import pytest
import numpy as np
from h03_robust_kernels import RobustKernels

@pytest.fixture
def kernels():
    return RobustKernels()

class TestRobustKernels:
    
    def test_huber_kernel_scalar(self, kernels):
        # Inlier (r <= threshold): 0.5 * r^2
        assert kernels.huber_loss(1.0, 2.0) == 0.5 * (1.0 ** 2)
        assert kernels.compute_weight(1.0, "huber", {"threshold": 2.0}) == 1.0
        
        # Outlier (r > threshold): threshold * (|r| - 0.5 * threshold)
        assert kernels.huber_loss(3.0, 2.0) == 2.0 * (3.0 - 0.5 * 2.0)
        assert kernels.compute_weight(3.0, "huber", {"threshold": 2.0}) == 2.0 / 3.0

    def test_cauchy_kernel_scalar(self, kernels):
        assert kernels.cauchy_loss(0.0, 1.0) == 0.0
        assert np.isclose(kernels.cauchy_loss(1.0, 1.0), 0.5 * np.log(2.0))
        
        assert kernels.compute_weight(0.0, "cauchy", {"k": 1.0}) == 1.0
        assert kernels.compute_weight(1.0, "cauchy", {"k": 1.0}) == 0.5
        assert kernels.compute_weight(3.0, "cauchy", {"k": 1.0}) == 0.1