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;

import io.reactivex.annotations.*;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.util.NotificationLite;

Represents the reactive signal types: onNext, onError and onComplete and
holds their parameter values (a value, a Throwable, nothing).
Type parameters:
<T> – the value type/**
 * Represents the reactive signal types: onNext, onError and onComplete and
 * holds their parameter values (a value, a Throwable, nothing).
 * @param <T> the value type
 */
public final class Notification<T> {

    final Object value;

    
Not meant to be implemented externally. /** Not meant to be implemented externally. */
    private Notification(Object value) {
        this.value = value;
    }

    
Returns true if this notification is an onComplete signal.
Returns:
true if this notification is an onComplete signal/**
     * Returns true if this notification is an onComplete signal.
     * @return true if this notification is an onComplete signal
     */
    public boolean isOnComplete() {
        return value == null;
    }

    
Returns true if this notification is an onError signal and getError() returns the contained Throwable. 
See Also:
getError()
Returns:
true if this notification is an onError signal/**
     * Returns true if this notification is an onError signal and
     * {@link #getError()} returns the contained Throwable.
     * @return true if this notification is an onError signal
     * @see #getError()
     */
    public boolean isOnError() {
        return NotificationLite.isError(value);
    }

    
Returns true if this notification is an onNext signal and getValue() returns the contained value. 
See Also:
getValue()
Returns:
true if this notification is an onNext signal/**
     * Returns true if this notification is an onNext signal and
     * {@link #getValue()} returns the contained value.
     * @return true if this notification is an onNext signal
     * @see #getValue()
     */
    public boolean isOnNext() {
        Object o = value;
        return o != null && !NotificationLite.isError(o);
    }

    
Returns the contained value if this notification is an onNext
signal, null otherwise.
See Also:
isOnNext()
Returns:
the value contained or null/**
     * Returns the contained value if this notification is an onNext
     * signal, null otherwise.
     * @return the value contained or null
     * @see #isOnNext()
     */
    @SuppressWarnings("unchecked")
    @Nullable
    public T getValue() {
        Object o = value;
        if (o != null && !NotificationLite.isError(o)) {
            return (T)value;
        }
        return null;
    }

    
Returns the container Throwable error if this notification is an onError
signal, null otherwise.
See Also:
isOnError()
Returns:
the Throwable error contained or null/**
     * Returns the container Throwable error if this notification is an onError
     * signal, null otherwise.
     * @return the Throwable error contained or null
     * @see #isOnError()
     */
    @Nullable
    public Throwable getError() {
        Object o = value;
        if (NotificationLite.isError(o)) {
            return NotificationLite.getError(o);
        }
        return null;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof Notification) {
            Notification<?> n = (Notification<?>) obj;
            return ObjectHelper.equals(value, n.value);
        }
        return false;
    }

    @Override
    public int hashCode() {
        Object o = value;
        return o != null ? o.hashCode() : 0;
    }

    @Override
    public String toString() {
        Object o = value;
        if (o == null) {
            return "OnCompleteNotification";
        }
        if (NotificationLite.isError(o)) {
            return "OnErrorNotification[" + NotificationLite.getError(o) + "]";
        }
        return "OnNextNotification[" + value + "]";
    }

    
Constructs an onNext notification containing the given value.
Params:
value – the value to carry around in the notification, not null
Type parameters:
<T> – the value type
Throws:
NullPointerException – if value is null
Returns:
the new Notification instance/**
     * Constructs an onNext notification containing the given value.
     * @param <T> the value type
     * @param value the value to carry around in the notification, not null
     * @return the new Notification instance
     * @throws NullPointerException if value is null
     */
    @NonNull
    public static <T> Notification<T> createOnNext(@NonNull T value) {
        ObjectHelper.requireNonNull(value, "value is null");
        return new Notification<T>(value);
    }

    
Constructs an onError notification containing the error.
Params:
error – the error Throwable to carry around in the notification, not null
Type parameters:
<T> – the value type
Throws:
NullPointerException – if error is null
Returns:
the new Notification instance/**
     * Constructs an onError notification containing the error.
     * @param <T> the value type
     * @param error the error Throwable to carry around in the notification, not null
     * @return the new Notification instance
     * @throws NullPointerException if error is null
     */
    @NonNull
    public static <T> Notification<T> createOnError(@NonNull Throwable error) {
        ObjectHelper.requireNonNull(error, "error is null");
        return new Notification<T>(NotificationLite.error(error));
    }

    
Returns the empty and stateless shared instance of a notification representing
an onComplete signal.
Type parameters:
<T> – the target value type
Returns:
the shared Notification instance representing an onComplete signal/**
     * Returns the empty and stateless shared instance of a notification representing
     * an onComplete signal.
     * @param <T> the target value type
     * @return the shared Notification instance representing an onComplete signal
     */
    @SuppressWarnings("unchecked")
    @NonNull
    public static <T> Notification<T> createOnComplete() {
        return (Notification<T>)COMPLETE;
    }

    
The singleton instance for createOnComplete. /** The singleton instance for createOnComplete. */
    static final Notification<Object> COMPLETE = new Notification<Object>(null);
}