feature: better entity extensions

- entity.Reduce(fact)
- entity.Reduce(facts)
- entity.Execute(command)
- entity.ExecuteAndReduce(command)
- entity.ExecuteAndReduce(commands)

Author: the-avid-engineer

EntityDb.Common/Extensions/EntityExtensions.cs

@@ -1,44 +1,64 @@
 using EntityDb.Abstractions.Commands;
 using EntityDb.Abstractions.Facts;
 using System.Collections.Generic;
-
+using System.Linq;
+
 namespace EntityDb.Common.Extensions
 {
     /// <summary>
     /// Extension methods for entities.
     /// </summary>
     public static class EntityExtensions
     {
+        /// <summary>
+        /// Returns a new <typeparamref name="TEntity"/> that incorporates the modification of a single fact into an entity.
+        /// </summary>
+        /// <typeparam name="TEntity">The type of the entity to be modified.</typeparam>
+        /// <param name="entity">The entity to be modified.</param>
+        /// <param name="fact">The fact that modifies the entity.</param>
+        /// <returns>A new <typeparamref name="TEntity"/> that incorporates the modification of <paramref name="fact"/> into <paramref name="entity"/>.</returns>
+        public static TEntity Reduce<TEntity>(this TEntity entity, IFact<TEntity> fact)
+        {
+            return fact.Reduce(entity);
+        }
+
         /// <summary>
         /// Returns a new <typeparamref name="TEntity"/> that incorporates the modifications of a set of facts into an entity.
         /// </summary>
         /// <typeparam name="TEntity">The type of the entity to be modified.</typeparam>
-        /// <param name="facts">The facts that modify the entity.</param>
         /// <param name="entity">The entity to be modified.</param>
+        /// <param name="facts">The facts that modify the entity.</param>
         /// <returns>A new <typeparamref name="TEntity"/> that incorporates the modifications of <paramref name="facts"/> into <paramref name="entity"/>.</returns>
-        public static TEntity Reduce<TEntity>(this IEnumerable<IFact<TEntity>> facts, TEntity entity)
+        public static TEntity Reduce<TEntity>(this TEntity entity, IEnumerable<IFact<TEntity>> facts)
         {
-            foreach (var fact in facts)
-            {
-                entity = fact.Reduce(entity);
-            }
+            return facts.Aggregate(entity, Reduce);
+        }
 
-            return entity;
+        /// <summary>
+        /// Returns the enumerated modifications of a command for a given entity.
+        /// </summary>
+        /// <typeparam name="TEntity">The type of the entity to be modified.</typeparam>
+        /// <param name="entity">The entity to be modified.</param>
+        /// <param name="command">The command to execute.</param>
+        /// <returns>The enumerated modifications of <paramref name="command"/> for <paramref name="entity"/>.</returns>
+        public static List<IFact<TEntity>> Execute<TEntity>(this TEntity entity, ICommand<TEntity> command)
+        {
+            return command.Execute(entity).ToList();
         }
 
         /// <summary>
-        /// Returns a new instance of <typeparamref name="TEntity"/> that incorporates the modification of a command into an entity.
+        /// Returns a new instance of <typeparamref name="TEntity"/> that incorporates the modifications of a command into an entity.
         /// </summary>
         /// <typeparam name="TEntity">The type of the entity to be modified.</typeparam>
         /// <param name="entity">The entity to be modified.</param>
         /// <param name="command">The command to execute.</param>
-        /// <returns>A new instace of <typeparamref name="TEntity"/> that incorporates the modification of <paramref name="command"/> into <paramref name="entity"/>.</returns>
+        /// <returns>A new instace of <typeparamref name="TEntity"/> that incorporates the modifications of <paramref name="command"/> into <paramref name="entity"/>.</returns>
         /// <remarks>
         /// This method is ONLY intended to be used for business logic tests.
         /// </remarks>
         public static TEntity ExecuteAndReduce<TEntity>(this TEntity entity, ICommand<TEntity> command)
         {
-            return command.Execute(entity).Reduce(entity);
+            return entity.Reduce(command.Execute(entity));
         }
 
         /// <summary>
@@ -53,12 +73,7 @@ public static TEntity ExecuteAndReduce<TEntity>(this TEntity entity, ICommand<TE
         /// </remarks>
         public static TEntity ExecuteAndReduce<TEntity>(this TEntity entity, IEnumerable<ICommand<TEntity>> commands)
         {
-            foreach (var command in commands)
-            {
-                entity = entity.ExecuteAndReduce(command);
-            }
-
-            return entity;
+            return commands.Aggregate(entity, ExecuteAndReduce);
         }
     }
 }

EntityDb.Common/Extensions/IServiceProviderExtensions.cs

@@ -189,7 +189,7 @@ public static async Task<TEntity> GetEntity<TEntity>(this IServiceProvider servi
 
             var facts = await transactionRepository.GetFacts(factQuery);
 
-            entity = facts.Reduce(entity);
+            entity = entity.Reduce(facts);
 
             if (serviceProvider.ShouldCache(snapshot, entity) && snapshotRepository != null)
             {

EntityDb.Common/Transactions/TransactionBuilder.cs

@@ -44,11 +44,11 @@ private void AddTransactionCommand(Guid entityId, ICommand<TEntity> command)
                 throw new CommandNotAuthorizedException();
             }
 
-            var nextFacts = command.Execute(previousEntity).ToList();
+            var nextFacts = previousEntity.Execute(command);
 
             nextFacts.Add(_serviceProvider.GetVersionNumberFact<TEntity>(previousVersionNumber + 1));
 
-            var nextEntity = nextFacts.Reduce(previousEntity);
+            var nextEntity = previousEntity.Reduce(nextFacts);
             var nextTags = _serviceProvider.GetTags(nextEntity);
 
             var transactionFacts = new List<TransactionFact<TEntity>>();