"""
Holiday Service
Configurable holiday calculation for different regions

Currently supports Italian holidays. Can be extended to support other regions
by adding new holiday sets and a configuration option.
"""
from datetime import datetime, date, timedelta


def calculate_easter(year: int) -> date:
    """Calculate Easter Sunday using the Computus algorithm"""
    a = year % 19
    b = year // 100
    c = year % 100
    d = b // 4
    e = b % 4
    f = (b + 8) // 25
    g = (b - f + 1) // 3
    h = (19 * a + b - d - g + 15) % 30
    i = c // 4
    k = c % 4
    l = (32 + 2 * e + 2 * i - h - k) % 7
    m = (a + 11 * h + 22 * l) // 451
    month = (h + l - 7 * m + 114) // 31
    day = ((h + l - 7 * m + 114) % 31) + 1
    return date(year, month, day)


def get_easter_monday(year: int) -> date:
    """Get Easter Monday for a given year"""
    easter = calculate_easter(year)
    return easter + timedelta(days=1)


# Italian fixed holidays (month, day)
ITALIAN_FIXED_HOLIDAYS = [
    (1, 1),    # New Year's Day
    (1, 6),    # Epiphany
    (4, 25),   # Liberation Day
    (5, 1),    # Labour Day
    (6, 2),    # Republic Day
    (8, 15),   # Assumption
    (11, 1),   # All Saints
    (12, 8),   # Immaculate Conception
    (12, 25),  # Christmas
    (12, 26),  # St. Stephen's
]


def is_italian_holiday(check_date: date | datetime) -> bool:
    """Check if a date is an Italian public holiday"""
    if isinstance(check_date, datetime):
        check_date = check_date.date()

    year = check_date.year
    month = check_date.month
    day = check_date.day

    # Check fixed holidays
    if (month, day) in ITALIAN_FIXED_HOLIDAYS:
        return True

    # Check Easter Monday
    easter_monday = get_easter_monday(year)
    if check_date == easter_monday:
        return True

    return False


def get_holidays_for_year(year: int) -> list[dict]:
    """
    Get all holidays for a given year.
    Returns list of {date: YYYY-MM-DD, name: string}
    """
    holidays = []

    # Fixed holidays
    holiday_names = [
        "New Year's Day", "Epiphany", "Liberation Day", "Labour Day",
        "Republic Day", "Assumption", "All Saints", "Immaculate Conception",
        "Christmas", "St. Stephen's Day"
    ]

    for (month, day), name in zip(ITALIAN_FIXED_HOLIDAYS, holiday_names):
        holidays.append({
            "date": f"{year}-{month:02d}-{day:02d}",
            "name": name
        })

    # Easter Monday
    easter_monday = get_easter_monday(year)
    holidays.append({
        "date": easter_monday.strftime("%Y-%m-%d"),
        "name": "Easter Monday"
    })

    # Sort by date
    holidays.sort(key=lambda h: h["date"])
    return holidays


def is_holiday(check_date: date | datetime | str, region: str = "IT") -> bool:
    """
    Check if a date is a holiday for the given region.
    Currently only supports IT (Italy).
    """
    if isinstance(check_date, str):
        check_date = datetime.strptime(check_date, "%Y-%m-%d").date()

    if region == "IT":
        return is_italian_holiday(check_date)

    # Default: no holidays
    return False