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

using System;
using System.Diagnostics;
using System.Threading;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;

using Microsoft.Singularity;
using Microsoft.SingSharp;

namespace Microsoft.Singularity.Channels {

    using Microsoft.Singularity.V1.Threads;
    using Microsoft.Singularity.V1.Services;
    using Microsoft.Singularity.V1.Types;
    using Microsoft.Singularity.V1.Security;
    using Allocation = Microsoft.Singularity.V1.Services.SharedHeapService.Allocation;
    using EndpointCore = Microsoft.Singularity.V1.Services.EndpointCore;

    [CLSCompliant(false)]
    public enum EndpointEvent : ushort
    {
        Notify = 10,
        Dispose = 1,
        Select = 2,
        RetrieveHook = 6,
        DeliverHook = 7,
    }

    /// <summary>
    /// Provides an adapter class between the runtime provided Endpoint and the compiler generated contract specific
    /// Imp and Exp endpoints.
    /// </summary>
    public rep struct Endpoint : EndpointCore, IEventCollectionElement {

        public const int ANY_MESSAGE_TAG = 1;
        public const int CHANNEL_CLOSED_TAG = -1;

        protected StateStack stateStack;

        // some cached info for Monitoring
#if MONITORING
        uint contractTag;
        uint peerContractTag;
#endif

        // Initialization of EndpointCore happens during Allocation!
        protected Endpoint(int initialState)
        {
          Initialize(initialState);
        }

#if SINGULARITY_KERNEL
        public
#endif
        void Initialize(int initialState) {
          stateStack = new StateStack(initialState);
          assert stateStack.Top() == initialState;
        }

        new public bool Closed { get { return EndpointCore.Closed(ref this); } }

        new public void Close() {
            EndpointCore.Close(ref this);
        }

        new public bool PeerClosed
        {
            get {
                return EndpointCore.PeerClosed(ref this);
            }
        }

        new public virtual SyncHandle GetWaitHandle() {
            return EndpointCore.GetWaitHandle(ref this);
        }

        new public virtual void ResetWaitSignal() {
            // dummy for now
        }

        new protected void NotifyPeer() {
            EndpointCore.NotifyPeer(ref this);
        }

#if false
        new protected void Notify() {
          // would like to determine if there are any outstanding messages
          // on this endpoint and only signal if there are not.
          // With new message allocation scheme, it is tricky to determine
          // this without grabbing locks, which I'm trying to avoid
          // So we just signal it all.
          //
          // The access to setHead also needs to change eventually when
          // we have endpoints in the shared heap. We'll need to figure out
          // how to encode sets again.
          //

          Monitoring.Log(Monitoring.Provider.Endpoint,
                         (ushort)EndpointEvent.Notify,
                         0, (uint)this.ChannelID, 0, 0, 0, 0);

          if (this.collectionEvent.id != UIntPtr.Zero) {
            AutoResetEventHandle.Set(this.collectionEvent);
          }
          base.Notify();
        }
#endif

        /// <summary>
        /// Wait for a message to arrive on this endpoint.
        /// </summary>
        new protected void Wait() {
          EndpointCore.Wait(ref this);
        }

        /// <summary>
        /// Obtain the channel identifier of this endpoint.
        /// </summary>
        public new int ChannelID {
            [NoHeapAllocation]
            get { 
                return EndpointCore.GetChannelID(ref this);
            }
        }

        /// <summary>
        /// Obtain the process identifier of the owner.
        /// </summary>
        public new int OwnerProcessID {
            [NoHeapAllocation]
            get { 
                return EndpointCore.GetOwnerProcessID(ref this);
            }
        }

        /// <summary>
        /// Obtain the principal identifier of the owner.
        /// </summary>
        public new PrincipalHandle OwnerPrincipalHandle {
            [NoHeapAllocation]
            get { 
                return EndpointCore.GetOwnerPrincipalHandle(ref this);
            }
        }

        /// <summary>
        /// Obtain the process identifier of the owner of the other endpoint
        /// </summary>
        public new int PeerProcessID {
            [NoHeapAllocation]
            get { 
                return EndpointCore.GetPeerProcessID(ref this);
            }
        }

