///////////////////////////////////////////////////////////////////////////////
//
//  Microsoft Research Singularity
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
//  File:   Services\ServiceManager\ResilientService.sg
//
//  Note:   
//
using System;
using System.Threading;
using Microsoft.SingSharp;
using Microsoft.Singularity;
using Microsoft.Singularity.Channels;
using Microsoft.Singularity.Directory;
using Microsoft.Singularity.ServiceManager;

namespace Microsoft.Singularity.Services.ServiceManager
{
    internal class ResilientService : Service
    {
        protected JournalService                        journalService;
        protected Object!                               recoveryLock;
        protected TRef<ServiceProxyContract.Imp:Start>  proxyRef;

        internal ResilientService(string! serviceName,
                                  string! binaryName,
                                  [Claims]DirectoryServiceContract.Imp:Ready! ds,
                                  [Claims]ServiceProxyContract.Imp:Start! sp,
                                  JournalService journal)
        {
            base(serviceName, binaryName, ServiceType.Resilient, ds);
            this.journalService = journal;
            this.recoveryLock = new Object();
            this.proxyRef = new TRef<ServiceProxyContract.Imp:Start>(sp);
        }

        internal override ServiceError StartServiceProcess()
        {
            ServiceError                    report;
            ManagedServiceContract.Imp!     msImp;
            ManagedServiceContract.Exp!     msExp;

            DebugStub.Print("RS: Create process '{0}'\n",
                            __arglist(binaryName));

            process = new Process(new String[1]{binaryName}, null, 3);

            // Create a channel to the service
            ManagedServiceContract.NewChannel(out msImp, out msExp);
            if (!process.SetStartupEndpoint(0, (Endpoint * in ExHeap)msExp)) {
                DebugStub.Print("Endpoint cannot be set. (ManagedService)\n");
                delete msImp;
                return ServiceError.TryAgain;
            }

            if (!process.SetStartupEndpoint(1, (Endpoint * in ExHeap)directory.Acquire())) {
                DebugStub.Print("Endpoint cannot be set. " +
                                "(DirectoryService)\n");
                delete msImp;
                return ServiceError.TryAgain;
            }

            if (!process.SetStartupEndpoint(2, (Endpoint * in ExHeap)proxyRef.Acquire())) {
                DebugStub.Print("Endpoint cannot be set. (ServiceProxy)\n");
                delete msImp;
                return ServiceError.TryAgain;
            }

            DebugStub.Print("RS: start process\n");
            process.Start();

            // Make sure the process has been started
            switch receive {
                case msImp.RecvSuccess():
                    managementEndpoint = new TRef<ManagedServiceContract.Imp:Ready>(msImp);
                    report = ServiceError.None;
                    break;
                case msImp.ChannelClosed():
                    DebugStub.Print("Service process's channel is closed.\n");
                    delete msImp;
                    report = ServiceError.ChannelClosed;
                    break;
            }
            return report;
        }

        internal override ServiceError RestartServiceProcess()
        {
            ServiceError report = ServiceError.Unknown;
            ManagedServiceContract.Imp!     msImp;
            ManagedServiceContract.Exp!     msExp;
            DirectoryServiceContract.Imp!   substituteImp;
            DirectoryServiceContract.Exp!   substituteExp;
            ServiceProxyContract.Imp!       proxyImp;
            ServiceProxyContract.Exp!       proxyExp;

            DebugStub.Print("ResilientService: ENTER RestartServiceProcess\n");
            if (!Monitor.TryEnter(recoveryLock)) {
                return ServiceError.TryAgain;
            }

            DebugStub.Print("RS: Stopping the process ...\n");
            process.Stop();


            DirectoryServiceContract.NewChannel(out substituteImp,
                                                out substituteExp);
            ServiceProxyContract.NewChannel(out proxyImp, out proxyExp);
            // Set substituteExp to JournalProducer and check the connection
            journalService.TransferDirectoryService(substituteExp, proxyExp);

            switch receive {
                case substituteImp.RecvSuccess():
                    report = ServiceError.None;
                    break;
                case substituteImp.ChannelClosed():
                    report = ServiceError.ChannelClosed;
                    break;
            }

            if (report != ServiceError.None) {
                delete substituteImp;
                delete proxyImp;
                goto exit;
            }
            DebugStub.Print("sub received\n");

            DebugStub.Print("RS: creating a new process ... ");
            process = new Process(new String[1]{binaryName}, null, 3);
            DebugStub.Print("done.\n");

            //
            // Create a channel to the service
            //
            ManagedServiceContract.NewChannel(out msImp, out msExp);
            if (!process.SetStartupEndpoint(0, (Endpoint * in ExHeap)msExp)) {
                DebugStub.Print("Endpoint cannot be set. (ManagedService)\n");
                delete msImp;
                delete substituteImp;
                delete proxyImp;
                report = ServiceError.TryAgain;
                goto exit;
            }

            if (!process.SetStartupEndpoint(1, (Endpoint * in ExHeap)substituteImp)) {
                DebugStub.Print("Endpoint cannot be set. " +
                                "(DirectoryService)\n");
                delete msImp;
                delete proxyImp;
                report = ServiceError.TryAgain;
                goto exit;
            }

            if (!process.SetStartupEndpoint(2, (Endpoint * in ExHeap)proxyImp)) {
                DebugStub.Print("Endpoint cannot be set. " +
                                "(ServiceProxy)\n");
                delete msImp;
                report = ServiceError.TryAgain;
                goto exit;
            }

            DebugStub.Print("RS: Restarting service process ... ");
            process.Start();
            DebugStub.Print("done.\n");

            // Make sure the process has been started
            switch receive {
                case msImp.RecvSuccess():
                    // Replace the existing endpoint
                    managementEndpoint = new TRef<ManagedServiceContract.Imp:Ready>(msImp);
                    report = ServiceError.None;
                    break;
                case msImp.ChannelClosed():
                    DebugStub.Print("Service process's channel is closed.\n");
                    delete msImp;
                    report = ServiceError.ChannelClosed;
                    break;
            }

exit:
            Monitor.Exit(recoveryLock);
            DebugStub.Print("RS: Exit RestartServiceProcess\n");
            return report;
        }

        internal override ServiceError RestartService()
        {
            ServiceError report;

            //this.StopService();
            // Currently, we don't know what condition the service
            // process is, so just kill the process and restart it.
            report = RestartServiceProcess();
            if (report == ServiceError.None) {
                report = StartService();
            }

            return report;
        }
    }
}