"""Unit tests for `runner.helpers.geo` — Vincenty distance + offset projection."""

from __future__ import annotations

import math

import pytest

from runner.helpers.geo import GeodeticDelta, delta, distance_m, offset


def test_distance_zero_for_same_point() -> None:
    assert distance_m(50.0, 30.0, 50.0, 30.0) == pytest.approx(0.0, abs=1e-6)


def test_distance_one_degree_latitude_around_111km() -> None:
    # ~111 km per degree of latitude at the equator; 1° at lat=50° is similar.
    d = distance_m(50.0, 30.0, 51.0, 30.0)
    assert 110_000 < d < 112_000


def test_offset_then_distance_round_trip() -> None:
    """Offsetting a point by N meters along a bearing recovers ~N when measured back."""
    # Arrange
    start_lat, start_lon = 50.0, 30.0
    bearing = 45.0
    target_distance = 5_000.0
    # Act
    end_lat, end_lon = offset(start_lat, start_lon, bearing, target_distance)
    measured = distance_m(start_lat, start_lon, end_lat, end_lon)
    # Assert
    assert measured == pytest.approx(target_distance, rel=1e-6)


def test_delta_returns_full_structure() -> None:
    d = delta(50.0, 30.0, 50.0, 31.0)
    assert isinstance(d, GeodeticDelta)
    assert d.distance_m > 0
    assert math.isfinite(d.forward_bearing_deg)
    assert math.isfinite(d.reverse_bearing_deg)


@pytest.mark.parametrize("bad", [float("nan")])
def test_distance_rejects_nan(bad: float) -> None:
    with pytest.raises(ValueError, match="NaN"):
        distance_m(bad, 30.0, 50.0, 30.0)