        /// <summary>
        /// Obtain the principal identifier of the owner of the other endpoint
        /// </summary>
        public new PrincipalHandle PeerPrincipalHandle {
            [NoHeapAllocation]
            get { 
                return EndpointCore.GetPeerPrincipalHandle(ref this);
            }
        }


        ///
        /// Closes this end of the channel and frees associated resources, EXCEPT the block
        /// of memory for this endpoint. It must be released by the caller. Sing# does this
        /// for the programmer.
        ///
        public void Dispose() {
            if (this.Closed) {
                throw new ApplicationException("Endpoint already closed");
            }
            Monitoring.Log(Monitoring.Provider.Endpoint,
                           (ushort)EndpointEvent.Dispose,
                           0, (uint)this.ChannelID, 0, 0, 0, 0);
            if (!EndpointCore.Dispose(ref this)) {
                throw new ApplicationException("ChannelService.Dispose returned false");
            }
        }


        [return:Borrowed]
        new unsafe protected Endpoint*! in ExHeap GetPeer(out bool marshall)
        {
            return (Endpoint* in ExHeap!)EndpointCore.GetPeer(ref this, out marshall);
        }


        unsafe public static SystemType RegisterSystemType(string! name,  long lower, long upper, SystemType systemType) 
        {
            char [] typeName = new char[name.Length]; 

            if (typeName == null) {
                throw new Exception("no more memory!");      
            }
            
            for(int i=0; i < name.Length; i++) {
                typeName[i] = name[i]; 
            }
            fixed (char* start = &typeName[0]) {
                return SystemType.Register(start, name.Length, lower, upper, systemType); 
            }
        }

        /// <summary>
        /// Connects up the endpoints and initializes
        /// the kernel part of the endpoints. The context needs to call the .ctor on the two
        /// endpoints returned in order to initialize the contract specific structures as well
        /// as those of the Endpoint struct itself.
        /// </summary>
        unsafe public static void Connect(Endpoint*! in ExHeap imp,
                                          Endpoint*! in ExHeap exp)
        {
#if MONITORING
            uint impContractTag = getContractTag(imp);
            uint expContractTag = getContractTag(exp);
            imp->contractTag = impContractTag;
            imp->peerContractTag = expContractTag;
            exp->contractTag = expContractTag;
            exp->peerContractTag = impContractTag;
#endif
            EndpointCore.Connect( (Allocation*)imp, (Allocation*)exp);
        }

        /// <summary>
        /// Transfer any content of this endpoint to target endpoint
        /// </summary>
        public void TransferContentsOwnership(ref Endpoint target) {
            EndpointCore.TransferContentOwnership(ref this, ref target);
        }


        /// <summary>
        /// Transfer actual block of data ownership to this endpoint.
        /// </summary>
        unsafe public void TransferBlockOwnership(void* in ExHeap data) {
            if (data != null) {
            EndpointCore.TransferBlockOwnership((Microsoft.Singularity.V1.Services.SharedHeapService.Allocation*)data, ref this);
        }
        }


        /// <summary>
        /// Instruct the selectable object to signal events on the given AutoResetEvent
        /// rather than its normal event in order to aggregate signalling into a set.
        /// A selectable object need only support being part of a single collection at
        /// any point in time.
        /// </summary>
        new public void LinkIntoCollection(AutoResetEventHandle ev) {
            //          Debug.Assert(this.collectionEvent.id == UIntPtr.Zero);
            EndpointCore.LinkIntoCollection(ref this, ev);
        }

        /// <summary>
        /// Instruct the selectable object to stop signalling events on the given
        /// AutoResetEvent.
        /// </summary>
        new public void UnlinkFromCollection(AutoResetEventHandle ev) {
            // Debug.Assert(this.collectionEvent.id != UIntPtr.Zero);
            EndpointCore.UnlinkFromCollection(ref this, ev);
        }

        void ITracked.Release() {
        }
        void ITracked.Acquire() {
        }
        void ITracked.Expose() {}
        void ITracked.UnExpose() {}

        public virtual bool HeadMatches(int tag, ref bool possible, ref object setMatch)
        {
          throw new ApplicationException("HeadMatches must be implemented by contract specific endpoints");
        }

        public static ISelectable[]! ThreadLocalObjectArray(int size) {
            return (!)(((!)Thread.CurrentThread).PopSelectObjects(size));
        }

