"""
Unit tests for knife-edge diffraction calculations.
"""

import sys
import os

sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..', '..'))

from app.geometry.diffraction import knife_edge_loss


def freq_to_wl(freq_mhz):
    return 300.0 / freq_mhz


class TestKnifeEdgeLoss:
    def test_no_obstruction_low_loss(self):
        """Negative h means clearance above LOS — loss should be small."""
        loss = knife_edge_loss(d1_m=500, d2_m=500, h_m=-10, wavelength_m=freq_to_wl(1800))
        assert loss >= 0
        assert loss < 3

    def test_grazing_obstruction(self):
        """h=0 means exactly at LOS line — ~6 dB loss."""
        loss = knife_edge_loss(d1_m=500, d2_m=500, h_m=0, wavelength_m=freq_to_wl(1800))
        assert 5 < loss < 8

    def test_obstruction_increases_loss(self):
        wl = freq_to_wl(1800)
        loss_low = knife_edge_loss(d1_m=500, d2_m=500, h_m=1, wavelength_m=wl)
        loss_high = knife_edge_loss(d1_m=500, d2_m=500, h_m=10, wavelength_m=wl)
        assert loss_high > loss_low

    def test_higher_freq_more_loss(self):
        """Higher frequency = shorter wavelength = more diffraction loss."""
        loss_low_f = knife_edge_loss(d1_m=500, d2_m=500, h_m=5, wavelength_m=freq_to_wl(450))
        loss_high_f = knife_edge_loss(d1_m=500, d2_m=500, h_m=5, wavelength_m=freq_to_wl(1800))
        assert loss_high_f > loss_low_f

    def test_zero_distance_safe(self):
        """Should not crash on zero distances."""
        loss = knife_edge_loss(d1_m=0, d2_m=500, h_m=5, wavelength_m=freq_to_wl(900))
        assert loss >= 0

    def test_large_clearance(self):
        """Very deep clearance (large negative h) should have near-zero loss."""
        loss = knife_edge_loss(d1_m=500, d2_m=500, h_m=-50, wavelength_m=freq_to_wl(900))
        assert loss < 1.0


if __name__ == "__main__":
    instance = TestKnifeEdgeLoss()
    for method_name in [m for m in dir(instance) if m.startswith("test_")]:
        try:
            getattr(instance, method_name)()
            print(f"  PASS  {method_name}")
        except Exception as e:
            print(f"  FAIL  {method_name}: {e}")
    print("\nAll tests completed.")