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 org.reactivestreams.Subscriber;

import io.reactivex.Flowable;
import io.reactivex.annotations.Nullable;
import io.reactivex.functions.*;
import io.reactivex.internal.fuseable.ConditionalSubscriber;
import io.reactivex.internal.subscribers.*;

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

    final Function<? super T, K> keySelector;

    final BiPredicate<? super K, ? super K> comparer;

    public FlowableDistinctUntilChanged(Flowable<T> source, Function<? super T, K> keySelector, BiPredicate<? super K, ? super K> comparer) {
        super(source);
        this.keySelector = keySelector;
        this.comparer = comparer;
    }

    @Override
    protected void subscribeActual(Subscriber<? super T> s) {
        if (s instanceof ConditionalSubscriber) {
            ConditionalSubscriber<? super T> cs = (ConditionalSubscriber<? super T>) s;
            source.subscribe(new DistinctUntilChangedConditionalSubscriber<T, K>(cs, keySelector, comparer));
        } else {
            source.subscribe(new DistinctUntilChangedSubscriber<T, K>(s, keySelector, comparer));
        }
    }

    static final class DistinctUntilChangedSubscriber<T, K> extends BasicFuseableSubscriber<T, T>
    implements ConditionalSubscriber<T> {

        final Function<? super T, K> keySelector;

        final BiPredicate<? super K, ? super K> comparer;

        K last;

        boolean hasValue;

        DistinctUntilChangedSubscriber(Subscriber<? super T> actual,
                Function<? super T, K> keySelector,
                BiPredicate<? super K, ? super K> comparer) {
            super(actual);
            this.keySelector = keySelector;
            this.comparer = comparer;
        }

        @Override
        public void onNext(T t) {
            if (!tryOnNext(t)) {
                upstream.request(1);
            }
        }

        @Override
        public boolean tryOnNext(T t) {
            if (done) {
                return false;
            }
            if (sourceMode != NONE) {
                downstream.onNext(t);
                return true;
            }

            K key;

            try {
                key = keySelector.apply(t);
                if (hasValue) {
                    boolean equal = comparer.test(last, key);
                    last = key;
                    if (equal) {
                        return false;
                    }
                } else {
                    hasValue = true;
                    last = key;
                }
            } catch (Throwable ex) {
               fail(ex);
               return true;
            }

            downstream.onNext(t);
            return true;
        }

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

        @Nullable
        @Override
        public T poll() throws Exception {
            for (;;) {
                T v = qs.poll();
                if (v == null) {
                    return null;
                }
                K key = keySelector.apply(v);
                if (!hasValue) {
                    hasValue = true;
                    last = key;
                    return v;
                }

                if (!comparer.test(last, key)) {
                    last = key;
                    return v;
                }
                last = key;
                if (sourceMode != SYNC) {
                    upstream.request(1);
                }
            }
        }

    }

    static final class DistinctUntilChangedConditionalSubscriber<T, K> extends BasicFuseableConditionalSubscriber<T, T> {

        final Function<? super T, K> keySelector;

        final BiPredicate<? super K, ? super K> comparer;

        K last;

        boolean hasValue;

        DistinctUntilChangedConditionalSubscriber(ConditionalSubscriber<? super T> actual,
                Function<? super T, K> keySelector,
                BiPredicate<? super K, ? super K> comparer) {
            super(actual);
            this.keySelector = keySelector;
            this.comparer = comparer;
        }

        @Override
        public void onNext(T t) {
            if (!tryOnNext(t)) {
                upstream.request(1);
            }
        }

        @Override
        public boolean tryOnNext(T t) {
            if (done) {
                return false;
            }
            if (sourceMode != NONE) {
                return downstream.tryOnNext(t);
            }

            K key;

            try {
                key = keySelector.apply(t);
                if (hasValue) {
                    boolean equal = comparer.test(last, key);
                    last = key;
                    if (equal) {
                        return false;
                    }
                } else {
                    hasValue = true;
                    last = key;
                }
            } catch (Throwable ex) {
               fail(ex);
               return true;
            }

            downstream.onNext(t);
            return true;
        }

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

        @Nullable
        @Override
        public T poll() throws Exception {
            for (;;) {
                T v = qs.poll();
                if (v == null) {
                    return null;
                }
                K key = keySelector.apply(v);
                if (!hasValue) {
                    hasValue = true;
                    last = key;
                    return v;
                }

                if (!comparer.test(last, key)) {
                    last = key;
                    return v;
                }
                last = key;
                if (sourceMode != SYNC) {
                    upstream.request(1);
                }
            }
        }

    }
}