        // Bugfix 167 BY SXIA -- make a consistent statement in previous comments.
        // This function (and its twin function below with an extra timeout parameter) 
        // End Bugfix 167
        // is the main interface for receiving on multiple
        // endpoints and endpoint sets.
        //
        // The first parameter is an array of patterns.  Each pattern is
        // an array of integers whose length is equal to the number of
        // endpoints.  Each integer in a pattern indicates the message
        // that must be received on the corresponding endpoint for that
        // pattern to match.  (All elements of a pattern must match for
        // the pattern to match.)  Possible pattern entries include:
        //
        //   > 1: wait for a message with this tag on this endpoint
        //     1: wait for any message on this endpoint
        //     0: don't wait on this endpoint
        //    -1: wait for channel closed
        //  < -1: illegal
        //
        // The second parameter contains ISelectable objects.
        //
        // The return value is the index of the pattern that matched or -1
        // if a match is impossible.
        //
        // the setMatch out parameter is used to indicate which object of an underlying
        // set was part of the match.
        //
        // NOTE: the endpoint array may contain more elements than the pattern refers to
        //       thus the patterns 2nd level array Lengths is the indication how many endpoints are actually used.
        //
        public static int Select(int[][]! patterns, ISelectable[]! endpoints, out object setMatch)
        {
            Thread currentThread = (!)Thread.CurrentThread;

            try 
              // Give back cache (caller should do this, but we do it here for now)
              // we assume that caller does not use this for any other purpose
              // true for the generated code, but might not be true for other Select
              // uses.
            {
                Monitoring.Log(Monitoring.Provider.Endpoint,
                               (ushort)EndpointEvent.Select);
                int numCases = patterns.Length;
                if (numCases == 0) {
                    setMatch = null;
                    return -1;
                }

                int numEndpoints = ((!)patterns[0]).Length;

                #region Debugging asserts
#if DEBUG_SELECT
                for (int i = 0; i < numCases; i++) {
                    if (((!)patterns[i]).Length != numEndpoints) {
                        throw new ArgumentException("Invalid pattern size.");
                    }
                }
#endif
                #endregion

                // local resources
                SyncHandle[] handles = null;
                bool[] possible = null;

                try 
                    // Give back bool array on all returns
                {
                    possible = (!)currentThread.PopSelectBools(numCases);

                    for (int i = 0; i < numCases; i++) {
                        possible[i] = true;
                    }

                    int match = -1;
                    int hint = -1;
                    int numPossible = numCases;
                    setMatch = null;

                    while (numPossible > 0 &&
                           ! FindRowMatch(hint, endpoints, patterns, possible,
                                          ref numPossible,
                                          out match,
                                          out setMatch))
                    {
                        // only wait if last FindMatch didn't decrement numPossible to 0.
                        if (numPossible > 0) {

                            // special case case where we have 1 endpoint.
                            if (numEndpoints == 1) {
                                hint = 0;
                                SyncHandle.WaitOne(((!)endpoints[0]).GetWaitHandle());
                            }
                            else {
                                if (handles == null) {
                                    // initialize
                                    handles = (!)currentThread.PopSelectSyncHandles(numEndpoints);
                                    for (int i = 0; i < numEndpoints; i++) {
                                        handles[i] = ((!)endpoints[i]).GetWaitHandle();
                                    }
                                }
                                hint = WaitAnyEndpoint(handles, numEndpoints);
                            }
                        }
                    }
                    return match;
                }
                finally {
                    // return thread local resources
                    if (possible != null) {
                        currentThread.PushSelectBools(possible);
                    }
                    if (handles != null) {
                        currentThread.PushSelectSyncHandles(handles);
                    }
                }
            }
            finally {
                // return thread local resources
                currentThread.PushSelectObjects(endpoints);
            }
        }

