001/*
002 * (C) Copyright 2019 Nuxeo SA (http://nuxeo.com/) and others.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 *
016 * Contributors:
017 *     bdelbosc
018 */
019package org.nuxeo.lib.stream.computation;
020
021import java.util.Map;
022
023import org.nuxeo.lib.stream.log.LogOffset;
024
025/**
026 * Record filtering enables to modify/skip record while it is append or read from a stream. Filter can also be used to add custom code.
027 *
028 * @since 11.1
029 */
030public interface RecordFilter {
031
032    /**
033     * Initialiaze the filter.
034     */
035    default void init(Map<String, String> options) {
036        // nothing
037    }
038
039    /**
040     * Called before appending a record to a stream. This hook enables to change the record or to skip it when returning
041     * null.
042     *
043     * @param record the record that will be appended to a stream
044     */
045    default Record beforeAppend(Record record) {
046        return record;
047    }
048
049    /**
050     * Called after a record is appended to a stream.
051     *
052     * @param record the written record
053     * @param offset the record's offset
054     */
055    default void afterAppend(Record record, LogOffset offset) {
056        // nothing
057    }
058
059    /**
060     * Called after reading a record. This hook enables to change the record or to skip it when returning null.
061     *
062     * @param record the record
063     * @param offset the offset of the record
064     */
065    default Record afterRead(Record record, LogOffset offset) {
066        return record;
067    }
068}