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.internal.fuseable.ConditionalSubscriber;
import io.reactivex.internal.subscriptions.*;
import io.reactivex.internal.util.BackpressureHelper;

Emits a range of long values.
/**
 * Emits a range of long values.
 */
public final class FlowableRangeLong extends Flowable<Long> {
    final long start;
    final long end;

    public FlowableRangeLong(long start, long count) {
        this.start = start;
        this.end = start + count;
    }

    @Override
    public void subscribeActual(Subscriber<? super Long> s) {
        if (s instanceof ConditionalSubscriber) {
            s.onSubscribe(new RangeConditionalSubscription(
                    (ConditionalSubscriber<? super Long>)s, start, end));
        } else {
            s.onSubscribe(new RangeSubscription(s, start, end));
        }
    }

    abstract static class BaseRangeSubscription extends BasicQueueSubscription<Long> {

        private static final long serialVersionUID = -2252972430506210021L;

        final long end;

        long index;

        volatile boolean cancelled;

        BaseRangeSubscription(long index, long end) {
            this.index = index;
            this.end = end;
        }

        @Override
        public final int requestFusion(int mode) {
            return mode & SYNC;
        }

        @Nullable
        @Override
        public final Long poll() {
            long i = index;
            if (i == end) {
                return null;
            }
            index = i + 1;
            return i;
        }

        @Override
        public final boolean isEmpty() {
            return index == end;
        }

        @Override
        public final void clear() {
            index = end;
        }

        @Override
        public final void request(long n) {
            if (SubscriptionHelper.validate(n)) {
                if (BackpressureHelper.add(this, n) == 0L) {
                    if (n == Long.MAX_VALUE) {
                        fastPath();
                    } else {
                        slowPath(n);
                    }
                }
            }
        }

        @Override
        public final void cancel() {
            cancelled = true;
        }

        abstract void fastPath();

        abstract void slowPath(long r);
    }

    static final class RangeSubscription extends BaseRangeSubscription {

        private static final long serialVersionUID = 2587302975077663557L;

        final Subscriber<? super Long> downstream;

        RangeSubscription(Subscriber<? super Long> actual, long index, long end) {
            super(index, end);
            this.downstream = actual;
        }

        @Override
        void fastPath() {
            long f = end;
            Subscriber<? super Long> a = downstream;

            for (long i = index; i != f; i++) {
                if (cancelled) {
                    return;
                }
                a.onNext(i);
            }
            if (cancelled) {
                return;
            }
            a.onComplete();
        }

        @Override
        void slowPath(long r) {
            long e = 0;
            long f = end;
            long i = index;
            Subscriber<? super Long> a = downstream;

            for (;;) {

                while (e != r && i != f) {
                    if (cancelled) {
                        return;
                    }

                    a.onNext(i);

                    e++;
                    i++;
                }

                if (i == f) {
                    if (!cancelled) {
                        a.onComplete();
                    }
                    return;
                }

                r = get();
                if (e == r) {
                    index = i;
                    r = addAndGet(-e);
                    if (r == 0L) {
                        return;
                    }
                    e = 0L;
                }
            }
        }
    }

    static final class RangeConditionalSubscription extends BaseRangeSubscription {

        private static final long serialVersionUID = 2587302975077663557L;

        final ConditionalSubscriber<? super Long> downstream;

        RangeConditionalSubscription(ConditionalSubscriber<? super Long> actual, long index, long end) {
            super(index, end);
            this.downstream = actual;
        }

        @Override
        void fastPath() {
            long f = end;
            ConditionalSubscriber<? super Long> a = downstream;

            for (long i = index; i != f; i++) {
                if (cancelled) {
                    return;
                }
                a.tryOnNext(i);
            }
            if (cancelled) {
                return;
            }
            a.onComplete();
        }

        @Override
        void slowPath(long r) {
            long e = 0;
            long f = end;
            long i = index;
            ConditionalSubscriber<? super Long> a = downstream;

            for (;;) {

                while (e != r && i != f) {
                    if (cancelled) {
                        return;
                    }

                    if (a.tryOnNext(i)) {
                        e++;
                    }

                    i++;
                }

                if (i == f) {
                    if (!cancelled) {
                        a.onComplete();
                    }
                    return;
                }

                r = get();
                if (e == r) {
                    index = i;
                    r = addAndGet(-e);
                    if (r == 0) {
                        return;
                    }
                    e = 0;
                }
            }
        }
    }
}