from decimal import Decimal

from app.domain.corporate_actions import calculate_stock_consolidation


def test_stock_consolidation_preserves_cost_and_scales_wac():
    result = calculate_stock_consolidation(Decimal(1452), Decimal(726), Decimal("1086.23"))
    assert result.average_price_after == Decimal("2172.46")
    assert result.total_cost_basis == Decimal("1577205.96000000")
    assert result.ratio == Decimal("0.5")

def test_stock_consolidation_rejects_fractional_result():
    import pytest

    from app.domain.corporate_actions import CorporateActionError
    with pytest.raises(CorporateActionError) as exc:
        calculate_stock_consolidation(Decimal(3), Decimal("1.5"), Decimal(10))
    assert exc.value.code == "FRACTIONAL_RESULT_UNSUPPORTED"


def test_stock_consolidation_allows_stored_wac_rounding_residue():
    result = calculate_stock_consolidation(
        Decimal(1452),
        Decimal(726),
        Decimal("1086.234145936639256198347107438016528926"),
    )

    assert result.average_price_before == Decimal("1086.23414594")
    assert result.average_price_after == Decimal("2172.46829187")
    assert result.total_cost_basis == Decimal("1577211.97990000")
    assert result.total_cost_basis - result.average_price_after * result.quantity_after == Decimal("0.00000238")