///////////////////////////////////////////////////////////////////////////////
//
//  Microsoft Research Singularity
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
//  File:   Fat/ClientManager/FatClientManager.sg
//
//  Note:
//

using Microsoft.SingSharp;
using Microsoft.Singularity.Channels;
using Microsoft.Singularity.Directory;
using Microsoft.Singularity.Services.Fat.Contracts;
using Microsoft.Singularity.Configuration;
using Microsoft.Singularity.ServiceManager;

using System;
using System.Collections;
using System.IO;
using System.Text;
using FileSystem.Utils;

namespace Microsoft.Singularity.Services.Fat.ClientManager
{
    [Category("Service")]
    internal class ServiceParameters
    {
        [CustomEndpoint]
        public readonly TRef<ServiceProcessContract.Exp:Starting> ControlEndpointRef;
        
        [CustomEndpoint]
        public readonly TRef<ServiceEventContract.Imp:Ready> EventEndpointRef;
        
        reflective private ServiceParameters();
    }

    public class ClientManager
    {
        internal static readonly char PathSeparator = Path.DirectorySeparatorChar;

        private static ArrayList! mounts = new ArrayList();

        internal class Client
        {
            TRef<FatClientContract.Imp:Running>! tref;
            string! diskPath;
            string! mountPath;
            bool    readOnly;
            uint    cacheMB;

            internal Client(
                [Claims] FatClientContract.Imp! imp,
                string! diskPath,
                string! mountPath,
                bool    readOnly,
                uint    cacheMB
                )
            {
                this.tref = new TRef<FatClientContract.Imp:Running>(imp);
                this.diskPath  = diskPath;
                this.mountPath = mountPath;
                this.readOnly  = readOnly;
                this.cacheMB   = cacheMB;
            }

            internal FatClientContract.Imp! Acquire()
            {
                return tref.Acquire();
            }

            internal void Release([Claims] FatClientContract.Imp! imp)
            {
                tref.Release(imp);
            }

            internal string! DiskPath  { get { return this.diskPath;  } }
            internal string! MountPath { get { return this.mountPath; } }
        }

        internal static void
        AddClient(Client newClient)
        {
            mounts.Add(newClient);
        }

        internal static Client GetClientByMountPath(string! path)
            requires (path.Length > 0 &&
                      path[path.Length - 1] != Path.DirectorySeparatorChar);
        {
            for (int i = 0; i < mounts.Count; i++) {
                Client! cs = (Client!)mounts[i];
                if (String.Compare(cs.MountPath, path, true) == 0) {
                    return cs;
                }
            }
            return null;
        }

        internal static Client GetClientByDiskPath(string! path)
            requires (path.Length > 0 &&
                      path[path.Length - 1] != Path.DirectorySeparatorChar);
        {
            for (int i = 0; i < mounts.Count; i++) {
                Client! cs = (Client!)mounts[i];
                if (String.Compare(cs.DiskPath, path, true) == 0) {
                    return cs;
                }
            }
            return null;
        }

        internal static void DeleteClient(Client! closedClient)
        {
            mounts.Remove(closedClient);
        }

        internal static bool ClientIsClosed(Client! client)
        {
            FatClientContract.Imp:Running! clientImp = client.Acquire();
            bool closed = false;

            switch receive {
                case clientImp.ChannelClosed():
                    closed = true;
                    break;
                case timeout:
                    break;
            }

            client.Release(clientImp);
            return closed;
        }

        private static void
        DoMount(FatControlContract.Exp:Ready! controller,
                [Claims]
                FatMountSettings*! in ExHeap  fms)
        {
            string! diskPath  = PathUtils.ToPath(fms->DiskPath);
            string! mountPath = PathUtils.ToPath(fms->MountPath);
            bool    readOnly  = fms->ReadOnly;
            uint    cacheMB   = fms->CacheMB;

            Client client = GetClientByDiskPath(diskPath);
            if (client != null) {
                if (!ClientIsClosed(client)) {
                    // Already using disk path
                    controller.SendFail(FatContractErrorCode.DiskUnavailable);
                    delete fms;
                    return;
                }
                else {
                    DeleteClient(client);
                    client = null;
                }
            }

            client = GetClientByMountPath(mountPath);
            if (client != null) {
                if (!ClientIsClosed(client)) {
                    // Already using mount path
                    controller.SendFail(FatContractErrorCode.PathUnavailable);
                    delete fms;
                    return;
                }
                else {
                    DeleteClient(client);
                    client = null;
                }
            }

            FatClientContract.Imp! clientImp;
            FatClientContract.Exp! clientExp;
            FatClientContract.NewChannel(out clientImp, out clientExp);

            string [] args = { "fatfs" };
            Process process = new Process(args);
            process.SetStartupEndpoint(0, clientExp);
            process.Start();

            clientImp.SendMount(fms);
            switch receive {
                case clientImp.Success():
                    AddClient(
                        new Client(clientImp, diskPath, mountPath,
                                   readOnly, cacheMB)
                        );
                    controller.SendSuccess();
                    break;

                case clientImp.ChannelClosed():
                    controller.SendSuccess();
                    delete clientImp;
                    break;

                case clientImp.Fail(reason):
                    controller.SendFail(reason);
                    delete clientImp;
                    break;
            }
        }

        private static void
        DoUnmount(
            FatControlContract.Exp:Ready! controller,
            [Claims] char[]! in ExHeap    mountPath,
            bool                          force
            )
        {
            string path = PathUtils.ToPath(Bitter.ToString2(mountPath));
            delete mountPath;

