Return Caching to Core.

Elsa.sln

@@ -250,6 +250,10 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Elsa.Resilience.Core", "src
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Elsa.Resilience", "src\modules\Elsa.Resilience\Elsa.Resilience.csproj", "{E7137FB0-1988-4562-AD8D-D0D9D2EE85F6}"
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "caching", "caching", "{02EA681E-C7D8-13C7-8484-4AC65E1B71E8}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Elsa.Caching", "src\modules\Elsa.Caching\Elsa.Caching.csproj", "{6F14B066-DF7B-2409-59D8-CCCA90A4974C}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -418,6 +422,10 @@ Global
 		{E7137FB0-1988-4562-AD8D-D0D9D2EE85F6}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{E7137FB0-1988-4562-AD8D-D0D9D2EE85F6}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{E7137FB0-1988-4562-AD8D-D0D9D2EE85F6}.Release|Any CPU.Build.0 = Release|Any CPU
+		{6F14B066-DF7B-2409-59D8-CCCA90A4974C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{6F14B066-DF7B-2409-59D8-CCCA90A4974C}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{6F14B066-DF7B-2409-59D8-CCCA90A4974C}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{6F14B066-DF7B-2409-59D8-CCCA90A4974C}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -489,6 +497,8 @@ Global
 		{CD7DC0D1-FFDC-417A-89BE-7F32408F583E} = {5BA4A8FA-F7F4-45B3-AEC8-8886D35AAC79}
 		{70593549-8B26-4D63-9857-6BA8BB3E31DB} = {CD7DC0D1-FFDC-417A-89BE-7F32408F583E}
 		{E7137FB0-1988-4562-AD8D-D0D9D2EE85F6} = {CD7DC0D1-FFDC-417A-89BE-7F32408F583E}
+		{02EA681E-C7D8-13C7-8484-4AC65E1B71E8} = {5BA4A8FA-F7F4-45B3-AEC8-8886D35AAC79}
+		{6F14B066-DF7B-2409-59D8-CCCA90A4974C} = {02EA681E-C7D8-13C7-8484-4AC65E1B71E8}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {D4B5CEAA-7D70-4FCB-A68E-B03FBE5E0E5E}

src/modules/Elsa.Caching/Contracts/ICacheManager.cs

@@ -0,0 +1,32 @@
+using Elsa.Caching.Options;
+using Microsoft.Extensions.Caching.Memory;
+using Microsoft.Extensions.Options;
+using Microsoft.Extensions.Primitives;
+
+namespace Elsa.Caching;
+
+/// <summary>
+/// A thin wrapper around <see cref="IMemoryCache"/>, allowing for centralized handling of cache entries.
+/// </summary>
+public interface ICacheManager
+{
+    /// <summary>
+    /// Provides options for configuring caching.
+    /// </summary>
+    IOptions<CachingOptions> CachingOptions { get; }
+
+    /// <summary>
+    /// Gets a change token for the specified key.
+    /// </summary>
+    IChangeToken GetToken(string key);
+
+    /// <summary>
+    /// Triggers the change token for the specified key.
+    /// </summary>
+    ValueTask TriggerTokenAsync(string key, CancellationToken cancellationToken = default);
+    
+    /// <summary>
+    /// Gets an item from the cache, or creates it if it doesn't exist.
+    /// </summary>
+    Task<TItem?> GetOrCreateAsync<TItem>(object key, Func<ICacheEntry, Task<TItem>> factory);
+}

src/modules/Elsa.Caching/Contracts/IChangeTokenSignalInvoker.cs

@@ -0,0 +1,19 @@
+using Microsoft.Extensions.Primitives;
+
+namespace Elsa.Caching;
+
+/// <summary>
+/// Triggers the change token associated with the specified key.
+/// </summary>
+public interface IChangeTokenSignalInvoker
+{
+    /// <summary>
+    /// Gets a change token for the specified key.
+    /// </summary>
+    IChangeToken GetToken(string key);
+    
+    /// <summary>
+    /// Triggers the change token for the specified key.
+    /// </summary>
+    ValueTask TriggerTokenAsync(string key, CancellationToken cancellationToken = default);
+}