        /// <summary>
        /// We compute the index of the row that represents timeout case
        /// See Parser.cs: the label for timeout is -2, unsatisfiable is -1 
        /// </summary>
        const int TimeOutIndex = -2;

        // Bugfix 167 By SXIA -- Add a different version of select here. I keep two versions of select here
        //                       which differs in whether there is an extra timeout parameter. If the only 
        //                       callee of this select is the compilation of switch-receive, then we probably should
        //                       delete the older version.
        // This function is the second version of the main interface for receiving on multiple
        // endpoints and endpoint sets.
        //
        // The first parameter is an array of patterns.  Each pattern is
        // an array of integers whose length is equal to the number of
        // endpoints.  Each integer in a pattern indicates the message
        // that must be received on the corresponding endpoint for that
        // pattern to match.  (All elements of a pattern must match for
        // the pattern to match.)  Possible pattern entries include:
        //
        //   > 1: wait for a message with this tag on this endpoint
        //     1: wait for any message on this endpoint
        //     0: don't wait on this endpoint
        //    -1: wait for channel closed
        //  < -1: illegal
        //
        // The second parameter contains ISelectable objects.
        //
        // The return value is the index of the pattern that matched or -1
        // if a match is impossible.
        //
        // the setMatch out parameter is used to indicate which object of an underlying
        // set was part of the match.
        //
        // We add an extra integer parameter that represents the timeout value (in milliseconds)
        // The timeout value is passed to the function call to SyncHandle.WaitXXXX in appropriate type
        //
        // NOTE: the endpoint array may contain more elements than the pattern refers to
        //       thus the patterns 2nd level array Lengths is the indication how many endpoints are actually used.
        //

        public static int Select(int[][]! patterns, ISelectable[]! endpoints, 
                                 out object setMatch, System.TimeSpan timeOutAfter)
        {
            Thread currentThread = (!)Thread.CurrentThread;

            try 
              // Give back cache (caller should do this, but we do it here for now)
              // we assume that caller does not use this for any other purpose
              // true for the generated code, but might not be true for other Select
              // uses.
            {

                Monitoring.Log(Monitoring.Provider.Endpoint,
                               (ushort)EndpointEvent.Select);
                           
                int numCases = patterns.Length;
                if (numCases == 0) {
                    setMatch = null;
                    return -1;
                }

                int numEndpoints = ((!)patterns[0]).Length;

                #region Debugging asserts
#if DEBUG_SELECT
                for (int i = 0; i < numCases; i++) {
                    if (((!)patterns[i]).Length != numEndpoints) {
                        throw new ArgumentException("Invalid pattern size.");
                    }
                }
#endif
                #endregion

                SyncHandle[] handles = null;
                bool[] possible = null;

                try 
                    // Give back thread local resources.
                {
                    possible = (!)currentThread.PopSelectBools(numCases);

                    for (int i = 0; i < numCases; i++) {
                        possible[i] = true;
                    }

                    int match = -1;
                    int hint = -1;
                    int numPossible = numCases;
                    setMatch = null;

                    SchedulerTime deadline = (timeOutAfter.Ticks == 0)?SchedulerTime.MinValue:SchedulerTime.Now + timeOutAfter;
            
                    while (numPossible > 0 &&
                           ! FindRowMatch(hint, endpoints, patterns, possible,
                                          ref numPossible,
                                          out match,
                                          out setMatch))
                    {
                        
                        // only wait if last FindMatch didn't decrement numPossible to 0.
                        if (numPossible > 0) {

                            // Optimization
                            //   If timeout is 0 and we got here, then we will definitely
                            //   take the timeout. So let's not call Wait at all
                            if (timeOutAfter.Ticks == 0) {
                                setMatch = null;
                                return Endpoint.TimeOutIndex;
                            }

                            // special case case where we have 1 endpoint.
                            if (numEndpoints == 1) {
                                hint = 0;
                                bool gotTimeout = ! SyncHandle.WaitOne(((!)endpoints[0]).GetWaitHandle(), deadline);
                                if (gotTimeout) {
                                    setMatch = null;
                                    return Endpoint.TimeOutIndex;
                                }
                            }
                            else {
                                if (handles == null) {
                                    // initialize
                                    handles = (!)currentThread.PopSelectSyncHandles(numEndpoints);
                                    for (int i = 0; i < numEndpoints; i++) {
                                        handles[i] = ((!)endpoints[i]).GetWaitHandle();
                                    }
                                }
                                
