breaking-change: remove facts as a concept

you can implement this yourself. entity db will persist your commands!

Author: the-avid-engineer

README.md

@@ -25,11 +25,10 @@ information on the statement. (If I'm wrong, you should consider getting a new b
 
 ## How does EntityDb.NET implement Event Sourcing?
 
-There are three core sets of data:
+There are two core sets of data:
 
 1. Sources
 2. Commands
-3. Facts
 
 ### Sources
 
@@ -41,15 +40,8 @@ record the headers and connection information of the request.
 A command represents the intent to perform some operation on the state. Going back to the bank account example, one
 command could be `PerformDeposit` while another could be `PerformWithdrawl`. The things that you can do are commands.
 
-### Facts
-
-A fact is the result of executing a command on the state. In our bank account example, the fact produced
-by `PerformDeposit` would be `DepositPerformed`; for `PerformWithdrawl` it would be `WithdrawlPerformed`. However,
-commands and facts **DO NOT** need to be one-to-one. A single command can yield as many facts as are needed. You should
-keep your facts _bite sized_/_small_.
-
 ### Tying it all together
 
-The source, commands, and facts, are all tied together under one transient object - the transaction. A transaction can
+The source and commands are all tied together under one transient object - the transaction. A transaction can
 have exactly one source and can have many commands; each command can have many facts. When you need to commit your
 changes, you commit the transaction - it's all or nothing.

src/EntityDb.Abstractions/Commands/ICommand.cs

@@ -1,7 +1,4 @@
-using EntityDb.Abstractions.Facts;
-using System.Collections.Generic;
-
-namespace EntityDb.Abstractions.Commands
+namespace EntityDb.Abstractions.Commands
 {
     /// <summary>
     ///     Represents the intent to modify a <typeparamref name="TEntity" />.
@@ -10,10 +7,10 @@ namespace EntityDb.Abstractions.Commands
     public interface ICommand<TEntity>
     {
         /// <summary>
-        ///     Returns a new set of modifiers for an entity by this command.
+        ///     Returns a new <typeparamref name="TEntity" /> that incorporates the modification into an entity.
         /// </summary>
         /// <param name="entity">The entity to be modified.</param>
-        /// <returns>A new set of modifiers for <paramref name="entity" /> by this command.</returns>
-        IEnumerable<IFact<TEntity>> Execute(TEntity entity);
+        /// <returns>A new <typeparamref name="TEntity" /> that incorporates the modification of this command into <paramref name="entity" />.</returns>
+        TEntity Reduce(TEntity entity);
     }
 }

src/EntityDb.Abstractions/EntityDb.Abstractions.csproj

@@ -30,7 +30,7 @@
         <PackageTags>EntityDb EventSourcing DDD CQRS</PackageTags>
         <Description>An abstraction layer for the EntityDb suite of packages.</Description>
         <PackageIcon>ICON.png</PackageIcon>
-        <PackageIconUrl/>
+        <PackageIconUrl />
     </PropertyGroup>
 
     <ItemGroup>

src/EntityDb.Abstractions/Facts/IFact.cs

@@ -1,6 +1,4 @@
-using EntityDb.Abstractions.Facts;
-
-namespace EntityDb.Abstractions.Strategies
+namespace EntityDb.Abstractions.Strategies
 {
     /// <summary>
     ///     Represents a type used to manage versioning for a <typeparamref name="TEntity" />.
@@ -14,12 +12,5 @@ public interface IVersioningStrategy<TEntity>
         /// <param name="entity">The entity.</param>
         /// <returns>The version number of <paramref name="entity" />.</returns>
         ulong GetVersionNumber(TEntity entity);
-
-        /// <summary>
-        ///     Creates a new version number modifier for an entity.
-        /// </summary>
-        /// <param name="versionNumber">The desired version number.</param>
-        /// <returns>A new version number modifier for on an entity.</returns>
-        IFact<TEntity> GetVersionNumberFact(ulong versionNumber);
     }
 }

src/EntityDb.Abstractions/Queries/FilterBuilders/IFactFilterBuilder.cs

@@ -5,7 +5,7 @@ namespace EntityDb.Abstractions.Transactions
 {
     /// <summary>
     ///     Represents a set of objects which must be committed together or not at all. Possible objects include: sources,
-    ///     commands, facts, and leases.
+    ///     commands, leases, and tags.
     /// </summary>
     /// <typeparam name="TEntity">The type of entities to be modified.</typeparam>
     public interface ITransaction<TEntity>