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/*--------------------------------------------------------------------------
 *  Copyright 2004 Taro L. Saito
 *
 *  Licensed 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.
 *--------------------------------------------------------------------------*/
//-----------------------------------
// XerialJ Project
// 
// XMLGenerator.java 
// Since: 2005/01/16
//
// $Author$
//--------------------------------------
package org.xerial.xml;

import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.Writer;
import java.util.HashMap;
import java.util.LinkedList;

import org.xerial.core.XerialError;

/**
 * XML Generator produces well-formed XML documents
 * 
 * [s1](1) [1][s1] [s2] (2)  [s3]
 * [s4]   
 * 
 * (1) newline before nested element (2) newline after leaf element [1] indent
 * before element (indent string SPACE or TAB, indent character size = 2)
 * 
 * 
 * states:
 * 
 * A (the previous output is starg tag) B (the previous output is text content)
 * C (the previous output is end tag)
 * 
 * TODO: on/off of indentation
 * 
 * @author leo
 */
public class XMLGenerator
{
    public enum IndentType {
        SPACE, TAB
    };

    private int _currentLevel = 0;
    private String _indent = "  ";
    private PrintWriter _out;
    private LinkedList _tagStack = new LinkedList();

    public enum FormatStab {
        NewlineBeforeNestedElement, NewlineAfterElement, IndentBeforeElement
    };

    private HashMap _formatEnableFlag = new HashMap();

    private enum PreviousOutput {
        StartTag, TextContent, EndTag
    }

    private PreviousOutput _prevOut = PreviousOutput.EndTag;

    private boolean isEnable(FormatStab stabType)
    {
        Boolean b = _formatEnableFlag.get(stabType);
        return b == null ? false : b;
    }

    public XMLGenerator text(String textContent)
    {
        _out.print(textContent);

        _prevOut = PreviousOutput.TextContent;

        return this;
    }

    public XMLGenerator startTag(String tagName)
    {
        return startTag(tagName, null);
    }

    void beforeStartTag()
    {
        switch (_prevOut)
        {
        case StartTag:
            if (isEnable(FormatStab.NewlineBeforeNestedElement))
                newline();
        case EndTag:
            if (isEnable(FormatStab.IndentBeforeElement))
                indent(_currentLevel);
            break;
        }
    }

    public static String replaceWhiteSpaces(String tagName)
    {
        return tagName.replaceAll("\\s+", "_");
    }

    public XMLGenerator startTag(String tagName, XMLAttribute attribute)
    {
        beforeStartTag();

        String tag = replaceWhiteSpaces(tagName);

        _out.print("<");
        _out.print(tag);

        if (attribute != null && attribute.length() > 0)
        {
            _out.print(" ");
            _out.print(attribute.toXMLString());
        }
        _out.print(">");

        _currentLevel++;
        _tagStack.add(tag);
        _prevOut = PreviousOutput.StartTag;

        return this;
    }

    public XMLGenerator element(String tagName, String textContent)
    {
        startTag(tagName, null);
        text(textContent);
        endTag();
        return this;
    }

    public XMLGenerator element(String tagName, XMLAttribute attribute, String textContent)
    {
        startTag(tagName, attribute);
        text(textContent);
        endTag();
        return this;
    }

    public XMLGenerator selfCloseTag(String tagName)
    {
        return selfCloseTag(tagName, null);
    }

    public XMLGenerator selfCloseTag(String tagName, XMLAttribute attribute)
    {
        beforeStartTag();

        _out.print("<");
        _out.print(tagName);

        if (attribute != null && attribute.length() > 0)
        {
            _out.print(" ");
            _out.print(attribute.toXMLString());
        }
        _out.print("/>");
        if (isEnable(FormatStab.NewlineAfterElement))
            newline();

        _prevOut = PreviousOutput.EndTag;
        return this;
    }

    public XMLGenerator endTag()
    {
        if (_currentLevel < 1)
            throw new XerialError(XMLErrorCode.NO_MORE_TAG_TO_CLOSE);

        switch (_prevOut)
        {
        case StartTag:
            if (isEnable(FormatStab.NewlineBeforeNestedElement))
                newline();
        case EndTag:
            if (isEnable(FormatStab.IndentBeforeElement))
                indent(_currentLevel - 1);
            break;
        }

        String tagName = _tagStack.getLast();

        _out.print("");
        if (isEnable(FormatStab.NewlineAfterElement))
            newline();

        _currentLevel--;
        _tagStack.removeLast();
        _prevOut = PreviousOutput.EndTag;

        return this;
    }

    public XMLGenerator flush()
    {
        _out.flush();
        return this;
    }

    public void endDocument()
    {
        while (!_tagStack.isEmpty())
            endTag();
        _out.flush();
    }

    private void init()
    {
        _formatEnableFlag.put(FormatStab.NewlineBeforeNestedElement, true);
        _formatEnableFlag.put(FormatStab.NewlineAfterElement, true);
        _formatEnableFlag.put(FormatStab.IndentBeforeElement, true);
    }

    public XMLGenerator()
    {
        init();
        setOutputStream(System.out);
    }

    public XMLGenerator(OutputStream out)
    {
        init();
        setOutputStream(out);
    }

    public XMLGenerator(Writer out)
    {
        init();
        setOutputWriter(out);
    }

    public void setOutputStream(OutputStream out)
    {
        _out = new PrintWriter(out);
    }

    public void setOutputWriter(Writer writer)
    {
        _out = new PrintWriter(writer);
    }

    /**
     * 
     * @param indentType
     *            SPACE or TAB
     * @param length
     *            indent size per level
     * 
     */
    public void setIndentCharacter(IndentType indentType, int length)
    {
        assert length >= 0;

        StringBuffer indent = new StringBuffer();
        switch (indentType)
        {
        case SPACE:
            for (int i = 0; i < length; i++)
                indent.append(" ");
            break;
        case TAB:
            for (int i = 0; i < length; i++)
                indent.append("\t");
            break;
        }
        _indent = indent.toString();
    }

    protected void indent(int level)
    {
        for (int i = 0; i < level; i++)
            _out.print(_indent);
    }

    protected void newline()
    {
        _out.println();
    }

}