                                hint = WaitAnyEndpoint(handles, numEndpoints, deadline);
                        
                                // if the return value is WaitHandle.WaitTimeOut (-1),
                                // then we know it is timeout
                                // currently, we check for all out of range cases.
                                if (hint <0 || hint > numEndpoints) {
                                    setMatch = null;
                                    return Endpoint.TimeOutIndex;
                                }
                            }
                        }
                    }
                    return match;
                }
                finally 
                {
                    // return thread local resources
                    if (possible != null) {
                        currentThread.PushSelectBools(possible);
                    }
                    if (handles != null) {
                        currentThread.PushSelectSyncHandles(handles);
                    }
                }
            }
            finally 
            {
                // return thread local resources
                currentThread.PushSelectObjects(endpoints);            
            }
        }

        // End Bugfix 167
        
        /// <summary>
        /// If hint &lt; 0, scan all patterns for a match. Otherwise, hint specifies which
        /// endpoint changed. Thus only that column has to be reexamined.
        /// If we find a row that matches, we return the row index, and true.
        /// Updates possibleCount and possible array. When possibleCount goes down to
        /// 0, no more matches are possible.
        /// match is set to -1 when false is returned.
        /// </summary>
        private static bool FindRowMatch(int hint, ISelectable[]! endpoints, int[][]! patterns,
                                        bool[]! possible, ref int possibleCount, out int match,
                                        out object setMatch)
        {
            int numRows = patterns.Length;
            setMatch = null;

            if (hint < 0) {
                // scan all patterns
                for (int i = 0; i < numRows; i++) {
                    if (possible[i]) {
                        if (RowMatches(endpoints, (!)patterns[i], out setMatch, ref possible[i])) {
                            match = i;
                            return true;
                        }

                        if ( ! possible[i] ) {
                            // i no longer possible
                            possibleCount--;
                        }
                    }
                }

                match = -1;
                return false;
            }
            else {
                // hint tells us which column to scan
                for (int i = 0; i < numRows; i++) {
                    
                    if (possible[i]) {
                        int pat = ((!)patterns[i])[hint];

                        if (pat != 0) {
                            if (((!)endpoints[hint]).HeadMatches(pat, ref possible[i], ref setMatch)) {
                                // matches. Check rest of this row
                                if (RowMatches(endpoints, (!)patterns[i], out setMatch, ref possible[i])) {
                                    // found a match.
                                    match = i;
                                    return true;
                                }
                            }
                            if ( ! possible[i] ) {
                                // i no longer possible
                                possibleCount--;
                            }
                        }
                    }
                }
                match = -1;
                return false;
            }
        }

        // This method determines whether a given pattern row has been matched.
        // It also indicates whether a match is possible in the future.
        // If the row involves an endpoint set, the particular endpoint in the set
        // that matches is returned in setMatch. Note there can be at most one
        // endpoint set per row pattern.
        //
        private static bool RowMatches(ISelectable[]! endpoints, int[]! conjuncts,
                                      out object setMatch,
                                      ref bool possible)
        {
            setMatch = null;
            int numEndpoints = conjuncts.Length;

            for (int i = 0; i < numEndpoints; i++)
            {
                int tag = conjuncts[i];
                if (tag != 0) {
                    if (! ((!)endpoints[i]).HeadMatches(tag, ref possible, ref setMatch)) {
                        return false;
                    }
                }
                // Otherwise, we don't care about this endpoint (conjunct[i] pattern == 0),
                // so anything is fine.
            }
            return true;
        }

        // Wait on all endpoints that have not yet received a message.
        // This function returns when any of these endpoints gets a
        // new message.
        unsafe private static int WaitAnyEndpoint(SyncHandle[]! handles, int handleCount)
        {
            // Debug.Assert(handles.Length > 0, "Can't wait on no handles");

            fixed (SyncHandle* start = &handles[0]) {
                return SyncHandle.WaitAny(start, handleCount);
            }
        }

