# Sanitized excerpt conceptually from geometry.py (LungLens inference-api)
# Verified by tests/test_geometry.py (2026-10-19): lovibond finite, dpd_ipd == 2.0 for unit vectors

def lovibond_angle_degrees(nail_matrix, proximal_nail_fold, nail_plate):
    v1 = (nail_matrix[0] - proximal_nail_fold[0], nail_matrix[1] - proximal_nail_fold[1])
    v2 = (nail_plate[0] - proximal_nail_fold[0], nail_plate[1] - proximal_nail_fold[1])
    return angle_between(v1, v2)

def dpd_ipd_ratio(dpd_a, dpd_b, ipd_a, ipd_b):
    dpd = euclidean(dpd_a, dpd_b)
    ipd = euclidean(ipd_a, ipd_b)
    if ipd == 0:
        raise ValueError("INVALID_GEOMETRY")
    return dpd / ipd

# Note: numbers are only as good as the landmarks supplied. Placeholder landmarks
# still produce a numeric output; that is not clinical validation.