import java.io.IOException;
import java.io.InputStream;
import java.util.Iterator;
import java.util.Properties;

import org.apache.commons.configuration.ConfigurationRuntimeException;
import org.apache.commons.configuration.MapConfiguration;
import org.apache.commons.io.IOUtils;
import org.apache.commons.lang.StringUtils;
import org.apache.commons.lang.SystemUtils;

/**
 * created 12.07.2007
 * <p>
 * A configuration based on the environment variables.
 * 
 * @author Vasily Ivanov
 */
public class EnvironmentConfiguration extends MapConfiguration
{

  public EnvironmentConfiguration() throws IOException
  {
    super(getEnvVariables());
  }

  private static Properties getEnvVariables() throws IOException
  {
    Process p;
    Runtime r = Runtime.getRuntime();
    if (SystemUtils.IS_OS_WINDOWS_95 || SystemUtils.IS_OS_WINDOWS_98) {
      p = r.exec("command.com /c set");
    } else if (SystemUtils.IS_OS_WINDOWS) {
      p = r.exec("cmd.exe /c set");
    } else if (SystemUtils.IS_OS_UNIX) {
      p = r.exec("env");
    } else {
      throw new ConfigurationRuntimeException("OS is not recognised");
    }

    return readEnvVariables(p.getInputStream());
  }

  private static Properties readEnvVariables(final InputStream in) throws IOException
  {
    Properties props = new Properties();

    Iterator itr = IOUtils.readLines(in).iterator();
    while (itr.hasNext()) {
      String[] var = StringUtils.split((String) itr.next(), '=');
      props.setProperty(var[0], var[1]);
    }

    return props;
  }
  
}