///////////////////////////////////////////////////////////////////////////////
//
//  Microsoft Research Singularity
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
//  File:   Contracts\ServiceManager.Contracts\ServiceManagementContracts.sg
//
//  Note:   SMS-clients contract
//
using System;
using Microsoft.SingSharp;
using Microsoft.Singularity.Channels;
using Microsoft.Singularity.Directory;

namespace Microsoft.Singularity.ServiceManager
{

    public rep struct ExSchedulerTime
    {
        public long Ticks;
    }

    /// <summary>
    /// This enumeration defines the activation mode for services, which controls when
    /// the Service Manager starts services.
    /// </summary>
    public enum ServiceActivationMode
    {
        /// <summary>
        /// In this mode, the Service Manager will start the service, if necessary, when clients
        /// attempt to connect to the service.  When the service is created, the Service Manager
        /// will not attempt to start the service.
        /// </summary>
        Demand = 1,

        /// <summary>
        /// In this mode, the Service Manager will always attempt to keep the service running.
        /// The StartService and StopService control messages cannot be used to control these
        /// services.  The only way to stop a service that uses this activation mode is to
        /// disable the service (set IsAdministrativelyDisabled to true), or to delete the service.
        /// If a service process terminates unexpectedly, the Service Manager may attempt to restart
        /// the service.
        /// </summary>
        AlwaysActive = 2,

        /// <summary>
        /// In this mode, management clients control the state of the service.  When the service
        /// is created, the Service Manager leaves the service in the Stopped state.
        /// </summary>
        Manual = 3,
    }

    /// <summary>
    /// This structure describes all of the configuration parameters of a service.
    /// </summary>
    public rep struct ServiceConfig : ITracked
    {
        /// <summary>
        /// Specifies the name of the service.  This field is arbitrary; the Service Manager does not
        /// impose any interpretation on the service name.  It only serves to distinguish services.
        /// The field is case-sensitive.
        /// </summary>
        public char[]! in ExHeap ServiceName;

        /// <summary>
        /// Specifies the name to display to the user for this service.
        /// </summary>
        public char[]! in ExHeap DisplayName;

        /// <summary>
        /// Specifies the name of the executable (a manifest name).
        /// </summary>
        public char[]! in ExHeap ExecutableName;


        /// <summary>
        /// Controls when the Service Manager starts the service.
        /// </summary>
        public ServiceActivationMode ActivationMode;

        /// <summary>
        /// If this field is set to true, then this service has been administratively disabled.
        /// This allows administrators to disable a service, without affecting any other aspect
        /// of its configuration.
        /// </summary>
        public bool IsAdministrativelyDisabled;

        /// <summary>
        /// Specifies the minimum number of processes that the Service Manager should create for this
        /// service.  If this field is 0, then the Service Manager will not create any processes for
        /// the service, until the Service Manager receives a Connect request.  Later, when demand
        /// for the service decreases, the Service Manager may stop the process (or processes) that
        /// it created.
        /// </summary>
        public int MinProcesses;

        /// <summary>
        /// Specifies the maximum number of processes that the Service Manager should create for
        /// this service.  If this field is 1, then the service is a singleton.  If this field is
        /// UnlimitedProcesses (-1), then the Service Manager will not limit the number of processes.
        /// </summary>
        public int MaxProcesses;

        /// <summary>
        /// Specifies the maximum number of clients that each service process should handle.  If this
        /// field is 1, then there is a 1:1 relationship between service processes and clients.
        /// If this field is UnlimitedClientsPerProcess, then the Service Manager will not create more
        /// than one service process (per service).
        /// </summary>
        public int MaxClientsPerProcess;

        /// <summary>
        /// The maximum age, in seconds, of each service process.  The Service Manager records the
        /// time when it created each service process.  When a process reaches the age specified by
        /// this field, the Service Manager will no longer route requests to that process.  Instead,
        /// it will route requests to an existing process (whose age limit has not yet been reached),
        /// or will create a new process, if needed.
        ///
        /// If this field is set to UnlimitedProcessAge, then the Service Manager will not perform
        /// service process aging.
        /// </summary>
        public int MaxProcessAgeInSeconds;

        public const int UnlimitedProcesses = -1;
        public const int UnlimitedClientsPerProcess = -1;
        public const int UnlimitedProcessAge = -1;
    }


    public enum ServiceProcessState
    {
        /// <summary>
        /// In this state, the Service Manager has created a new service process,
        /// and is waiting for the process to indicate that it has finished starting.
        /// The process must either indicate that it has finished starting by sending
        /// a StartSucceeded message, indicate that it failed to start by sending a
        /// StartFailed message.  If the service process does not send either of these
        /// messages within a reasonable period of time, then the Service Manager will
        /// mark the process as Defective.
        /// </summary>
        Starting = 1,

