"""VideoSource in-flight cap + VAAPI stale-frame drop (encoder behind)."""
from latency import (
    should_drop_encoder_queue_depth,
    should_drop_stale_vaapi_frame,
    video_capture_gate_acquire,
    video_capture_gate_release,
)


def test_vaapi_keeps_fresh_delta_frame():
    # 30 fps, 33 ms old — still inside the 3-frame budget.
    assert should_drop_stale_vaapi_frame(
        now_us=1_000_000, capture_us=967_000, fps=30, max_frames_behind=3,
        is_keyframe=False,
    ) is False


def test_vaapi_drops_delta_older_than_three_frame_periods():
    # 30 fps × 3 = 100 ms. 150 ms on EncoderQueue → drop before ToI420.
    assert should_drop_stale_vaapi_frame(
        now_us=1_000_000, capture_us=850_000, fps=30, max_frames_behind=3,
        is_keyframe=False,
    ) is True


def test_vaapi_never_drops_keyframe():
    assert should_drop_stale_vaapi_frame(
        now_us=1_000_000, capture_us=1, fps=30, max_frames_behind=3,
        is_keyframe=True,
    ) is False


def test_vaapi_missing_timestamp_is_not_dropped():
    assert should_drop_stale_vaapi_frame(
        now_us=1_000_000, capture_us=0, fps=30, max_frames_behind=3,
        is_keyframe=False,
    ) is False


def test_gate_admits_until_max_in_flight():
    gate = {"in_flight": 0, "dropped": 0, "max_in_flight": 3}
    assert video_capture_gate_acquire(gate) is True
    assert video_capture_gate_acquire(gate) is True
    assert video_capture_gate_acquire(gate) is True
    assert gate["in_flight"] == 3
    assert video_capture_gate_acquire(gate) is False
    assert gate["dropped"] == 1
    assert gate["in_flight"] == 3


def test_gate_release_allows_another_capture():
    gate = {"in_flight": 3, "dropped": 0, "max_in_flight": 3}
    video_capture_gate_release(gate)
    assert gate["in_flight"] == 2
    assert video_capture_gate_acquire(gate) is True
    assert gate["in_flight"] == 3


def test_queue_depth_keeps_slot_when_empty():
    assert should_drop_encoder_queue_depth(queued=0, max_queued=1) is False


def test_queue_depth_drops_when_at_max():
    # Latest-frame cap: one in-flight OnFrame/Encode, overwrite don't push.
    assert should_drop_encoder_queue_depth(queued=1, max_queued=1) is True


def test_queue_depth_drops_when_over_max():
    assert should_drop_encoder_queue_depth(queued=3, max_queued=1) is True