org.metafacture.metamorph.functions.Unique Maven / Gradle / Ivy

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/*
 * Copyright 2013, 2014 Deutsche Nationalbibliothek
 *
 * Licensed 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.metafacture.metamorph.functions;

import java.util.HashSet;
import java.util.Set;

import org.metafacture.metamorph.api.helpers.AbstractStatefulFunction;

/**
 * Checks whether the received value was not received before.
 *
 * @author Markus Michael Geipel
 *
 */
public final class Unique extends AbstractStatefulFunction {

    private static final String ENTITY = "entity";
    private static final String NAME = "name";
    private static final String VALUE = "value";

    private final Set set = new HashSet();

    private boolean uniqueInEntity;

    private KeyGenerator keyGenerator = new KeyGenerator() {
        @Override
        public String createKey(final String name, final String value) {
            return name + "\0" + value;
        }
    };

    @Override
    public String process(final String value) {
        final String key = keyGenerator.createKey(getLastName(), value);
        if (set.contains(key)) {
            return null;
        }
        set.add(key);
        return value;
    }

    @Override
    protected void reset() {
        set.clear();
    }

    @Override
    protected boolean doResetOnEntityChange() {
        return uniqueInEntity;
    }

    public void setIn(final String scope) {
        uniqueInEntity = ENTITY.equals(scope);
    }

    public void setPart(final String part) {
        if (NAME.equals(part)) {
            keyGenerator = new KeyGenerator() {
                @Override
                public String createKey(final String name, final String value) {
                    return name;
                }
            };
        } else if (VALUE.equals(part)) {
            keyGenerator = new KeyGenerator() {
                @Override
                public String createKey(final String name, final String value) {
                    return value;
                }
            };
        }
    }

    /**
     * To implement different uniqueness strategies
     */
    private interface KeyGenerator {
        String createKey(String name, String value);
    }

}