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/*******************************************************************************
 *  Copyright (C) 2007, 2014:
 *  
 *    - Ferdinando Villa 
 *    - integratedmodelling.org
 *    - any other authors listed in @author annotations
 *
 *    All rights reserved. This file is part of the k.LAB software suite,
 *    meant to enable modular, collaborative, integrated 
 *    development of interoperable data and model components. For
 *    details, see http://integratedmodelling.org.
 *    
 *    This program is free software; you can redistribute it and/or
 *    modify it under the terms of the Affero General Public License 
 *    Version 3 or any later version.
 *
 *    This program 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
 *    Affero General Public License for more details.
 *  
 *     You should have received a copy of the Affero General Public License
 *     along with this program; if not, write to the Free Software
 *     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *     The license is also available at: https://www.gnu.org/licenses/agpl.html
 *******************************************************************************/
package org.integratedmodelling.utils.sexpr;

import java.io.IOException;
import java.io.InputStream;

import org.integratedmodelling.exceptions.KlabException;
import org.integratedmodelling.exceptions.KlabIOException;

/**
 * Wraps an InputStream and reads s-expr by s-expr, using Clojure (and I guess any 
 * Lisp's) reader conventions for strings and quotes. Allows "listening" to all 
 * forms in a stream.
 * 
 * @author Ferdinando
 *
 */
public class FormReader {

    private boolean inDquote = false;
    private boolean inSquote = false;
    private boolean inEscape = false;
    private boolean inComment = false;

    private InputStream input = null;
    private boolean isEof = false;

    public interface FormListener {
        public void onFormRead(String s) throws KlabException;
    }

    public FormReader(InputStream input) {
        this.input = input;
    }

    public void close() throws KlabException {
        try {
            this.input.close();
        } catch (IOException e) {
            throw new KlabIOException(e);
        }
    }

    private boolean quoted(int ch) {

        boolean wasEscape = inEscape;
        boolean wasInDquote = inDquote;
        boolean wasInSquote = inSquote;
        boolean wasComment = inComment;

        if (wasComment && ch == '\n')
            inComment = false;

        if (wasEscape)
            inEscape = false;

        if (!wasEscape) {
            if (wasInDquote && ch == '"') {
                inDquote = false;
            }
        }

        return wasInDquote || wasInSquote || wasEscape || wasComment;
    }

    /**
     * Read a single form from input.
     */
    public String readForm() throws KlabException {

        StringBuffer ret = new StringBuffer(2048);
        int plevel = -2;

        for (;;) {
            try {

                int ch = this.input.read();

                if (ch < 0) {
                    this.isEof = true;
                    break;
                }

                if (!quoted(ch)) {

                    switch (ch) {

                    case '(':
                        if (plevel == -2)
                            plevel = -1;
                        plevel++;
                        break;
                    case ')':
                        plevel--;
                        break;
                    case '"':
                        inDquote = true;
                        break;
                    //					case '\'':
                    //						inSquote = true;
                    //						break;
                    case '\\':
                        inEscape = true;
                        break;
                    case ';':
                        inComment = true;
                        break;
                    }
                }

                ret.append((char) ch);
                if (plevel == -1)
                    break;

            } catch (IOException e) {
                throw new KlabIOException(e);
            }
        }

        return ret.toString();
    }

    public boolean isEof() {
        return this.isEof;
    }

    public void read(FormListener listener) throws KlabException {
        while (!isEof()) {
            listener.onFormRead(readForm());
        }
    }

}