/*
 * 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.directmemory.lightning.internal.io;

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;

public class ReaderInputStream
    extends InputStream
{

    /** Source Reader */
    private Reader in;

    private String encoding = System.getProperty( "file.encoding" );

    private byte[] slack;

    private int begin;

    /**
     * Construct a <CODE>ReaderInputStream</CODE> for the specified <CODE>Reader</CODE>.
     * 
     * @param reader <CODE>Reader</CODE>. Must not be <code>null</code>.
     */
    public ReaderInputStream( Reader reader )
    {
        in = reader;
    }

    /**
     * Construct a <CODE>ReaderInputStream</CODE> for the specified <CODE>Reader</CODE>, with the specified encoding.
     * 
     * @param reader non-null <CODE>Reader</CODE>.
     * @param encoding non-null <CODE>String</CODE> encoding.
     */
    public ReaderInputStream( Reader reader, String encoding )
    {
        this( reader );
        if ( encoding == null )
        {
            throw new IllegalArgumentException( "encoding must not be null" );
        }
        else
        {
            this.encoding = encoding;
        }
    }

    /**
     * Reads from the <CODE>Reader</CODE>, returning the same value.
     * 
     * @return the value of the next character in the <CODE>Reader</CODE>.
     * @exception IOException if the original <code>Reader</code> fails to be read
     */
    @Override
    public synchronized int read()
        throws IOException
    {
        if ( in == null )
        {
            throw new IOException( "Stream Closed" );
        }

        byte result;
        if ( slack != null && begin < slack.length )
        {
            result = slack[begin];
            if ( ++begin == slack.length )
            {
                slack = null;
            }
        }
        else
        {
            byte[] buf = new byte[1];
            if ( read( buf, 0, 1 ) <= 0 )
            {
                result = -1;
            }
            result = buf[0];
        }

        if ( result < -1 )
        {
            result += 256;
        }

        return result;
    }

    /**
     * Reads from the <code>Reader</code> into a byte array
     * 
     * @param b the byte array to read into
     * @param off the offset in the byte array
     * @param len the length in the byte array to fill
     * @return the actual number read into the byte array, -1 at the end of the stream
     * @exception IOException if an error occurs
     */
    @Override
    public synchronized int read( byte[] b, int off, int len )
        throws IOException
    {
        if ( in == null )
        {
            throw new IOException( "Stream Closed" );
        }

        while ( slack == null )
        {
            char[] buf = new char[len]; // might read too much
            int n = in.read( buf );
            if ( n == -1 )
            {
                return -1;
            }
            if ( n > 0 )
            {
                slack = new String( buf, 0, n ).getBytes( encoding );
                begin = 0;
            }
        }

        if ( len > slack.length - begin )
        {
            len = slack.length - begin;
        }

        System.arraycopy( slack, begin, b, off, len );

        if ( ( begin += len ) >= slack.length )
        {
            slack = null;
        }

        return len;
    }

    /**
     * Marks the read limit of the StringReader.
     * 
     * @param limit the maximum limit of bytes that can be read before the mark position becomes invalid
     */
    @Override
    public synchronized void mark( final int limit )
    {
        try
        {
            in.mark( limit );
        }
        catch ( IOException ioe )
        {
            throw new RuntimeException( ioe.getMessage() );
        }
    }

    /**
     * @return the current number of bytes ready for reading
     * @exception IOException if an error occurs
     */
    @Override
    public synchronized int available()
        throws IOException
    {
        if ( in == null )
        {
            throw new IOException( "Stream Closed" );
        }
        if ( slack != null )
        {
            return slack.length - begin;
        }
        if ( in.ready() )
        {
            return 1;
        }
        else
        {
            return 0;
        }
    }

    /**
     * @return false - mark is not supported
     */
    @Override
    public boolean markSupported()
    {
        return false; // would be imprecise
    }

    /**
     * Resets the StringReader.
     * 
     * @exception IOException if the StringReader fails to be reset
     */
    @Override
    public synchronized void reset()
        throws IOException
    {
        if ( in == null )
        {
            throw new IOException( "Stream Closed" );
        }
        slack = null;
        in.reset();
    }

    /**
     * Closes the Stringreader.
     * 
     * @exception IOException if the original StringReader fails to be closed
     */
    @Override
    public synchronized void close()
        throws IOException
    {
        if ( in != null )
        {
            in.close();
            slack = null;
            in = null;
        }
    }
}