"""Renderer backend selection for the render-bridge scripts.

Default = the dpl3-revive GPU backend (vrview_gl.GLRenderer, moderngl);
VRVIEW_SOFT=1 forces the software rasterizer (vrview.Renderer), which stays
the debugging reference. Both share SceneCache/cam_matrix/draw/last_frame,
so scripts only swap the class.

Run under the Windows CPython with the wheels installed (py -3.13):
    numpy pygame-ce moderngl pillow
(the MSYS2 python has no pip; 3.14 has no moderngl/glcontext wheel yet).
"""
import os
import sys

sys.path.insert(0, os.path.join(os.path.dirname(os.path.abspath(__file__)),
                                '..', '..', 'dpl3-revive', 'patha'))


def pick_renderer():
    """Return (RendererClass, backend_name)."""
    if os.environ.get('VRVIEW_SOFT') == '1':
        from vrview import Renderer
        return Renderer, 'software'
    try:
        from vrview_gl import GLRenderer
        return GLRenderer, 'GL'
    except Exception as e:
        print(f"GL backend unavailable ({e}); using software rasterizer",
              file=sys.stderr)
        from vrview import Renderer
        return Renderer, 'software'


def save_frame(r, out):
    """Save the last rendered frame. Works headless on both backends
    (GL has no screen surface -- read the FBO via last_frame)."""
    arr = r.last_frame
    if arr is None:
        raise RuntimeError('no frame rendered yet')
    from PIL import Image
    Image.fromarray(arr).save(out)