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A library to reliably execute external processes from within the JVM
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/*
 * 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
 *
 *      https://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.commons.exec.util;

import java.util.HashMap;
import java.util.Map;
import java.util.Objects;

/**
 * Helper classes to manipulate maps to pass substition map to the CommandLine. This class is not part of the public API and could change without warning.
 */
public class MapUtils {
    /**
     * Clones a map.
     *
     * @param source the Map to clone.
     * @param     the map key type.
     * @param     the map value type.
     * @return the cloned map.
     */
    public static  Map copy(final Map source) {
        return source == null ? null : new HashMap<>(source);
    }

    /**
     * Clones the lhs map and add all things from the rhs map.
     *
     * @param lhs the first map.
     * @param rhs the second map.
     * @param  the map key type.
     * @param  the map value type.
     * @return the merged map.
     */
    public static  Map merge(final Map lhs, final Map rhs) {
        Map result = null;
        if (lhs == null || lhs.isEmpty()) {
            result = copy(rhs);
        } else if (rhs == null || rhs.isEmpty()) {
            result = copy(lhs);
        } else {
            result = copy(lhs);
            result.putAll(rhs);
        }
        return result;
    }

    /**
     * Clones a map and prefixes the keys in the clone, e.g. for mapping "JAVA_HOME" to "env.JAVA_HOME" to simulate the behavior of Ant.
     *
     * @param source the source map.
     * @param prefix the prefix used for all names.
     * @param     the map key type.
     * @param     the map value type.
     * @return the clone of the source map.
     */
    public static  Map prefix(final Map source, final String prefix) {
        if (source == null) {
            return null;
        }
        final Map result = new HashMap<>();
        for (final Map.Entry entry : source.entrySet()) {
            result.put(prefix + '.' + Objects.toString(entry.getKey(), ""), entry.getValue());
        }
        return result;
    }

    /**
     * Constructs a new instance.
     *
     * @deprecated Will be private in the next major version.
     */
    @Deprecated
    public MapUtils() {
        // empty
    }
}