/*
 * Copyright (c) 2012, 2019 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package jakarta.ws.rs.container;

import java.util.Collection;
import java.util.Date;
import java.util.Map;
import java.util.concurrent.TimeUnit;

An injectable JAX-RS asynchronous response that provides means for asynchronous server side response processing.
 A new instance of AsyncResponse may be injected into a resource or sub-resource
method parameter using the @Suspended annotation. 
Each asynchronous response instance is bound to the running request and can be used to asynchronously provide the
request processing result or otherwise manipulate the suspended client connection. The available operations include:

updating suspended state data (time-out value, response ...)
resuming the suspended request processing
canceling the suspended request processing

 Following example demonstrates the use of the AsyncResponse for asynchronous HTTP request processing: 
@Path("/messages/next")
public class MessagingResource {
    private static final BlockingQueue<AsyncResponse> suspended = new ArrayBlockingQueue<AsyncResponse>(5);
    @GET
    public void readMessage(@Suspended AsyncResponse ar) throws InterruptedException {
        suspended.put(ar);
    }
    @POST
    public String postMessage(final String message) throws InterruptedException {
        final AsyncResponse ar = suspended.take();
        ar.resume(message); // resumes the processing of one GET request
        return "Message sent";
    }
}


If the asynchronous response was suspended with a positive timeout value, and has not been explicitly resumed before
the timeout has expired, the processing will be resumed once the specified timeout threshold is reached, provided a
positive timeout value was set on the response.

 By default a timed-out asynchronous response is resumed with a WebApplicationException that has HTTP 503 (Service unavailable) error response status code set. This default behavior may be overridden by setting a custom time-out handler. 
Author:
Marek Potociar
Since:
2.0/**
 * An injectable JAX-RS asynchronous response that provides means for asynchronous server side response processing.
 * <p>
 * A new instance of {@code AsyncResponse} may be injected into a {@link jakarta.ws.rs.HttpMethod resource or sub-resource
 * method} parameter using the {@link Suspended &#64;Suspended} annotation.
 * </p>
 * Each asynchronous response instance is bound to the running request and can be used to asynchronously provide the
 * request processing result or otherwise manipulate the suspended client connection. The available operations include:
 * <ul>
 * <li>updating suspended state data (time-out value, response ...)</li>
 * <li>resuming the suspended request processing</li>
 * <li>canceling the suspended request processing</li>
 * </ul>
 * <p>
 * Following example demonstrates the use of the {@code AsyncResponse} for asynchronous HTTP request processing:
 * </p>
 *
 * <pre>
 * &#64;Path("/messages/next")
 * public class MessagingResource {
 *     private static final BlockingQueue&lt;AsyncResponse&gt; suspended = new ArrayBlockingQueue&lt;AsyncResponse&gt;(5);
 *
 *     &#64;GET
 *     public void readMessage(&#64;Suspended AsyncResponse ar) throws InterruptedException {
 *         suspended.put(ar);
 *     }
 *
 *     &#64;POST
 *     public String postMessage(final String message) throws InterruptedException {
 *         final AsyncResponse ar = suspended.take();
 *         ar.resume(message); // resumes the processing of one GET request
 *         return "Message sent";
 *     }
 * }
 * </pre>
 * <p>
 * If the asynchronous response was suspended with a positive timeout value, and has not been explicitly resumed before
 * the timeout has expired, the processing will be resumed once the specified timeout threshold is reached, provided a
 * positive timeout value was set on the response.
 * </p>
 * <p>
 * By default a timed-out asynchronous response is resumed with a {@link jakarta.ws.rs.WebApplicationException} that has
 * {@link jakarta.ws.rs.core.Response.Status#SERVICE_UNAVAILABLE HTTP 503 (Service unavailable)} error response status
 * code set. This default behavior may be overridden by {@link AsyncResponse#setTimeoutHandler(TimeoutHandler) setting}
 * a custom {@link TimeoutHandler time-out handler}.
 * </p>
 *
 * @author Marek Potociar
 * @since 2.0
 */
public interface AsyncResponse {
    
Constant specifying no suspend timeout value.
/**
     * Constant specifying no suspend timeout value.
     */
    public static final long NO_TIMEOUT = 0;

    
Resume the suspended request processing using the provided response data. The provided response data can be of any Java type that can be returned from a JAX-RS
resource method. 
 The asynchronous response must be still in a suspended state for this method to succeed. 