src/modules/Elsa.Caching/Contracts/IChangeTokenSignaler.cs

@@ -0,0 +1,19 @@
+using Microsoft.Extensions.Primitives;
+
+namespace Elsa.Caching;
+
+/// <summary>
+/// Provides change tokens for memory caches, allowing code to evict cache entries by triggering a signal.
+/// </summary>
+public interface IChangeTokenSignaler
+{
+    /// <summary>
+    /// Gets a change token for the specified key.
+    /// </summary>
+    IChangeToken GetToken(string key);
+    
+    /// <summary>
+    /// Triggers the change token for the specified key.
+    /// </summary>
+    ValueTask TriggerTokenAsync(string key, CancellationToken cancellationToken = default);
+}

src/modules/Elsa.Caching/Elsa.Caching.csproj

@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <Description>
+            Provides caching services and utility functions common to Elsa modules.
+        </Description>
+        <PackageTags>elsa module caching</PackageTags>
+    </PropertyGroup>
+
+    <ItemGroup>
+		<PackageReference Include="Microsoft.Extensions.Caching.Memory" />
+		<PackageReference Include="Scrutor" />
+    </ItemGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\..\common\Elsa.Features\Elsa.Features.csproj" />
+    </ItemGroup>
+
+</Project>

src/modules/Elsa.Caching/Elsa.Caching.csproj.DotSettings

@@ -0,0 +1,2 @@
+<wpf:ResourceDictionary xml:space="preserve" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:ss="urn:shemas-jetbrains-com:settings-storage-xaml" xmlns:wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
+	<s:Boolean x:Key="/Default/CodeInspection/NamespaceProvider/NamespaceFoldersToSkip/=contracts/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>

src/modules/Elsa.Caching/Extensions/ModuleExtensions.cs

@@ -0,0 +1,19 @@
+using Elsa.Caching.Features;
+using Elsa.Features.Services;
+
+// ReSharper disable once CheckNamespace
+namespace Elsa.Extensions;
+
+/// <summary>
+/// Provides methods to install and configure the distributed caching feature.
+/// </summary>
+public static class ModuleExtensions
+{
+    /// <summary>
+    /// Adds the <see cref="MemoryCacheFeature"/> feature to the system.
+    /// </summary>
+    public static MemoryCacheFeature UseMemoryCache(this IModule module, Action<MemoryCacheFeature>? configure = default)
+    {
+        return module.Configure(configure);
+    }
+}

src/modules/Elsa.Caching/Features/MemoryCacheFeature.cs

@@ -0,0 +1,31 @@
+using Elsa.Caching.Options;
+using Elsa.Caching.Services;
+using Elsa.Features.Abstractions;
+using Elsa.Features.Services;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Elsa.Caching.Features;
+
+/// <summary>
+/// Configures the MemoryCache.
+/// </summary>
+public class MemoryCacheFeature(IModule module) : FeatureBase(module)
+{
+    /// <summary>
+    /// A delegate to configure the <see cref="CachingOptions"/>.
+    /// </summary>
+    public Action<CachingOptions> CachingOptions { get; set; } = _ => { };
+
+    /// <inheritdoc />
+    public override void Apply()
+    {
+        Services.Configure(CachingOptions);
+
+        Services
+            .AddMemoryCache()
+            .AddSingleton<ICacheManager, CacheManager>()
+            .AddSingleton<IChangeTokenSignalInvoker, ChangeTokenSignalInvoker>()
+            .AddSingleton<IChangeTokenSignaler, ChangeTokenSignaler>()
+            ;
+    }
+}

src/modules/Elsa.Caching/FodyWeavers.xml

@@ -0,0 +1,3 @@
+<Weavers xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="FodyWeavers.xsd">
+  <ConfigureAwait />
+</Weavers>

