/* TclShell: a simple Tcl shell for Jacl
 *
 * Copyright (c) 1998 The Regents of the University of California.
 *       All Rights Reserved.  See the COPYRIGHT file for details.
 */

package tutorial.tcltk98;
 
import tcl.lang.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;

public class TclShell extends Panel {

  // The command input
  private StringBuffer commandBuffer = new StringBuffer();

  // The Tcl interpreter
  private Interp tclInterp = new Interp();

  // The TextArea widget for displaying commands and results
  public TextArea textArea;

  // Prompts
  public String mainPrompt = "% ";
  public String contPrompt = "> ";

  // Cursors
  private int promptCursor = 0;
  private int commandCursor = 0;

  // History
  public int historyLength = 10;
  private int historyCursor = 0;
  private Vector historyCommands = new Vector();

  // Platform dependent newline
  private static String newline = System.getProperty("line.separator");

  // Create a new Shell instance
  public TclShell () {
    // Graphics part
    super(new BorderLayout());
    textArea = new TextArea("", 10, 40, TextArea.SCROLLBARS_BOTH);
    add("Center", textArea);
    
    // Event handling part
    textArea.addKeyListener(new ShellKeyListener());

    // Initialize the interpreter
    try {
      tclInterp.setVar("tclShell",
         ReflectObject.newInstance(tclInterp, this), 0);
      tclInterp.eval("proc puts {s} {global tclShell; $tclShell putText $s\\n}");
    }
    catch (TclException e) {
      System.out.println(tclInterp.getResult());
    }
  }

  // Override this to initialize the prompt. We need to do
  // because we can't write to the TextArea until the peer
  // has been created
  public void addNotify () {
    super.addNotify();
    putText(mainPrompt);
  }

  // Print output to the console, update the prompt cursor
  public void putText (String s) {
    if (s.length() != 0) {
      textArea.append(s);
      promptCursor += s.length();
      textArea.setCaretPosition(promptCursor);
    }
  }

  // Evaluate the command so far, if possible, printing
  // a continuation prompt if not.
  protected void evalCommand () {
    String newtext = textArea.getText().substring(promptCursor);
    promptCursor += newtext.length();
    if (commandBuffer.length() > 0) {
      commandBuffer.append("\n");
    }
    commandBuffer.append(newtext);
    String command = commandBuffer.toString();

    if (tclInterp.commandComplete(command)) {
      // Process it
      putText("\n");
      Cursor oldCursor = textArea.getCursor();
      textArea.setCursor(new Cursor(Cursor.WAIT_CURSOR));
      try {
	tclInterp.eval(command);
      }
      catch (TclException e) {
	// ignore
      }
      String result = tclInterp.getResult().toString();
      if (result.length() > 0) {
	putText(result + "\n" + mainPrompt);
      } else {
	putText(mainPrompt);
      }
      commandBuffer.setLength(0);
      commandCursor = promptCursor;
      textArea.setCursor(oldCursor);
      updateHistory(command);
    } else {
      putText("\n" + contPrompt);
    }
  }

  // Update the command history
  void updateHistory (String command) {
      historyCursor = 0;
      if (historyCommands.size() == historyLength) {
	historyCommands.removeElementAt(0);
      }
      historyCommands.addElement(command);
  }

  // Replace the command with an entry from the history
  void nextCommand () {
    String text;
    if (historyCursor == 0) {
      text = "";
    } else {
      historyCursor --;
      text = (String)historyCommands.elementAt(
           historyCommands.size() - historyCursor - 1);
    }
    textArea.replaceRange(text, commandCursor, textArea.getText().length());
  }

  void previousCommand () {
    String text;
    if (historyCursor == historyCommands.size()) {
      return;
    } else {
      historyCursor ++;
      text = (String)historyCommands.elementAt(
            historyCommands.size() - historyCursor);
    }
    textArea.replaceRange(text, commandCursor, textArea.getText().length());
  }

  // The key listener
  class ShellKeyListener extends KeyAdapter {
    public void keyPressed (KeyEvent keyEvent) {
      // Process keys
      switch (keyEvent.getKeyCode()) {
      case KeyEvent.VK_ENTER:
	keyEvent.consume();
	evalCommand();
	break;
      case KeyEvent.VK_BACK_SPACE:
	if (textArea.getCaretPosition() == promptCursor) {
	  keyEvent.consume(); // don't backspace over prompt!
	}
	break;
      case KeyEvent.VK_LEFT:
	if (textArea.getCaretPosition() == promptCursor) {
	  keyEvent.consume();
	}
	break;
      case KeyEvent.VK_UP:
	previousCommand();
	keyEvent.consume();
	break;
      case KeyEvent.VK_DOWN:
	nextCommand();
	keyEvent.consume();
	break;
      default:
	// Otherwise we got a regular character. Don't consume it,
	// and TextArea will take care of displaying it.
      }
    }
  }
}