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Grails Web Application Framework

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/*
 * Copyright 2013 SpringSource
 *
 * 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 grails.async

import groovy.transform.CompileStatic
import java.util.concurrent.TimeUnit

/**
 * Encapsulates the notion of a Promise, a Future-like interface designed to easy integration of asynchronous functions
 *
 * @author Graeme Rocher
 * @since 2.3
 */
@CompileStatic
interface Promise {

    /**
     * Retrieves the result, blocking until the value is available
     *
     * @return The result
     */
    T get() throws Throwable

    /**
     * Retrieves the result, blocking until the value is available or the timeout is reached
     *
     * @param timeout The timeout
     * @param units The timeout units
     * @return The value
     * @throws Throwable
     */
    T get(final long timeout, final TimeUnit units) throws Throwable

    /**
     * Execute the given closure when the promise completes
     *
     * @param callable
     * @return The Promise
     */
    Promise onComplete(Closure callable)

    /**
     * Execute the given closure when an error occurs
     *
     * @param callable
     * @return The Promise
     */
    Promise onError(Closure callable)

    /**
     * Same as #onComplete
     */
    Promise then(Closure callable)
}