        /// <summary>
        /// In this state, the service process is ready for use; the Service Manager
        /// will route client connection requests to the process.
        /// </summary>
        Running = 2,

        /// <summary>
        /// In this state, the Service Manager is stopping the service process.
        /// There may be important substates to consider, but this is the overall
        /// state of the service.
        /// </summary>
        Stopping = 3,

        /// <summary>
        /// In this state, the Service Manager considers this process to be defective.
        /// The Service Manager has (or will) close all channels to this process, and
        /// will not route any new client connections to the service.
        /// </summary>
        Defective = 4,
    }


    public enum ServiceState
    {
        Stopped = 1,
        Starting,
        Running,
        Stopping,
    }

    /// <summary>
    /// This structure describes the operational status of a service.
    /// </summary>
    public rep struct ServiceStatus
    {
        public ServiceState State;

        /// <summary>
        /// The total number of clients that are connect to the service.
        /// </summary>
        public int TotalActiveClients;

        /// <summary>
        /// The total number of processes that the Service Manager has created for this service.
        /// </summary>
        public int TotalActiveProcesses;

        public int ConnectQueueLength;

        public long ProcessId;

        public bool LastStartFailed;
        public ServiceError LastStartError;
    }

    public rep struct ServiceProcessStatus
    {
        public long ProcessId;

        public ServiceProcessState State;

        /// <summary>
        /// The total number of client connections that have ever been routed to this
        /// service process.
        /// </summary>
        public int TotalConnects;

        /// <summary>
        /// The system time (actually, scheduler time) when the process was created.
        /// </summary>
        public ExSchedulerTime TimeCreated;

        /// <summary>
        /// The number of clients that the Service Manager believes are being
        /// serviced by this process.
        /// </summary>
        public int ActiveClientCount;

        public ServiceHealth Health;

        public ServiceLoad Load;
    }

    public rep struct ServiceInfo : ITracked
    {
        public ServiceConfig Config;
        public ServiceStatus Status;
    }

    [Flags]
    public enum ServiceManagerEventMask
    {
        AnyServiceConfig = 1,
        AnyServiceStatus = 2,
    }

    //
//
    //This contract is implemented (exported) by the Service Manager, and is published at
    //the well-known path "/service/services".  This contract allows management clients (such as
    //svconf) to connect to the Service Manager, and:
//
    //  * query the status of the Service Manager,
    //  * enumerate services,
    //  * query the status of services,
    //  * subscribe to the status of a service or services,
    //  * start and stop services,
    //  * create, modify, and delete services,
//
    //
    public contract ServiceManagerContract : ServiceContract
    {
        public const string ModuleName = "/service/services";

        out message Success();
        override state Start : one {
            Success! -> Ready;
        }

        //
        // Enumeration of services
        //
        in message EndEnumeration();
        out message EnumerationTerminated(ServiceInfo[]! in ExHeap infos, int count);
        out message NextServiceInfo(ServiceInfo[]! in ExHeap infos, int count);

        state EnumeratingServices : one {
            NextServiceInfo! -> EnumerateAck;
            EnumerationTerminated! -> Ready;
        }

        state EnumerateAck : one {
            EnumerateServices? -> EnumeratingServices;
            EndEnumeration? -> Ready;
        }

        //
        // Main request state.
        //

        state Ready : one {
            EnumerateServices? -> EnumeratingServices;
            SelectService? -> SelectingService;
            CreateService? -> (Ok! or RequestFailed!);
            WatchServiceManager? -> RequestingWatchServiceManager;
        }

        in message WatchServiceManager(ServiceManagerEventMask mask);
        in message EnumerateServices(ServiceInfo[]! in ExHeap infos);
        in message CreateService(ServiceConfig config);
        in message SelectService(char[]! in ExHeap serviceName);

        state SelectingService : one {
            Ok! -> ServiceSelected;
            RequestFailed! -> Ready;
        }

        state RequestingWatchServiceManager : one {
            Ok! -> ReadyWatchServiceManager;
            RequestFailed! -> Ready;
        }