        // Bugfix 167 by SXIA -- duplicate a version of WaitAnyEndpoint, adding a timeout deadline
        // Same as above, with an extra timeout (stop) parameter
        unsafe private static int WaitAnyEndpoint(SyncHandle[]! handles, int handleCount,
                                                  System.SchedulerTime deadline)
        {
            // Debug.Assert(handles.Length > 0, "Can't wait on no handles");

            fixed (SyncHandle* start = &handles[0]) {
                return SyncHandle.WaitAny(start, handleCount, deadline);
            }
        }
        // End Bugfix 167
        
        
        /// <summary>
        /// Return a uint tag uniquely identifying the contract
        /// which endpoint "ep" adheres to.
        /// XXX: HACK: austind: this isn't 64-bit clean, nor is the
        /// tag returned particularly stable (it depends on the
        /// order in which types and handles are allocated).  Ideally we
        /// would use the SystemType's MD5 hash, but we can't access
        /// it here; is this correct, MAF?
        /// </summary>
        unsafe private static uint getContractTag(Endpoint*! in ExHeap ep)
        {
            UIntPtr runtimeSystemTypeHandle =
                SharedHeapService.GetType((Allocation*)ep);
            return (uint)runtimeSystemTypeHandle;
        }

        /// <summary>
        /// Called whenever a message is retrieved from on an endpoint.
        /// </summary>
        public static void RetrieveHook(ref Endpoint receiver, uint channelId, int messageTag)
        {
#if MONITORING
            Monitoring.Log(Monitoring.Provider.Endpoint,
                           (ushort)EndpointEvent.RetrieveHook, 0,
                           (uint)messageTag, channelId,
                           receiver.contractTag, 0, 0);
#endif
        }

        /// <summary>
        /// Called whenever a message is retrieved from an endpoint. The "this" parameter
        /// is the receiving endpoint. In order to get a pointer to the descriptor block
        /// that includes a pointer to the system type, we use the funky this.Peer->Peer
        /// expression.
        /// </summary>
        [Conditional("DEBUG")]
        protected void RetrieveHookInternal(int messageTag) {
            RetrieveHook(ref this, (uint)this.ChannelID, messageTag);
        }

        /// <summary>
        /// Called whenever a message is actually on an endpoint.
        /// </summary>
        public static void DeliverHook(ref Endpoint receiver, uint channelId, int messageTag)
        {
#if MONITORING
            Monitoring.Log(Monitoring.Provider.Endpoint,
                           (ushort)EndpointEvent.DeliverHook, 0,
                           (uint)messageTag, channelId,
                           receiver.peerContractTag, 0, 0);
#endif
        }


        /// <summary>
        /// Called whenever a message is delivered on an endpoint. The "this" parameter
        /// is the receiving endpoint, but the static ReceiveHook is called with the
        /// sender.
        /// </summary>
        [Conditional("DEBUG")]
        protected void DeliverHookInternal(int messageTag) {
            DeliverHook(ref this, (uint)this.ChannelID, messageTag);
        }


        new unsafe public void MarshallMessage(byte*! basep, byte*! source,
                                               int*! tagAddress, System.Type! type)
        {
            // assert type!=null;
#if PAGING
            EndpointCore.MarshallMessage(ref this, 
                                         basep, source, tagAddress, Marshal.StructSize(type));
#else
            DebugStub.WriteLine("MarshallMessage source offset:{0:x} tagLoc offset:{1:x} type:{2}",
                                __arglist((uint)source-(uint)basep,
                                          (uint)tagAddress-(uint)basep,
                                          type.FullName));
#endif
        }

        new unsafe public void MarshallPointer(byte*! basep, void**! target, System.Type! type) {
            // assert type!=null;
            if (*target == null) return;
#if PAGING
            EndpointCore.MarshallPointer(ref this,
                                         basep, (byte**)target, type.GetSystemType());
#else
            DebugStub.WriteLine("MarshallPointer source offset:{0:x} type:{1}",
                                __arglist((uint)target-(uint)basep, type.FullName));
#endif
        }

    }
}