/*
 * 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 com.cherry.lib.doc.office.fc.codec;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * Abstract superclass for Base-N output streams.
 * 
 * @since 1.5
 */
public class BaseNCodecOutputStream extends FilterOutputStream {

    private final boolean doEncode;

    private final BaseNCodec baseNCodec;

    private final byte[] singleByte = new byte[1];

    public BaseNCodecOutputStream(OutputStream out, BaseNCodec basedCodec, boolean doEncode) {
        super(out);
        this.baseNCodec = basedCodec;
        this.doEncode = doEncode;
    }

    /**
     * Writes the specified <code>byte</code> to this output stream.
     * 
     * @param i
     *            source byte
     * @throws IOException
     *             if an I/O error occurs.
     */
    public void write(int i) throws IOException {
        singleByte[0] = (byte) i;
        write(singleByte, 0, 1);
    }

    /**
     * Writes <code>len</code> bytes from the specified <code>b</code> array starting at <code>offset</code> to this
     * output stream.
     * 
     * @param b
     *            source byte array
     * @param offset
     *            where to start reading the bytes
     * @param len
     *            maximum number of bytes to write
     * 
     * @throws IOException
     *             if an I/O error occurs.
     * @throws NullPointerException
     *             if the byte array parameter is null
     * @throws IndexOutOfBoundsException
     *             if offset, len or buffer size are invalid
     */
    public void write(byte b[], int offset, int len) throws IOException {
        if (b == null) {
            throw new NullPointerException();
        } else if (offset < 0 || len < 0) {
            throw new IndexOutOfBoundsException();
        } else if (offset > b.length || offset + len > b.length) {
            throw new IndexOutOfBoundsException();
        } else if (len > 0) {
            if (doEncode) {
                baseNCodec.encode(b, offset, len);
            } else {
                baseNCodec.decode(b, offset, len);
            }
            flush(false);
        }
    }

    /**
     * Flushes this output stream and forces any buffered output bytes to be written out to the stream. If propogate is
     * true, the wrapped stream will also be flushed.
     * 
     * @param propogate
     *            boolean flag to indicate whether the wrapped OutputStream should also be flushed.
     * @throws IOException
     *             if an I/O error occurs.
     */
    private void flush(boolean propogate) throws IOException {
        int avail = baseNCodec.available();
        if (avail > 0) {
            byte[] buf = new byte[avail];
            int c = baseNCodec.readResults(buf, 0, avail);
            if (c > 0) {
                out.write(buf, 0, c);
            }
        }
        if (propogate) {
            out.flush();
        }
    }

    /**
     * Flushes this output stream and forces any buffered output bytes to be written out to the stream.
     * 
     * @throws IOException
     *             if an I/O error occurs.
     */
    public void flush() throws IOException {
        flush(true);
    }

    /**
     * Closes this output stream and releases any system resources associated with the stream.
     * 
     * @throws IOException
     *             if an I/O error occurs.
     */
    public void close() throws IOException {
        // Notify encoder of EOF (-1).
        if (doEncode) {
            baseNCodec.encode(singleByte, 0, -1);
        } else {
            baseNCodec.decode(singleByte, 0, -1);
        }
        flush();
        out.close();
    }

}