        //
        // ReadyWatchServiceManager - In this state, a client is watching the overall status
        // of the Service Manager, and uses WaitNextChange() to be notified of the next change
        // in the configuration or in status of any service.  The client and SM then
        // oscillate between ReadyWatchAll <--> WaitingNext
        //

        state ReadyWatchServiceManager : one {
            WaitNextServiceManagerChange? -> WaitingServiceManagerChange;
            StopWatchingServiceManager? -> Ready;
        }

        state WaitingServiceManagerChange : one {
            ServiceManagerChanged! -> ReadyWatchServiceManager;
        }

        in message StopWatchingServiceManager();
        in message WaitNextServiceManagerChange();
        out message ServiceManagerChanged(ServiceManagerEventMask mask);

        //
        // In this state, the client has chosen a specific service to act on, using the
        // SelectService request.  All of the requests in this state act on that server,
        // except for UnselectService, which returns the client to the Ready state.
        //

        state ServiceSelected : one {
            WatchServiceStatus? -> RequestingWatchServiceStatus;
            StartServiceWait? -> StartingServiceWait;
            StartServiceNoWait? -> StartingServiceNoWait;
            StopServiceWait? -> StoppingServiceWait;
            StopServiceNoWait? -> StoppingServiceNoWait;
            QueryServiceStatus? -> (CurrentServiceStatus! or RequestFailed!) -> ServiceSelected;
            QueryServiceConfig? -> (CurrentServiceConfig! or RequestFailed!) -> ServiceSelected;
            DeleteService? -> (Ok! or RequestFailed!);
            UnselectService? -> Ready;
            EnableService? -> (Ok! or RequestFailed!);
            TerminateServiceAllProcesses? -> (Ok! or RequestFailed!);
            TerminateServiceProcess? -> (Ok! or RequestFailed!);
        }

        in message StartServiceNoWait();
        in message StartServiceWait();
        in message StopServiceWait();
        in message StopServiceNoWait();
        in message DeleteService();
        in message UnselectService();
        in message QueryServiceConfig();
        in message QueryServiceStatus();
        in message WatchServiceStatus();
        in message EnableService(bool enable);
        in message TerminateServiceAllProcesses();
        in message TerminateServiceProcess(int processId);

        state RequestingWatchServiceStatus : one {
            Ok! -> ReadyWatchService;
            RequestFailed! -> Ready;
        }

        state StartingServiceWait : one {
            ServiceStarted! -> ServiceSelected;           // service has successfully started
            RequestFailed! -> ServiceSelected;
        }

        state StartingServiceNoWait : one {
            ServiceStarting! -> ServiceSelected;          // service is starting, but may not be finished.
            RequestFailed! -> ServiceSelected;
        }

        state StoppingServiceWait : one {
            ServiceStopped! -> ServiceSelected;           // service has stopped.
            RequestFailed! -> ServiceSelected;
        }

        state StoppingServiceNoWait : one {
            ServiceStopping! -> ServiceSelected;          // service is stopping, but may not be finished.
            RequestFailed! -> ServiceSelected;
        }

        out message CurrentServiceConfig(ServiceConfig config);
        out message CurrentServiceStatus(ServiceStatus status);

        out message ServiceStarting();
        out message ServiceStarted();
        out message ServiceStopping();
        out message ServiceStopped();


        //
        // ReadyWatchService - In this state, the client has subscribed to the status of a
        // service (the Service Manager has already approved the subscription), and the client
        // is the next message sender.  The client can now wait for the next notification,
        // or can end the subscription.
        //

        state ReadyWatchService : one {
            WaitServiceChange? -> WaitingServiceChange;
            StopWatchingService? -> Ready;
        }

        state WaitingServiceChange : one {
            ServiceStatusChanged! -> ReadyWatchService;
            RequestFailed! -> Ready;
        }

        in message WaitServiceChange();
        in message StopWatchingService();
        out message ServiceStatusChanged(ServiceStatus status, bool missedChanges);


        //
        // Generic response codes.
        //

        out message Ok();
        out message RequestFailed(ServiceError err);
    }
}