///////////////////////////////////////////////////////////////////////////////
//
//  Microsoft Research Singularity
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
//  File:   UdpExpManager.sg
//
//  Note:   Provider-side helper for the IP Channel Contract
//

using System.Threading;
using System.Net.IP;
using Microsoft.SingSharp;
using Microsoft.Singularity;
using Microsoft.Singularity.Channels;
using Microsoft.Singularity.Directory;
using NetStack.Contracts;
using NetStack.Runtime;
using System.Collections;
using System;

namespace NetStack.Channels.Private
{
    public class UdpExpManager
    {
        public void Run()
        {
            // Here is the set of client channels we service
            ESet<UdpContract.Exp:ReadyState> epSet = new ESet<UdpContract.Exp:ReadyState>();

            // 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. When we become a
            // process, this will be present automatically,
            // somehow.
            DirectoryServiceContract.Imp epNS = DirectoryService.NewClientEndpoint();

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

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

                    case epNS.NakRegister(ServiceProviderContract.Imp:Start rejectedEP, error) :
                        // All is very much not well; abort.
                        DebugStub.Print("Failed to register the Udp module.\n");
                        delete rejectedEP;
                        delete nsExp;
                        epSet.Dispose();
                        return;
                        break;
                }
            }
            finally {
                delete epNS;
            }

            while(true) {
                switch receive {
                    //
                    // Don't forget that we're selecting UdpContract endpoints
                    // from the epSet endpoint-set. In each case that we
                    // receive a message from one of those endpoints, we
                    // need to remember to put the endpoint back into epSet
                    // if we want to keep listening to it.
                    //
                    case ep.CreateUdpSession(UdpConnectionContract.Exp:Start! newEP) in epSet :
                        {
                            // Move the endpoint to the ReadyState
                            newEP.SendReady();
                            // Create a dedicated thread to service this connection
                            UdpConnectionExpThread udpThread = new UdpConnectionExpThread(newEP);
                            udpThread.Start();
                            ep.SendAck();
                            epSet.Add(ep);
                        }
                        break;

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

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

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

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

        public void Start()
        {
            Thread newThread = new Thread(new ThreadStart(Run));
            newThread.Start();
        }
    }
}