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 integer values.
/**
 * Emits a range of integer values.
 */
public final class FlowableRange extends Flowable<Integer> {
    final int start;
    final int end;
    public FlowableRange(int start, int count) {
        this.start = start;
        this.end = start + count;
    }

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

    abstract static class BaseRangeSubscription extends BasicQueueSubscription<Integer> {
        private static final long serialVersionUID = -2252972430506210021L;

        final int end;

        int index;

        volatile boolean cancelled;

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

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

        @Nullable
        @Override
        public final Integer poll() {
            int 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 Integer> downstream;

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

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

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

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

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

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

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

        @Override
        void slowPath(long r) {
            long e = 0;
            int f = end;
            int i = index;
            ConditionalSubscriber<? super Integer> 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;
                }
            }
        }
    }
}