/*
 * 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.jackrabbit.vault.util.xml.serialize;


import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;


/**
 * Extends {@link Printer} and adds support for indentation and line
 * wrapping.
 *
 * @author <a href="mailto:arkin@intalio.com">Assaf Arkin</a>
 * @version $Revision$ $Date$
 */
public class IndentPrinter
        extends Printer {


    /**
     * Holds the currently accumulating text line. This buffer will constantly
     * be reused by deleting its contents instead of reallocating it.
     */
    private StringBuffer _line;


    /**
     * Holds the currently accumulating text that follows {@link #_line}.
     * When the end of the part is identified by a call to {@link #printSpace}
     * or {@link #breakLine}, this part is added to the accumulated line.
     */
    private StringBuffer _text;


    /**
     * Counts how many white spaces come between the accumulated line and the
     * current accumulated text. Multiple spaces at the end of the a line
     * will not be printed.
     */
    private int _spaces;


    /**
     * Holds the indentation for the current line that is now accumulating in
     * memory and will be sent for printing shortly.
     */
    private int _thisIndent;


    /**
     * Holds the indentation for the next line to be printed. After this line is
     * printed, {@link #_nextIndent} is assigned to {@link #_thisIndent}.
     */
    private int _nextIndent;


    public IndentPrinter(Writer writer, OutputFormat format) {
        super(writer, format);
        // Initialize everything for a first/second run.
        _line = new StringBuffer(80);
        _text = new StringBuffer(20);
        _spaces = 0;
        _thisIndent = _nextIndent = 0;
    }


    /**
     * Called by any of the DTD handlers to enter DTD mode.
     * Once entered, all output will be accumulated in a string
     * that can be printed as part of the document's DTD.
     * This method may be called any number of time but will only
     * have affect the first time it's called. To exist DTD state
     * and get the accumulated DTD, call {@link #leaveDTD}.
     */
    public void enterDTD() {
        // Can only enter DTD state once. Once we're out of DTD
        // state, can no longer re-enter it.
        if (_dtdWriter == null) {
            _line.append(_text);
            _text = new StringBuffer(20);
            flushLine(false);
            _dtdWriter = new StringWriter();
            _docWriter = _writer;
            _writer = _dtdWriter;
        }
    }


    /**
     * Called by the root element to leave DTD mode and if any
     * DTD parts were printer, will return a string with their
     * textual content.
     */
    public String leaveDTD() {
        // Only works if we're going out of DTD mode.
        if (_writer == _dtdWriter) {
            _line.append(_text);
            _text = new StringBuffer(20);
            flushLine(false);
            _writer = _docWriter;
            return _dtdWriter.toString();
        } else
            return null;
    }


    /**
     * Called to print additional text. Each time this method is called
     * it accumulates more text. When a space is printed ({@link
     * #printSpace}) all the accumulated text becomes one part and is
     * added to the accumulate line. When a line is long enough, it can
     * be broken at its text boundary.
     *
     * @param text The text to print
     */
    public void printText(String text) {
        _text.append(text);
    }


    public void printText(StringBuffer text) {
        _text.append(text.toString());
    }


    public void printText(char ch) {
        _text.append(ch);
    }


    public void printText(char[] chars, int start, int length) {
        _text.append(chars, start, length);
    }


    /**
     * Called to print a single space between text parts that may be
     * broken into separate lines. Must not be called to print a space
     * when preserving spaces. The text accumulated so far with {@link
     * #printText} will be added to the accumulated line, and a space
     * separator will be counted. If the line accumulated so far is
     * long enough, it will be printed.
     */
    public void printSpace() {
        // The line consists of the text accumulated in _line,
        // followed by one or more spaces as counted by _spaces,
        // followed by more space accumulated in _text:
        // -  Text is printed and accumulated into _text.
        // -  A space is printed, so _text is added to _line and
        //    a space is counted.
        // -  More text is printed and accumulated into _text.
        // -  A space is printed, the previous spaces are added
        //    to _line, the _text is added to _line, and a new
        //    space is counted.

