"""Fast mesh data access with numpy."""

import numpy as np


def polygon_arrays(mesh):
    """Return (loop_start, loop_total, loop_vertex_index) as int arrays."""
    n_polys = len(mesh.polygons)
    starts = np.empty(n_polys, dtype=np.int32)
    totals = np.empty(n_polys, dtype=np.int32)
    mesh.polygons.foreach_get("loop_start", starts)
    mesh.polygons.foreach_get("loop_total", totals)
    loop_verts = np.empty(len(mesh.loops), dtype=np.int32)
    mesh.loops.foreach_get("vertex_index", loop_verts)
    return starts, totals, loop_verts


def loop_polygon_index(totals):
    """Polygon index of every loop."""
    return np.repeat(np.arange(len(totals), dtype=np.int32), totals)


def vertex_coords(mesh):
    co = np.empty(len(mesh.vertices) * 3, dtype=np.float64)
    mesh.vertices.foreach_get("co", co)
    return co.reshape(-1, 3)


def polygon_normals(mesh):
    normals = np.empty(len(mesh.polygons) * 3, dtype=np.float64)
    mesh.polygon_normals.foreach_get("vector", normals)
    return normals.reshape(-1, 3)