// ----------------------------------------------------------------------------
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ----------------------------------------------------------------------------

namespace Microsoft.Singularity.Security
{
    using System;
    using System.Collections;
    using System.Text;
    using System.Threading;

    using Microsoft.Contracts;
    using Microsoft.SingSharp;
    using Microsoft.Singularity;
    using Microsoft.Singularity.Channels;
    using Microsoft.Singularity.Directory;
    using Microsoft.Singularity.Security;

    /// <summary>
    /// The implementation of the <code>SecurityService</code> state machine.
    /// </summary>
    public class SecurityDiagnostics
    {
        /// <summary>
        /// The exporting endpoint of the security service.
        /// </summary>
        private TRef<ServiceProviderContract.Exp:Start> channel;
        private bool run = true;

        private ArrayList! coreList;

        public SecurityDiagnostics()
        {
            coreList = new ArrayList();
        }

        /// <summary>
        /// Starts the service and registers it in the namespace
        /// </summary>
        public void Start()
        {
            DebugStub.WriteLine("Starting the Security Diagnostics provider");

            // register the service with the namespace
            ServiceProviderContract.Imp! nsImp;
            ServiceProviderContract.Exp! nsExp;
            ServiceProviderContract.NewChannel(out nsImp, out nsExp);

            DirectoryServiceContract.Imp epNS = DirectoryService.NewClientEndpoint();

            try {
                epNS.SendRegister(Bitter.FromString2(SecurityDiagnosticsContract.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.WriteLine("Failed to register the Security Service under: {0}",
                                        __arglist(SecurityDiagnosticsContract.ModuleName));
                    delete nsExp;
                    delete rejectedEP;
                    throw new Exception("Failed to register the Security Diagnostics provider");
                case epNS.ChannelClosed():
                    delete nsExp;
                    DebugStub.WriteLine(
                               "Failed to register the Security Diagnostics provider under: {0}",
                               __arglist(SecurityDiagnosticsContract.ModuleName));
                    throw new Exception("Failed to register the Security Diagnostics provider");
                }
            }
            finally {
                delete epNS;
            }

            channel = new TRef<ServiceProviderContract.Exp:Start>(nsExp);

            Thread thread = Thread.CreateThread(((!)Thread.CurrentThread).Process,
                                                new ThreadStart(StateMachine));

            if (thread != null) {
                thread.Start();
            }
            else {
                throw new Exception("Could not create worker thread");
            }
        }

        public void RegisterAclCore(AclCore core)
        {
            //*** need locking here, but it doesn't work for now
            //we're called at the wrong point in the init sequence
            coreList.Add(core);
        }

        /// <summary>
        /// State machine for the security namespace
        /// </summary>
        private void StateMachine()
            requires this.channel != null;
        {
            // get the endpoint and start listening
            ServiceProviderContract.Exp! exp = channel.Acquire();
            // the clients
            ESet<SecurityDiagnosticsContract.Exp, SecurityDiagnosticsContract.ReadyState> clients =
               new ESet<SecurityDiagnosticsContract.Exp, SecurityDiagnosticsContract.ReadyState>();

            while (run) {
                switch receive {
                    case exp.Connect(ServiceContract.Exp:Start! epClient):
                    {
                        // incoming bind request: always grant, anyone should be able to talk to us
                        SecurityDiagnosticsContract.Exp client =
                                       epClient as SecurityDiagnosticsContract.Exp;
                        if (client == null) {
                            exp.SendNackConnect(epClient);
                        }
                        else {
                            exp.SendAckConnect();
                            client.SendReady();
                            clients.Add(client);
                        }
                    }

                    break;

                    case client.GetStatistics() in clients:
                    {
                        StringBuilder sb = new StringBuilder();
                        DumpAllStats(sb);
                        client.SendGetStatisticsAck(Bitter.FromString2(sb.ToString()));
                        clients.Add(client);
                    }
                    break;

                    case client.ClearStatistics() in clients:
                    {
                        ClearAllStats();
                        client.SendAck();
                        clients.Add(client);
                    }
                    break;

                    case client.Disable(bool yes) in clients:
                    {
                        DisableAll(yes);
                        client.SendAck();
                        clients.Add(client);
                    }
                    break;

                    case client.FlushCaches() in clients:
                    {
                        FlushAllCaches();
                        client.SendAck();
                        clients.Add(client);
                    }
                    break;

                    case client.ChannelClosed() in clients:
                    {
                        delete client;
                    }
                    break;

                    case exp.ChannelClosed():
                    {
                        run = false;
                    }
                    break;
                }
            }

            delete exp;
            clients.Dispose();
        }

        private void DisableAll(bool value) {
            lock (coreList) {
                for (int i = 0; (i < coreList.Count); i++) {
                    AclCore core = (AclCore!) coreList[i];
                    core.Disable = value;
                }
            }
        }

        private void DumpAllStats(StringBuilder! sb)
        {
            lock (coreList) {
                for (int i = 0; (i < coreList.Count); i++) {
                    AclCore core = (AclCore!) coreList[i];
                    core.DumpStats(sb);
                }
            }
        }

        private void ClearAllStats()
        {
            lock (coreList) {
                for (int i = 0; (i < coreList.Count); i++) {
                    AclCore core = (AclCore!) coreList[i];
                    core.ClearStats();
                }
            }
        }

        private void FlushAllCaches()
        {
            lock (coreList) {
                for (int i = 0; (i < coreList.Count); i++) {
                    AclCore core = (AclCore!) coreList[i];
                    core.FlushCache();
                }
            }
        }
    }
}