JMathTextField.java

/*
 *  MathExercisesJavaAppletBase
 * 
 * by Albert Zeyer / developed for Lehrstuhl A für Mathematik at the RWTH Aachen University
 * code under GPLv3+
 */
package applets.Termumformungen$in$der$Technik_08_Ethanolloesungen;

import javax.swing.JTextField;
import javax.swing.text.*;
import java.awt.*;
import java.awt.event.*;

public class JMathTextField extends JTextField {

	private static final long serialVersionUID = 3991754180692357067L;

	{
		this.addFocusListener(new FocusListener() {
			public void focusGained(FocusEvent e) {
				moveCaretPosition(0);
				setCaretPosition(getText().length());
			}
			public void focusLost(FocusEvent e) {}
		});

		this.addInputMethodListener(new InputMethodListener() {
			public void inputMethodTextChanged(final InputMethodEvent event) {
				//System.out.println(event);
				event.consume();
				JMathTextField.this.getInputContext().endComposition();
				if(event.getText() == null) return;
				if(event.getCommittedCharacterCount() > 0) return;
				final char c = event.getText().last();
				if(c == '^') {
					final KeyEvent ke = new KeyEvent(
							JMathTextField.this, KeyEvent.KEY_TYPED,
							EventQueue.getMostRecentEventTime(),
							0, KeyEvent.VK_UNDEFINED, c);
					JMathTextField.this.processKeyEvent(ke);
				}
			}
			public void caretPositionChanged(InputMethodEvent event) {}
		});
	}

	private OperatorTree operatorTree = new OperatorTree();
	public OperatorTree getOperatorTree() { return operatorTree; }

	protected void updateByOpTree(javax.swing.text.DocumentFilter.FilterBypass fb) {
		String oldStr = JMathTextField.this.getText();
		String newStr = operatorTree.toString();
		int commonStart = Utils.equalStartLen(oldStr, newStr);
		int commonEnd = Utils.equalEndLen(oldStr, newStr);
		if(commonEnd + commonStart >= Math.min(oldStr.length(), newStr.length()))
			commonEnd = Math.min(oldStr.length(), newStr.length()) - commonStart;

		try {
			fb.replace(commonStart, oldStr.length() - commonEnd - commonStart, newStr.substring(commonStart, newStr.length() - commonEnd), null);
		} catch (BadLocationException e) {
			// this should not happen. we should have checked this. this whole function should be safe
			throw new AssertionError(e);
		}	
	}
	
	@Override
	protected Document createDefaultModel() {
		PlainDocument d = (PlainDocument) super.createDefaultModel();

		d.setDocumentFilter(new DocumentFilter() {
			@Override
			public void insertString(FilterBypass fb, int offset,
					String string, AttributeSet attr)
					throws BadLocationException {					
				replace(fb, offset, 0, string, attr);
			}
			@Override
			public void remove(FilterBypass fb, int offset, int length)
					throws BadLocationException {
				replace(fb, offset, length, "", null);
			}
			@Override
			public void replace(FilterBypass fb, int replOffset, int replLen,
					String string, AttributeSet attrs)
					throws BadLocationException {
				String s = JMathTextField.this.getText();
				boolean insertedDummyChar = false;
				boolean insertedBrackets = false;
				String replStr = s.substring(replOffset, replOffset + replLen);

				if(string.matches(" |\\)") && replOffset + 1 <= s.length() && s.substring(replOffset, replOffset + 1).equals(string)) {
					JMathTextField.this.setCaretPosition(replOffset + 1);
					return;
				}

				if(string.isEmpty() && replStr.equals(" ")) {
					JMathTextField.this.setCaretPosition(replOffset);
					return;
				}

				string = string.replace(" ", "");
				if(string.isEmpty() && replStr.equals("(")) {
					int count = 1;
					while(replOffset + replLen < s.length()) {
						replLen++;
						replStr = s.substring(replOffset, replOffset + replLen); // just update in case we need it later again
						if(replStr.charAt(0) == '(') count++;
						else if(replStr.charAt(0) == ')') count--;
						if(count == 0) break;
					}
				}
				else if(string.isEmpty() && replStr.equals(")")) {
					int count = -1;
					while(replOffset > 0) {
						replOffset--;
						replLen++;
						replStr = s.substring(replOffset, replOffset + replLen);
						if(replStr.charAt(0) == '(') count++;
						else if(replStr.charAt(0) == ')') count--;
						if(count == 0) break;
					}
				}
				
				if(string.matches("\\+|-|\\*|/|\\^|=")) {
					if(s.substring(replOffset+replLen).matches("( *(\\+|-|∙|/|\\^|=|\\)).*)|")) {
						string = string + "_";
						insertedDummyChar = true;
					} else if(s.substring(replOffset+replLen).matches(" .*")) {
						string = "_" + string;
						insertedDummyChar = true;
					}
				}
				else if(string.matches("\\(")) {
					if(Utils.reveresedString(s.substring(0,replOffset)).matches("( )*([^\\+\\-∙/\\^= ].*|)") || replStr.equals("_")) {
						string = "(_)";
						insertedDummyChar = true;
					}
					else if(!replStr.isEmpty()) {
						string = "(" + replStr + ")";
						insertedBrackets = true;
					}
					else
						return; // ignore this
				}
				else if(string.matches("\\)"))
					return; // ignore that
				
				// situation: A = B, press DEL -> make it A = _
				if(string.isEmpty() && Utils.reveresedString(s.substring(0,replOffset)).matches("( )*(\\+|-|∙|/|\\^|=).*") && !replStr.matches("_|\\+|-|∙|/|\\^|=")) {
					string = "_";
					insertedDummyChar = true;
				}
				else if(string.isEmpty() && Utils.reveresedString(s.substring(0,replOffset)).matches("( )*(\\+|-|∙|/|\\^|=).*") && replStr.equals("_")) {
					while(s.substring(replOffset-1,replOffset).equals(" ")) {
						replOffset--;
						replLen++;
					}
					replOffset--; replLen++; // go just before the op
					// just update in case we need it later again
					// noinspection UnusedAssignment
					replStr = s.substring(replOffset, replOffset + replLen);
				}

				setNewString(fb, s.substring(0, replOffset) + string + s.substring(replOffset + replLen));
				
				if(insertedDummyChar) {
					int p = JMathTextField.this.getText().indexOf('_');
					if(p >= 0) {
						JMathTextField.this.setCaretPosition(p);
						JMathTextField.this.moveCaretPosition(p + 1);						
					}
				}
				else if(insertedBrackets) {
					// move just before the ')'
					if(JMathTextField.this.getCaretPosition() > 0)
						JMathTextField.this.setCaretPosition(JMathTextField.this.getCaretPosition() - 1);
				}
			}

			synchronized void setNewString(FilterBypass fb, String tempStr) throws BadLocationException {
				operatorTree = OTParser.parse(tempStr, null);
				JMathTextField.this.updateByOpTree(fb);
			}
		});
		
		return d;
	}

}