///////////////////////////////////////////////////////////////////////////////
//
//  Microsoft Research Singularity
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
//  File:   Libraries\Resiliency\Journalet2.sg
//
//  Note:   
//
using System;
using System.Threading;
using Microsoft.Singularity;
using Microsoft.Singularity.Channels;
using Microsoft.Singularity.Directory;

namespace Microsoft.Singularity.Resiliency
{
    public enum ProxyState : uint {
        Waiting,
        Running,
        Synchronize,
    }

    public abstract class Journalet2 : ICheckpoint
    {
        protected bool              running;
        protected Thread            thread;
        protected JournaletGroup    group;
        protected ManualResetEvent  recoveryEvent;
        protected ManualResetEvent  suspendEvent;
        protected ProxyState        proxyState;

        public Journalet2()
        {
            this.recoveryEvent = new ManualResetEvent(false);
            this.suspendEvent = new ManualResetEvent(false);
            this.proxyState = ProxyState.Waiting;
        }

        //NOTE: Be sure the thread is stopped when calling this.
        public abstract void CreateEndpoint(out ServiceContract.Exp! newExp);
        protected abstract bool Initialize();
        protected abstract bool HandleMessages();
        protected abstract bool Recover();

        public virtual void Start()
        {
            if (thread == null) {
                thread = new Thread(new ThreadStart(Run));
                thread.Start();
            }
            else {
                recoveryEvent.Set();
            }
        }

        public virtual void Stop() {}

        public virtual void Run() {
            if (group == null) {
                DebugStub.Print("J: group is not set!\n");
                return;
            }

            if (!Initialize()) {
                return;
            }

            for (;;) {
                if (!HandleMessages()) {
                    break;
                }
                // Now you can create another endpoint.

                running = false;
                group.NotifyRecovery();

                recoveryEvent.WaitOne();

                DebugStub.Print("J: Start recovery\n");
                try {
                    if (!Recover()) {
                        break;
                    }
                }
                catch (ChannelClosedException) {
                    DebugStub.Print("Channel closed during recovery.\n");
                    break;
                }
                recoveryEvent.Reset();
                Thread.Sleep(0);
            }
        }

        ///
        /// Suspends this journalet at the nearest synchronization point.
        /// This method blocks the caller until the journalet suspends.
        ///
        public void Suspend()
        {
            if (running && group != null && group.SyncRequest) {
                suspendEvent.WaitOne();
            }
        }

        public abstract void Flush();
        public void Resume() {}

        // Checks if receiving a synchronization request.
        protected void Sync()
        {
            proxyState = ProxyState.Synchronize;
            if (group != null && group.SyncRequest) {
                running = false;
                suspendEvent.Set();
                DebugStub.Print("J: Syncronize\n");
                group.SyncEvent.WaitOne();
                running = true;
            }
        }

        protected void Checkpoint()
        {
            //DebugStub.Print("J: Enter Checkpoint\n");
            group.UpdateCheckpoint();
            //DebugStub.Print("J: Exit Checkpoint\n");
        }

        public ProxyState State
        {
            get { return proxyState; }
            private set
            {
                lock (this) {
                    proxyState = value;
                }
            }
        }

        // Invoked by JournaletGroup.
        internal JournaletGroup Group
        {
            get { return group; }
            set { group = value; }
        }
    }
}