANCE_DAYS)
    max_date = today + timedelta(days=MAX_ADVANCE_DAYS)
    return min_date, max_date


def validate_date_in_range(
    d: date,
    *,
    context: str = "action",
) -> None:
    """
    Validate a date is within the bookable range.

    Args:
        d: The date to validate
        context: Description for error messages (e.g., "book", "set availability")

    Raises:
        HTTPException: If the date is outside the valid range
    """
    min_date, max_date = get_bookable_date_range()

    if d < min_date:
        raise HTTPException(
            status_code=400,
            detail=f"Cannot {context} for past dates. Earliest allowed: {min_date}",
        )
    if d > max_date:
        raise HTTPException(
            status_code=400,
            detail=f"Cannot {context} more than {MAX_ADVANCE_DAYS} days ahead. "
            f"Latest allowed: {max_date}",
        )