/*
 * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.mdsal.binding.api;

import org.eclipse.jdt.annotation.NonNull;
import org.opendaylight.yangtools.yang.binding.Rpc;

/**
 * Provides access to registered Remote Procedure Call (RPC) service implementations. The RPCs are defined in YANG
 * models. {@link RpcProviderService} is this inferface's counterpart allowing registering RPC implementations.
 */
public interface RpcService extends BindingService {
    /**
     * Returns an implementation of a requested RPC service.
     *
     * <p>
     * The returned instance is not an actual implementation of the RPC service interface, but a proxy implementation of
     * the interface that forwards to an actual implementation, if any.
     *
     * <p>
     * The following describes the behavior of the proxy when invoking RPC methods:
     * <ul>
     *   <li>If an actual implementation is registered with the MD-SAL, all invocations are forwarded to the registered
     *       implementation.</li>
     *   <li>If no actual implementation is registered, all invocations will fail by throwing
     *       {@link IllegalStateException}.</li>
     *   <li>Prior to invoking the actual implementation, the method arguments are are validated. If any are invalid, an
     *       {@link IllegalArgumentException} is thrown.
     * </ul>
     * The returned proxy is automatically updated with the most recent registered implementation.
     *
     * <p>
     * The generated RPC method APIs require implementors to return a
     * {@link java.util.concurrent.Future Future} instance that wraps the
     * {@link org.opendaylight.yangtools.yang.common.RpcResult RpcResult}. Since RPC methods may be
     * implemented asynchronously, callers should avoid blocking on the
     * {@link java.util.concurrent.Future Future} result. Instead, it is recommended to use
     * {@link com.google.common.util.concurrent.JdkFutureAdapters#listenInPoolThread(java.util.concurrent.Future)}
     * or
     * {@link com.google.common.util.concurrent.JdkFutureAdapters#listenInPoolThread(java.util.concurrent.Future,
     * java.util.concurrent.Executor)} to listen for Rpc Result. This will asynchronously listen for future result
     * in executor and will not block current thread.
     *
     * <pre>
     *   final Future&lt;RpcResult&lt;SomeRpcOutput&gt;&gt; future = someRpc.invoke( ... );
     *   Futures.addCallback(JdkFutureAdapters.listenInThreadPool(future), new FutureCallback&lt;RpcResult&lt;
     *   SomeRpcOutput&gt;&gt;() {
     *
     *       public void onSuccess(RpcResult&lt;SomeRpcOutput&gt; result) {
     *          // process result ...
     *       }
     *
     *       public void onFailure(Throwable t) {
     *          // RPC failed
     *       }
     *   );
     * </pre>
     *
     * @param <R> {@link Rpc} type
     * @param rpcInterface the interface of the RPC. Typically this is an interface generated from a YANG model.
     * @return the proxy for the requested RPC service. This method never returns null.
     */
    <R extends Rpc<?, ?>> @NonNull R getRpc(@NonNull Class<R> rpcInterface);
}