tests/test_alphageometry_modules.py

"""Unit tests exercising the new alphageometry modules (utils + visualizer).

These tests are intentionally small and dependency-free so they run in CI and
local developer environments without extra setup.
"""

from __future__ import annotations

import tempfile

from alphageometry.modules import utils, visualizer


def test_polygon_area_and_triangulation():
    # simple unit square
    square = [(0.0, 0.0), (1.0, 0.0), (1.0, 1.0), (0.0, 1.0)]
    area = utils.polygon_area(square)
    assert abs(area - 1.0) < 1e-12
    tris = utils.earclip_triangulate(square)
    # triangulation of quad -> 2 triangles
    assert len(tris) == 2
    # triangles should use indices from 0..3
    for t in tris:
        assert all(0 <= i < 4 for i in t)


def test_rdp_simplify():
    # stair-step polyline: many points but simplifiable
    pts = [(float(i), 0.0) for i in range(20)]
    simplified = utils.rdp_simplify(pts, epsilon=0.5)
    assert len(simplified) < len(pts)
    assert simplified[0] == pts[0]
    assert simplified[-1] == pts[-1]


def test_visualizer_svg_and_json_roundtrip():
    tri_verts = [(0.0, 0.0), (1.0, 0.0), (0.5, 0.8)]
    triangles = [(0, 1, 2)]
    svg = visualizer.mesh_to_svg(tri_verts, triangles)
    assert svg.startswith("<svg")
    j = visualizer.mesh_to_json(tri_verts, triangles)
    assert "vertices" in j and "triangles" in j


def test_visualizer_writes_svg_file(tmp_path):
    square = [(0.0, 0.0), (1.0, 0.0), (1.0, 1.0), (0.0, 1.0)]
    svg = visualizer.polygon_to_svg(square)
    out = tmp_path / "out.svg"
    out.write_text(svg, encoding="utf-8")
    # ensure file exists and contains svg markup
    txt = out.read_text(encoding="utf-8")
    assert "<svg" in txt and "polygon" in txt