/**
 * Copyright 2016 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 io.reactivex.observers;

import io.reactivex.Observer;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.*;
import io.reactivex.internal.disposables.*;
import io.reactivex.plugins.RxJavaPlugins;

/**
 * Wraps another Subscriber and ensures all onXXX methods conform the protocol
 * (except the requirement for serialized access).
 *
 * @param <T> the value type
 */
public final class SafeObserver<T> implements Observer<T>, Disposable {
    /** The actual Subscriber. */
    final Observer<? super T> actual;
    /** The subscription. */
    Disposable s;
    /** Indicates a terminal state. */
    boolean done;
    
    /**
     * Constructs a SafeObserver by wrapping the given actual Observer
     * @param actual the actual Observer to wrap, not null (not validated)
     */
    public SafeObserver(Observer<? super T> actual) {
        this.actual = actual;
    }
    
    @Override
    public void onSubscribe(Disposable s) {
        if (DisposableHelper.validate(this.s, s)) {
            this.s = s;
            try {
                actual.onSubscribe(this);
            } catch (Throwable e) {
                Exceptions.throwIfFatal(e);
                done = true;
                // can't call onError because the actual's state may be corrupt at this point
                try {
                    s.dispose();
                } catch (Throwable e1) {
                    Exceptions.throwIfFatal(e1);
                    RxJavaPlugins.onError(new CompositeException(e, e1));
                }
                RxJavaPlugins.onError(e);
            }
        }
    }
    

    @Override
    public void dispose() {
        s.dispose();
    }
    
    @Override
    public boolean isDisposed() {
        return s.isDisposed();
    }

    @Override
    public void onNext(T t) {
        if (done) {
            return;
        }
        if (s == null) {
            onNextNoSubscription();
            return;
        }

        if (t == null) {
            Throwable ex = new NullPointerException();
            try {
                s.dispose();
            } catch (Throwable e1) {
                Exceptions.throwIfFatal(e1);
                onError(new CompositeException(ex, e1));
                return;
            }
            onError(ex);
            return;
        }
        
        try {
            actual.onNext(t);
        } catch (Throwable e) {
            Exceptions.throwIfFatal(e);
            try {
                s.dispose();
            } catch (Throwable e1) {
                Exceptions.throwIfFatal(e1);
                onError(new CompositeException(e, e1));
                return;
            }
            onError(e);
        }
    }
    
    void onNextNoSubscription() {
        
        Throwable ex = new NullPointerException("Subscription not set!");
        
        try {
            actual.onSubscribe(EmptyDisposable.INSTANCE);
        } catch (Throwable e) {
            Exceptions.throwIfFatal(e);
            // can't call onError because the actual's state may be corrupt at this point
            RxJavaPlugins.onError(new CompositeException(ex, e));
            return;
        }
        try {
            actual.onError(ex);
        } catch (Throwable e) {
            Exceptions.throwIfFatal(e);
            // if onError failed, all that's left is to report the error to plugins
            RxJavaPlugins.onError(new CompositeException(ex, e));
        }
    }
    
    @Override
    public void onError(Throwable t) {
        if (done) {
            return;
        }
        done = true;
        
        if (s == null) {
            CompositeException t2 = new CompositeException(t, new NullPointerException("Subscription not set!"));
            
            try {
                actual.onSubscribe(EmptyDisposable.INSTANCE);
            } catch (Throwable e) {
                Exceptions.throwIfFatal(e);
                // can't call onError because the actual's state may be corrupt at this point
                t2.suppress(e);
                
                RxJavaPlugins.onError(t2);
                return;
            }
            try {
                actual.onError(t2);
            } catch (Throwable e) {
                Exceptions.throwIfFatal(e);
                // if onError failed, all that's left is to report the error to plugins
                t2.suppress(e);
                
                RxJavaPlugins.onError(t2);
            }
            return;
        }
        
        if (t == null) {
            t = new NullPointerException();
        }

        try {
            actual.onError(t);
        } catch (Throwable ex) {
            Exceptions.throwIfFatal(ex);
            
            RxJavaPlugins.onError(new CompositeException(t, ex));
        }
    }
    
    @Override
    public void onComplete() {
        if (done) {
            return;
        }
        if (s == null) {
            onCompleteNoSubscription();
            return;
        }

        done = true;

        try {
            actual.onComplete();
        } catch (Throwable e) {
            Exceptions.throwIfFatal(e);
            RxJavaPlugins.onError(e);
        }
    }

    void onCompleteNoSubscription() {
        
        Throwable ex = new NullPointerException("Subscription not set!");
        
        try {
            actual.onSubscribe(EmptyDisposable.INSTANCE);
        } catch (Throwable e) {
            Exceptions.throwIfFatal(e);
            // can't call onError because the actual's state may be corrupt at this point
            RxJavaPlugins.onError(new CompositeException(ex, e));
            return;
        }
        try {
            actual.onError(ex);
        } catch (Throwable e) {
            Exceptions.throwIfFatal(e);
            // if onError failed, all that's left is to report the error to plugins
            RxJavaPlugins.onError(new CompositeException(ex, e));
        }
    }

}