/source/library/Interlace/ReactorUtilities/DeferredObject.cs

#region Using Directives and Copyright Notice



// Copyright (c) 2007-2010, Computer Consultancy Pty Ltd

// All rights reserved.

// 

// 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 the Computer Consultancy Pty Ltd 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 COMPUTER CONSULTANCY PTY LTD 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.



using System;

using System.Collections.Generic;

using System.Text;



#endregion



namespace Interlace.ReactorUtilities

{

    public delegate object ObjectFailback(DeferredFailure failure);

    public delegate object ObjectCallback(object value);





    public class DeferredObject

    {

        object _result = null;



        bool _completed = false;



        ObjectCallback _callback = null;

        ObjectFailback _failback = null;



        DeferredObject _next = null;



        public DeferredObject()

        {

        }



        public void SucceedObject(object value)

        {

            if (_completed) throw new InvalidOperationException();



            _result = value;

            _completed = true;



            RunBacks();

        }



        public void Fail(DeferredFailure failure)

        {

            if (_completed) throw new InvalidOperationException();



            _result = failure;

            _completed = true;



            RunBacks();

        }



        public void Fail(Exception ex)

        {

            Fail(DeferredFailure.FromException(ex));

        }



        void RunBacks()

        {

            if (_callback == null) return;



            try

            {

                if (!(_result is DeferredFailure))

                {

                    _result = _callback(_result);

                }

                else

                {

                    _result = _failback(_result as DeferredFailure);

                }

            }

            catch (Exception e)

            {

                _result = DeferredFailure.FromException(e);

            }



            if (_next != null)

            {

                if (!(_result is DeferredFailure))

                {

                    _next.SucceedObject(_result);

                }

                else

                {

                    _next.Fail(_result as DeferredFailure);

                }

            }

        }



        public void ObjectCompletion(ObjectCallback callback, ObjectFailback failback, DeferredObject nextOrNull)

        {

            if (callback == null) throw new ArgumentNullException("callback");

            if (failback == null) throw new ArgumentNullException("failback");



            if (_callback != null) throw new InvalidOperationException(

                "A completion callback has already been set on this deferred.");



            _callback = callback;

            _failback = failback;

            _next = nextOrNull;



            if (_completed)

            {

                RunBacks();

            }

        }



        public void ObjectCompletion(DeferredObject nextOrNull)

        {

            ObjectCompletion(IdentityCallback, IdentityFailback, nextOrNull);

        }



        public static object IdentityCallback(object result)

        {

            return result;

        }



        public static object IdentityFailback(DeferredFailure failback)

        {

            return failback;

        }

    }

}