from datetime import date, timedelta

import pytest

from app.services.stock import StockError, check_in, check_out, current_stock


def _checkin(db, product, qty, unit, best_before=None):
    lot = check_in(db, product, qty, unit, best_before, None, None)
    db.commit()
    return lot


def test_checkin_creates_lot_in_base_units(db, rice):
    _checkin(db, rice, 3, "package")  # 1500 g
    assert current_stock(db, rice.id) == 1500


def test_checkout_partial_amount(db, rice):
    _checkin(db, rice, 3, "package")  # 1500 g
    check_out(db, rice, 200, "g", None)
    db.commit()
    assert current_stock(db, rice.id) == 1300


def test_fefo_takes_earliest_expiry_first(db, rice):
    soon = date.today() + timedelta(days=5)
    later = date.today() + timedelta(days=60)
    # Zuerst die später ablaufende Charge einlagern ...
    _checkin(db, rice, 500, "g", best_before=later)
    # ... dann die früher ablaufende.
    _checkin(db, rice, 500, "g", best_before=soon)

    check_out(db, rice, 400, "g", None)
    db.commit()

    # Die früh ablaufende Charge (soon) muss zuerst reduziert worden sein.
    from app.models import Lot

    lots = {l.best_before: l.quantity for l in db.query(Lot).all()}
    assert lots[soon] == 100
    assert lots[later] == 500


def test_fefo_spans_multiple_lots_and_removes_empty(db, rice):
    soon = date.today() + timedelta(days=5)
    later = date.today() + timedelta(days=60)
    _checkin(db, rice, 500, "g", best_before=soon)
    _checkin(db, rice, 500, "g", best_before=later)

    check_out(db, rice, 700, "g", None)  # 500 (soon) + 200 (later)
    db.commit()

    from app.models import Lot

    lots = db.query(Lot).all()
    assert len(lots) == 1  # leere soon-Charge entfernt
    assert lots[0].best_before == later
    assert lots[0].quantity == 300


def test_null_best_before_is_last(db, rice):
    dated = date.today() + timedelta(days=30)
    _checkin(db, rice, 300, "g", best_before=None)
    _checkin(db, rice, 300, "g", best_before=dated)

    check_out(db, rice, 300, "g", None)
    db.commit()

    from app.models import Lot

    remaining = db.query(Lot).all()
    # Die datierte Charge wird zuerst genommen, die NULL-Charge bleibt.
    assert len(remaining) == 1
    assert remaining[0].best_before is None


def test_checkout_more_than_available_raises(db, rice):
    _checkin(db, rice, 100, "g")
    with pytest.raises(StockError):
        check_out(db, rice, 200, "g", None)