hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/backend/query/EdgesQueryIterator.java

/*
 * 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.hugegraph.backend.query;

import java.util.Iterator;
import java.util.List;

import org.apache.hugegraph.backend.id.Id;
import org.apache.hugegraph.backend.tx.GraphTransaction;
import org.apache.hugegraph.type.define.Directions;

public class EdgesQueryIterator implements Iterator<Query> {

    private final List<Id> labels;
    private final Directions directions;
    private final long limit;
    private final Iterator<Id> sources;

    public EdgesQueryIterator(Iterator<Id> sources,
                              Directions directions,
                              List<Id> labels,
                              long limit) {
        this.sources = sources;
        this.labels = labels;
        this.directions = directions;
        // Traverse NO_LIMIT 和 Query.NO_LIMIT 不同
        this.limit = limit < 0 ? Query.NO_LIMIT : limit;
    }

    @Override
    public boolean hasNext() {
        return sources.hasNext();
    }

    @Override
    public Query next() {
        Id sourceId = this.sources.next();
        ConditionQuery query = GraphTransaction.constructEdgesQuery(sourceId,
                                                                    this.directions,
                                                                    this.labels);
        if (this.limit != Query.NO_LIMIT) {
            query.limit(this.limit);
            query.capacity(this.limit);
        } else {
            query.capacity(Query.NO_CAPACITY);
        }
        return query;
    }
}