/*
 *                 Sun Public License Notice
 *
 * The contents of this file are subject to the Sun Public License
 * Version 1.0 (the "License"). You may not use this file except in
 * compliance with the License. A copy of the License is available at
 * http://www.sun.com/
 *
 * The Original Code is NetBeans. The Initial Developer of the Original
 * Code is Sun Microsystems, Inc. Portions Copyright 1997-2002 Sun
 * Microsystems, Inc. All Rights Reserved.
 */
package org.netbeans.tax.decl.parser;

import java.io.*;

import org.netbeans.tax.*;

/**
 * A simple kind of reader with some enhanced methods
 *  suitable for parsing purposes.
 */
public class ParserReader extends PushbackReader {
    
    /** */
    //      private TreeElementDecl elementDecl;
    
    
    //
    // init
    //
    
    public ParserReader (String source) {
        super (new StringReader (source), 20);
        
        //          this.elementDecl = elementDecl;
    }
    
    
    //
    // itself
    //
    
    //      /**
    //       */
    //      public final TreeElementDecl getRoot () {
    //          return elementDecl;
    //      }
    
    /** Trim out starting whitespaces. */
    public ParserReader trim () {
        int ch;
        while ( true ) {
            // read until non WS or EOF
            try {
                ch = read ();
                if (ch == -1 || ! Character.isWhitespace ((char)ch))
                    break;
            } catch (IOException ex) {
                ex.printStackTrace ();
            }
        }
        
        try {
            if (ch != -1) unread (ch);
        } catch (IOException ex) {
            ex.printStackTrace ();
        }
        
        return this;
    }
    
    /** SE: Move on if true with otherwise push back.
     * @return true if prefix is at the beginig of the stream
     */
    public boolean startsWith (String prefix) {
        char buf[] = new char[prefix.length ()];
        try {
            read (buf);
            //                if ( Util.THIS.isLoggable() ) /* then */ Util.THIS.debug("startsWith(" + prefix + " got " + new String(buf)); // NOI18N
            boolean ret = new String (buf).equals (prefix);
            if (ret) return true;
        } catch (IOException ex) {
            ex.printStackTrace ();
            return false;
        }
        
        try {
            unread (buf);
        } catch (IOException ex) {
            ex.printStackTrace ();
        }
        return false;
    }
    
    /** @return next character or -1 */
    public int peek () {
        try {
            int ch = read ();
            unread (ch);
            return ch;
        } catch (IOException ex) {
            return -1;
        }
    }
    
    /** @return whitespace or "()?+*" separated token or "". */ // NOI18N
    public String getToken () {
        StringBuffer sb = new StringBuffer ();
        
        int ch = -1;
        
        trim ();
        
        boolean reading = true; //is a char in reading buffer
        int len = 0;
        
        try {
            readChars:
                while (reading) {  //read until token recognized
                    ch = read ();
                    if ( ch == -1 || Character.isWhitespace ((char)ch) )
                        break;
                    switch (ch) {
                        //do not eat interesting chars
                        case ')': case '(': case '?': case '+': case '*':
                            break readChars;
                            
                            //these are tokens alone
                        case ',': case '|':
                            if (len == 0) {
                                reading = false;  //  finnish, no unread
                            } else {
                                break readChars;  // finnish current token
                            }
                    }
                    
                    sb.append ((char)ch);
                    len++;
                }
                if (ch != -1 && reading) unread (ch);
        } catch (IOException ex) {
            // return most of recognized
        }
        
        String toret = sb.toString ();
        //            if ( Util.THIS.isLoggable() ) /* then */ Util.THIS.debug("Token: " + toret); // NOI18N
        return toret;
    }
}