// 简易熔断器：连续失败 N 次后，在冷却期内直接抛错
const circuitState = { failures: 0, openUntil: 0 };
const CIRCUIT_THRESHOLD = 5;      // 连续失败 5 次触发熔断
const CIRCUIT_COOLDOWN_MS = 60000; // 熔断冷却 60 秒

function checkCircuit(label) {
  if (Date.now() < circuitState.openUntil) {
    throw new Error(`[circuit-breaker] ${label} 熔断中，${Math.ceil((circuitState.openUntil - Date.now()) / 1000)}s 后恢复`);
  }
}

function recordSuccess() {
  circuitState.failures = 0;
  circuitState.openUntil = 0;
}

function recordFailure(label) {
  circuitState.failures++;
  if (circuitState.failures >= CIRCUIT_THRESHOLD) {
    circuitState.openUntil = Date.now() + CIRCUIT_COOLDOWN_MS;
    console.warn(`  🔌 [circuit-breaker] ${label} 连续失败 ${circuitState.failures} 次，熔断 ${CIRCUIT_COOLDOWN_MS / 1000}s`);
  }
}

async function withRetry(fn, { maxRetries = 3, baseDelay = 1000, label = "operation" } = {}) {
  checkCircuit(label);
  let lastError;
  for (let attempt = 1; attempt <= maxRetries; attempt++) {
    try {
      const result = await fn();
      recordSuccess();
      return result;
    } catch (error) {
      lastError = error;
      recordFailure(label);
      if (attempt < maxRetries) {
        // 指数退避 + 随机抖动（避免雷群效应）
        const jitter = Math.random() * baseDelay * 0.5;
        const delay = baseDelay * Math.pow(2, attempt - 1) + jitter;
        console.warn(`  ⚠ ${label} 第${attempt}次失败，${(delay / 1000).toFixed(1)}s后重试...`);
        await new Promise((resolve) => setTimeout(resolve, delay));
        // 每次重试前检查熔断
        checkCircuit(label);
      }
    }
  }
  throw lastError;
}

export { withRetry };