        // If text was accumulated with printText(), then the space
        // means we have to move that text into the line and
        // start accumulating new text with printText().
        if (_text.length() > 0) {
            // If the text breaks a line bounary, wrap to the next line.
            // The printed line size consists of the indentation we're going
            // to use next, the accumulated line so far, some spaces and the
            // accumulated text so far.
            if (_format.getLineWidth() > 0 &&
                    _thisIndent + _line.length() + _spaces + _text.length() > _format.getLineWidth()) {
                flushLine(false);
                try {
                    // Print line and new line, then zero the line contents.
                    _writer.write(_format.getLineSeparator());
                } catch (IOException except) {
                    // We don't throw an exception, but hold it
                    // until the end of the document.
                    if (_exception == null)
                        _exception = except;
                }
            }

            // Add as many spaces as we accumulaed before.
            // At the end of this loop, _spaces is zero.
            while (_spaces > 0) {
                _line.append(' ');
                --_spaces;
            }
            _line.append(_text);
            _text = new StringBuffer(20);
        }
        // Starting a new word: accumulate the text between the line
        // and this new word; not a new word: just add another space.
        ++_spaces;
    }


    /**
     * Called to print a line consisting of the text accumulated so
     * far. This is equivalent to calling {@link #printSpace} but
     * forcing the line to print and starting a new line ({@link
     * #printSpace} will only start a new line if the current line
     * is long enough).
     */
    public void breakLine() {
        breakLine(false);
    }


    public void breakLine(boolean preserveSpace) {
        // Equivalent to calling printSpace and forcing a flushLine.
        if (_text.length() > 0) {
            while (_spaces > 0) {
                _line.append(' ');
                --_spaces;
            }
            _line.append(_text);
            _text = new StringBuffer(20);
        }
        flushLine(preserveSpace);
        try {
            // Print line and new line, then zero the line contents.
            _writer.write(_format.getLineSeparator());
        } catch (IOException except) {
            // We don't throw an exception, but hold it
            // until the end of the document.
            if (_exception == null)
                _exception = except;
        }
    }


    /**
     * Flushes the line accumulated so far to the writer and get ready
     * to accumulate the next line. This method is called by {@link
     * #printText} and {@link #printSpace} when the accumulated line plus
     * accumulated text are two long to fit on a given line. At the end of
     * this method _line is empty and _spaces is zero.
     */
    public void flushLine(boolean preserveSpace) {
        int indent;

        if (_line.length() > 0) {
            try {

                if (_format.getIndenting() && !preserveSpace) {
                    // Make sure the indentation does not blow us away.
                    indent = _thisIndent;
                    if ((2 * indent) > _format.getLineWidth() && _format.getLineWidth() > 0)
                        indent = _format.getLineWidth() / 2;
                    // Print the indentation as spaces and set the current
                    // indentation to the next expected indentation.
                    while (indent > 0) {
                        _writer.write(' ');
                        --indent;
                    }
                }
                _thisIndent = _nextIndent;

                // There is no need to print the spaces at the end of the line,
                // they are simply stripped and replaced with a single line
                // separator.
                _spaces = 0;
                _writer.write(_line.toString());

                _line = new StringBuffer(40);
            } catch (IOException except) {
                // We don't throw an exception, but hold it
                // until the end of the document.
                if (_exception == null)
                    _exception = except;
            }
        }
    }


    /**
     * Flush the output stream. Must be called when done printing
     * the document, otherwise some text might be buffered.
     */
    public void flush() {
        if (_line.length() > 0 || _text.length() > 0)
            breakLine();
        try {
            _writer.flush();
        } catch (IOException except) {
            // We don't throw an exception, but hold it
            // until the end of the document.
            if (_exception == null)
                _exception = except;
        }
    }


    /**
     * Increment the indentation for the next line.
     */
    public void indent() {
        _nextIndent += _format.getIndent();
    }


    /**
     * Decrement the indentation for the next line.
     */
    public void unindent() {
        _nextIndent -= _format.getIndent();
        if (_nextIndent < 0)
            _nextIndent = 0;
        // If there is no current line and we're de-identing then
        // this indentation level is actually the next level.
        if ((_line.length() + _spaces + _text.length()) == 0)
            _thisIndent = _nextIndent;
    }


    public int getNextIndent() {
        return _nextIndent;
    }


    public void setNextIndent(int indent) {
        _nextIndent = indent;
    }


    public void setThisIndent(int indent) {
        _thisIndent = indent;
    }


}
