/*
 * Copyright (C) 2006 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtIncompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;

import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;

/**
 * Produces proxies that impose a time limit on method calls to the proxied object. For example, to
 * return the value of {@code target.someMethod()}, but substitute {@code DEFAULT_VALUE} if this
 * method call takes over 50 ms, you can use this code:
 *
 * <pre>
 *   TimeLimiter limiter = . . .;
 *   TargetType proxy = limiter.newProxy(
 *       target, TargetType.class, 50, TimeUnit.MILLISECONDS);
 *   try {
 *     return proxy.someMethod();
 *   } catch (UncheckedTimeoutException e) {
 *     return DEFAULT_VALUE;
 *   }
 * </pre>
 *
 * <p>Please see {@code SimpleTimeLimiterTest} for more usage examples.
 *
 * @author Kevin Bourrillion
 * @since 1.0
 */
@Beta
@GwtIncompatible
public interface TimeLimiter {

  /**
   * Returns an instance of {@code interfaceType} that delegates all method calls to the
   * {@code target} object, enforcing the specified time limit on each call. This time-limited
   * delegation is also performed for calls to {@link Object#equals}, {@link Object#hashCode}, and
   * {@link Object#toString}.
   *
   * <p>If the target method call finishes before the limit is reached, the return value or
   * exception is propagated to the caller exactly as-is. If, on the other hand, the time limit is
   * reached, the proxy will attempt to abort the call to the target, and will throw an
   * {@link UncheckedTimeoutException} to the caller.
   *
   * <p>It is important to note that the primary purpose of the proxy object is to return control to
   * the caller when the timeout elapses; aborting the target method call is of secondary concern.
   * The particular nature and strength of the guarantees made by the proxy is
   * implementation-dependent. However, it is important that each of the methods on the target
   * object behaves appropriately when its thread is interrupted.
   *
   * @param target the object to proxy
   * @param interfaceType the interface you wish the returned proxy to implement
   * @param timeoutDuration with timeoutUnit, the maximum length of time that callers are willing to
   *     wait on each method call to the proxy
   * @param timeoutUnit with timeoutDuration, the maximum length of time that callers are willing to
   *     wait on each method call to the proxy
   * @return a time-limiting proxy
   * @throws IllegalArgumentException if {@code interfaceType} is a regular class, enum, or
   *     annotation type, rather than an interface
   */
  <T> T newProxy(T target, Class<T> interfaceType, long timeoutDuration, TimeUnit timeoutUnit);

  /**
   * Invokes a specified Callable, timing out after the specified time limit. If the target method
   * call finished before the limit is reached, the return value or exception is propagated to the
   * caller exactly as-is. If, on the other hand, the time limit is reached, we attempt to abort the
   * call to the target, and throw an {@link UncheckedTimeoutException} to the caller.
   *
   * @param callable the Callable to execute
   * @param timeoutDuration with timeoutUnit, the maximum length of time to wait
   * @param timeoutUnit with timeoutDuration, the maximum length of time to wait
   * @param interruptible whether to respond to thread interruption by aborting the operation and
   *     throwing InterruptedException; if false, the operation is allowed to complete or time out,
   *     and the current thread's interrupt status is re-asserted.
   * @return the result returned by the Callable
   * @throws InterruptedException if {@code interruptible} is true and our thread is interrupted
   *     during execution
   * @throws UncheckedTimeoutException if the time limit is reached
   * @throws Exception
   */
  @CanIgnoreReturnValue
  <T> T callWithTimeout(
      Callable<T> callable, long timeoutDuration, TimeUnit timeoutUnit, boolean interruptible)
      throws Exception;
}
