import numpy as np
import tempfile
from pathlib import Path
import pytest


def _make_tiny_ply(path: Path) -> None:
    import open3d as o3d
    pcd = o3d.geometry.PointCloud()
    pts = np.random.rand(1000, 3).astype(np.float64)
    pcd.points = o3d.utility.Vector3dVector(pts)
    o3d.io.write_point_cloud(str(path), pcd)


def test_decimate_reduces_points():
    from scripts.pre_decimate import decimate_ply
    with tempfile.TemporaryDirectory() as tmp:
        src = Path(tmp) / "model.ply"
        dst = Path(tmp) / "model_decimated.ply"
        _make_tiny_ply(src)
        decimate_ply(str(src), str(dst), max_pts=100)
        import open3d as o3d
        pcd = o3d.io.read_point_cloud(str(dst))
        # voxel downsampling is approximate — assert significantly fewer than original 1000
        assert len(pcd.points) < 500


def test_decimate_small_cloud_unchanged():
    from scripts.pre_decimate import decimate_ply
    with tempfile.TemporaryDirectory() as tmp:
        src = Path(tmp) / "small.ply"
        dst = Path(tmp) / "small_decimated.ply"
        _make_tiny_ply(src)
        decimate_ply(str(src), str(dst), max_pts=5000)
        import open3d as o3d
        pcd = o3d.io.read_point_cloud(str(dst))
        assert len(pcd.points) == 1000


def test_decimate_missing_src_raises():
    from scripts.pre_decimate import decimate_ply
    with tempfile.TemporaryDirectory() as tmp:
        with pytest.raises(FileNotFoundError):
            decimate_ply("/nonexistent.ply", str(Path(tmp) / "out.ply"))


def test_find_ply_candidates():
    from scripts.pre_decimate import find_ply
    with tempfile.TemporaryDirectory() as tmp:
        d = Path(tmp)
        assert find_ply(d) is None
        (d / "model.ply").touch()
        assert find_ply(d) == d / "model.ply"