from hop_shm import HopReader, HopWriter, hop_bytes


def test_hop_ring_preserves_order(tmp_path):
    path = str(tmp_path / "cam-01.pcm")
    n = hop_bytes(16000, 2, 0.1)
    w = HopWriter(path, n, nslots=4)
    r = HopReader(path)
    for i in range(3):
        payload = bytes([i]) * n
        w.write(payload)
    got = [r.read() for _ in range(3)]
    assert got[0] is not None and got[0][0] == 0
    assert got[1] is not None and got[1][0] == 1
    assert got[2] is not None and got[2][0] == 2
    assert r.read() is None
    w.close()


def test_hop_ring_skips_when_reader_lags(tmp_path):
    path = str(tmp_path / "cam-01.pcm")
    n = 32
    w = HopWriter(path, n, nslots=4)
    r = HopReader(path)
    for i in range(10):
        w.write(bytes([i]) * n)
    last = r.read()
    assert last is not None
    w.close()


def test_reader_follows_writer_restart(tmp_path):
    """Cameras-only restart zeros seq; the wall must not stay stuck on _last."""
    path = str(tmp_path / "cam-01.pcm")
    n = 32
    w = HopWriter(path, n, nslots=4)
    r = HopReader(path)
    for i in range(8):
        w.write(bytes([i]) * n)
    assert r.read() is not None
    w.close()
    w2 = HopWriter(path, n, nslots=4)
    w2.write(bytes([99]) * n)
    got = r.read()
    assert got is not None and got[0] == 99
    assert r.read() is None
    w2.close()