//******************************************************************************************************
//  ISynchronizedOperation.cs - Gbtc
//
//  Copyright © 2014, Grid Protection Alliance.  All Rights Reserved.
//
//  Licensed to the Grid Protection Alliance (GPA) under one or more contributor license agreements. See
//  the NOTICE file distributed with this work for additional information regarding copyright ownership.
//  The GPA licenses this file to you under the MIT License (MIT), 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.opensource.org/licenses/MIT
//
//  Unless agreed to in writing, the subject software distributed under the License is distributed on an
//  "AS-IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. Refer to the
//  License for the specific language governing permissions and limitations.
//
//  Code Modification History:
//  ----------------------------------------------------------------------------------------------------
//  03/21/2014 - Stephen C. Wills
//       Generated original version of source code.
//
//******************************************************************************************************

namespace GSF.Threading
{
    /// <summary>
    /// Represents the available types of synchronized operations.
    /// </summary>
    public enum SynchronizedOperationType
    {
        /// <summary>
        /// <see cref="ShortSynchronizedOperation"/>
        /// </summary>
        Short,

        /// <summary>
        /// <see cref="LongSynchronizedOperation"/>
        /// </summary>
        Long,

        /// <summary>
        /// <see cref="LongSynchronizedOperation"/> with IsBackground set to <c>true</c>
        /// </summary>
        LongBackground,

        /// <summary>
        /// <see cref="MixedSynchronizedOperation"/>
        /// </summary>
        Mixed,

        /// <summary>
        /// <see cref="DedicatedSynchronizedOperation"/> with IsBackground set to <c>false</c>
        /// </summary>
        DedicatedForeground,

        /// <summary>
        /// <see cref="DedicatedSynchronizedOperation"/> with IsBackground set to <c>true</c>
        /// </summary>
        DedicatedBackground,
    }

    /// <summary>
    /// Represents an operation that cannot run while it is already in progress.
    /// </summary>
    public interface ISynchronizedOperation
    {
        /// <summary>
        /// Gets a value to indicate whether the synchronized
        /// operation is currently executing its action.
        /// </summary>
        bool IsRunning
        {
            get;
        }

        /// <summary>
        /// Gets a value to indiate whether the synchronized operation
        /// has an additional operation that is pending execution after
        /// the currently running action has completed.
        /// </summary>
        bool IsPending
        {
            get;
        }

        /// <summary>
        /// Executes the action on this thread or marks the
        /// operation as pending if the operation is already running.
        /// </summary>
        /// <remarks>
        /// <para>When the operation is marked as pending, it will run again after
        /// the operation that is currently running has completed. This is useful
        /// if an update has invalidated the operation that is currently running
        /// and will therefore need to be run again.</para>
        /// 
        /// <para>This method does not guarantee that control will be returned to the
        /// thread that called it. If other threads continuously mark the operation as
        /// pending, this thread will continue to run the operation indefinitely.</para>
        /// </remarks>
        void Run();

        /// <summary>
        /// Attempts to execute the action on this thread.
        /// Does nothing if the operation is already running.
        /// </summary>
        /// <remarks>
        /// This method does not guarantee that control will be returned to the thread
        /// that called it. If other threads continuously mark the operation as pending,
        /// this thread will continue to run the operation indefinitely.
        /// </remarks>
        void TryRun();

        /// <summary>
        /// Executes the action on this thread or marks the
        /// operation as pending if the operation is already running.
        /// </summary>
        /// <remarks>
        /// When the operation is marked as pending, it will run again after the
        /// operation that is currently running has completed. This is useful if
        /// an update has invalidated the operation that is currently running and
        /// will therefore need to be run again.
        /// </remarks>
        void RunOnce();

        /// <summary>
        /// Executes the action on another thread or marks the
        /// operation as pending if the operation is already running.
        /// </summary>
        /// <remarks>
        /// When the operation is marked as pending, it will run again after the
        /// operation that is currently running has completed. This is useful if
        /// an update has invalidated the operation that is currently running and
        /// will therefore need to be run again.
        /// </remarks>
        void RunOnceAsync();

        /// <summary>
        /// Attempts to execute the action on this thread.
        /// Does nothing if the operation is already running.
        /// </summary>
        void TryRunOnce();

        /// <summary>
        /// Attempts to execute the action on another thread.
        /// Does nothing if the operation is already running.
        /// </summary>
        void TryRunOnceAsync();
    }
}