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.flowable;

import java.util.Collection;
import java.util.concurrent.Callable;

import org.reactivestreams.Subscriber;

import io.reactivex.Flowable;
import io.reactivex.annotations.Nullable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.fuseable.QueueFuseable;
import io.reactivex.internal.subscribers.BasicFuseableSubscriber;
import io.reactivex.internal.subscriptions.EmptySubscription;
import io.reactivex.plugins.RxJavaPlugins;

public final class FlowableDistinct<T, K> extends AbstractFlowableWithUpstream<T, T> {

    final Function<? super T, K> keySelector;

    final Callable<? extends Collection<? super K>> collectionSupplier;

    public FlowableDistinct(Flowable<T> source, Function<? super T, K> keySelector, Callable<? extends Collection<? super K>> collectionSupplier) {
        super(source);
        this.keySelector = keySelector;
        this.collectionSupplier = collectionSupplier;
    }

    @Override
    protected void subscribeActual(Subscriber<? super T> subscriber) {
        Collection<? super K> collection;

        try {
            collection = ObjectHelper.requireNonNull(collectionSupplier.call(), "The collectionSupplier returned a null collection. Null values are generally not allowed in 2.x operators and sources.");
        } catch (Throwable ex) {
            Exceptions.throwIfFatal(ex);
            EmptySubscription.error(ex, subscriber);
            return;
        }

        source.subscribe(new DistinctSubscriber<T, K>(subscriber, keySelector, collection));
    }

    static final class DistinctSubscriber<T, K> extends BasicFuseableSubscriber<T, T> {

        final Collection<? super K> collection;

        final Function<? super T, K> keySelector;

        DistinctSubscriber(Subscriber<? super T> actual, Function<? super T, K> keySelector, Collection<? super K> collection) {
            super(actual);
            this.keySelector = keySelector;
            this.collection = collection;
        }

        @Override
        public void onNext(T value) {
            if (done) {
                return;
            }
            if (sourceMode == NONE) {
                K key;
                boolean b;

                try {
                    key = ObjectHelper.requireNonNull(keySelector.apply(value), "The keySelector returned a null key");
                    b = collection.add(key);
                } catch (Throwable ex) {
                    fail(ex);
                    return;
                }

                if (b) {
                    downstream.onNext(value);
                } else {
                    upstream.request(1);
                }
            } else {
                downstream.onNext(null);
            }
        }

        @Override
        public void onError(Throwable e) {
            if (done) {
                RxJavaPlugins.onError(e);
            } else {
                done = true;
                collection.clear();
                downstream.onError(e);
            }
        }

        @Override
        public void onComplete() {
            if (!done) {
                done = true;
                collection.clear();
                downstream.onComplete();
            }
        }

        @Override
        public int requestFusion(int mode) {
            return transitiveBoundaryFusion(mode);
        }

        @Nullable
        @Override
        public T poll() throws Exception {
            for (;;) {
                T v = qs.poll();

                if (v == null || collection.add(ObjectHelper.requireNonNull(keySelector.apply(v), "The keySelector returned a null key"))) {
                    return v;
                } else {
                    if (sourceMode == QueueFuseable.ASYNC) {
                        upstream.request(1);
                    }
                }
            }
        }

        @Override
        public void clear() {
            collection.clear();
            super.clear();
        }
    }
}