/*
 * RTree.java
 *
 * Copyright (C) 1997 Shugo Maeda
 *
 * 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.
 */

package JP.ac.osaka_u.ender.util.regex;

/*
 * A regular expression tree node.
 */
class RTree {
    /* operations */
    public static final int OP_EMPTY	= 0;  // empty
    public static final int OP_CHAR	= 1;  // normal character
    public static final int OP_CONCAT	= 2;  // XY
    public static final int OP_UNION	= 3;  // X|Y
    public static final int OP_CLOSURE	= 4;  // X*
    public static final int OP_LHEAD	= 5;  // '^'
    public static final int OP_LTAIL	= 6;  // '$'

    private int operation;
    private Chars chars;
    private RTree left;
    private RTree right;

    /*
     * Constructs a leaf.
     */
    public RTree(Chars chars) {
	this(OP_CHAR, chars, null, null);
    }

    /*
     * Constructs a node.
     */
    public RTree(int operation, RTree left, RTree right) {
	this(operation, null, left, right);
    }

    /*
     * Constructs a node.
     */
    public RTree(int operation, Chars chars, RTree left, RTree right) {
	this.operation = operation;
	this.chars = chars;
	this.left = left;
	this.right = right;
    }

    public int operation() {
	return operation;
    }

    public Chars chars() {
	return chars;
    }

    public RTree left() {
	return left;
    }

    public RTree right() {
	return right;
    }

    public void removeChars(Chars cs) {
	if (operation == RTree.OP_CHAR) {
	    if (chars.hasChars(cs)) {
		if (cs.begin() <= chars.begin() && chars.end() <= cs.end()) {
		    /* Don't match to any chars. c1 > c2! */
		    chars.setType(Chars.NONE);
		    return;
		} else if (cs.begin() <= chars.end() && chars.end() <= cs.end()) {
		    chars.setEnd((char)(cs.begin() - 1));
		} else if (cs.begin() <= chars.begin() && chars.begin() <= cs.end()) {
		    chars.setBegin((char)(cs.end() + 1));
		} else if (chars.begin() <= cs.begin() && cs.end() <= chars.end()) {
		    operation = RTree.OP_UNION;
		    left = new RTree(new Chars(chars.begin(), (char)(cs.begin() - 1)));
		    right = new RTree(new Chars((char)(cs.end() + 1), chars.end()));
		}
	    }
	}	    
	if (left != null) left.removeChars(cs);
	if (right != null) right.removeChars(cs);
    }
}