from decimal import Decimal

import pytest

from opengoods.units import (
    UnitError,
    canonical_unit_code,
    kcal_to_kj,
    kj_to_kcal,
    normalize,
)


def test_normalize_mass_kg_to_g():
    result = normalize("1.5", "kg")
    assert result.dimension == "mass"
    assert result.canonical_unit == "g"
    assert result.canonical_value == Decimal("1500.0")


def test_normalize_volume_litre_alias():
    result = normalize(2, "升")
    assert result.dimension == "volume"
    assert result.canonical_value == Decimal("2000")
    assert result.canonical_unit == "ml"


def test_normalize_energy_kcal_to_kj():
    result = normalize("539", "kcal")
    assert result.dimension == "energy"
    assert result.canonical_unit == "kJ"
    assert result.canonical_value == Decimal("539") * Decimal("4.184")


def test_canonical_unit_code_alias():
    assert canonical_unit_code("公斤") == "kg"
    assert canonical_unit_code(" G ") == "g"


def test_unknown_unit_raises():
    with pytest.raises(UnitError):
        normalize(1, "parsec")


def test_energy_roundtrip():
    assert kcal_to_kj(1) == Decimal("4.184")
    assert kj_to_kcal(Decimal("4.184")) == Decimal("1")