/**
 * Copyright 2014 Netflix, 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 rx.operators;

import java.util.ArrayList;
import java.util.List;

import rx.Observable.Operator;
import rx.Subscriber;

/**
 * Returns an Observable that emits a single item, a list composed of all the items emitted by the
 * source Observable.
 * <p>
 * <img width="640" src="https://github.com/Netflix/RxJava/wiki/images/rx-Observers/toList.png">
 * <p>
 * Normally, an Observable that returns multiple items will do so by invoking its Observer's
 * <code>onNext</code> method for each such item. You can change this behavior, instructing the
 * Observable to compose a list of all of these multiple items and then to invoke the Observer's
 * <code>onNext</code> method once, passing it the entire list, by using the toList Observer.
 * <p>
 * Be careful not to use this Observer on Observables that emit infinite or very large numbers of
 * items, as you do not have the option to unsubscribe.
 */
public final class OperatorToObservableList<T> implements Operator<List<T>, T> {

    @Override
    public Subscriber<? super T> call(final Subscriber<? super List<T>> o) {
        return new Subscriber<T>(o) {

            final List<T> list = new ArrayList<T>();

            @Override
            public void onCompleted() {
                try {
                    o.onNext(new ArrayList<T>(list));
                    o.onCompleted();
                } catch (Throwable e) {
                    onError(e);
                }
            }

            @Override
            public void onError(Throwable e) {
                o.onError(e);
            }

            @Override
            public void onNext(T value) {
                list.add(value);
            }

        };
    }

}
