/**
 * License Agreement.
 *
 * Rich Faces - Natural Ajax for Java Server Faces (JSF)
 *
 * Copyright (C) 2007 Exadel, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License version 2.1 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
 */
package org.ajax4jsf.io;

import java.io.IOException;
import java.io.Reader;
import java.io.Writer;

/**
 * Class for reading from a char array chain.
 *
 * @author glory
 */
public class FastBufferReader extends Reader {
    /**
     * Currently read link.
     */
    CharBuffer current;
    /**
     * The first link in the chain of char arrays.
     */
    CharBuffer firstLink;
    /**
     * Position of next char in current link.
     */
    int index;

    public FastBufferReader(CharBuffer buffer) {
        firstLink = buffer;
        current = firstLink;
        index = 0;
    }

    /**
     * Creates instance for given writer.
     *
     * @param writer
     */
    @Deprecated
    public FastBufferReader(FastBufferWriter writer) {
        firstLink = writer.getFirstBuffer();
        current = firstLink;
        index = 0;
    }

    public void close() throws IOException {
    }

    /**
     * @see java.io.Reader.read()
     */
    public int read() throws IOException {
        if (current == null) {
            return -1;
        }

        if (current.getUsedSize() <= index) {
            current = current.getNext();

            if (current == null) {
                return -1;
            }

            index = 0;
        }

        char c = current.getCharAt(index);

        index++;

        return c;
    }

    /**
     * @see java.io.Reader.read(char[] cbuf, int off, int len)
     */
    public int read(char[] cbuf, int off, int len) throws IOException {
        if ((off < 0) || (off > cbuf.length) || (len < 0) || ((off + len) > cbuf.length) || ((off + len) < 0)) {
            throw new IndexOutOfBoundsException();
        } else if (len == 0) {
            return 0;
        }

        if (current == null) {
            return -1;
        }

        int actuallyRead = 0;

        while ((current != null) && (len > 0)) {
            int av = current.getUsedSize() - index;

            if (av <= 0) {
                current = current.getNext();
                index = 0;

                continue;
            }

            if (av > len) {
                av = len;
            }

            System.arraycopy(current.getChars(), index, cbuf, off, av);
            index += av;
            off += av;
            actuallyRead += av;
            len -= av;
        }

        return (actuallyRead == 0) ? -1 : actuallyRead;
    }

    /**
     * Returns the number of chars that may be read from this storage.
     *
     * @return
     * @throws IOException
     */
    public int available() throws IOException {
        if (current == null) {
            return 0;
        }

        CharBuffer b = current;
        int result = -index;

        while (b != null) {
            result += b.getUsedSize();
            b = b.getNext();
        }

        return result;
    }

    /**
     * Writes rest of data written up to the moment to out.
     *
     * @param out
     * @throws IOException
     */
    public void writeTo(Writer writer) throws IOException {
        if (current == null) {
            return;
        }

        if (current.getUsedSize() > index) {
            writer.write(current.getChars(), index, current.getUsedSize() - index);
            current = current.getNext();
        }

        while (current != null) {
            writer.write(current.getChars(), 0, current.getUsedSize());
            current = current.getNext();
        }

        index = 0;
    }
}
