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package org.codehaus.plexus.interpolation.os;

/*
 * The MIT License
 *
 * Copyright (c) 2004, The Codehaus
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is furnished to do
 * so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

import java.io.IOException;
import java.util.Locale;
import java.util.Map;
import java.util.Properties;

/**
 * NOTE: This class was copied from plexus-utils, to allow this library
 * to stand completely self-contained.
 *
 * @author Trygve Laugstøl 
 */
public final class OperatingSystemUtils {

    private static EnvVarSource envVarSource = new DefaultEnvVarSource();

    private OperatingSystemUtils() {}

    public static Properties getSystemEnvVars() throws IOException {
        return getSystemEnvVars(true);
    }

    /**
     * Return the shell environment variables. If caseSensitive == true, then envar
     * keys will all be upper-case.
     *
     * @param caseSensitive Whether environment variable keys should be treated case-sensitively.
     * @return Properties object of (possibly modified) envar keys mapped to their values.
     * @throws IOException in case of an error.
     */
    public static Properties getSystemEnvVars(boolean caseSensitive) throws IOException {
        Properties envVars = new Properties();
        Map envs = envVarSource.getEnvMap();
        for (String key : envs.keySet()) {
            String value = envs.get(key);
            if (!caseSensitive) {
                key = key.toUpperCase(Locale.ENGLISH);
            }
            envVars.put(key, value);
        }
        return envVars;
    }

    /**
     * Set the source object to load the environment variables from.
     * Default implementation should suffice. This is mostly for testing.
     * @param source the EnvVarSource instance that loads the environment variables.
     *
     * @since 3.1.2
     */
    public static void setEnvVarSource(EnvVarSource source) {
        envVarSource = source;
    }

    /**
     * Defines the functionality to load a Map of environment variables.
     *
     * @since 3.1.2
     */
    public interface EnvVarSource {
        public Map getEnvMap();
    }

    /**
     * Default implementation to load environment variables.
     *
     * @since 3.1.2
     */
    public static class DefaultEnvVarSource implements EnvVarSource {

        public Map getEnvMap() {
            return System.getenv();
        }
    }
}