nifi-commons/nifi-record/src/main/java/org/apache/nifi/serialization/record/PushBackRecordSet.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.nifi.serialization.record;

import java.io.IOException;

public class PushBackRecordSet implements RecordSet {
    private final RecordSet original;
    private Record pushback;

    public PushBackRecordSet(final RecordSet original) {
        this.original = original;
    }

    @Override
    public RecordSchema getSchema() throws IOException {
        return original.getSchema();
    }

    @Override
    public Record next() throws IOException {
        if (pushback != null) {
            final Record record = pushback;
            pushback = null;
            return record;
        }

        return original.next();
    }

    public void pushback(final Record record) {
        if (pushback != null) {
            throw new IllegalStateException("RecordSet already has a Record pushed back. Cannot push back more than one record at a time.");
        }

        this.pushback = record;
    }

    public boolean isAnotherRecord() throws IOException {
        if (pushback != null) {
            return true;
        }

        final Record nextRecord = next();
        if (nextRecord == null) {
            return false;
        }

        pushback(nextRecord);
        return true;
    }
}