/* Copyright 2002-2005, 2010 Elliotte Rusty Harold
   
   This library is free software; you can redistribute it and/or modify
   it under the terms of version 2.1 of the GNU Lesser General Public 
   License as published by the Free Software Foundation.
   
   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, see
   <https://www.gnu.org/licenses/>.
   
   You can contact Elliotte Rusty Harold by sending e-mail to
   elharo@ibiblio.org. Please include the word "XOM" in the
   subject line. The XOM home page is located at https://xom.nu/
*/

package nu.xom;

import java.io.UnsupportedEncodingException;

/**
 * <p>
 *   This class represents a run of text. 
 *   CDATA sections are not treated differently than 
 *   normal text. <code>Text</code> objects may be adjacent to other 
 *   <code>Text</code> objects.
 * </p>
 * 
 * <p>
 *   The maximum size of a String or an array in Java limits the maximum
 *   size of a text node to about 2 gigabytes. If you're stuffing Base-64 
 *   encoded movies inside one node, you will have problems. Try breaking 
 *   up the text into smaller, contiguous chunks. Even then you will
 *   probably not be able to use XPath on the result. 
 * </p>
 *
 * @author Elliotte Rusty Harold
 * @version 1.3.0
 *
 */
public class Text extends Node {

    
    private byte[] data;
    
    
    /**
     * <p>
     * This constructor creates a new <code>Text</code> object. 
     * The data is checked for  legality according to XML 1.0 rules. 
     * Characters that can be serialized by escaping them 
     * such as &lt; and &amp; are allowed. However, characters  
     * such as the form feed, null, vertical tab,
     * unmatched halves of surrogate pairs,
     * and 0xFFFE and 0xFFFF are not allowed.
     * </p>
     * 
     * @param data the initial text of the object
     *
     * @throws IllegalCharacterDataException if data contains any 
     *     characters which are illegal in well-formed XML 1.0 such as 
     *     null, vertical tab, or unmatched halves of surrogate pairs
     */
    public Text(String data) {
        _setValue(data);
    }

    
    /**
     * <p>
     * Creates a copy of the specified <code>Text</code> object.
     * </p>
     * 
     * @param text the <code>Text</code> object to copy
     */
    public Text(Text text) {
        // I'm relying here on the data array being immutable.
        // If this ever changes, e.g. by adding an append method,
        // this method needs to change too.
        this.data = text.data;
    }

    
    private Text() {}
    
    
    static Text build(String data) {
        
        Text result = new Text();
        try {
            result.data = data.getBytes("UTF8");   
        }
        catch (UnsupportedEncodingException ex) {
            throw new RuntimeException(
              "Bad VM! Does not support UTF-8"
            );
        } 
        return result;
        
    }

    
    /**
     * <p>
     * Sets the content of the <code>Text</code> object 
     * to the specified data. The data is checked for 
     * legality according to XML 1.0 rules. Characters that 
     * can be serialized such as &lt; and &amp; are allowed.   
     * However, characters such as the form feed, null, 
     * vertical tab, unmatched halves of surrogate pairs,
     * and 0xFFFE and 0xFFFF are not allowed. Passing null is the same 
     * as passing the empty string.
     * </p>
     * 
     * @param data the text to install in the object
     * 
     * @throws IllegalCharacterDataException if data contains any 
     *     characters which are illegal in well-formed XML 1.0 such as 
     *     null, vertical tab, or unmatched halves of surrogate pairs
     */
    public void setValue(String data) {
        _setValue(data);
    }

    
    private void _setValue(String data) {
        
        if (data == null) data = "";
        else Verifier.checkPCDATA(data);
        try {
            this.data = data.getBytes("UTF8");   
        }
        catch (UnsupportedEncodingException ex) {
            throw new RuntimeException(
              "Bad VM! Does not support UTF-8"
            );
        }
        
    }

    /**
     * <p>
     * Returns the XPath 1.0 string-value of this <code>Text</code> 
     * node. The XPath string-value of a text node is the same as 
     * the text of the node.
     * </p>
     *  
     * @return the content of the node
     */
    public final String getValue() {
        
        try {
            return new String(data, "UTF8");
        } 
        catch (UnsupportedEncodingException ex) {
            throw new RuntimeException(
              "Bad VM! Does not support UTF-8"
            );
        }
        
    }

    
    /**
     * <p>
     * Throws <code>IndexOutOfBoundsException</code> because 
     * texts do not have children.
     * </p>
     * 
     * @return never returns because texts do not have children;
     *     always throws an exception.
     * 
     * @param position the index of the child node to return
     * 
     * @throws IndexOutOfBoundsException because texts 
     *     do not have children
     */
    public final Node getChild(int position) {
        throw new IndexOutOfBoundsException(
          "LeafNodes do not have children");        
    }

    
    /**
     * <p>
     * Returns 0 because texts do not have children.
     * </p>
     * 
     * @return zero
     */
    public final int getChildCount() {
        return 0;   
    }
    
