@zerothrow/resilience/dist/index.js

Production-grade resilience patterns for ZeroThrow

// src/types.ts
var RetryExhaustedError = class extends Error {
  constructor(policyName, attempts, lastError, context) {
    super(`Retry exhausted after ${attempts} attempts`);
    this.policyName = policyName;
    this.attempts = attempts;
    this.lastError = lastError;
    this.context = context;
    this.name = "RetryExhaustedError";
  }
  type = "retry-exhausted";
};
var CircuitOpenError = class extends Error {
  constructor(policyName, openedAt, failureCount, context) {
    super(`Circuit breaker is open`);
    this.policyName = policyName;
    this.openedAt = openedAt;
    this.failureCount = failureCount;
    this.context = context;
    this.name = "CircuitOpenError";
  }
  type = "circuit-open";
};
var TimeoutError = class extends Error {
  constructor(policyName, timeout, elapsed, context) {
    super(`Operation timed out after ${elapsed}ms (limit: ${timeout}ms)`);
    this.policyName = policyName;
    this.timeout = timeout;
    this.elapsed = elapsed;
    this.context = context;
    this.name = "TimeoutError";
  }
  type = "timeout";
};

// src/policies/retry.ts
import { ZT as ZT2 } from "@zerothrow/core";

// src/policy.ts
import { ZT } from "@zerothrow/core";

// src/clock.ts
var SystemClock = class {
  now() {
    return /* @__PURE__ */ new Date();
  }
  async sleep(ms) {
    return new Promise((resolve) => setTimeout(resolve, ms));
  }
};
var TestClock = class {
  currentTime = Date.now();
  sleepers = [];
  now() {
    return new Date(this.currentTime);
  }
  async sleep(ms) {
    const wakeTime = this.currentTime + ms;
    return new Promise((resolve) => {
      this.sleepers.push({ wakeTime, resolve });
      this.sleepers.sort((a, b) => a.wakeTime - b.wakeTime);
    });
  }
  advance(ms) {
    this.currentTime += ms;
    while (this.sleepers.length > 0) {
      const nextSleeper = this.sleepers[0];
      if (nextSleeper && nextSleeper.wakeTime <= this.currentTime) {
        this.sleepers.shift();
        nextSleeper.resolve();
      } else {
        break;
      }
    }
  }
  setTime(time) {
    this.currentTime = typeof time === "number" ? time : time.getTime();
  }
};

// src/policy.ts
var BasePolicy = class {
  constructor(name, clock = new SystemClock()) {
    this.name = name;
    this.clock = clock;
  }
  async runOperation(operation) {
    return ZT.tryAsync(operation);
  }
};

// src/policies/retry.ts
var RetryPolicy = class extends BasePolicy {
  constructor(count, options = {}, clock) {
    super("retry", clock);
    this.count = count;
    this.options = options;
  }
  retryCallback;
  async execute(operation) {
    let lastError;
    for (let attempt = 0; attempt <= this.count; attempt++) {
      const result = await this.runOperation(operation);
      if (result.ok) {
        return result;
      }
      lastError = result.error;
      if (this.options.handle && !this.options.handle(result.error)) {
        return result;
      }
      if (attempt < this.count) {
        const delayTime = this.calculateDelay(attempt + 1);
        if (this.retryCallback) {
          this.retryCallback(attempt + 1, lastError, delayTime);
        }
        await this.clock.sleep(delayTime);
      }
    }
    return ZT2.err(new RetryExhaustedError(
      this.name,
      this.count + 1,
      lastError
    ));
  }
  onRetry(callback) {
    this.retryCallback = callback;
    return this;
  }
  calculateDelay(attempt) {
    const { backoff = "constant", delay = 1e3, maxDelay = 3e4 } = this.options;
    let calculatedDelay;
    switch (backoff) {
      case "constant":
        calculatedDelay = delay;
        break;
      case "linear":
        calculatedDelay = delay * attempt;
        break;
      case "exponential":
        calculatedDelay = delay * Math.pow(2, attempt - 1);
        break;
      default:
        calculatedDelay = delay;
    }
    return Math.min(calculatedDelay, maxDelay);
  }
};

