/*
 *
 * 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.qpid.proton.driver;

import java.io.IOException;
import java.nio.channels.SelectableChannel;
import java.nio.channels.ServerSocketChannel;
import org.apache.qpid.proton.driver.impl.DriverImpl;

/**
 * A driver for the proton engine.
 *
 * Manages {@link Connector}'s and {@link Listener}'s, which act as intermediaries between
 * the proton engine and the network.
 *
 * Provides methods for the application to access the "top half" of the engine API when the state
 * of the engine may have changed due to I/O or timing events - see {@link #connector()}.
 *
 * Connectors incorporate the SASL engine in order to provide a complete network stack:
 * AMQP over SASL over TCP.
 *
 * Unless otherwise stated, methods on Driver implementations are not necessarily thread-safe.
 */
public interface Driver
{

    public static final class Factory
    {
        public static Driver create() throws IOException {
            return new DriverImpl();
        }
    }

    /**
     * Force {@link #doWait(long)} to return.
     *
     * If the driver is not currently waiting then the next invocation of {@link #doWait(long)}
     * will return immediately unless the {@link #connector()} method is invoked in the meantime.
     *
     * Thread-safe.
     */
    void wakeup();

    /**
     * Wait for an active connector or listener, or for {@link #wakeup()} to be called.
     *
     * Thread-safe.
     *
     * @param timeout maximum time in milliseconds to wait. -1 means wait indefinitely.
     *
     * @return true if woken up
     */
    boolean doWait(long timeout);

    /**
     * Get the next listener with pending data in the driver.
     *
     * @return null if no active listener available
     */
    @SuppressWarnings("rawtypes")
    Listener listener();

    /**
     * Get the next active connector in the driver.
     *
     * Returns the next connector with pending inbound data, available capacity
     * for outbound data, or pending tick.
     *
     * Clears the wake-up status that is set by {@link #wakeup()}.
     *
     * @return null if no active connector available
     */
    @SuppressWarnings("rawtypes")
    Connector connector();

    /**
     * Destruct the driver and all associated listeners, connectors and other resources.
     */
    void destroy();

    /**
     * Construct a listener for the given address.
     *
     * @param host local host address to listen on
     * @param port local port to listen on
     * @param context application-supplied, can be accessed via
     *                {@link Listener#getContext() getContext()} method on a listener.
     * @return a new listener on the given host:port, null if error
     */
    <C> Listener<C> createListener(String host, int port, C context);

    /**
     * Create a listener using the existing channel.
     *
     * @param c   existing SocketChannel for listener to listen on
     * @param context application-supplied, can be accessed via
     *                {@link Listener#getContext() getContext()} method on a listener.
     * @return a new listener on the given channel, null if error
     */
    <C> Listener<C> createListener(ServerSocketChannel c, C context);

    /**
     * Construct a connector to the given remote address.
     *
     * @param host remote host to connect to.
     * @param port remote port to connect to.
     * @param context application-supplied, can be accessed via
     *                {@link Connector#getContext() getContext()} method on a listener.
     *
     * @return a new connector to the given remote, or null on error.
     */
    <C> Connector<C> createConnector(String host, int port, C context);

    /**
     * Create a connector using the existing file descriptor.
     *
     * @param fd   existing SocketChannel for listener to listen on
     * @param context application-supplied, can be accessed via
     *                {@link Connector#getContext() getContext()} method on a listener.
     *
     * @return a new connector to the given host:port, null if error.
     */
    <C> Connector<C> createConnector(SelectableChannel fd, C context);

    /**
     * Return an iterator over all listeners.
     */
    Iterable<Listener> listeners();
    /**
     * Return an iterator over all connectors.
     */
    Iterable<Connector> connectors();

}