    
    /**
     * <p>
     * Returns a deep copy of this <code>Text</code> with no parent,
     * that can be added to this document or a different one.
     * </p>
     *
     * @return a deep copy of this text node with no parent
     */
    public Text copy() {
        
        if (isCDATASection()) {
            return new CDATASection(this);
        }
        else {
            return new Text(this);
        }
        
    }

    
    /**
     * <p>
     * Returns a string containing the XML serialization of this text 
     * node.  Unlike <code>getValue</code>, this method escapes 
     * characters such as &amp; and &lt; using entity references such
     * as <code>&amp;amp;</code> and <code>&amp;lt;</code>.
     * It escapes the carriage return (\r) as <code>&amp;#x0D;</code>.
     * If this text node is a CDATA section, then it may wrap the value 
     * in CDATA section delimiters instead of escaping.
     * </p>
     * 
     * @return the string form of this text node
     */
    public final String toXML() {
        return escapeText();    
    }

    
    String escapeText() {
        
        String s = getValue();
        int length = s.length();
        // Give the string builder enough room for a couple of escaped characters 
        StringBuilder result = new StringBuilder(length+12);
        for (int i = 0; i < length; i++) {
            char c = s.charAt(i);
            switch (c) {
                case '\r':
                    result.append("&#x0D;");
                    break;
                case 14:
                    // impossible
                    break;
                case 15:
                    // impossible
                    break;
                case 16:
                    // impossible
                    break;
                case 17:
                    // impossible
                    break;
                case 18:
                    // impossible
                    break;
                case 19:
                    // impossible
                    break;
                case 20:
                    // impossible
                    break;
                case 21:
                    // impossible
                    break;
                case 22:
                    // impossible
                    break;
                case 23:
                    // impossible
                    break;
                case 24:
                    // impossible
                    break;
                case 25:
                    // impossible
                    break;
                case 26:
                    // impossible
                    break;
                case 27:
                    // impossible
                    break;
                case 28:
                    // impossible
                    break;
                case 29:
                    // impossible
                    break;
                case 30:
                    // impossible
                    break;
                case 31:
                    // impossible
                    break;
                case ' ':
                    result.append(' ');
                    break;
                case '!':
                    result.append('!');
                    break;
                case '"':
                    result.append('"');
                    break;
                case '#':
                    result.append('#');
                    break;
                case '$':
                    result.append('$');
                    break;
                case '%':
                    result.append('%');
                    break;
                case '&':
                    result.append("&amp;");
                    break;
                case '\'':
                    result.append('\'');
                    break;
                case '(':
                    result.append('(');
                    break;
                case ')':
                    result.append(')');
                    break;
                case '*':
                    result.append('*');
                    break;
                case '+':
                    result.append('+');
                    break;
                case ',':
                    result.append(',');
                    break;
                case '-':
                    result.append('-');
                    break;
                case '.':
                    result.append('.');
                    break;
                case '/':
                    result.append('/');
                    break;
                case '0':
                    result.append('0');
                    break;
                case '1':
                    result.append('1');
                    break;
                case '2':
                    result.append('2');
                    break;
                case '3':
                    result.append('3');
                    break;
                case '4':
                    result.append('4');
                    break;
                case '5':
                    result.append('5');
                    break;
                case '6':
                    result.append('6');
                    break;
                case '7':
                    result.append('7');
                    break;
                case '8':
                    result.append('8');
                    break;
                case '9':
                    result.append('9');
                    break;
                case ':':
                    result.append(':');
                    break;
                case ';':
                    result.append(';');
                    break;
                case '<':
                    result.append("&lt;");
                    break;
                case '=':
                    result.append('=');
                    break;
                case '>':
                    result.append("&gt;");
                    break;
                default: 
                    result.append(c); 
            }  
        }
        
        return result.toString();
        
    }
    
    
    boolean isText() {
        return true;   
    } 


    /**
     * <p>
     * Returns a <code>String</code> 
     * representation of this <code>Text</code> suitable for
     * debugging and diagnosis. This is <em>not</em>
     * the XML representation of this <code>Text</code> node.
     * </p>
     * 
     * @return a non-XML string representation of this node
     */
    public final String toString() {
        
        return "[" + getClass().getName() + ": " 
          + escapeLineBreaksAndTruncate(getValue()) + "]";
          
    }
    
    
    static String escapeLineBreaksAndTruncate(String s) {
        
        int length = s.length();
        boolean tooLong = length > 40;
        if (length > 40) {
            length = 35;
            s = s.substring(0, 35);
        }
        
        StringBuilder result = new StringBuilder(length);
        for (int i = 0; i < length; i++) {
            char c = s.charAt(i);
            switch (c) {
                case '\n': 
                    result.append("\\n");
                    break;
                case '\r': 
                    result.append("\\r");
                    break;
                case '\t': 
                    result.append("\\t");
                    break;
                default:
                    result.append(c);
            }
        }
        if (tooLong) result.append("...");
        
        return result.toString();
        
    }

    
    boolean isCDATASection() {
        return false;
    }


    boolean isEmpty() {
        return this.data.length == 0;
    }

    
}