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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
 *
 *      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.apache.commons.exec.environment;

import java.io.BufferedReader;
import java.io.IOException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import org.apache.commons.exec.CommandLine;

/**
 * Helper class to determine the environment variable
 * for VMS.
 */
public class OpenVmsProcessingEnvironment extends DefaultProcessingEnvironment {

    /**
     * Find the list of environment variables for this process.
     *
     * @return a amp containing the environment variables
     * @throws IOException the operation failed
     */    
    protected synchronized Map createProcEnvironment() throws IOException {
        if (procEnvironment == null) {
            procEnvironment = new HashMap();

            BufferedReader in = runProcEnvCommand();

            procEnvironment = addVMSLogicals(procEnvironment, in);
            return procEnvironment;
        }

        return procEnvironment;
    }

    /**
     * Determine the OS specific command line to get a list of environment
     * variables.
     *
     * @return the command line
     */    
    protected CommandLine getProcEnvCommand() {
        CommandLine commandLine = new CommandLine("show");
        commandLine.addArgument("logical");
        return commandLine;
    }

    /**
     * This method is VMS specific and used by getProcEnvironment(). Parses VMS
     * logicals from in and adds them to environment.
     * in is expected to be the output of "SHOW LOGICAL". The
     * method takes care of parsing the output correctly as well as making sure
     * that a logical defined in multiple tables only gets added from the
     * highest order table. Logicals with multiple equivalence names are mapped
     * to a variable with multiple values separated by a comma (,).
     *
     * @param environment the current environment
     * @param in the reader from the process to determine VMS env variables
     * @return the updated environment
     * @throws IOException operation failed
     */
    private Map addVMSLogicals(final Map environment,
            final BufferedReader in) throws IOException {
        String line;
        HashMap logicals = new HashMap();
        String logName = null, logValue = null, newLogName;
        while ((line = in.readLine()) != null) {
            // parse the VMS logicals into required format ("VAR=VAL[,VAL2]")
            if (line.startsWith("\t=")) {
                // further equivalence name of previous logical
                if (logName != null) {
                    logValue += "," + line.substring(4, line.length() - 1);
                }
            } else if (line.startsWith("  \"")) {
                // new logical?
                if (logName != null) {
                    logicals.put(logName, logValue);
                }
                int eqIndex = line.indexOf('=');
                newLogName = line.substring(3, eqIndex - 2);
                if (logicals.containsKey(newLogName)) {
                    // already got this logical from a higher order table
                    logName = null;
                } else {
                    logName = newLogName;
                    logValue = line.substring(eqIndex + 3, line.length() - 1);
                }
            }
        }
        // Since we "look ahead" before adding, there's one last env var.
        if (logName != null) {
            logicals.put(logName, logValue);
        }

        for (Iterator i = logicals.keySet().iterator(); i.hasNext();) {
            String logical = (String) i.next();
            environment.put(logical, logicals.get(logical));
        }
        return environment;
    }
}