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/**
 * 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.internal.operators;

/**
 * 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.
 */

import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;

import rx.Observable;
import rx.Observable.Operator;
import rx.Scheduler;
import rx.Subscriber;
import rx.functions.Action0;
import rx.schedulers.Schedulers;
import rx.subscriptions.SerialSubscription;

public final class OperatorRetry implements Operator> {

    private static final int INFINITE_RETRY = -1;

    private final int retryCount;

    private static Scheduler scheduler = Schedulers.trampoline();

    public OperatorRetry(int retryCount) {
        this.retryCount = retryCount;
    }

    public OperatorRetry() {
        this(INFINITE_RETRY);
    }

    @Override
    public Subscriber> call(final Subscriber child) {
        final Scheduler.Worker inner = scheduler.createWorker();
        child.add(inner);
        
        final SerialSubscription serialSubscription = new SerialSubscription();
        // add serialSubscription so it gets unsubscribed if child is unsubscribed
        child.add(serialSubscription);
        
        return new SourceSubscriber(child, retryCount, inner, serialSubscription);
    }
    
    static final class SourceSubscriber extends Subscriber> {
        final Subscriber child;
        final int retryCount;
        final Scheduler.Worker inner;
        final SerialSubscription serialSubscription;
        
        volatile int attempts;
        @SuppressWarnings("rawtypes")
        static final AtomicIntegerFieldUpdater ATTEMPTS_UPDATER
                = AtomicIntegerFieldUpdater.newUpdater(SourceSubscriber.class, "attempts");

        public SourceSubscriber(Subscriber child, int retryCount, Scheduler.Worker inner, 
                SerialSubscription serialSubscription) {
            this.child = child;
            this.retryCount = retryCount;
            this.inner = inner;
            this.serialSubscription = serialSubscription;
        }
        
        
        @Override
            public void onCompleted() {
                // ignore as we expect a single nested Observable
            }

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

            @Override
            public void onNext(final Observable o) {
                inner.schedule(new Action0() {

                    @Override
                    public void call() {
                        final Action0 _self = this;
                        ATTEMPTS_UPDATER.incrementAndGet(SourceSubscriber.this);

                        // new subscription each time so if it unsubscribes itself it does not prevent retries
                        // by unsubscribing the child subscription
                        Subscriber subscriber = new Subscriber() {

                            @Override
                            public void onCompleted() {
                                child.onCompleted();
                            }

                            @Override
                            public void onError(Throwable e) {
                                if ((retryCount == INFINITE_RETRY || attempts <= retryCount) && !inner.isUnsubscribed()) {
                                    // retry again
                                    inner.schedule(_self);
                                } else {
                                    // give up and pass the failure
                                    child.onError(e);
                                }
                            }

                            @Override
                            public void onNext(T v) {
                                child.onNext(v);
                            }

                        };
                        // register this Subscription (and unsubscribe previous if exists) 
                        serialSubscription.set(subscriber);
                        o.unsafeSubscribe(subscriber);
                    }
                });
            }
    }
}