Initial commit for EventBag and EventChannel

Src/PChecker/CheckerCore/Runtime/StateMachines/EventQueues/EventBag.cs

@@ -0,0 +1,337 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using PChecker.Runtime.Events;
+using PChecker.Runtime.StateMachines.Managers;
+
+
+namespace PChecker.Runtime.StateMachines.EventQueues;
+
+/// <summary>
+/// Implements a bag of events that is used during testing.
+/// </summary>
+internal sealed class EventBag : IEventQueue
+{
+    /// <summary>
+    /// Manages the state machine that owns this queue.
+    /// </summary>
+    private readonly IStateMachineManager StateMachineManager;
+
+    /// <summary>
+    /// The state machine that owns this queue.
+    /// </summary>
+    private readonly StateMachine StateMachine;
+
+    /// <summary>
+    /// The internal queue that contains events with their metadata.
+    /// </summary>
+    private readonly List<(Event e, EventInfo info)> Bag;
+
+    /// <summary>
+    /// The raised event and its metadata, or null if no event has been raised.
+    /// </summary>
+    private (Event e, EventInfo info) RaisedEvent;
+
+    /// <summary>
+    /// Map from the types of events that the owner of the queue is waiting to receive
+    /// to an optional predicate. If an event of one of these types is enqueued, then
+    /// if there is no predicate, or if there is a predicate and evaluates to true, then
+    /// the event is received, else the event is deferred.
+    /// </summary>
+    private Dictionary<Type, Func<Event, bool>> EventWaitTypes;
+
+    /// <summary>
+    /// Task completion source that contains the event obtained using an explicit receive.
+    /// </summary>
+    private TaskCompletionSource<Event> ReceiveCompletionSource;
+
+    /// <summary>
+    /// Checks if the queue is accepting new events.
+    /// </summary>
+    private bool IsClosed;
+
+    /// <summary>
+    /// The size of the queue.
+    /// </summary>
+    public int Size => Bag.Count;
+
+    /// <summary>
+    /// Checks if an event has been raised.
+    /// </summary>
+    public bool IsEventRaised => RaisedEvent != default;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="EventBag"/> class.
+    /// </summary>
+    internal EventBag(IStateMachineManager stateMachineManager, StateMachine stateMachine)
+    {
+        StateMachineManager = stateMachineManager;
+        StateMachine = stateMachine;
+        Bag = new List<(Event, EventInfo)>();
+        EventWaitTypes = new Dictionary<Type, Func<Event, bool>>();
+        IsClosed = false;
+    }
+
+    /// <inheritdoc/>
+    public EnqueueStatus Enqueue(Event e, EventInfo info)
+    {
+        if (IsClosed)
+        {
+            return EnqueueStatus.Dropped;
+        }
+
+        if (EventWaitTypes.TryGetValue(e.GetType(), out var predicate) &&
+            (predicate is null || predicate(e)))
+        {
+            EventWaitTypes.Clear();
+            StateMachineManager.OnReceiveEvent(e, info);
+            ReceiveCompletionSource.SetResult(e);
+            return EnqueueStatus.EventHandlerRunning;
+        }
+
+        StateMachineManager.OnEnqueueEvent(e, info);
+        Bag.Add((e, info));
+
+        if (!StateMachineManager.IsEventHandlerRunning)
+        {
+            if (TryDequeueEvent(true).e is null)
+            {
+                return EnqueueStatus.NextEventUnavailable;
+            }
+            else
+            {
+                StateMachineManager.IsEventHandlerRunning = true;
+                return EnqueueStatus.EventHandlerNotRunning;
+            }
+        }
+
+        return EnqueueStatus.EventHandlerRunning;
+    }
+
+    /// <inheritdoc/>
+        public (DequeueStatus status, Event e, EventInfo info) Dequeue()
+        {
+            // Try to get the raised event, if there is one. Raised events
+            // have priority over the events in the inbox.
+            if (RaisedEvent != default)
+            {
+                if (StateMachineManager.IsEventIgnored(RaisedEvent.e, RaisedEvent.info))
+                {
+                    // TODO: should the user be able to raise an ignored event?
+                    // The raised event is ignored in the current state.
+                    RaisedEvent = default;
+                }
+                else
+                {
+                    var raisedEvent = RaisedEvent;
+                    RaisedEvent = default;
+                    return (DequeueStatus.Raised, raisedEvent.e, raisedEvent.info);
+                }
+            }
+
+            var hasDefaultHandler = StateMachineManager.IsDefaultHandlerAvailable();
+            if (hasDefaultHandler)
+            {
+                StateMachine.Runtime.NotifyDefaultEventHandlerCheck(StateMachine);
+            }
+
+            // Try to dequeue the next event, if there is one.
+            var (e, info) = TryDequeueEvent();
+            if (e != null)
+            {
+                // Found next event that can be dequeued.
+                return (DequeueStatus.Success, e, info);
+            }
+
+            // No event can be dequeued, so check if there is a default event handler.
+            if (!hasDefaultHandler)
+            {
+                // There is no default event handler installed, so do not return an event.
+                StateMachineManager.IsEventHandlerRunning = false;
+                return (DequeueStatus.NotAvailable, null, null);
+            }
+
+            // TODO: check op-id of default event.
+            // A default event handler exists.
+            var stateName = StateMachine.CurrentState.GetType().Name;
+            var eventOrigin = new EventOriginInfo(StateMachine.Id, StateMachine.GetType().FullName, stateName);
+            return (DequeueStatus.Default, DefaultEvent.Instance, new EventInfo(DefaultEvent.Instance, eventOrigin, StateMachine.VectorTime));
+        }
+
+    /// <summary>
+    /// Dequeues the next event and its metadata, if there is one available, else returns null.
