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/***
 * Julia
 * Copyright (C) 2005-2006 INRIA, France Telecom, USTL
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Contact: [email protected]
 *
 * Author: Lionel Seinturier
 */

package org.objectweb.fractal.koch.loader;

import java.util.ArrayList;
import java.util.List;

import org.objectweb.fractal.julia.loader.Tree;

/**
 * A class for parsing string representations of {@link Tree} structures.
 * These string representations follow a LISP like syntax such as
 * "(foo (bar foo))".
 * 
 * @author Lionel Seinturier 
 * @since 2.5
 */
public class TreeParser {
    
    /** The string to parse. */
    private String str;
    
    public TreeParser( String str ) {
        this.str = str;
        read();
    }

    /**
     * Copy/paste from
     * {@link org.objectweb.fractal.julia.loader.BasicLoader#parseTree()}.
     * 
     * Recursive method to parse a tree. The first character of the tree to be
     * parsed is supposed to have already been read, and available in {@link #car
     * car}. After parsing, the character immediately following the parsed tree
     * is also supposed to have already been parsed, and available in {@link #car
     * car}.
     *
     * @return a tree parsed from {@link #str}.
     * @throws TreeParserException if a syntax error is found.
     */
    public Tree parseTree() throws TreeParserException {
      int c = car;
      if (c == -1) {
        throw new TreeParserException("Unexpected end of string");
      } else if (c == ')') {
        throw new TreeParserException("Unmatched closing parenthesis");
      } else if (c == '(') {
        // parses a tree of the form "(subTree1 ... subTreeN)"
        read();
        List subTrees = new ArrayList();
        while (true) {
          c = parseSpaces();
          if (c == ')') {
            read();
            return new Tree((Tree[])subTrees.toArray(new Tree[subTrees.size()]));
          } else {
            subTrees.add(parseTree());
          }
        }
      } else {
        // parses a tree of the form "tree"
        StringBuffer buf = new StringBuffer();
        while (true) {
          buf.append((char)c);
          c = read();
          if (c == -1 || c == ' ' || c == '\t' || c == '\n' ||
              c == '\r' || c == '#' || c == '(' || c == ')')
          {
            car = c;
            return new Tree(buf.toString());
          }
        }
      }
    }

    /**
     * Copy/paste from
     * {@link org.objectweb.fractal.julia.loader.BasicLoader#parseTree()}.
     * 
     * Parses spaces and comments until a non space character is found.
     *
     * @return the first non space character found, which is also stored in
     *      {@link #car car}.
     */
    private int parseSpaces() {
      int c = car;
      while (c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '#') {
        if (c == '#') {
          // parses a single line comment
          do {
            c = read();
          } while (c != '\n' && c != '\r');
        }
        c = read();
      }
      return car = c;
    }
    
    private int read() {
        car = (idx>=str.length()) ? -1 : str.charAt(idx);
        idx++;
        return car;
    }

    /** Last character read from {@link #str}. */
    private int car;
    
    /** Index of the next character to be read from {@link #str}. */
    private int idx = 0;
}