By executing this method, the request is guaranteed to complete either successfully or with an error. The data
processing by the JAX-RS runtime follows the same path as it would for the response data returned synchronously by a
JAX-RS resource, except that unmapped exceptions are not re-thrown by JAX-RS runtime to be handled by a hosting I/O
container. Instead, any unmapped exceptions are propagated to the hosting I/O container via a container-specific
callback mechanism. Depending on the container implementation, propagated unmapped exceptions typically result in an
error status being sent to the client and/or the connection being closed.

Params:
response – data to be sent back in response to the suspended request.
See Also:
resume(Throwable)
Returns:
true if the request processing has been resumed, returns false in case the request processing is not suspended and could not be resumed./**
     * Resume the suspended request processing using the provided response data.
     *
     * The provided response data can be of any Java type that can be returned from a {@link jakarta.ws.rs.HttpMethod JAX-RS
     * resource method}.
     * <p>
     * The asynchronous response must be still in a {@link #isSuspended() suspended} state for this method to succeed.
     * </p>
     * <p>
     * By executing this method, the request is guaranteed to complete either successfully or with an error. The data
     * processing by the JAX-RS runtime follows the same path as it would for the response data returned synchronously by a
     * JAX-RS resource, except that unmapped exceptions are not re-thrown by JAX-RS runtime to be handled by a hosting I/O
     * container. Instead, any unmapped exceptions are propagated to the hosting I/O container via a container-specific
     * callback mechanism. Depending on the container implementation, propagated unmapped exceptions typically result in an
     * error status being sent to the client and/or the connection being closed.
     * </p>
     *
     * @param response data to be sent back in response to the suspended request.
     * @return {@code true} if the request processing has been resumed, returns {@code false} in case the request processing
     * is not {@link #isSuspended() suspended} and could not be resumed.
     * @see #resume(Throwable)
     */
    public boolean resume(Object response);

    
Resume the suspended request processing using the provided throwable. For the provided throwable same rules apply as for an exception thrown by a JAX-RS
resource method. 

By executing this method, the request is guaranteed to complete either successfully or with an error. The throwable
processing by the JAX-RS runtime follows the same path as it would for the response data returned synchronously by a
JAX-RS resource, except that unmapped exceptions are not re-thrown by JAX-RS runtime to be handled by a hosting I/O
container. Instead, any unmapped exceptions are propagated to the hosting I/O container via a container-specific
callback mechanism. Depending on the container implementation, propagated unmapped exceptions typically result in an
error status being sent to the client and/or the connection being closed.

Params:
response – an exception to be raised in response to the suspended request.
See Also:
resume(Object)
Returns:
true if the response has been resumed, returns false in case the response is not suspended and could not be resumed./**
     * Resume the suspended request processing using the provided throwable.
     *
     * For the provided throwable same rules apply as for an exception thrown by a {@link jakarta.ws.rs.HttpMethod JAX-RS
     * resource method}.
     * <p>
     * By executing this method, the request is guaranteed to complete either successfully or with an error. The throwable
     * processing by the JAX-RS runtime follows the same path as it would for the response data returned synchronously by a
     * JAX-RS resource, except that unmapped exceptions are not re-thrown by JAX-RS runtime to be handled by a hosting I/O
     * container. Instead, any unmapped exceptions are propagated to the hosting I/O container via a container-specific
     * callback mechanism. Depending on the container implementation, propagated unmapped exceptions typically result in an
     * error status being sent to the client and/or the connection being closed.
     * </p>
     *
     * @param response an exception to be raised in response to the suspended request.
     * @return {@code true} if the response has been resumed, returns {@code false} in case the response is not
     * {@link #isSuspended() suspended} and could not be resumed.
     * @see #resume(Object)
     */
    public boolean resume(Throwable response);

