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.Iterator;

import io.reactivex.*;
import io.reactivex.annotations.Nullable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.internal.disposables.EmptyDisposable;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.observers.BasicQueueDisposable;

public final class ObservableFromIterable<T> extends Observable<T> {
    final Iterable<? extends T> source;
    public ObservableFromIterable(Iterable<? extends T> source) {
        this.source = source;
    }

    @Override
    public void subscribeActual(Observer<? super T> observer) {
        Iterator<? extends T> it;
        try {
            it = source.iterator();
        } catch (Throwable e) {
            Exceptions.throwIfFatal(e);
            EmptyDisposable.error(e, observer);
            return;
        }
        boolean hasNext;
        try {
            hasNext = it.hasNext();
        } catch (Throwable e) {
            Exceptions.throwIfFatal(e);
            EmptyDisposable.error(e, observer);
            return;
        }
        if (!hasNext) {
            EmptyDisposable.complete(observer);
            return;
        }

        FromIterableDisposable<T> d = new FromIterableDisposable<T>(observer, it);
        observer.onSubscribe(d);

        if (!d.fusionMode) {
            d.run();
        }
    }

    static final class FromIterableDisposable<T> extends BasicQueueDisposable<T> {

        final Observer<? super T> downstream;

        final Iterator<? extends T> it;

        volatile boolean disposed;

        boolean fusionMode;

        boolean done;

        boolean checkNext;

        FromIterableDisposable(Observer<? super T> actual, Iterator<? extends T> it) {
            this.downstream = actual;
            this.it = it;
        }

        void run() {
            boolean hasNext;

            do {
                if (isDisposed()) {
                    return;
                }
                T v;

                try {
                    v = ObjectHelper.requireNonNull(it.next(), "The iterator returned a null value");
                } catch (Throwable e) {
                    Exceptions.throwIfFatal(e);
                    downstream.onError(e);
                    return;
                }

                downstream.onNext(v);

                if (isDisposed()) {
                    return;
                }
                try {
                    hasNext = it.hasNext();
                } catch (Throwable e) {
                    Exceptions.throwIfFatal(e);
                    downstream.onError(e);
                    return;
                }
            } while (hasNext);

            if (!isDisposed()) {
                downstream.onComplete();
            }
        }

        @Override
        public int requestFusion(int mode) {
            if ((mode & SYNC) != 0) {
                fusionMode = true;
                return SYNC;
            }
            return NONE;
        }

        @Nullable
        @Override
        public T poll() {
            if (done) {
                return null;
            }
            if (checkNext) {
                if (!it.hasNext()) {
                    done = true;
                    return null;
                }
            } else {
                checkNext = true;
            }

            return ObjectHelper.requireNonNull(it.next(), "The iterator returned a null value");
        }

        @Override
        public boolean isEmpty() {
            return done;
        }

        @Override
        public void clear() {
            done = true;
        }

        @Override
        public void dispose() {
            disposed = true;
        }

        @Override
        public boolean isDisposed() {
            return disposed;
        }
    }
}