from resonance_engine.tasks.infra import MAX_CONCURRENCY, get_recommended_concurrency


class TestRecommendedConcurrency:
    def test_cold_start_seeds_from_nominal(self) -> None:
        # no observed rps → ceil(11 * 0.85 * 0.5) = 5
        assert get_recommended_concurrency(11, latency_s=0.5) == 5

    def test_minimum_is_one(self) -> None:
        assert get_recommended_concurrency(0, latency_s=0.5) == 1

    def test_capped_at_max(self) -> None:
        assert get_recommended_concurrency(100_000, latency_s=0.5) == MAX_CONCURRENCY

    def test_grows_when_no_throttle(self) -> None:
        # ran = 20 * 0.5 = 10 concurrency; clean → 10 / 0.85 = 11.76 → 12 (grow)
        assert get_recommended_concurrency(11, observed_rps=20, latency_s=0.5) == 12

    def test_backs_off_when_throttled(self) -> None:
        # ran = 10; 20% throttled → 10 * 0.8 = 8 (shrink below what ran)
        assert (
            get_recommended_concurrency(
                11, observed_rps=20, latency_s=0.5, throttle_rate=0.2
            )
            == 8
        )