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.util;

import java.util.concurrent.atomic.*;

import org.reactivestreams.Subscription;

import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.ProtocolViolationException;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.plugins.RxJavaPlugins;

Utility class to help report multiple subscriptions with the same
consumer type instead of the internal "Disposable already set!" message
that is practically reserved for internal operators and indicate bugs in them.
/**
 * Utility class to help report multiple subscriptions with the same
 * consumer type instead of the internal "Disposable already set!" message
 * that is practically reserved for internal operators and indicate bugs in them.
 */
public final class EndConsumerHelper {

    
Utility class.
/**
     * Utility class.
     */
    private EndConsumerHelper() {
        throw new IllegalStateException("No instances!");
    }

    
Ensures that the upstream Disposable is null and returns true, otherwise
disposes the next Disposable and if the upstream is not the shared
disposed instance, reports a ProtocolViolationException due to
multiple subscribe attempts.
Params:
upstream – the upstream current value
next – the Disposable to check for nullness and dispose if necessary
observer – the class of the consumer to have a personalized
error message if the upstream already contains a non-cancelled Disposable.
Returns:
true if successful, false if the upstream was non null/**
     * Ensures that the upstream Disposable is null and returns true, otherwise
     * disposes the next Disposable and if the upstream is not the shared
     * disposed instance, reports a ProtocolViolationException due to
     * multiple subscribe attempts.
     * @param upstream the upstream current value
     * @param next the Disposable to check for nullness and dispose if necessary
     * @param observer the class of the consumer to have a personalized
     * error message if the upstream already contains a non-cancelled Disposable.
     * @return true if successful, false if the upstream was non null
     */
    public static boolean validate(Disposable upstream, Disposable next, Class<?> observer) {
        ObjectHelper.requireNonNull(next, "next is null");
        if (upstream != null) {
            next.dispose();
            if (upstream != DisposableHelper.DISPOSED) {
                reportDoubleSubscription(observer);
            }
            return false;
        }
        return true;
    }

    
Atomically updates the target upstream AtomicReference from null to the non-null
next Disposable, otherwise disposes next and reports a ProtocolViolationException
if the AtomicReference doesn't contain the shared disposed indicator.
Params:
upstream – the target AtomicReference to update
next – the Disposable to set on it atomically
observer – the class of the consumer to have a personalized
error message if the upstream already contains a non-cancelled Disposable.
Returns:
true if successful, false if the content of the AtomicReference was non null/**
     * Atomically updates the target upstream AtomicReference from null to the non-null
     * next Disposable, otherwise disposes next and reports a ProtocolViolationException
     * if the AtomicReference doesn't contain the shared disposed indicator.
     * @param upstream the target AtomicReference to update
     * @param next the Disposable to set on it atomically
     * @param observer the class of the consumer to have a personalized
     * error message if the upstream already contains a non-cancelled Disposable.
     * @return true if successful, false if the content of the AtomicReference was non null
     */
    public static boolean setOnce(AtomicReference<Disposable> upstream, Disposable next, Class<?> observer) {
        ObjectHelper.requireNonNull(next, "next is null");
        if (!upstream.compareAndSet(null, next)) {
            next.dispose();
            if (upstream.get() != DisposableHelper.DISPOSED) {
                reportDoubleSubscription(observer);
            }
            return false;
        }
        return true;
    }

    
Ensures that the upstream Subscription is null and returns true, otherwise
cancels the next Subscription and if the upstream is not the shared
cancelled instance, reports a ProtocolViolationException due to
multiple subscribe attempts.
Params:
upstream – the upstream current value
next – the Subscription to check for nullness and cancel if necessary
subscriber – the class of the consumer to have a personalized
error message if the upstream already contains a non-cancelled Subscription.
Returns:
true if successful, false if the upstream was non null/**
     * Ensures that the upstream Subscription is null and returns true, otherwise
     * cancels the next Subscription and if the upstream is not the shared
     * cancelled instance, reports a ProtocolViolationException due to
     * multiple subscribe attempts.
     * @param upstream the upstream current value
     * @param next the Subscription to check for nullness and cancel if necessary
     * @param subscriber the class of the consumer to have a personalized
     * error message if the upstream already contains a non-cancelled Subscription.
     * @return true if successful, false if the upstream was non null
     */
    public static boolean validate(Subscription upstream, Subscription next, Class<?> subscriber) {
        ObjectHelper.requireNonNull(next, "next is null");
        if (upstream != null) {
            next.cancel();
            if (upstream != SubscriptionHelper.CANCELLED) {
                reportDoubleSubscription(subscriber);
            }
            return false;
        }
        return true;
    }

    
Atomically updates the target upstream AtomicReference from null to the non-null
next Subscription, otherwise cancels next and reports a ProtocolViolationException
if the AtomicReference doesn't contain the shared cancelled indicator.
Params:
upstream – the target AtomicReference to update
next – the Subscription to set on it atomically
subscriber – the class of the consumer to have a personalized
error message if the upstream already contains a non-cancelled Subscription.
Returns:
true if successful, false if the content of the AtomicReference was non null/**
     * Atomically updates the target upstream AtomicReference from null to the non-null
     * next Subscription, otherwise cancels next and reports a ProtocolViolationException
     * if the AtomicReference doesn't contain the shared cancelled indicator.
     * @param upstream the target AtomicReference to update
     * @param next the Subscription to set on it atomically
     * @param subscriber the class of the consumer to have a personalized
     * error message if the upstream already contains a non-cancelled Subscription.
     * @return true if successful, false if the content of the AtomicReference was non null
     */
    public static boolean setOnce(AtomicReference<Subscription> upstream, Subscription next, Class<?> subscriber) {
        ObjectHelper.requireNonNull(next, "next is null");
        if (!upstream.compareAndSet(null, next)) {
            next.cancel();
            if (upstream.get() != SubscriptionHelper.CANCELLED) {
                reportDoubleSubscription(subscriber);
            }
            return false;
        }
        return true;
    }

    
Builds the error message with the consumer class.
Params:
consumer – the class of the consumer
Returns:
the error message string/**
     * Builds the error message with the consumer class.
     * @param consumer the class of the consumer
     * @return the error message string
     */
    public static String composeMessage(String consumer) {
        return "It is not allowed to subscribe with a(n) " + consumer + " multiple times. "
                + "Please create a fresh instance of " + consumer + " and subscribe that to the target source instead.";
    }

    
Report a ProtocolViolationException with a personalized message referencing
the simple type name of the consumer class and report it via
RxJavaPlugins.onError.
Params:
consumer – the class of the consumer/**
     * Report a ProtocolViolationException with a personalized message referencing
     * the simple type name of the consumer class and report it via
     * RxJavaPlugins.onError.
     * @param consumer the class of the consumer
     */
    public static void reportDoubleSubscription(Class<?> consumer) {
        RxJavaPlugins.onError(new ProtocolViolationException(composeMessage(consumer.getName())));
    }
}