#region Copyright notice and license

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// http://github.com/jskeet/dotnet-protobufs/
// Original C++/Java/Python code:
// http://code.google.com/p/protobuf/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#endregion

using System;

namespace Google.ProtocolBuffers
{
    /// <summary>
    /// Mediates a single method call. The primary purpose of the controller
    /// is to provide a way to manipulate settings specific to the
    /// RPC implementation and to find out about RPC-level errors.
    /// 
    /// The methods provided by this interface are intended to be a "least
    /// common denominator" set of features which we expect all implementations to
    /// support. Specific implementations may provide more advanced features,
    /// (e.g. deadline propagation).
    /// </summary>
    public interface IRpcController
    {
        #region Client side calls

        // These calls may be made from the client side only.  Their results
        // are undefined on the server side (may throw exceptions).

        /// <summary>
        /// Resets the controller to its initial state so that it may be reused in
        /// a new call.  This can be called from the client side only.  It must not
        /// be called while an RPC is in progress.
        /// </summary>
        void Reset();

        /// <summary>
        /// After a call has finished, returns true if the call failed.  The possible
        /// reasons for failure depend on the RPC implementation. Failed must
        /// only be called on the client side, and must not be called before a call has
        /// finished.
        /// </summary>
        bool Failed { get; }

        /// <summary>
        /// If Failed is true, ErrorText returns a human-readable description of the error.
        /// </summary>
        string ErrorText { get; }

        /// <summary>
        /// Advises the RPC system that the caller desires that the RPC call be
        /// canceled. The RPC system may cancel it immediately, may wait awhile and
        /// then cancel it, or may not even cancel the call at all. If the call is
        /// canceled, the "done" callback will still be called and the RpcController
        /// will indicate that the call failed at that time.
        /// </summary>
        void StartCancel();

        #endregion

        #region Server side calls

        // These calls may be made from the server side only.  Their results
        // are undefined on the client side (may throw exceptions).

        /// <summary>
        /// Causes Failed to return true on the client side. <paramref name="reason"/>
        /// will be incorporated into the message returned by ErrorText.
        /// If you find you need to return machine-readable information about
        /// failures, you should incorporate it into your response protocol buffer
        /// and should *not* call SetFailed.
        /// </summary>
        void SetFailed(string reason);

        /// <summary>
        /// If true, indicates that the client canceled the RPC, so the server may as
        /// well give up on replying to it. This method must be called on the server
        /// side only. The server should still call the final "done" callback.
        /// </summary>
        bool IsCanceled();

        /// <summary>
        /// Requests that the given callback be called when the RPC is canceled.
        /// The parameter passed to the callback will always be null. The callback will
        /// be called exactly once. If the RPC completes without being canceled, the
        /// callback will be called after completion. If the RPC has already been canceled
        /// when NotifyOnCancel is called, the callback will be called immediately.
        /// 
        /// NotifyOnCancel must be called no more than once per request. It must be
        /// called on the server side only.
        /// </summary>
        /// <param name="callback"></param>
        void NotifyOnCancel(Action<object> callback);

        #endregion
    }
}