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// Protocol Buffers - Google's data interchange format
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// Copyright 2008 Google Inc.  All rights reserved.
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// http://code.google.com/p/protobuf/
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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//     * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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//     * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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//     * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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package com.google.protobuf;
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/**
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 * <p>An {@code RpcController} mediates a single method call.  The primary
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 * purpose of the controller is to provide a way to manipulate settings
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 * specific to the RPC implementation and to find out about RPC-level errors.
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 *
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 * <p>Starting with version 2.3.0, RPC implementations should not try to build
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 * on this, but should instead provide code generator plugins which generate
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 * code specific to the particular RPC implementation.  This way the generated
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 * code can be more appropriate for the implementation in use and can avoid
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 * unnecessary layers of indirection.
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 *
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 * <p>The methods provided by the {@code RpcController} interface are intended
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 * to be a "least common denominator" set of features which we expect all
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 * implementations to support.  Specific implementations may provide more
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 * advanced features (e.g. deadline propagation).
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 *
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 * @author kenton@google.com Kenton Varda
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 */
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public interface RpcController {
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  // -----------------------------------------------------------------
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  // These calls may be made from the client side only.  Their results
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  // are undefined on the server side (may throw RuntimeExceptions).
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  /**
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   * Resets the RpcController to its initial state so that it may be reused in
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   * a new call.  This can be called from the client side only.  It must not
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   * be called while an RPC is in progress.
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   */
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  void reset();
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  /**
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   * After a call has finished, returns true if the call failed.  The possible
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   * reasons for failure depend on the RPC implementation.  {@code failed()}
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   * most only be called on the client side, and must not be called before a
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   * call has finished.
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   */
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  boolean failed();
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  /**
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   * If {@code failed()} is {@code true}, returns a human-readable description
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   * of the error.
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   */
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  String errorText();
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  /**
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   * Advises the RPC system that the caller desires that the RPC call be
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   * canceled.  The RPC system may cancel it immediately, may wait awhile and
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   * then cancel it, or may not even cancel the call at all.  If the call is
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   * canceled, the "done" callback will still be called and the RpcController
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   * will indicate that the call failed at that time.
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   */
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  void startCancel();
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  // -----------------------------------------------------------------
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  // These calls may be made from the server side only.  Their results
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  // are undefined on the client side (may throw RuntimeExceptions).
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  /**
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   * Causes {@code failed()} to return true on the client side.  {@code reason}
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   * will be incorporated into the message returned by {@code errorText()}.
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   * If you find you need to return machine-readable information about
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   * failures, you should incorporate it into your response protocol buffer
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   * and should NOT call {@code setFailed()}.
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   */
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  void setFailed(String reason);
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  /**
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   * If {@code true}, indicates that the client canceled the RPC, so the server
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   * may as well give up on replying to it.  This method must be called on the
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   * server side only.  The server should still call the final "done" callback.
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   */
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  boolean isCanceled();
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  /**
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   * Asks that the given callback be called when the RPC is canceled.  The
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   * parameter passed to the callback will always be {@code null}.  The
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   * callback will always be called exactly once.  If the RPC completes without
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   * being canceled, the callback will be called after completion.  If the RPC
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   * has already been canceled when NotifyOnCancel() is called, the callback
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   * will be called immediately.
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   *
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   * <p>{@code notifyOnCancel()} must be called no more than once per request.
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   * It must be called on the server side only.
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   */
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  void notifyOnCancel(RpcCallback<Object> callback);
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}