OptionListConverter.java

/*
 * Copyright (c) 2015. David Sowerby
 *
 * 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 uk.q3c.krail.core.data;

import com.google.common.base.Splitter;
import org.apache.commons.lang3.StringEscapeUtils;
import uk.q3c.krail.core.option.OptionList;

import javax.annotation.Nonnull;
import java.util.ArrayList;
import java.util.List;

import static com.google.common.base.Preconditions.checkNotNull;


/**
 * Converts a OptionList<?><X> where X is an element with its own Converter, to and from a String representation (specifically a single String with elements
 * quoted and comma-separated as defined by {@link StringEscapeUtils#escapeCsv(String)})
 * <p>
 * Created by David Sowerby on 04/08/15.
 */
public class OptionListConverter<E> {

    public final static String separator = "~~";
    private OptionElementConverter converter;


    public OptionListConverter(@Nonnull OptionElementConverter converter) {
        checkNotNull(converter);
        this.converter = converter;
    }


    /**
     * {@inheritDoc}
     */

    public String convertToString(@Nonnull OptionList<E> value) {
        checkNotNull(value);
        if (value.isEmpty()) {
            return "";
        }

        StringBuilder buf = new StringBuilder();
        boolean first = true;
        for (E e : value.getList()) {
            if (!first) {
                buf.append(separator);
            } else {
                first = false;
            }
            String s = converter.convertValueToString(e);
            buf.append(StringEscapeUtils.escapeCsv(s));
        }
        return buf.toString();
    }


    public <E> OptionList<E> convertToModel(@Nonnull OptionList<E> defaultValue, @Nonnull String value) {
        checkNotNull(value);
        checkNotNull(defaultValue);
        Class<E> elementClass = defaultValue.getElementClass();
        if (value.isEmpty()) {
            return new OptionList<>(elementClass);
        }
        final List<String> strings = Splitter.on(separator)
                                             .splitToList(value);
        List<E> elementList = new ArrayList<>();
        strings.forEach(s -> {
            String unescaped = StringEscapeUtils.unescapeCsv(s);
            elementList.add(converter.convertStringToValue(elementClass, unescaped));
        });
        return new OptionList<E>(elementList, elementClass);
    }
}