            Client client = GetClientByMountPath(path);
            if (client == null) {
                controller.SendFail(FatContractErrorCode.NotMounted);
                return;
            }
            else if (ClientIsClosed(client)) {
                controller.SendSuccess();
                return;
            }

            FatClientContract.Imp! clientImp = client.Acquire();
            clientImp.SendUnmount(force);
            switch receive {
                case clientImp.Success():
                    controller.SendSuccess();
                    client.Release(clientImp);
                    DeleteClient(client);
                    break;
                case clientImp.Fail(reason):
                    controller.SendFail(reason);
                    client.Release(clientImp);
                    break;
                case clientImp.ChannelClosed():
                    controller.SendFail(FatContractErrorCode.InternalError);
                    client.Release(clientImp);
                    DeleteClient(client);
                    break;
            }
        }

        private static void
        DoGetPreferredFormatSettings(
            FatControlContract.Exp:Ready! controller,
            [Claims] char[]! in ExHeap diskPath
            )
        {
            string! cleanPath = PathUtils.ToPath(Bitter.ToString2(diskPath));
            delete diskPath;

            FatClientContract.Imp! clientImp;
            FatClientContract.Exp! clientExp;
            FatClientContract.NewChannel(out clientImp, out clientExp);

            string [] args = { "fatfs" };
            Process process = new Process(args);
            process.SetStartupEndpoint(0, clientExp);
            process.Start();

            clientImp.SendGetPreferredFormatSettings(
                Bitter.FromString2(cleanPath)
                );
            try {
                switch receive {
                    case clientImp.PreferredFormatSettings(settings):
                        controller.SendPreferredFormatSettings(settings);
                        break;
                    case clientImp.Fail(error):
                        controller.SendFail(error);
                        break;
                    case clientImp.ChannelClosed():
                        DebugStub.Break();
                        break;
                }
            }
            finally {
                delete clientImp;
            }
        }

        private static void
        DoFormat(
            FatControlContract.Exp:Ready! controller,
            [Claims] char[]! in ExHeap diskPath,
            [Claims] char[]! in ExHeap volumeLabel,
            [Claims] FatFormatSettings*! in ExHeap settings
            )
        {
            string! cleanPath = PathUtils.ToPath(Bitter.ToString2(diskPath));
            delete diskPath;

            FatClientContract.Imp! clientImp;
            FatClientContract.Exp! clientExp;
            FatClientContract.NewChannel(out clientImp, out clientExp);

            string [] args = { "fatfs" };
            Process process = new Process(args);
            process.SetStartupEndpoint(0, clientExp);
            process.Start();

            clientImp.SendFormat(Bitter.FromString2(cleanPath),
                                 volumeLabel,
                                 settings);
            try {
                switch receive {
                    case clientImp.Success():
                        controller.SendSuccess();
                        break;
                    case clientImp.Fail(error):
                        controller.SendFail(error);
                        break;
                    case clientImp.ChannelClosed():
                        DebugStub.Break();
                        break;
                }
            }
            finally {
                delete clientImp;
            }
        }

        private static void Shutdown()
        {
        }

        private static void ServiceClients(ServiceProcessContract.Exp! svcontrol)
        {
            ESet<FatControlContract.Exp:Ready> controllers =
                new ESet<FatControlContract.Exp:Ready>();

            svcontrol.SendStartSucceeded();
            
            bool run = true;
            while (run) {
                switch receive {
                    case svcontrol.Connect(expath, candidate):
                        if (expath != null) {
                            // This service does not use subpaths.  Reject request.
                            delete expath;
                            delete candidate;
                            svcontrol.SendNakConnect(ErrorCode.NotFound, null);
                            break;
                        }
                        
                        FatControlContract.Exp controller =
                            candidate as FatControlContract.Exp;
                        if (controller != null) {
                            controller.SendSuccess();
                            controllers.Add(controller);
                            svcontrol.SendAckConnect();
                        }
                        else {
                            delete candidate;
                            svcontrol.SendNakConnect(ErrorCode.ContractNotSupported, null);
                        }
                        break;
                        
                    case svcontrol.Stop():
                        DebugStub.WriteLine("FAT: Received 'Stop' request from Service Manager.");
                        run = false;
                        svcontrol.SendAckStop();
                        break;
                        
                    case svcontrol.Knock():
                        DebugStub.WriteLine("FAT: Received 'Knock' request from Service Manager.");
                        svcontrol.SendAlive();
                        break;

                    case svcontrol.ChannelClosed():
                        run = false;
                        break;

                    case controller.Mount(settings) in controllers:
                        DoMount(controller, settings);
                        controllers.Add(controller);
                        break;

                    case controller.Unmount(mountPath, force) in controllers:
                        DoUnmount(controller, mountPath, force);
                        controllers.Add(controller);
                        break;

                    case controller.GetPreferredFormatSettings(diskPath) in controllers:
                        DoGetPreferredFormatSettings(controller, diskPath);
                        controllers.Add(controller);
                        break;

                    case controller.Format(diskPath, volumeLabel, fms) in controllers:
                        DoFormat(controller, diskPath, volumeLabel, fms);
                        controllers.Add(controller);
                        break;

                    case controller.ChannelClosed() in controllers:
                        delete controller;
                        break;
                }
            }
            Shutdown();
            controllers.Dispose();
        }

        internal static int AppMain(ServiceParameters! parameters)
        {
            if (parameters.ControlEndpointRef == null)
                throw new Exception("The parent process did not provide a ServiceProcessContract channel.");
                
            ServiceProcessContract.Exp! svcontrol = parameters.ControlEndpointRef.Acquire();
            try {
                ServiceClients(svcontrol);            
                return 0;
            }
            finally {
                delete svcontrol;
            }
        }            
    }
}