/*
 * Copyright 2014 NAVER Corp.
 *
 * 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.
 */

package com.navercorp.pinpoint.thrift.io;

import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.util.Arrays;

/**
 * @author emeroad
 */
public class UnsafeByteArrayOutputStream extends ResettableByteArrayOutputStream {

    private static final String UTF8 = "UTF8";
    private static final Charset UTF8_CHARSET = Charset.forName(UTF8);

	private final boolean autoExpand;

    /**
     * Creates a new byte array output stream. The buffer capacity is
     * initially 32 bytes, though its size increases if necessary.
     */
    public UnsafeByteArrayOutputStream() {
        this(32);
    }

    /**
     * Creates a new byte array output stream, with a buffer capacity of
     * the specified size, in bytes.
     *
     * @param size the initial size.
     * @throws IllegalArgumentException if size is negative.
     */
    public UnsafeByteArrayOutputStream(int size) {
        this(size, true);
    }

    public UnsafeByteArrayOutputStream(int size, boolean autoExpand) {
        super(size);
        this.autoExpand = autoExpand;
    }
    
    /**
     * Writes the specified byte to this byte array output stream.
     *
     * @param b the byte to be written.
     */
    public void write(int b) {
        int newcount = count + 1;
        if (isOverflow(newcount)) {
        	if (autoExpand) {
        		buf = Arrays.copyOf(buf, Math.max(buf.length << 1, newcount));
        	} else {
        		throw new BufferOverflowException("Buffer size cannot exceed " + buf.length + ". (now:" + count + ", input-size:1");
        	}
        }
        
        buf[count] = (byte) b;
        count = newcount;
    }

    /**
     * Writes <code>len</code> bytes from the specified byte array
     * starting at offset <code>off</code> to this byte array output stream.
     *
     * @param b   the data.
     * @param off the start offset in the data.
     * @param len the number of bytes to write.
     */
    public void write(byte b[], int off, int len) {
        if ((off < 0) || (off > b.length) || (len < 0) ||
                ((off + len) > b.length) || ((off + len) < 0)) {
            throw new IndexOutOfBoundsException();
        } else if (len == 0) {
            return;
        }
        
        int newcount = count + len;
        if (isOverflow(newcount)) {
        	if (autoExpand) {
        		buf = Arrays.copyOf(buf, Math.max(buf.length << 1, newcount));
        	} else {
        		throw new BufferOverflowException("Buffer size cannot exceed " + buf.length + ". (now:" + count + ", input-size:" + len);
        	}
        }
        
        System.arraycopy(b, off, buf, count, len);
        count = newcount;
    }

    /**
     * Writes the complete contents of this byte array output stream to
     * the specified output stream argument, as if by calling the output
     * stream's write method using <code>out.write(buf, 0, count)</code>.
     *
     * @param out the output stream to which to write the data.
     * @throws java.io.IOException if an I/O error occurs.
     */
    public void writeTo(OutputStream out) throws IOException {
        out.write(buf, 0, count);
    }

    /**
     * Resets the <code>count</code> field of this byte array output
     * stream to zero, so that all currently accumulated output in the
     * output stream is discarded. The output stream can be used again,
     * reusing the already allocated buffer space.
     *
     * @see java.io.ByteArrayInputStream#count
     */
    public void reset() {
        count = 0;
    }

    /**
     * Creates a newly allocated byte array. Its size is the current
     * size of this output stream and the valid contents of the buffer
     * have been copied into it.
     *
     * @return the current contents of this output stream, as a byte array.
     * @see java.io.ByteArrayOutputStream#size()
     */
    public byte toByteArray()[] {
        return buf;
    }

    /**
     * Returns the current size of the buffer.
     *
     * @return the value of the <code>count</code> field, which is the number
     *         of valid bytes in this output stream.
     * @see java.io.ByteArrayOutputStream#count
     */
    public int size() {
        return count;
    }

    /**
     * Converts the buffer's contents into a string decoding bytes using the
     * platform's default character set. The length of the new <tt>String</tt>
     * is a function of the character set, and hence may not be equal to the
     * size of the buffer.
     * <p/>
     * <p> This method always replaces malformed-input and unmappable-character
     * sequences with the default replacement string for the platform's
     * default character set. The {@linkplain java.nio.charset.CharsetDecoder}
     * class should be used when more control over the decoding process is
     * required.
     *
     * @return String decoded from the buffer's contents.
     * @since JDK1.1
     */
    public String toString() {
        try {
            return toString(UTF8);
        } catch (UnsupportedEncodingException ex) {
            return new String(buf, 0, count, UTF8_CHARSET);
        }
    }

    /**
     * Converts the buffer's contents into a string by decoding the bytes using
     * the specified {@link java.nio.charset.Charset charsetName}. The length of
     * the new <tt>String</tt> is a function of the charset, and hence may not be
     * equal to the length of the byte array.
     * <p/>
     * <p> This method always replaces malformed-input and unmappable-character
     * sequences with this charset's default replacement string. The {@link
     * java.nio.charset.CharsetDecoder} class should be used when more control
     * over the decoding process is required.
     *
     * @param charsetName the name of a supported
     *                    {@linkplain java.nio.charset.Charset </code>charset<code>}
     * @return String decoded from the buffer's contents.
     * @throws java.io.UnsupportedEncodingException
     *          If the named charset is not supported
     * @since JDK1.1
     */
    public String toString(String charsetName)
            throws UnsupportedEncodingException {
        return new String(buf, 0, count, charsetName);
    }


    /**
     * Closing a <tt>ByteArrayOutputStream</tt> has no effect. The methods in
     * this class can be called after the stream has been closed without
     * generating an <tt>IOException</tt>.
     * <p/>
     */
    public void close() throws IOException {
    }
    
    private boolean isOverflow(int minCapacity) {
        if (minCapacity - buf.length > 0) {
        	return true;
        }
        return false;
    }
	
}
