Rework expressions and expression compilation

Collapse multiple expression classes into a few generic ones; unify the code.
Compare expressions for node sharing prior to compilation, thereby improving compilation performance in those cases where there is node sharing.
Eliminate some unnecessary allocations during rule compilation (should help with #191 ).

src/NRules/NRules/AgendaFilters/ActivationExpression.cs

@@ -5,25 +5,25 @@
 
 namespace NRules.AgendaFilters
 {
-    internal interface IActivationExpression
+    internal interface IActivationExpression<out TResult>
     {
-        object Invoke(AgendaContext context, Activation activation);
+        TResult Invoke(AgendaContext context, Activation activation);
     }
 
-    internal class ActivationExpression : IActivationExpression
+    internal class ActivationExpression<TResult> : IActivationExpression<TResult>
     {
         private readonly LambdaExpression _expression;
-        private readonly FastDelegate<Func<object[], object>> _compiledExpression;
+        private readonly FastDelegate<Func<object[], TResult>> _compiledExpression;
         private readonly IndexMap _tupleFactMap;
 
-        public ActivationExpression(LambdaExpression expression, FastDelegate<Func<object[], object>> compiledExpression, IndexMap tupleFactMap)
+        public ActivationExpression(LambdaExpression expression, FastDelegate<Func<object[], TResult>> compiledExpression, IndexMap tupleFactMap)
         {
             _expression = expression;
             _compiledExpression = compiledExpression;
             _tupleFactMap = tupleFactMap;
         }
 
-        public object Invoke(AgendaContext context, Activation activation)
+        public TResult Invoke(AgendaContext context, Activation activation)
         {
             var tuple = activation.Tuple;
             var activationFactMap = activation.FactMap;
@@ -39,7 +39,7 @@ public object Invoke(AgendaContext context, Activation activation)
             }
 
             Exception exception = null;
-            object result = null;
+            TResult result = default;
             try
             {
                 result = _compiledExpression.Delegate.Invoke(args);

src/NRules/NRules/AgendaFilters/KeyChangeAgendaFilter.cs

@@ -6,11 +6,11 @@ namespace NRules.AgendaFilters
     internal class KeyChangeAgendaFilter : IAgendaFilter
     {
         private const string KeyName = "ChangeKeys";
-        private readonly List<IActivationExpression> _keySelectors;
+        private readonly List<IActivationExpression<object>> _keySelectors;
 
-        public KeyChangeAgendaFilter(IEnumerable<IActivationExpression> keySelectors)
+        public KeyChangeAgendaFilter(IEnumerable<IActivationExpression<object>> keySelectors)
         {
-            _keySelectors = new List<IActivationExpression>(keySelectors);
+            _keySelectors = new List<IActivationExpression<object>>(keySelectors);
         }
 
         public bool Accept(AgendaContext context, Activation activation)

src/NRules/NRules/AgendaFilters/PredicateAgendaFilter.cs

@@ -4,11 +4,11 @@ namespace NRules.AgendaFilters
 {
     internal class PredicateAgendaFilter : IAgendaFilter
     {
-        private readonly List<IActivationCondition> _conditions;
+        private readonly List<IActivationExpression<bool>> _conditions;
 
-        public PredicateAgendaFilter(IEnumerable<IActivationCondition> conditions)
+        public PredicateAgendaFilter(IEnumerable<IActivationExpression<bool>> conditions)
         {
-            _conditions = new List<IActivationCondition>(conditions);
+            _conditions = new List<IActivationExpression<bool>>(conditions);
         }
 
         public bool Accept(AgendaContext context, Activation activation)

src/NRules/NRules/Aggregators/AggregateExpression.cs

@@ -1,8 +1,5 @@
-using System;
-using System.Linq.Expressions;
-using NRules.Rete;
+using NRules.Rete;
 using NRules.RuleModel;
-using NRules.Utilities;
 
 namespace NRules.Aggregators
 {
@@ -26,54 +23,12 @@ public interface IAggregateExpression
         object Invoke(AggregationContext context, ITuple tuple, IFact fact);
     }
 
