import java.io.IOException;
import java.nio.file.Path;

/**
 * Realization of class dedicated to the control
 * of GNU Screen sessions
 * <p>
 * Created by daniil on 02.04.16.
 */
public class ScreenLib {

    /**
     * Start a screen with certain ID
     * and execute a command inside it
     *
     * @param screenName Screen ID
     * @param runPath    Home path of started screen
     * @param command    Command [+args] to execute inside the screen
     * @throws IOException
     */
    public void startScreen(String screenName, Path runPath, String... command) throws IOException {
        assert screenName != null && screenName.length() != 0;
        assert runPath != null;

        // Merge two arrays
        String[] commandBase = new String[command.length + 3];
        commandBase[0] = "screen";
        commandBase[1] = "-dmS";
        commandBase[2] = screenName;

        System.arraycopy(command, 0, commandBase, 3, command.length);

        ProcessBuilder processBuilder = new ProcessBuilder(commandBase);
        processBuilder.directory(runPath.toFile());
        processBuilder.start();
    }

    /**
     * Send command to specific screen
     *
     * @param screenName Screen ID
     * @param command    Command to send
     * @throws IOException
     */
    public void sendCommand(String screenName, String command) throws IOException {
        assert screenName != null;
        assert command != null;

        ProcessBuilder processBuilder = new ProcessBuilder("screen", "-S", screenName, "-p", "0", "-X", "stuff", String.format(command + "%n"));
        processBuilder.start();
    }

    /**
     * Force terminate a screen session
     *
     * @param screenName Screen ID
     * @throws IOException
     */
    public void killScreen(String screenName) throws IOException {
        assert screenName != null;

        ProcessBuilder processBuilder = new ProcessBuilder("screen", "-X", "-S", screenName, "quit");
        processBuilder.start();
    }
}