src/modules/Elsa.Caching/Options/CachingOptions.cs

@@ -0,0 +1,12 @@
+namespace Elsa.Caching.Options;
+
+/// <summary>
+/// Provides options for configuring caching.
+/// </summary>
+public class CachingOptions
+{
+    /// <summary>
+    /// Gets or sets the duration for which cache entries are stored.
+    /// </summary>
+    public TimeSpan CacheDuration { get; set; } = TimeSpan.FromMinutes(1);
+}

src/modules/Elsa.Caching/Services/CacheManager.cs

@@ -0,0 +1,31 @@
+using Elsa.Caching.Options;
+using Microsoft.Extensions.Caching.Memory;
+using Microsoft.Extensions.Options;
+using Microsoft.Extensions.Primitives;
+
+namespace Elsa.Caching.Services;
+
+/// <inheritdoc />
+public class CacheManager(IMemoryCache memoryCache, IChangeTokenSignaler changeTokenSignaler, IOptions<CachingOptions> options) : ICacheManager
+{
+    /// <inheritdoc />
+    public IOptions<CachingOptions> CachingOptions => options;
+
+    /// <inheritdoc />
+    public IChangeToken GetToken(string key)
+    {
+        return changeTokenSignaler.GetToken(key);
+    }
+
+    /// <inheritdoc />
+    public ValueTask TriggerTokenAsync(string key, CancellationToken cancellationToken = default)
+    {
+        return changeTokenSignaler.TriggerTokenAsync(key, cancellationToken);
+    }
+    
+    /// <inheritdoc />
+    public async Task<TItem?> GetOrCreateAsync<TItem>(object key, Func<ICacheEntry, Task<TItem>> factory)
+    {
+        return await memoryCache.GetOrCreateAsync(key, async entry => await factory(entry));
+    }
+}

src/modules/Elsa.Caching/Services/ChangeTokenSignalInvoker.cs

@@ -0,0 +1,38 @@
+using System.Collections.Concurrent;
+using Microsoft.Extensions.Primitives;
+
+namespace Elsa.Caching.Services;
+
+/// <inheritdoc />
+public class ChangeTokenSignalInvoker : IChangeTokenSignalInvoker
+{
+    private readonly ConcurrentDictionary<string, ChangeTokenInfo> _changeTokens = new();
+
+    /// <inheritdoc />
+    public IChangeToken GetToken(string key)
+    {
+        return _changeTokens.GetOrAdd(
+            key,
+            _ =>
+            {
+                var cancellationTokenSource = new CancellationTokenSource();
+                var changeToken = new CancellationChangeToken(cancellationTokenSource.Token);
+                return new ChangeTokenInfo(changeToken, cancellationTokenSource);
+            }).ChangeToken;
+    }
+
+    /// <inheritdoc />
+    public ValueTask TriggerTokenAsync(string key, CancellationToken cancellationToken = default)
+    {
+        if (_changeTokens.TryRemove(key, out var changeTokenInfo))
+            changeTokenInfo.TokenSource.Cancel();
+        
+        return default;
+    }
+
+    private readonly struct ChangeTokenInfo(IChangeToken changeToken, CancellationTokenSource tokenSource)
+    {
+        public IChangeToken ChangeToken { get; } = changeToken;
+        public CancellationTokenSource TokenSource { get; } = tokenSource;
+    }
+}

src/modules/Elsa.Caching/Services/ChangeTokenSignaler.cs

@@ -0,0 +1,19 @@
+using Microsoft.Extensions.Primitives;
+
+namespace Elsa.Caching.Services;
+
+/// <inheritdoc />
+public class ChangeTokenSignaler(IChangeTokenSignalInvoker invoker) : IChangeTokenSignaler
+{
+    /// <inheritdoc />
+    public IChangeToken GetToken(string key)
+    {
+        return invoker.GetToken(key);
+    }
+
+    /// <inheritdoc />
+    public ValueTask TriggerTokenAsync(string key, CancellationToken cancellationToken = default)
+    {
+        return invoker.TriggerTokenAsync(key, cancellationToken);
+    }
+}