    
Cancel the suspended request processing.
 When a request processing is cancelled using this method, the JAX-RS implementation MUST indicate to the client that the request processing has been cancelled by sending back a HTTP 503 (Service unavailable) error response. 
 Invoking a cancel(...) method multiple times to cancel request processing has the same effect as canceling the request processing only once. Invoking a cancel(...) method on an asynchronous response instance that has already been cancelled or resumed has no effect and the method call is ignored while returning true, in case the request has been cancelled previously. Otherwise, in case the request has been resumed regularly (using a resume(...) method) or resumed due to a time-out, method returns false. 
See Also:
cancel(int)
cancel(Date)
Returns:
true if the request processing has been cancelled, returns false in case the request processing is not suspended and could not be cancelled and is not 
cancelled already./**
     * Cancel the suspended request processing.
     * <p>
     * When a request processing is cancelled using this method, the JAX-RS implementation MUST indicate to the client that
     * the request processing has been cancelled by sending back a
     * {@link jakarta.ws.rs.core.Response.Status#SERVICE_UNAVAILABLE HTTP 503 (Service unavailable)} error response.
     * </p>
     * <p>
     * Invoking a {@code cancel(...)} method multiple times to cancel request processing has the same effect as canceling
     * the request processing only once. Invoking a {@code cancel(...)} method on an asynchronous response instance that has
     * already been cancelled or resumed has no effect and the method call is ignored while returning {@code true}, in case
     * the request has been cancelled previously. Otherwise, in case the request has been resumed regularly (using a
     * {@code resume(...) method}) or resumed due to a time-out, method returns {@code false}.
     * </p>
     *
     * @return {@code true} if the request processing has been cancelled, returns {@code false} in case the request
     * processing is not {@link #isSuspended() suspended} and could not be cancelled and is not {@link #isCancelled()
     * cancelled} already.
     * @see #cancel(int)
     * @see #cancel(java.util.Date)
     */
    public boolean cancel();

    
Cancel the suspended request processing.
 When a request processing is cancelled using this method, the JAX-RS implementation MUST indicate to the client that the request processing has been cancelled by sending back a HTTP 503 (Service unavailable) error response with a Retry-After header set to the value provided by the method parameter. 
 Invoking a cancel(...) method multiple times to cancel request processing has the same effect as canceling the request processing only once. Invoking a cancel(...) method on an asynchronous response instance that has already been cancelled or resumed has no effect and the method call is ignored while returning true, in case the request has been cancelled previously. Otherwise, in case the request has been resumed regularly (using a resume(...) method) or resumed due to a time-out, method returns false. 
Params:
retryAfter – a decimal integer number of seconds after the response is sent to the client that indicates how
long the service is expected to be unavailable to the requesting client.
See Also:
cancel
cancel(Date)
Returns:
true if the request processing has been cancelled, returns false in case the request processing is not suspended and could not be cancelled and is not 
cancelled already./**
     * Cancel the suspended request processing.
     * <p>
     * When a request processing is cancelled using this method, the JAX-RS implementation MUST indicate to the client that
     * the request processing has been cancelled by sending back a
     * {@link jakarta.ws.rs.core.Response.Status#SERVICE_UNAVAILABLE HTTP 503 (Service unavailable)} error response with a
     * {@code Retry-After} header set to the value provided by the method parameter.
     * </p>
     * <p>
     * Invoking a {@code cancel(...)} method multiple times to cancel request processing has the same effect as canceling
     * the request processing only once. Invoking a {@code cancel(...)} method on an asynchronous response instance that has
     * already been cancelled or resumed has no effect and the method call is ignored while returning {@code true}, in case
     * the request has been cancelled previously. Otherwise, in case the request has been resumed regularly (using a
     * {@code resume(...) method}) or resumed due to a time-out, method returns {@code false}.
     * </p>
     *
     * @param retryAfter a decimal integer number of seconds after the response is sent to the client that indicates how
     * long the service is expected to be unavailable to the requesting client.
     * @return {@code true} if the request processing has been cancelled, returns {@code false} in case the request
     * processing is not {@link #isSuspended() suspended} and could not be cancelled and is not {@link #isCancelled()
     * cancelled} already.
     * @see #cancel
     * @see #cancel(java.util.Date)
     */
    public boolean cancel(int retryAfter);

