/**
 * Copyright 2007-2016, Kaazing Corporation. All rights reserved.
 *
 * 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 org.apache.mina.handler.stream;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.SocketTimeoutException;

import org.apache.mina.core.buffer.IoBuffer;
import org.apache.mina.core.service.IoHandler;
import org.apache.mina.core.service.IoHandlerAdapter;
import org.apache.mina.core.session.AttributeKey;
import org.apache.mina.core.session.IdleStatus;
import org.apache.mina.core.session.IoSession;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A {@link IoHandler} that adapts asynchronous MINA events to stream I/O.
 * <p>
 * Please extend this class and implement
 * {@link #processStreamIo(IoSession, InputStream, OutputStream)} to
 * execute your stream I/O logic; <b>please note that you must forward
 * the process request to other thread or thread pool.</b>
 *
 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
 */
public abstract class StreamIoHandler extends IoHandlerAdapter {
    private static final Logger LOGGER = LoggerFactory.getLogger(StreamIoHandler.class);
    
    private static final AttributeKey KEY_IN = new AttributeKey(StreamIoHandler.class, "in");
    private static final AttributeKey KEY_OUT = new AttributeKey(StreamIoHandler.class, "out");

    private int readTimeout;

    private int writeTimeout;

    protected StreamIoHandler() {
        // Do nothing
    }

    /**
     * Implement this method to execute your stream I/O logic;
     * <b>please note that you must forward the process request to other
     * thread or thread pool.</b>
     */
    protected abstract void processStreamIo(IoSession session, InputStream in,
            OutputStream out);

    /**
     * Returns read timeout in seconds.
     * The default value is <tt>0</tt> (disabled).
     */
    public int getReadTimeout() {
        return readTimeout;
    }

    /**
     * Sets read timeout in seconds.
     * The default value is <tt>0</tt> (disabled).
     */
    public void setReadTimeout(int readTimeout) {
        this.readTimeout = readTimeout;
    }

    /**
     * Returns write timeout in seconds.
     * The default value is <tt>0</tt> (disabled).
     */
    public int getWriteTimeout() {
        return writeTimeout;
    }

    /**
     * Sets write timeout in seconds.
     * The default value is <tt>0</tt> (disabled).
     */
    public void setWriteTimeout(int writeTimeout) {
        this.writeTimeout = writeTimeout;
    }

    /**
     * Initializes streams and timeout settings.
     */
    @Override
    public void sessionOpened(IoSession session) {
        // Set timeouts
        session.getConfig().setWriteTimeout(writeTimeout);
        session.getConfig().setIdleTime(IdleStatus.READER_IDLE, readTimeout);

        // Create streams
        InputStream in = new IoSessionInputStream();
        OutputStream out = new IoSessionOutputStream(session);
        session.setAttribute(KEY_IN, in);
        session.setAttribute(KEY_OUT, out);
        processStreamIo(session, in, out);
    }

    /**
     * Closes streams
     */
    @Override
    public void sessionClosed(IoSession session) throws Exception {
        final InputStream in = (InputStream) session.getAttribute(KEY_IN);
        final OutputStream out = (OutputStream) session.getAttribute(KEY_OUT);
        try {
            in.close();
        } finally {
            out.close();
        }
    }

    /**
     * Forwards read data to input stream.
     */
    @Override
    public void messageReceived(IoSession session, Object buf) {
        final IoSessionInputStream in = (IoSessionInputStream) session
                .getAttribute(KEY_IN);
        in.write((IoBuffer) buf);
    }

    /**
     * Forwards caught exceptions to input stream.
     */
    @Override
    public void exceptionCaught(IoSession session, Throwable cause) {
        final IoSessionInputStream in = (IoSessionInputStream) session
                .getAttribute(KEY_IN);

        IOException e = null;
        if (cause instanceof StreamIoException) {
            e = (IOException) cause.getCause();
        } else if (cause instanceof IOException) {
            e = (IOException) cause;
        }

        if (e != null && in != null) {
            in.throwException(e);
        } else {
            LOGGER.warn("Unexpected exception.", cause);
            session.close(true);
        }
    }

    /**
     * Handles read timeout.
     */
    @Override
    public void sessionIdle(IoSession session, IdleStatus status) {
        if (status == IdleStatus.READER_IDLE) {
            throw new StreamIoException(new SocketTimeoutException(
                    "Read timeout"));
        }
    }

    private static class StreamIoException extends RuntimeException {
        private static final long serialVersionUID = 3976736960742503222L;

        public StreamIoException(IOException cause) {
            super(cause);
        }
    }
}