// src/policies/circuit.ts
import { ZT as ZT3 } from "@zerothrow/core";
var CircuitBreakerPolicy = class extends BasePolicy {
  constructor(options, clock) {
    super("circuit-breaker", clock);
    this.options = options;
  }
  state = "closed";
  failures = 0;
  lastFailureTime;
  nextAllowedTime;
  stateChangeCallback;
  async execute(operation) {
    if (this.state === "open") {
      const now = this.clock.now().getTime();
      if (this.nextAllowedTime && now >= this.nextAllowedTime) {
        this.setState("half-open");
      } else {
        return ZT3.err(new CircuitOpenError(
          this.name,
          new Date(this.lastFailureTime || now),
          this.failures
        ));
      }
    }
    const result = await this.runOperation(operation);
    if (result.ok) {
      this.onSuccess();
      return result;
    } else {
      this.onFailure();
      const currentState = this.state;
      if (currentState === "open") {
        return ZT3.err(new CircuitOpenError(
          this.name,
          new Date(this.lastFailureTime || Date.now()),
          this.failures
        ));
      }
      return result;
    }
  }
  onSuccess() {
    if (this.state === "half-open") {
      this.reset();
      this.options.onClose?.();
    }
  }
  onFailure() {
    this.failures++;
    this.lastFailureTime = this.clock.now().getTime();
    if (this.state === "half-open") {
      this.open();
    } else if (this.failures >= this.options.threshold) {
      this.open();
    }
  }
  open() {
    this.setState("open");
    this.nextAllowedTime = this.clock.now().getTime() + this.options.duration;
    this.options.onOpen?.();
  }
  reset() {
    this.setState("closed");
    this.failures = 0;
    delete this.lastFailureTime;
    delete this.nextAllowedTime;
  }
  setState(newState) {
    if (this.state !== newState) {
      this.state = newState;
      this.stateChangeCallback?.(newState);
    }
  }
  onCircuitStateChange(callback) {
    this.stateChangeCallback = callback;
    return this;
  }
};

// src/policies/timeout.ts
import { ZT as ZT4 } from "@zerothrow/core";
var TimeoutPolicy = class extends BasePolicy {
  constructor(options, clock) {
    super("timeout", clock);
    this.options = options;
  }
  async execute(operation) {
    const startTime = this.clock.now().getTime();
    const timeoutPromise = new Promise((_, reject) => {
      setTimeout(() => {
        const elapsed = this.clock.now().getTime() - startTime;
        reject(new TimeoutError(
          this.name,
          this.options.timeout,
          elapsed
        ));
      }, this.options.timeout);
    });
    try {
      const result = await Promise.race([
        operation(),
        timeoutPromise
      ]);
      return ZT4.ok(result);
    } catch (error) {
      if (error instanceof TimeoutError) {
        return ZT4.err(error);
      }
      return ZT4.err(error instanceof Error ? error : new Error(String(error)));
    }
  }
};

// src/compose.ts
function wrap(outer, inner) {
  return {
    async execute(operation) {
      return outer.execute(
        () => (
          // The inner policy executes the actual operation
          inner.execute(operation).then((result) => {
            if (!result.ok) {
              throw result.error;
            }
            return result.value;
          })
        )
      );
    }
  };
}
function compose(...policies) {
  if (policies.length === 0) {
    throw new Error("compose requires at least one policy");
  }
  if (policies.length === 1) {
    return policies[0];
  }
  return policies.reduce((acc, policy) => wrap(policy, acc));
}

// src/policy-factory.ts
var Policy = {
  /**
   * Creates a retry policy
   */
  retry(count, options, clock) {
    return new RetryPolicy(count, options, clock);
  },
  /**
   * Creates a circuit breaker policy
   */
  circuitBreaker(options, clock) {
    return new CircuitBreakerPolicy(options, clock);
  },
  /**
   * Creates a timeout policy
   */
  timeout(options, clock) {
    const opts = typeof options === "number" ? { timeout: options } : options;
    return new TimeoutPolicy(opts, clock);
  },
  /**
   * Wraps one policy with another
   * The outer policy executes first
   */
  wrap,
  /**
   * Composes multiple policies from left to right
   * The leftmost policy is the outermost wrapper
   */
  compose
};
export {
  CircuitBreakerPolicy,
  CircuitOpenError,
  Policy as PolicyFactory,
  RetryExhaustedError,
  RetryPolicy,
  SystemClock,
  TestClock,
  TimeoutError,
  TimeoutPolicy,
  compose,
  wrap
};
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