///////////////////////////////////////////////////////////////////////////////
//
//  Microsoft Research Singularity
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
//  File:   ChannelModule.sg
//  Note:   Channel diagnostic module
//

using System.Threading;
using Microsoft.SingSharp;
using Microsoft.Contracts;
using Microsoft.Singularity;
using Microsoft.Singularity.Memory;
using Microsoft.Singularity.Channels;
using Microsoft.Singularity.Diagnostics.Contracts;
using Microsoft.Singularity.Directory;
using System;

namespace Microsoft.Singularity.Diagnostics
{
    using SystemType = Microsoft.Singularity.V1.Types.SystemType;

    public class ChannelModule
    {
        private void Run()
        {
            // Here is the channel we use to communicate with
            // the NameServer
            ServiceProviderContract.Imp! nsImp;
            ServiceProviderContract.Exp! nsExp;
            ServiceProviderContract.NewChannel(out nsImp, out nsExp);

            // Here is our NameServer connection over which we
            // receive new client channels.
            DirectoryServiceContract.Imp! epNS = DirectoryService.NewClientEndpoint();

            try
            {
                epNS.SendRegister(Bitter.FromString2(ChannelContract.ModuleName), nsImp);

                switch receive
                {
                    case epNS.AckRegister() :
                        // All is well.
                        break;

                    case epNS.NakRegister(ServiceProviderContract.Imp:Start rejectedEP, ErrorCode error) :
                        // All is very much not well; abort.
                        DebugStub.Print("Failed to register the Channel Diagnostic module.\n");
                        if (rejectedEP != null) {
                            delete rejectedEP;
                        }
                        delete nsExp;
                        return;
                }
            }
            finally
            {
                delete epNS;
            }

            // Here is the set of client channels we service
            ESet<ChannelContract.Exp:ReadyState> epSet = new ESet<ChannelContract.Exp:ReadyState>();
            while(true)
            {
                switch receive
                {
                    // ------------------------------- Requests for new connections

                    case nsExp.Connect(ServiceContract.Exp:Start! newEp) :
                        {
                            // We expect people top give us ChannelContract.Exp instances
                            ChannelContract.Exp newDiagEp = newEp as ChannelContract.Exp;

                            if (newDiagEp == null)
                            {
                                // Invalid contract type. Fail.
                                nsExp.SendNackConnect(newEp);
                            }
                            else
                            {
                                // Signal ready and start servicing this contract
                                nsExp.SendAckConnect();
                                newDiagEp.SendReady();
                                epSet.Add(newDiagEp);
                            }
                        }
                        break;

                    // ------------------------------- Requests on existing connections
                    //

                    /// TODO: Move this to the Channel specific contract once we get there.
                    case ep.GetChannels() in epSet :
                        {
                            ChannelInfo[]! in ExHeap channels = ChannelModule.GetChannelInfo();
                            ep.SendChannels(channels);
                            epSet.Add(ep);
                        }
                        break;

                    case ep.GetChannelStats() in epSet :
                        {
                            long msgs  = PerfCounters.MsgsSent; 
                            long bytes = PerfCounters.BytesSent; 
                            long chan  = PerfCounters.ChannelsCreated; 
                            ep.SendChannelStats(msgs, bytes, chan);
                            epSet.Add(ep);
                        }
                        break;

                    case ep.ChannelClosed() in epSet :
                        {
                            delete ep;
                        }
                        break;

                    case epSet.Empty() && nsExp.ChannelClosed():
                        // Exit this thread
                        delete nsExp;
                        epSet.Dispose();
                        return;
                }
            }
        }

        private class ChannelInfoAccumulator
        {
            unsafe private ChannelInfo[]! in ExHeap infoVector;
            private int used = 0;

            [NotDelayed]
            private ChannelInfoAccumulator()
            {
                this.infoVector = new[ExHeap] ChannelInfo[EndpointCore.OpenChannelCount];
                base();
                ((!)SharedHeap.KernelSharedHeap).EndpointOwnerId.Iterate(
                    new SharedHeap.AllocationVisitor(this.Accumulate));

            }

            public static ChannelInfo[]! in ExHeap GetChannels() {
                ChannelInfoAccumulator acc = new ChannelInfoAccumulator();
                return acc.infoVector;
            }

            private unsafe void Accumulate(SharedHeap.Allocation* alloc)
            {
                SystemType endpointType = typeof(Endpoint).GetSystemType();

                ChannelInfo[]! in ExHeap infoVector = this.infoVector;

                if (SystemType.IsSubtype(alloc, endpointType))
                {
                    unsafe {
                        // Note that we use Unchecked access here, since we don't
                        // actually own this data.
                        //
                        UIntPtr data = SharedHeap.Allocation.GetDataUnchecked(alloc);
                        EndpointCore*! ep = (!)(EndpointCore*)data;
                        int id = ep->ChannelId;
                        if (id > 0) {
                            int index = this.used++;
                            if (index >= infoVector.Length) {
                                // more channels materialized after we allocated vector
                                // skip the remaining ones

                                // suck back ownership
                                this.infoVector = infoVector;
                                return;
                            }
                            infoVector[index].ChannelId = id;
                            infoVector[index].ExpProcessId = ep->ProcessId;
                            infoVector[index].ImpProcessId = ep->PeerProcessId;
                            infoVector[index].MessagesDeliveredToExp = ep->ReceiveCount;
                            infoVector[index].MessagesDeliveredToImp = ep->PeerReceiveCount;
                        }
                    }
                }
            }
        }


        public static ChannelInfo[]! in ExHeap GetChannelInfo() {
            return ChannelInfoAccumulator.GetChannels();
        }

        internal static void Initialize()
        {
            ChannelModule module = new ChannelModule();
            Thread thread = Thread.CreateThread(Thread.CurrentProcess,
                                                new ThreadStart(module.Run));
            if (thread != null) {
                thread.Start();
            }
        }
    }
}