import sys
from pathlib import Path

_EXAMPLES = Path(__file__).resolve().parents[1] / "examples"
if str(_EXAMPLES) not in sys.path:
    sys.path.insert(0, str(_EXAMPLES))

from viz.contact_arrow import (
    ContactArrowStyle,
    DEFAULT_CONTACT_ARROW_STYLE,
    force_visual_strength,
    length_from_force,
    thickness_scale_from_force,
)

REFERENCE_NORMAL_FORCE = DEFAULT_CONTACT_ARROW_STYLE.reference_normal_force


def test_force_visual_strength_monotonic():
    forces = [0.0, 50.0, 175.0, 1000.0, 5000.0, REFERENCE_NORMAL_FORCE, 20000.0]
    strengths = [force_visual_strength(f) for f in forces]
    assert strengths[0] == 0.0
    assert all(strengths[i] <= strengths[i + 1] for i in range(len(strengths) - 1))
    assert strengths[-1] == 1.0


def test_log_mode_more_sensitive_than_linear_at_low_force():
    low = 175.0
    log_style = ContactArrowStyle(force_strength_mode="log")
    lin_style = ContactArrowStyle(force_strength_mode="linear")
    assert force_visual_strength(low, style=log_style) > force_visual_strength(low, style=lin_style)


def test_length_and_thickness_track_same_strength():
    force = 2500.0
    mesh_span = 10.0
    strength = force_visual_strength(force)
    length = length_from_force(force, mesh_span)
    thick = thickness_scale_from_force(force)
    assert length > mesh_span * 0.02
    assert thick > 0.20
    assert strength == force_visual_strength(force)