Copyright (c) 2016-present, RxJava Contributors.
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.
/**
 * Copyright (c) 2016-present, RxJava Contributors.
 *
 * 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 io.reactivex.internal.operators.observable;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.*;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.functions.Consumer;
import io.reactivex.internal.disposables.*;
import io.reactivex.observables.ConnectableObservable;
import io.reactivex.plugins.RxJavaPlugins;

Returns an observable sequence that stays connected to the source as long as
there is at least one subscription to the observable sequence.
Type parameters:
<T> – 
           the value type/**
 * Returns an observable sequence that stays connected to the source as long as
 * there is at least one subscription to the observable sequence.
 *
 * @param <T>
 *            the value type
 */
public final class ObservableRefCount<T> extends Observable<T> {

    final ConnectableObservable<T> source;

    final int n;

    final long timeout;

    final TimeUnit unit;

    final Scheduler scheduler;

    RefConnection connection;

    public ObservableRefCount(ConnectableObservable<T> source) {
        this(source, 1, 0L, TimeUnit.NANOSECONDS, null);
    }

    public ObservableRefCount(ConnectableObservable<T> source, int n, long timeout, TimeUnit unit,
            Scheduler scheduler) {
        this.source = source;
        this.n = n;
        this.timeout = timeout;
        this.unit = unit;
        this.scheduler = scheduler;
    }

    @Override
    protected void subscribeActual(Observer<? super T> observer) {

        RefConnection conn;

        boolean connect = false;
        synchronized (this) {
            conn = connection;
            if (conn == null) {
                conn = new RefConnection(this);
                connection = conn;
            }

            long c = conn.subscriberCount;
            if (c == 0L && conn.timer != null) {
                conn.timer.dispose();
            }
            conn.subscriberCount = c + 1;
            if (!conn.connected && c + 1 == n) {
                connect = true;
                conn.connected = true;
            }
        }

        source.subscribe(new RefCountObserver<T>(observer, this, conn));

        if (connect) {
            source.connect(conn);
        }
    }

    void cancel(RefConnection rc) {
        SequentialDisposable sd;
        synchronized (this) {
            if (connection == null || connection != rc) {
                return;
            }
            long c = rc.subscriberCount - 1;
            rc.subscriberCount = c;
            if (c != 0L || !rc.connected) {
                return;
            }
            if (timeout == 0L) {
                timeout(rc);
                return;
            }
            sd = new SequentialDisposable();
            rc.timer = sd;
        }

        sd.replace(scheduler.scheduleDirect(rc, timeout, unit));
    }

    void terminated(RefConnection rc) {
        synchronized (this) {
            if (connection != null && connection == rc) {
                connection = null;
                if (rc.timer != null) {
                    rc.timer.dispose();
                }
            }
            if (--rc.subscriberCount == 0) {
                if (source instanceof Disposable) {
                    ((Disposable)source).dispose();
                } else if (source instanceof ResettableConnectable) {
                    ((ResettableConnectable)source).resetIf(rc.get());
                }
            }
        }
    }

    void timeout(RefConnection rc) {
        synchronized (this) {
            if (rc.subscriberCount == 0 && rc == connection) {
                connection = null;
                Disposable connectionObject = rc.get();
                DisposableHelper.dispose(rc);

                if (source instanceof Disposable) {
                    ((Disposable)source).dispose();
                } else if (source instanceof ResettableConnectable) {
                    if (connectionObject == null) {
                        rc.disconnectedEarly = true;
                    } else {
                        ((ResettableConnectable)source).resetIf(connectionObject);
                    }
                }
            }
        }
    }

    static final class RefConnection extends AtomicReference<Disposable>
    implements Runnable, Consumer<Disposable> {

        private static final long serialVersionUID = -4552101107598366241L;

        final ObservableRefCount<?> parent;

        Disposable timer;

        long subscriberCount;

        boolean connected;

        boolean disconnectedEarly;

        RefConnection(ObservableRefCount<?> parent) {
            this.parent = parent;
        }

        @Override
        public void run() {
            parent.timeout(this);
        }

        @Override
        public void accept(Disposable t) throws Exception {
            DisposableHelper.replace(this, t);
            synchronized (parent) {
                if (disconnectedEarly) {
                    ((ResettableConnectable)parent.source).resetIf(t);
                }
            }
        }
    }

    static final class RefCountObserver<T>
    extends AtomicBoolean implements Observer<T>, Disposable {

        private static final long serialVersionUID = -7419642935409022375L;

        final Observer<? super T> downstream;

        final ObservableRefCount<T> parent;

        final RefConnection connection;

        Disposable upstream;

        RefCountObserver(Observer<? super T> downstream, ObservableRefCount<T> parent, RefConnection connection) {
            this.downstream = downstream;
            this.parent = parent;
            this.connection = connection;
        }

        @Override
        public void onNext(T t) {
            downstream.onNext(t);
        }

        @Override
        public void onError(Throwable t) {
            if (compareAndSet(false, true)) {
                parent.terminated(connection);
                downstream.onError(t);
            } else {
                RxJavaPlugins.onError(t);
            }
        }

        @Override
        public void onComplete() {
            if (compareAndSet(false, true)) {
                parent.terminated(connection);
                downstream.onComplete();
            }
        }

        @Override
        public void dispose() {
            upstream.dispose();
            if (compareAndSet(false, true)) {
                parent.cancel(connection);
            }
        }

        @Override
        public boolean isDisposed() {
            return upstream.isDisposed();
        }

        @Override
        public void onSubscribe(Disposable d) {
            if (DisposableHelper.validate(upstream, d)) {
                this.upstream = d;

                downstream.onSubscribe(this);
            }
        }
    }
}