"""Circuit breaker behaviour (架构文档 §8.1 故障转移)."""

from __future__ import annotations

from packages.llm.circuit import CircuitBreaker, CircuitBreakerRegistry, CircuitState


class FakeClock:
    def __init__(self) -> None:
        self.now = 0.0

    def __call__(self) -> float:
        return self.now

    def advance(self, seconds: float) -> None:
        self.now += seconds


def state_of(breaker: CircuitBreaker) -> CircuitState:
    """Read the state through a call so mypy does not narrow it across mutations.

    `state` is a property; mypy treats it like an attribute and keeps the narrowed
    literal from an earlier assert, then reports later asserts as unreachable.
    """
    return breaker.state


def test_starts_closed_and_allows_traffic() -> None:
    breaker = CircuitBreaker("p", failure_threshold=3, clock=FakeClock())
    assert state_of(breaker) is CircuitState.CLOSED
    assert breaker.allow()


def test_opens_only_after_threshold_consecutive_failures() -> None:
    breaker = CircuitBreaker("p", failure_threshold=3, clock=FakeClock())
    breaker.record_failure()
    breaker.record_failure()
    assert state_of(breaker) is CircuitState.CLOSED
    breaker.record_failure()
    assert state_of(breaker) is CircuitState.OPEN
    assert not breaker.allow()


def test_success_resets_the_failure_streak() -> None:
    breaker = CircuitBreaker("p", failure_threshold=3, clock=FakeClock())
    breaker.record_failure()
    breaker.record_failure()
    breaker.record_success()
    breaker.record_failure()
    assert state_of(breaker) is CircuitState.CLOSED


def test_half_open_probe_after_cooldown_then_closes_on_success() -> None:
    clock = FakeClock()
    breaker = CircuitBreaker("p", failure_threshold=1, cooldown_seconds=30.0, clock=clock)
    breaker.record_failure()
    assert state_of(breaker) is CircuitState.OPEN

    clock.advance(29.0)
    assert not breaker.allow()

    clock.advance(2.0)
    assert breaker.allow()
    assert state_of(breaker) is CircuitState.HALF_OPEN
    # only one probe is admitted
    assert not breaker.allow()

    breaker.record_success()
    assert state_of(breaker) is CircuitState.CLOSED
    assert breaker.allow()


def test_half_open_failure_reopens_and_restarts_cooldown() -> None:
    clock = FakeClock()
    breaker = CircuitBreaker("p", failure_threshold=1, cooldown_seconds=10.0, clock=clock)
    breaker.record_failure()
    clock.advance(11.0)
    assert breaker.allow()

    breaker.record_failure()
    assert state_of(breaker) is CircuitState.OPEN
    assert not breaker.allow()

    clock.advance(11.0)
    assert breaker.allow()


def test_registry_returns_one_breaker_per_provider() -> None:
    registry = CircuitBreakerRegistry(failure_threshold=2, cooldown_seconds=5.0)
    assert registry.get("deepseek") is registry.get("deepseek")
    assert registry.get("deepseek") is not registry.get("zhipu")
    registry.get("deepseek").record_failure()
    registry.get("deepseek").record_failure()
    assert registry.snapshot() == {"deepseek": "open", "zhipu": "closed"}