    
Cancel the suspended request processing.
 When a request processing is cancelled using this method, the JAX-RS implementation MUST indicate to the client that the request processing has been cancelled by sending back a HTTP 503 (Service unavailable) error response with a Retry-After header set to the value provided by the method parameter. 
 Invoking a cancel(...) method multiple times to cancel request processing has the same effect as canceling the request processing only once. Invoking a cancel(...) method on an asynchronous response instance that has already been cancelled or resumed has no effect and the method call is ignored while returning true, in case the request has been cancelled previously. Otherwise, in case the request has been resumed regularly (using a resume(...) method) or resumed due to a time-out, method returns false. 
Params:
retryAfter – a date that indicates how long the service is expected to be unavailable to the requesting client.
See Also:
cancel
cancel(int)
Returns:
true if the request processing has been cancelled, returns false in case the request processing is not suspended and could not be cancelled and is not 
cancelled already./**
     * Cancel the suspended request processing.
     * <p>
     * When a request processing is cancelled using this method, the JAX-RS implementation MUST indicate to the client that
     * the request processing has been cancelled by sending back a
     * {@link jakarta.ws.rs.core.Response.Status#SERVICE_UNAVAILABLE HTTP 503 (Service unavailable)} error response with a
     * {@code Retry-After} header set to the value provided by the method parameter.
     * </p>
     * <p>
     * Invoking a {@code cancel(...)} method multiple times to cancel request processing has the same effect as canceling
     * the request processing only once. Invoking a {@code cancel(...)} method on an asynchronous response instance that has
     * already been cancelled or resumed has no effect and the method call is ignored while returning {@code true}, in case
     * the request has been cancelled previously. Otherwise, in case the request has been resumed regularly (using a
     * {@code resume(...) method}) or resumed due to a time-out, method returns {@code false}.
     * </p>
     *
     * @param retryAfter a date that indicates how long the service is expected to be unavailable to the requesting client.
     * @return {@code true} if the request processing has been cancelled, returns {@code false} in case the request
     * processing is not {@link #isSuspended() suspended} and could not be cancelled and is not {@link #isCancelled()
     * cancelled} already.
     * @see #cancel
     * @see #cancel(int)
     */
    public boolean cancel(Date retryAfter);

    
Check if the asynchronous response instance is in a suspended state. Method returns true if this asynchronous response is still suspended and has not finished processing yet (either by resuming or canceling the response). 
See Also:
isCancelled()
isDone()
Returns:
true if this asynchronous response is in a suspend state, false otherwise./**
     * Check if the asynchronous response instance is in a suspended state.
     *
     * Method returns {@code true} if this asynchronous response is still suspended and has not finished processing yet
     * (either by resuming or canceling the response).
     *
     * @return {@code true} if this asynchronous response is in a suspend state, {@code false} otherwise.
     * @see #isCancelled()
     * @see #isDone()
     */
    public boolean isSuspended();

    
Check if the asynchronous response instance has been cancelled. Method returns true if this asynchronous response has been canceled before completion. 
See Also:
isSuspended()
isDone()
Returns:
true if this task was canceled before completion./**
     * Check if the asynchronous response instance has been cancelled.
     *
     * Method returns {@code true} if this asynchronous response has been canceled before completion.
     *
     * @return {@code true} if this task was canceled before completion.
     * @see #isSuspended()
     * @see #isDone()
     */
    public boolean isCancelled();

    
Check if the processing of a request this asynchronous response instance belongs to has finished. Method returns true if the processing of a request this asynchronous response is bound to is finished. 
 The request processing may be finished due to a normal termination, a suspend timeout, or cancellation -- in all of these cases, this method will return true. 
See Also:
isSuspended()
isCancelled()
Returns:
true if this execution context has finished processing./**
     * Check if the processing of a request this asynchronous response instance belongs to has finished.
     *
     * Method returns {@code true} if the processing of a request this asynchronous response is bound to is finished.
     * <p>
     * The request processing may be finished due to a normal termination, a suspend timeout, or cancellation -- in all of
     * these cases, this method will return {@code true}.
     * </p>
     *
     * @return {@code true} if this execution context has finished processing.
     * @see #isSuspended()
     * @see #isCancelled()
     */
    public boolean isDone();

    
Set/update the suspend timeout.
 The new suspend timeout values override any timeout value previously specified. The asynchronous response must be still in a suspended state for this method to succeed. 
Params:
time – suspend timeout value in the give time unit. Value lower or equal to 0 causes the context to suspend indefinitely.
unit – suspend timeout value time unit.
Returns:
true if the suspend time out has been set, returns false in case the request processing is not in the suspended state./**
     * Set/update the suspend timeout.
     * <p>
     * The new suspend timeout values override any timeout value previously specified. The asynchronous response must be
     * still in a {@link #isSuspended() suspended} state for this method to succeed.
     * </p>
     *
     * @param time suspend timeout value in the give time {@code unit}. Value lower or equal to 0 causes the context to
     * suspend indefinitely.
     * @param unit suspend timeout value time unit.
     * @return {@code true} if the suspend time out has been set, returns {@code false} in case the request processing is
     * not in the {@link #isSuspended() suspended} state.
     */
    public boolean setTimeout(long time, TimeUnit unit);

    
Set/replace a time-out handler for the suspended asynchronous response.