+    /// </summary>
+    private (Event e, EventInfo info) TryDequeueEvent(bool checkOnly = false)
+    {
+        (Event e, EventInfo info) availableEvent = default;
+        List<(Event, EventInfo)> deferredEvents = new List<(Event, EventInfo)>();
+
+        // Iterates through the events and metadata in the inbox.
+        while (availableEvent == default)
+        {
+            if (Bag.Count == 0)
+            {
+                break;
+            }
+            var index = StateMachine.RandomInteger(Bag.Count);
+            availableEvent = Bag[index];
+
+            if (StateMachineManager.IsEventIgnored(availableEvent.e, availableEvent.info))
+            {
+                if (!checkOnly)
+                {
+                    // Removes an ignored event.
+                    Bag.Remove(availableEvent);
+                    availableEvent = default;
+                }
+
+                continue;
+            }
+
+            // Skips a deferred event.
+            if (StateMachineManager.IsEventDeferred(availableEvent.Item1, availableEvent.Item2))
+            {
+                Bag.Remove(availableEvent);
+                deferredEvents.Add(availableEvent);
+                availableEvent = default;
+
+            }
+
+        }
+
+        Bag.AddRange(deferredEvents);
+        if (!checkOnly)
+        {
+            Bag.Remove(availableEvent);
+        }
+
+        return availableEvent;
+    }
+
+    /// <inheritdoc/>
+    public void RaiseEvent(Event e)
+    {
+        var stateName = StateMachine.CurrentState.GetType().Name;
+        var eventOrigin = new EventOriginInfo(StateMachine.Id, StateMachine.GetType().FullName, stateName);
+        var info = new EventInfo(e, eventOrigin, StateMachine.VectorTime);
+        RaisedEvent = (e, info);
+        StateMachineManager.OnRaiseEvent(e, info);
+    }
+
+    /// <inheritdoc/>
+    public Task<Event> ReceiveEventAsync(Type eventType, Func<Event, bool> predicate = null)
+    {
+        var eventWaitTypes = new Dictionary<Type, Func<Event, bool>>
+        {
+            { eventType, predicate }
+        };
+
+        return ReceiveEventAsync(eventWaitTypes);
+    }
+
+    /// <inheritdoc/>
+    public Task<Event> ReceiveEventAsync(params Type[] eventTypes)
+    {
+        var eventWaitTypes = new Dictionary<Type, Func<Event, bool>>();
+        foreach (var type in eventTypes)
+        {
+            eventWaitTypes.Add(type, null);
+        }
+
+        return ReceiveEventAsync(eventWaitTypes);
+    }
+
+    /// <inheritdoc/>
+    public Task<Event> ReceiveEventAsync(params Tuple<Type, Func<Event, bool>>[] events)
+    {
+        var eventWaitTypes = new Dictionary<Type, Func<Event, bool>>();
+        foreach (var e in events)
+        {
+            eventWaitTypes.Add(e.Item1, e.Item2);
+        }
+
+        return ReceiveEventAsync(eventWaitTypes);
+    }
+
+    /// <summary>
+    /// Waits for an event to be enqueued.
+    /// </summary>
+    private Task<Event> ReceiveEventAsync(Dictionary<Type, Func<Event, bool>> eventWaitTypes)
+    {
+        StateMachine.Runtime.NotifyReceiveCalled(StateMachine);
+
+        (Event e, EventInfo info) receivedEvent = default;
+        int index = 0;
+        while (Bag.Count != 0)
+        {
+            receivedEvent = Bag[index];
+            // Dequeue the first event that the caller waits to receive, if there is one in the queue.
+            if (eventWaitTypes.TryGetValue(receivedEvent.e.GetType(), out var predicate) &&
+                (predicate is null || predicate(receivedEvent.e)))
+            {
+                Bag.Remove(receivedEvent);
+                break;
+            }
+
+            index++;
+        }
+
+        if (receivedEvent == default)
+        {
+            ReceiveCompletionSource = new TaskCompletionSource<Event>();
+            EventWaitTypes = eventWaitTypes;
+            StateMachineManager.OnWaitEvent(EventWaitTypes.Keys);
+            return ReceiveCompletionSource.Task;
+        }
+
+        StateMachineManager.OnReceiveEventWithoutWaiting(receivedEvent.e, receivedEvent.info);
+        return Task.FromResult(receivedEvent.e);
+    }
+
+    /// <inheritdoc/>
+    public int GetCachedState()
+    {
+        unchecked
+        {
+            var hash = 19;
+            foreach (var (_, info) in Bag)
+            {
+                hash = (hash * 31) + info.EventName.GetHashCode();
+            }
+
+            return hash;
+        }
+    }
+
+    /// <inheritdoc/>
+    public void Close()
+    {
+        IsClosed = true;
+    }
+
+    /// <summary>
+    /// Disposes the queue resources.
+    /// </summary>
+    private void Dispose(bool disposing)
+    {
+        if (!disposing)
+        {
+            return;
+        }
+
+        foreach (var (e, info) in Bag)
+        {
+            StateMachineManager.OnDropEvent(e, info);
+        }
+
+        Bag.Clear();
+    }
+
+    /// <inheritdoc/>
+    public void Dispose()
+    {
+        Dispose(true);
+        GC.SuppressFinalize(this);
+    }
+
+}