/*

   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You under the Apache License, Version 2.0
   (the "License"); you may not use this file except in compliance with
   the License.  You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

 */
package org.apache.batik.util.gui.xmleditor;

import org.apache.batik.xml.XMLUtilities;

/**
 * XML scanner for parsing xml text
 *
 * @author <a href="mailto:tonny@kiyut.com">Tonny Kohar</a>
 * @version $Id$
 */
public class XMLScanner {

    public static final int TEMP_ERROR_CONTEXT = -2;
    public static final int EOF_CONTEXT = -1;
    public static final int DEFAULT_CONTEXT = 0;
    public static final int COMMENT_CONTEXT = 1;
    public static final int ELEMENT_CONTEXT = 2;
    public static final int CHARACTER_DATA_CONTEXT = 3;
    public static final int ATTRIBUTE_NAME_CONTEXT = 4;
    public static final int ATTRIBUTE_VALUE_CONTEXT = 5;
    public static final int XML_DECLARATION_CONTEXT = 6;
    public static final int DOCTYPE_CONTEXT = 7;
    public static final int ENTITY_CONTEXT = 8;
    public static final int ELEMENT_DECLARATION_CONTEXT = 9;
    public static final int CDATA_CONTEXT = 10;
    public static final int PI_CONTEXT = 11;
    
    
    private int position;
    private String string;
    private int current;
    private int scanValue;
    private int startOffset;
    
    public XMLScanner() {
        reset();
    }
    
    public void reset() {
        position = 0;
        startOffset = 0;
    }
    
    public void setString(String string) {
        this.string = string;
    }
    
    protected int nextChar() {
        try {
            current = (int)string.charAt(position);
            position++;
        } catch (Exception ex) {
            current = -1;
        }
        
        return current;
    }
    

    protected int skipSpaces() {
        do {
            nextChar();
        } while (current != -1 && XMLUtilities.isXMLSpace((char)current));
        return current;
    }
    
    public int getScanValue() {
        return scanValue;
    }
    
    public int getStartOffset() {
        return startOffset;
    }
    
    public int scan(int context) {
        nextChar();
        switch(context) {
            case XML_DECLARATION_CONTEXT:
                scanValue = scanXMLDeclaration();
                break;
            case DOCTYPE_CONTEXT:
                scanValue = scanDOCTYPE();
                break;
            case COMMENT_CONTEXT:
                scanValue = scanComment();
                break;
            case ELEMENT_CONTEXT:
                scanValue = scanElement();
                break;
            case ATTRIBUTE_NAME_CONTEXT:
                scanValue = scanAttributeName();
                break;
            case ATTRIBUTE_VALUE_CONTEXT:
                scanValue = scanAttributeValue();
                break;
            case CDATA_CONTEXT:
                scanValue = scanCDATA();
                break;
            default:
                scanValue = scanCharacterData();
                break;
        }
        return position;
    }
    
    private int scanCharacterData() {
        while (current != -1) {
            if (current == '<') {
                nextChar();
                if (current == '?') {
                    position = position - 2;
                    return XML_DECLARATION_CONTEXT;
                } else if (current == '!') {
                    nextChar();
                    if (current == 'D') {
                        position = position - 3;
                        return DOCTYPE_CONTEXT;
                    } else if (current == '-') {
                        nextChar();
                        if (current == '-') {
                            position = position - 4;
                            return COMMENT_CONTEXT;
                        }
                    } else if (current == '[') {
                        if (nextChar() == 'C') {
                            if (nextChar() == 'D') {
                                if (nextChar() == 'A') {
                                    if (nextChar() == 'T') {
                                        if (nextChar() == 'A') {
                                            if (nextChar() == '[') {
                                                position = position - 9;
                                                return CDATA_CONTEXT;
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                } else {
                    position = position - 2;
                    return ELEMENT_CONTEXT;
                }
            }
            nextChar();
        }
        
        if (current == -1) {
            return EOF_CONTEXT;
        }
        
        return CHARACTER_DATA_CONTEXT;
    }
    
    private int scanXMLDeclaration() {
        position = position + 2;    // to skip the first <?
        while(current != -1) {
            if (current == '?') {
                if (nextChar() == '>') {
                    return CHARACTER_DATA_CONTEXT;
                } else {
                    return TEMP_ERROR_CONTEXT;
                }
            }
            nextChar();
        }
        
        if (current == -1) {
            return EOF_CONTEXT;
        }
        
        return XML_DECLARATION_CONTEXT;
    }
    
    private int scanDOCTYPE() {
        position = position + 3;    // to skip the first <!D
        boolean end = true;
        while(current != -1) {
            if (current == '[') {
                end = false;
            } else if (current == ']') {
                end = true;
            } else if (current == '>' && end) {
                return CHARACTER_DATA_CONTEXT;
            }
            nextChar();
        }
        
        if (current == -1) {
            return EOF_CONTEXT;
        }
        
        return DOCTYPE_CONTEXT;
    }
    
    private int scanComment() {
        //position = position + 4;    // to skip the first <!--
        
        while(current != -1) {
            if (current == '-') {
                if (nextChar() == '-') {
                    if (nextChar() == '>') {
                        return CHARACTER_DATA_CONTEXT;
                    }
                }
            }
            nextChar();
        }
        
        if (current == -1) {
            return EOF_CONTEXT;
        }
        
        
        return COMMENT_CONTEXT;
    }
    
    /**
     * Returns the next lexical unit in the context of a start tag.
     */
    private int scanElement() {
        //position = position + 1;    // to skip the first <
        while (current != -1) {
            if (current == '>') {
                return CHARACTER_DATA_CONTEXT;
            } else if (XMLUtilities.isXMLSpace((char)current)) {
                return ATTRIBUTE_NAME_CONTEXT;
            } 
            
            nextChar();
        }
        
        if (current == -1) {
            return EOF_CONTEXT;
        }
        
        return ELEMENT_CONTEXT;
    }
    
    private int scanAttributeName() {
        while (current != -1) {
            if (current == '=') {
                return ATTRIBUTE_VALUE_CONTEXT;
            } else if (current == '/') {
                position--;
                return ELEMENT_CONTEXT;
            } else if (current == '>') {
                position--;
                return ELEMENT_CONTEXT;
            }
            nextChar();
        }
        
        if (current == -1) {
            return EOF_CONTEXT;
        }
        
        return ATTRIBUTE_NAME_CONTEXT;
    }
    
    private int scanAttributeValue() {
        
        int delim = '"';
        
        // looking for the first delimiter
        while (current != -1) {
            if ((current == '"') || (current == '\'')) {
                delim = current;
                break;
            }
            nextChar();
        }
        
        nextChar();
        
        // looking for the second delimiter
        while (current != -1) {
            if (current == delim) {
                return ELEMENT_CONTEXT;
            }
            nextChar();
        }
        
        if (current == -1) {
            return EOF_CONTEXT;
        }
        
        return ATTRIBUTE_VALUE_CONTEXT;
    }
    
    private int scanCDATA() {
        //position = position + 9;    // to skip the first <![CDATA[
        
        while(current != -1) {
            if (current == ']') {
                if (nextChar() == ']') {
                    if (nextChar() == '>') {
                        return CHARACTER_DATA_CONTEXT;
                    }
                }
            }
            nextChar();
        }
        
        if (current == -1) {
            return EOF_CONTEXT;
        }
        
        return CDATA_CONTEXT;
    }
}