The time-out handler will be invoked when the suspend period of this asynchronous response times out. The job of the
time-out handler is to resolve the time-out situation by either


resuming the suspended response
cancelling the suspended response
extending the suspend period by setting a new suspend time-out

 Note that in case the response is suspended indefinitely, the time-out handler may never be invoked. 
Params:
handler – response time-out handler./**
     * Set/replace a time-out handler for the suspended asynchronous response.
     * <p>
     * The time-out handler will be invoked when the suspend period of this asynchronous response times out. The job of the
     * time-out handler is to resolve the time-out situation by either
     * </p>
     * <ul>
     * <li>resuming the suspended response</li>
     * <li>cancelling the suspended response</li>
     * <li>extending the suspend period by setting a new suspend time-out</li>
     * </ul>
     * <p>
     * Note that in case the response is suspended {@link #NO_TIMEOUT indefinitely}, the time-out handler may never be
     * invoked.
     * </p>
     *
     * @param handler response time-out handler.
     */
    public void setTimeoutHandler(TimeoutHandler handler);

    
Register an asynchronous processing lifecycle callback class to receive lifecycle events for the asynchronous
response based on the implemented callback interfaces.
Params:
callback – callback class.
Throws:
NullPointerException – in case the callback class is null.
Returns:
collection of registered callback interfaces. If the callback class does not implement any recognized
callback interfaces, the returned collection will be empty./**
     * Register an asynchronous processing lifecycle callback class to receive lifecycle events for the asynchronous
     * response based on the implemented callback interfaces.
     *
     * @param callback callback class.
     * @return collection of registered callback interfaces. If the callback class does not implement any recognized
     * callback interfaces, the returned collection will be empty.
     * @throws NullPointerException in case the callback class is {@code null}.
     */
    public Collection<Class<?>> register(Class<?> callback);

    
Register asynchronous processing lifecycle callback classes to receive lifecycle events for the asynchronous response
based on the implemented callback interfaces.
Params:
callback – callback class.
callbacks – additional callback classes.
Throws:
NullPointerException – in case any of the callback classes is null.
Returns:
map of registered classes and the callback interfaces registered for each class. If a callback class does not
implement any recognized callback interfaces, the associated collection of registered interfaces for the class will
be empty./**
     * Register asynchronous processing lifecycle callback classes to receive lifecycle events for the asynchronous response
     * based on the implemented callback interfaces.
     *
     * @param callback callback class.
     * @param callbacks additional callback classes.
     * @return map of registered classes and the callback interfaces registered for each class. If a callback class does not
     * implement any recognized callback interfaces, the associated collection of registered interfaces for the class will
     * be empty.
     * @throws NullPointerException in case any of the callback classes is {@code null}.
     */
    public Map<Class<?>, Collection<Class<?>>> register(Class<?> callback, Class<?>... callbacks);

    
Register an asynchronous processing lifecycle callback instance to receive lifecycle events for the asynchronous
response based on the implemented callback interfaces.
Params:
callback – callback instance implementing one or more of the recognized callback interfaces.
Throws:
NullPointerException – in case the callback instance is null.
Returns:
collection of registered callback interfaces. If the callback class does not implement any recognized
callback interfaces, the returned collection will be empty./**
     * Register an asynchronous processing lifecycle callback instance to receive lifecycle events for the asynchronous
     * response based on the implemented callback interfaces.
     *
     * @param callback callback instance implementing one or more of the recognized callback interfaces.
     * @return collection of registered callback interfaces. If the callback class does not implement any recognized
     * callback interfaces, the returned collection will be empty.
     * @throws NullPointerException in case the callback instance is {@code null}.
     */
    public Collection<Class<?>> register(Object callback);

    
Register an asynchronous processing lifecycle callback instances to receive lifecycle events for the asynchronous
response based on the implemented callback interfaces.
Params:
callback – callback instance.
callbacks – additional callback instances.
Throws:
NullPointerException – in case any of the callback instances is null.
Returns:
map of registered classes and the callback interfaces registered for each class. If a callback class does not
implement any recognized callback interfaces, the associated collection of registered interfaces for the class will
be empty./**
     * Register an asynchronous processing lifecycle callback instances to receive lifecycle events for the asynchronous
     * response based on the implemented callback interfaces.
     *
     * @param callback callback instance.
     * @param callbacks additional callback instances.
     * @return map of registered classes and the callback interfaces registered for each class. If a callback class does not
     * implement any recognized callback interfaces, the associated collection of registered interfaces for the class will
     * be empty.
     * @throws NullPointerException in case any of the callback instances is {@code null}.
     */
    public Map<Class<?>, Collection<Class<?>>> register(Object callback, Object... callbacks);
}