import numpy as np
import pytest

from pg_rad.objects import PointSource
from pg_rad.isotopes import Isotope


@pytest.fixture
def test_sources():
    iso = Isotope("test", E=662, b=0)
    pos_a = np.random.rand(3)
    pos_b = np.random.rand(3)

    a = PointSource(pos_a, activity=None, isotope=iso)
    b = PointSource(pos_b, activity=None, isotope=iso)

    return pos_a, pos_b, a, b


def test_if_distances_equal(test_sources):
    """
    Verify whether distance from PointSource A to B is the same as B to A.
    """

    _, _, a, b = test_sources

    assert a.distance_to(b) == b.distance_to(a)


def test_distance_calculation(test_sources):
    """
    Verify whether distance between PointSources is calculated correctly.
    """

    pos_a, pos_b, a, b = test_sources

    dx = pos_b[0] - pos_a[0]
    dy = pos_b[1] - pos_a[1]
    dz = pos_b[2] - pos_a[2]

    assert np.isclose(
        a.distance_to(b),
        np.sqrt(dx**2 + dy**2 + dz**2),
        rtol=1e-12)