-    internal class AggregateFactExpression : IAggregateExpression
-    {
-        private readonly LambdaExpression _expression;
-        private readonly FastDelegate<Func<object, object>> _compiledExpression;
-
-        public AggregateFactExpression(string name, LambdaExpression expression, FastDelegate<Func<object, object>> compiledExpression)
-        {
-            Name = name;
-            _expression = expression;
-            _compiledExpression = compiledExpression;
-        }
-
-        public string Name { get; }
-
-        public object Invoke(AggregationContext context, ITuple tuple, IFact fact)
-        {
-            var factValue = fact.Value;
-            Exception exception = null;
-            object result = null;
-            try
-            {
-                result = _compiledExpression.Delegate(factValue);
-                return result;
-            }
-            catch (Exception e)
-            {
-                exception = e;
-                bool isHandled = false;
-                context.EventAggregator.RaiseLhsExpressionFailed(context.Session, e, _expression, factValue, tuple, fact, context.NodeInfo, ref isHandled);
-                throw new ExpressionEvaluationException(e, _expression, isHandled);
-            }
-            finally
-            {
-                context.EventAggregator.RaiseLhsExpressionEvaluated(context.Session, exception, _expression, factValue, result, tuple, fact, context.NodeInfo);
-            }
-        }
-    }
-
     internal class AggregateExpression : IAggregateExpression
     {
-        private readonly LambdaExpression _expression;
-        private readonly IndexMap _factMap;
-        private readonly FastDelegate<Func<object[], object>> _compiledExpression;
+        private readonly ILhsExpression<object> _compiledExpression;
 
-        public AggregateExpression(string name, LambdaExpression expression, FastDelegate<Func<object[], object>> compiledExpression, IndexMap factMap)
+        public AggregateExpression(string name, ILhsExpression<object> compiledExpression)
         {
-            _expression = expression;
-            _factMap = factMap;
             _compiledExpression = compiledExpression;
             Name = name;
         }
@@ -82,38 +37,7 @@ public AggregateExpression(string name, LambdaExpression expression, FastDelegat
 
         public object Invoke(AggregationContext context, ITuple tuple, IFact fact)
         {
-            var args = new object[_compiledExpression.ArrayArgumentCount];
-            int index = tuple.Count - 1;
-            foreach (var tupleFact in tuple.Facts)
-            {
-                IndexMap.SetElementAt(args, _factMap[index], tupleFact.Value);
-                index--;
-            }
-            IndexMap.SetElementAt(args, _factMap[tuple.Count], fact.Value);
-
-            Exception exception = null;
-            object result = null;
-            try
-            {
-                result = _compiledExpression.Delegate(args);
-                return result;
-            }
-            catch (Exception e)
-            {
-                exception = e;
-                bool isHandled = false;
-                context.EventAggregator.RaiseLhsExpressionFailed(context.Session, e, _expression, args, tuple, fact, context.NodeInfo, ref isHandled);
-                throw new ExpressionEvaluationException(e, _expression, isHandled);
-            }
-            finally
-            {
-                context.EventAggregator.RaiseLhsExpressionEvaluated(context.Session, exception, _expression, args, result, tuple, fact, context.NodeInfo);
-            }
-        }
-
-        public override string ToString()
-        {
-            return _expression.ToString();
+            return _compiledExpression.Invoke(context.ExecutionContext, context.NodeInfo, tuple, fact);
         }
     }
 }

src/NRules/NRules/Aggregators/AggregationContext.cs

@@ -1,5 +1,4 @@
-using NRules.Diagnostics;
-using NRules.Rete;
+using NRules.Rete;
 
 namespace NRules.Aggregators
 {
@@ -8,14 +7,12 @@ namespace NRules.Aggregators
     /// </summary>
     public class AggregationContext
     {
-        internal ISessionInternal Session { get; }
-        internal IEventAggregator EventAggregator { get; }
+        internal IExecutionContext ExecutionContext { get; }
         internal NodeDebugInfo NodeInfo { get; }
 
