"""
Business day calculations for the standard-vs-expedited delay system.

Used by canada_crtc.py and formation_worker.py to insert 3-business-day delays
between pipeline steps for standard service. Expedited orders skip these delays.

Skips weekends + US/Canada federal holidays.
"""
from __future__ import annotations

from datetime import datetime, timedelta, date


# US + Canada federal holidays (2026 + 2027 — extend as needed)
HOLIDAYS: set[date] = {
    # 2026
    date(2026, 1, 1),    # New Year's Day (US + CA)
    date(2026, 1, 19),   # MLK Day (US)
    date(2026, 2, 16),   # Presidents Day (US) / Family Day (CA)
    date(2026, 5, 18),   # Victoria Day (CA)
    date(2026, 5, 25),   # Memorial Day (US)
    date(2026, 7, 1),    # Canada Day (CA)
    date(2026, 7, 3),    # Independence Day observed (US)
    date(2026, 9, 7),    # Labor Day (US + CA)
    date(2026, 10, 12),  # Columbus Day (US) / Thanksgiving (CA)
    date(2026, 11, 11),  # Veterans Day / Remembrance Day
    date(2026, 11, 26),  # Thanksgiving (US)
    date(2026, 12, 25),  # Christmas (US + CA)
    date(2026, 12, 26),  # Boxing Day (CA)

    # 2027
    date(2027, 1, 1),    # New Year's Day
    date(2027, 1, 18),   # MLK Day
    date(2027, 2, 15),   # Presidents Day / Family Day
    date(2027, 5, 24),   # Victoria Day
    date(2027, 5, 31),   # Memorial Day
    date(2027, 7, 1),    # Canada Day
    date(2027, 7, 5),    # Independence Day observed
    date(2027, 9, 6),    # Labor Day
    date(2027, 10, 11),  # Columbus Day / Thanksgiving (CA)
    date(2027, 11, 11),  # Veterans Day / Remembrance Day
    date(2027, 11, 25),  # Thanksgiving (US)
    date(2027, 12, 24),  # Christmas Eve (observed)
    date(2027, 12, 27),  # Boxing Day (observed)
}


def is_business_day(d: date) -> bool:
    """A weekday that isn't a holiday."""
    return d.weekday() < 5 and d not in HOLIDAYS


def business_days_from_now(n: int, base: datetime | None = None) -> datetime:
    """Return a datetime n business days from base (default: now).

    Skips weekends + holidays. n=3 starting Friday → next Wednesday.
    """
    if n <= 0:
        return base or datetime.now()
    cur = base or datetime.now()
    added = 0
    while added < n:
        cur = cur + timedelta(days=1)
        if is_business_day(cur.date()):
            added += 1
    return cur


if __name__ == "__main__":
    # Quick smoke test
    from datetime import datetime as dt
    cases = [
        (dt(2026, 4, 13), 3, "Mon → Thu"),       # Mon Apr 13 + 3 = Thu Apr 16
        (dt(2026, 4, 17), 3, "Fri → Wed"),       # Fri Apr 17 + 3 = Wed Apr 22 (skip Sat/Sun)
        (dt(2026, 5, 22), 3, "Fri → Wed (Victoria Day)"),  # Fri May 22 + 3 = Wed May 27 (skip Mon May 25 = Memorial Day, but May 18 was Victoria — wait, this skips Memorial Day)
        (dt(2026, 12, 24), 3, "Wed → Wed (Christmas + Boxing Day)"),  # skip Fri 25, Sat 26 (Boxing observed), Sun 27 → next Mon 28, Tue 29, Wed 30
    ]
    for base, n, label in cases:
        result = business_days_from_now(n, base)
        print(f"  {label}: {base.strftime('%a %Y-%m-%d')} + {n} biz days = {result.strftime('%a %Y-%m-%d')}")