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The MongoDB Asynchronous Driver
There is a newer version: 3.12.14
/*
 * Copyright 2008-present MongoDB, Inc.
 *
 * 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.mongodb.async.client;

import com.mongodb.Block;
import com.mongodb.async.SingleResultCallback;

import java.util.List;


/**
 * Observable helpers.
 *
 * Allows async methods to be converted into event-based {@link Observable}s.
 *
 * @since 3.1
 * @deprecated Prefer the Reactive Streams-based asynchronous driver (mongodb-driver-reactivestreams artifactId)
 */
@Deprecated
public final class Observables {

    /**
     * Convert a {@link MongoIterable} into an {@link Observable}.
     *
     * @param mongoIterable the MongoIterable to subscribe to
     * @param      The type of result being observed
     * @return the observable version of the mongoIterable
     */
    public static  Observable observe(final MongoIterable mongoIterable) {
        return new Observable() {
            @Override
            public void subscribe(final Observer observer) {
                new MongoIterableSubscription(mongoIterable, observer);
            }
        };
    }

    /**
     * Allows the conversion of {@link SingleResultCallback} based operations into an {@link Observable}
     *
     * Requires a {@link Block} that is passed the callback to be used with the operation.
     * This is required to make sure that the operation only occurs once the {@link Subscription} signals for data.
     * 
     * A typical example would be when wrapping callback based methods to make them observable. 

     * For example, converting {@link MongoCollection#count(SingleResultCallback)} into an {@link Observable}:
     * 
     * {@code
     *    Observable countObservable = observe(new Block>() {
     *        public void apply(final SingleResultCallback callback) {
     *            collection.countDocuments(callback);
     *        }
     *    });
     * }
     * 
     *
     * @param operation the block that implements the operation.
     * @param  The type of result being observed
     * @return the observable version of the callback based operation
     */
    public static  Observable observe(final Block> operation) {
        return new Observable() {
            @Override
            public void subscribe(final Observer observer) {
                new SingleResultCallbackSubscription(operation, observer);
            }
        };
    }

    /**
     * Allows the conversion of {@link SingleResultCallback} based operations and flattens the results in an {@link Observable}.
     *
     * Requires a {@link Block} that is passed the callback to be used with the operation.
     * This is required to make sure that the operation only occurs once the {@link Subscription} signals for data.
     *
     * @param operation the operation that is passed a callback and is used to delay execution of an operation until demanded.
     * @param  The type of result being observed
     * @return a subscription
     */
    public static  Observable observeAndFlatten(final Block>> operation) {
        return new Observable() {
            @Override
            public void subscribe(final Observer observer) {
                new FlatteningSingleResultCallbackSubscription(operation, observer);
            }
        };
    }

    private Observables() {
    }
}