-        internal AggregationContext(ISessionInternal session, IEventAggregator eventAggregator, NodeDebugInfo nodeInfo)
+        internal AggregationContext(IExecutionContext executionContext, NodeDebugInfo nodeInfo)
         {
-            Session = session;
-            EventAggregator = eventAggregator;
+            ExecutionContext = executionContext;
             NodeInfo = nodeInfo;
         }
     }

src/NRules/NRules/Diagnostics/NodeInfo.cs

@@ -47,7 +47,7 @@ internal static NodeInfo Create(TypeNode node)
 
         internal static NodeInfo Create(SelectionNode node)
         {
-            var conditions = new[] {node.Condition.ToString()};
+            var conditions = new[] {node.ExpressionElement.Expression.ToString()};
             return new NodeInfo(NodeType.Selection, string.Empty, conditions, Empty, Empty);
         }
 
@@ -59,7 +59,7 @@ internal static NodeInfo Create(AlphaMemoryNode node, IAlphaMemory memory)
 
         internal static NodeInfo Create(JoinNode node)
         {
-            var conditions = node.Conditions.Select(c => c.ToString());
+            var conditions = node.ExpressionElements.Select(c => c.Expression.ToString());
             return new NodeInfo(NodeType.Join, string.Empty, conditions, Empty, Empty);
         }
 
@@ -86,7 +86,7 @@ internal static NodeInfo Create(ObjectInputAdapter node)
 
         internal static NodeInfo Create(BindingNode node)
         {
-            var expressions = new[] {node.BindingExpression.ToString()};
+            var expressions = new[] {node.ExpressionElement.Expression.ToString()};
             return new NodeInfo(NodeType.Binding, string.Empty, Empty, expressions, Empty);
         }
 

src/NRules/NRules/Rete/AggregateNode.cs

@@ -23,7 +23,7 @@ public AggregateNode(ITupleSource leftSource, IObjectSource rightSource, string
 
         public override void PropagateAssert(IExecutionContext context, List<Tuple> tuples)
         {
-            var aggregationContext = new AggregationContext(context.Session, context.EventAggregator, NodeInfo);
+            var aggregationContext = new AggregationContext(context, NodeInfo);
             var joinedSets = JoinedSets(context, tuples);
             var aggregation = new Aggregation();
             foreach (var set in joinedSets)
@@ -37,7 +37,7 @@ public override void PropagateAssert(IExecutionContext context, List<Tuple> tupl
 
         public override void PropagateUpdate(IExecutionContext context, List<Tuple> tuples)
         {
-            var aggregationContext = new AggregationContext(context.Session, context.EventAggregator, NodeInfo);
+            var aggregationContext = new AggregationContext(context, NodeInfo);
             var joinedSets = JoinedSets(context, tuples);
             var aggregation = new Aggregation();
             foreach (var set in joinedSets)
@@ -79,7 +79,7 @@ public override void PropagateRetract(IExecutionContext context, List<Tuple> tup
 
         public override void PropagateAssert(IExecutionContext context, List<Fact> facts)
         {
-            var aggregationContext = new AggregationContext(context.Session, context.EventAggregator, NodeInfo);
+            var aggregationContext = new AggregationContext(context, NodeInfo);
             var joinedSets = JoinedSets(context, facts);
             var aggregation = new Aggregation();
             foreach (var set in joinedSets)
@@ -106,7 +106,7 @@ public override void PropagateAssert(IExecutionContext context, List<Fact> facts
 
         public override void PropagateUpdate(IExecutionContext context, List<Fact> facts)
         {
-            var aggregationContext = new AggregationContext(context.Session, context.EventAggregator, NodeInfo);
+            var aggregationContext = new AggregationContext(context, NodeInfo);
             var joinedSets = JoinedSets(context, facts);
             var aggregation = new Aggregation();
             foreach (var set in joinedSets)
@@ -134,7 +134,7 @@ public override void PropagateUpdate(IExecutionContext context, List<Fact> facts
 
         public override void PropagateRetract(IExecutionContext context, List<Fact> facts)
         {
-            var aggregationContext = new AggregationContext(context.Session, context.EventAggregator, NodeInfo);
+            var aggregationContext = new AggregationContext(context, NodeInfo);
             var joinedSets = JoinedSets(context, facts);
             var aggregation = new Aggregation();
             foreach (var set in joinedSets)