"""ML device-selection env parsing (#872). Pure logic — no models/GPU/DB."""

from backend.app.services.ml import device


def test_gpu_requested_default_is_auto(monkeypatch):
    monkeypatch.delenv("FC_ML_DEVICE", raising=False)
    assert device.gpu_requested() is True


def test_gpu_requested_modes(monkeypatch):
    for v in ("auto", "cuda", "gpu", "CUDA", " Auto "):
        monkeypatch.setenv("FC_ML_DEVICE", v)
        assert device.gpu_requested() is True
    for v in ("cpu", "CPU", "none", "0"):
        monkeypatch.setenv("FC_ML_DEVICE", v)
        assert device.gpu_requested() is False


def test_onnx_gpu_mem_bytes(monkeypatch):
    monkeypatch.delenv("FC_ML_ONNX_GPU_MEM_GB", raising=False)
    assert device.onnx_gpu_mem_bytes() == 3 * 1024 ** 3
    monkeypatch.setenv("FC_ML_ONNX_GPU_MEM_GB", "2")
    assert device.onnx_gpu_mem_bytes() == 2 * 1024 ** 3


def test_torch_mem_fraction(monkeypatch):
    monkeypatch.delenv("FC_ML_TORCH_MEM_FRACTION", raising=False)
    assert device.torch_mem_fraction() == 0.6
    monkeypatch.setenv("FC_ML_TORCH_MEM_FRACTION", "0.5")
    assert device.torch_mem_fraction() == 0.5