import numpy as np


def write_ngl(path_or_buf, vertices, triangles):
    try:
        _write_ngl_buffer(path_or_buf)
    except AttributeError as e:
        if "write" not in str(e):
            raise e
        with open(path_or_buf, 'wb') as f:
            _write_ngl_buffer(path_or_buf, vertices, triangles)


def _write_ngl_buffer(buf, vertices, triangles):
    buf.write(np.uint32(len(vertices)))
    buf.write(np.asarray(vertices, dtype=np.float32).tobytes())
    buf.write(np.asarray(triangles, dtype=np.uint32).tobytes())


def read_ngl(path_or_buf):
    try:
        _read_ngl_buffer(path_or_buf)
    except AttributeError as e:
        if "read" not in str(e):
            raise e
        with open(path_or_buf, 'rb') as f:
            _read_ngl_buffer(f)


def _read_ngl_buffer(buf):
    n_vertices = int.from_bytes(buf.read(4), byteorder="little")
    vertices = np.frombuffer(buf, np.float32, 3 * n_vertices).reshape((n_vertices, 3))
    triangles = np.frombuffer(buf, np.uint32)
    triangles.reshape([len(triangles) // 3, 3])
    return vertices, triangles