/*
 * 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.hadoop.structure.io;

import org.apache.tinkerpop.gremlin.hadoop.structure.HadoopGraph;
import org.apache.tinkerpop.gremlin.hadoop.structure.HadoopVertex;
import org.apache.tinkerpop.gremlin.process.traversal.util.FastNoSuchElementException;
import org.apache.tinkerpop.gremlin.structure.Vertex;

import java.io.IOException;

/**
 * @author Marko A. Rodriguez (http://markorodriguez.com)
 */
public final class HadoopVertexIterator extends HadoopElementIterator<Vertex> {

    private HadoopVertex nextVertex = null;

    public HadoopVertexIterator(final HadoopGraph graph) throws IOException {
        super(graph);
    }

    @Override
    public Vertex next() {
        try {
            if (this.nextVertex != null) {
                final Vertex temp = this.nextVertex;
                this.nextVertex = null;
                return temp;
            } else {
                while (!this.readers.isEmpty()) {
                    if (this.readers.peek().nextKeyValue())
                        return new HadoopVertex(this.readers.peek().getCurrentValue().get(), this.graph);
                    else
                        this.readers.remove().close();
                }
            }
            throw FastNoSuchElementException.instance();
        } catch (final Exception e) {
            throw new IllegalStateException(e.getMessage(), e);
        }
    }

    @Override
    public boolean hasNext() {
        try {
            if (null != this.nextVertex) return true;
            else {
                while (!this.readers.isEmpty()) {
                    if (this.readers.peek().nextKeyValue()) {
                        this.nextVertex = new HadoopVertex(this.readers.peek().getCurrentValue().get(), this.graph);
                        return true;
                    } else
                        this.readers.remove().close();
                }
            }
        } catch (final Exception e) {
            throw new IllegalStateException(e.getMessage(), e);
        }
        return false;
    }
}