/* dCache - http://www.dcache.org/
 *
 * Copyright (C) 2001 - 2016 Deutsches Elektronen-Synchrotron
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) 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
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.dcache.util;

import com.google.common.base.CharMatcher;

import java.io.PrintWriter;
import java.io.Writer;

/**
 * This class provides a PrintWriter that strips off any trailing
 * whitespace at the end of a line.  This class assumes that newlines are
 * introduced by one of the println methods and not by using one of the append,
 * print or write methods with the '\n' character.
 */
public class NoTrailingWhitespacePrintWriter extends PrintWriter
{
    private StringBuilder padding;

    public NoTrailingWhitespacePrintWriter(Writer inner)
    {
        super(inner);
    }

    private StringBuilder getPadding()
    {
        if (padding == null) {
            padding = new StringBuilder();
        }
        return padding;
    }

    private void flushPadding()
    {
        if (padding != null) {
            String pad = padding.toString();
            super.write(pad, 0, pad.length());
            padding = null;
        }
    }

    private int lastTrailingWhitespace(char[] buf, int off, int len)
    {
        int idx = -1;
        for (int i = off+len-1; i >= off; i--) {
            if (!CharMatcher.whitespace().matches(buf [i])) {
                break;
            }
            idx = i;
        }
        return idx;
    }

    private int lastTrailingWhitespace(String s, int off, int len)
    {
        int idx = -1;
        for (int i = off+len-1; i >= off; i--) {
            if (!CharMatcher.whitespace().matches(s.charAt(i))) {
                break;
            }
            idx = i;
        }
        return idx;
    }

    @Override
    public void println()
    {
        super.println();
        padding = null;
    }

    @Override
    public void write(String s)
    {
        write(s, 0, s.length());
    }

    @Override
    public void write(char[] buf)
    {
        write(buf, 0, buf.length);
    }

    @Override
    public void write(int c)
    {
        if (CharMatcher.whitespace().matches((char)c)) {
            getPadding().append((char)c);
        } else {
            flushPadding();
            super.write(c);
        }
    }

    @Override
    public void write(char buf[], int off, int len)
    {
        int idx = lastTrailingWhitespace(buf, off, len);
        if (idx != 0) {
            flushPadding();
            super.write(buf, off, idx == -1 ? len : (idx-off));
        }
        if (idx > -1) {
            getPadding().append(buf, idx, len-(idx-off));
        }
    }

    @Override
    public void write(String s, int off, int len)
    {
        int idx = lastTrailingWhitespace(s, off, len);
        if (idx != 0) {
            flushPadding();
            super.write(s, off, idx == -1 ? len : (idx-off));
        }
        if (idx > -1) {
            getPadding().append(s, idx, off+len);
        }
    }
}