import pytest

from pricing.discounts import apply_discounts


def test_no_discounts():
    assert apply_discounts(100.0, []) == 100.0


def test_single_discount():
    assert apply_discounts(100.0, [25]) == 75.0


def test_single_discount_rounding():
    assert apply_discounts(19.99, [15]) == 16.99


def test_stacked_discounts():
    # two seasonal discounts stacked on one order
    assert apply_discounts(100.0, [10, 20]) == 70.0


def test_stacked_same_discount_twice():
    assert apply_discounts(100.0, [50, 50]) == 25.0


def test_full_discount_is_allowed():
    assert apply_discounts(80.0, [100]) == 0.0


def test_rejects_discount_over_100():
    with pytest.raises(ValueError):
        apply_discounts(100.0, [120])


def test_rejects_negative_discount():
    with pytest.raises(ValueError):
        apply_discounts(100.0, [-5])


def test_rejects_negative_base_price():
    with pytest.raises(ValueError):
        apply_discounts(-10.0, [10])