Console.java

/*
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 2 of the License, or (at your option) any later
 * version. You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

package org.aitools.programd.interfaces;

import java.io.OutputStreamWriter;
import java.io.PrintStream;

import org.aitools.programd.Core;
import org.aitools.programd.Core.Status;
import org.aitools.programd.interfaces.shell.Shell;
import org.apache.log4j.Logger;

/**
 * Creating a Console essentially means that loggers (as configured) will (may) also print output to the console.
 * 
 * @author <a href="mailto:noel@aitools.org">Noel Bush</a>
 */
public class Console {

  /** The Core to which this console is (may be) attached. */
  private Core _core;

  /** The stdout handler. */
  private ConsoleStreamAppender stdOutAppender;

  /** The stderr handler. */
  private ConsoleStreamAppender stdErrAppender;

  /** The Shell that will (may) be activated for this console. */
  private Shell _shell;

  /**
   * Creates a <code>Console</code> with default output streams.
   */
  public Console() {
    this.initialize(System.out, System.err);
  }

  /**
   * Creates a <code>Console</code> with specified input, output and prompt streams (this implies that a shell will be
   * enabled).
   * 
   * @param out the stream to use for normal messages
   * @param err the stream to use for error messages
   */
  public Console(PrintStream out, PrintStream err) {
    this.initialize(out, err);
  }

  /**
   * Adds the given Shell to the Console
   * 
   * @param shell the Shell to add
   * @param core the core to which to attach the Shell
   */
  public void addShell(Shell shell, Core core) {
    this._shell = shell;
    this._shell.attachTo(core);
    if (this.stdOutAppender != null) {
      this.stdOutAppender.watch(this._shell);
    }
    if (this.stdErrAppender != null) {
      this.stdErrAppender.watch(this._shell);
    }
  }

  /**
   * Attaches the console to the given core.
   * 
   * @param core the core to which to attach
   */
  public void attachTo(Core core) {
    this._core = core;

    if (this._core.getSettings().useShell()) {
      this.addShell(new Shell(), this._core);
    }
    else {
      Logger.getLogger("programd").info("Interactive shell disabled.  Awaiting SIGHUP to shut down.");
    }
  }

  /**
   * Sets up the stdout and stderr appenders (if they are defined in the log4j configuration).
   * 
   * @param out the stream to use for normal output messages
   * @param err the stream to use for error messages
   */
  protected void initialize(PrintStream out, PrintStream err) {
    this.stdOutAppender = (ConsoleStreamAppender) Logger.getLogger("programd").getAppender("stdout");
    if (this.stdOutAppender != null) {
      this.stdOutAppender.setWriter(new OutputStreamWriter(out));
    }

    this.stdErrAppender = (ConsoleStreamAppender) Logger.getLogger("programd").getAppender("stderr");
    if (this.stdErrAppender != null) {
      this.stdErrAppender.setWriter(new OutputStreamWriter(err));
    }
  }

  /**
   * Starts the attached shell (if one exists and the shell is enabled).
   */
  public void startShell() {
    if (this._core.getSettings().useShell()) {
      this._shell.start();
    }

    // Now just run as long as the core status stays at READY.
    while (this._core.getStatus() == Status.READY) {
      try {
        Thread.sleep(1000);
      }
      catch (InterruptedException e) {
        this._core.getLogger().warn("Console was interrupted; shell will not run anymore.");
      }
    }
  }
}