/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.tinkerpop.gremlin.process.traversal.step.filter;

import org.apache.tinkerpop.gremlin.process.traversal.Step;
import org.apache.tinkerpop.gremlin.process.traversal.step.Bypassing;
import org.apache.tinkerpop.gremlin.process.traversal.step.FilteringBarrier;
import org.apache.tinkerpop.gremlin.process.traversal.step.GValue;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.ExpandableStepIterator;
import org.apache.tinkerpop.gremlin.process.traversal.traverser.util.TraverserSet;
import org.apache.tinkerpop.gremlin.process.traversal.util.FastNoSuchElementException;
import org.apache.tinkerpop.gremlin.util.iterator.IteratorUtils;

import java.util.List;
import java.util.NoSuchElementException;

public interface TailGlobalStepContract<S> extends Step<S, S>, Bypassing, FilteringBarrier<TraverserSet<S>> {

    /**
     * Concrete implementations of this contract that can be referenced as TinkerPop implementations.
     */
    List<Class<? extends Step>> CONCRETE_STEPS = List.of(TailGlobalStep.class, TailGlobalStepPlaceholder.class);

    Long getLimit();

    default GValue<Long> getLimitAsGValue() {
        return GValue.of(getLimit());
    }

    ExpandableStepIterator<S> getStarts();

    default TraverserSet<S> getEmptyBarrier() {
        return new TraverserSet<>();
    }

    default boolean hasNextBarrier() {
        return this.getStarts().hasNext();
    }

    default TraverserSet<S> nextBarrier() throws NoSuchElementException {
        if (!this.getStarts().hasNext())
            throw FastNoSuchElementException.instance();
        final TraverserSet<S> barrier = (TraverserSet<S>) this.getTraversal().getTraverserSetSupplier().get();
        while (this.getStarts().hasNext()) {
            barrier.add(this.getStarts().next());
        }
        return barrier;
    }

    default void addBarrier(final TraverserSet<S> barrier) {
        IteratorUtils.removeOnNext(barrier.iterator()).forEachRemaining(traverser -> {
            traverser.setSideEffects(this.getTraversal().getSideEffects());
            this.addStart(traverser);
        });
    }
}
