"""
熔断器 - 每个云端模型独立实例

状态机: CLOSED -> OPEN -> HALF_OPEN -> CLOSED/OPEN
- 连续 threshold 次失败 -> OPEN
- 冷却 cooldown 秒后 -> HALF_OPEN（允许一次探测）
- 探测成功 -> CLOSED；探测失败 -> 重新 OPEN
"""
from collections import deque
import time
import threading


class CircuitBreaker:
    def __init__(self, threshold: int = 5, cooldown: int = 900, enabled: bool = True):
        self.enabled = enabled
        if enabled:
            self.failures = deque(maxlen=threshold)
        else:
            self.failures = None
        self.threshold = threshold
        self.cooldown = cooldown
        self.state = 'CLOSED'
        self.last_failure = None
        self._lock = threading.Lock()  # 状态转换加锁，防多线程竞争

    def record_failure(self):
        if not self.enabled:
            return
        with self._lock:
            self.failures.append(time.time())
            if len(self.failures) >= self.threshold:
                self.state = 'OPEN'
                self.last_failure = time.time()

    def record_success(self):
        if not self.enabled:
            return
        with self._lock:
            self.failures.clear()
            self.state = 'CLOSED'

    def is_open(self):
        if not self.enabled:
            return False
        with self._lock:
            if self.state == 'OPEN' and self.last_failure and time.time() - self.last_failure > self.cooldown:
                self.state = 'HALF_OPEN'
            return self.state == 'OPEN'

    def __repr__(self):
        return f"CircuitBreaker(state={self.state}, enabled={self.enabled})"