From 7d065953070f9fcc8fa5f8893323222bc960862a Mon Sep 17 00:00:00 2001
From: Alex Macocian <amacocian@yahoo.com>
Date: Thu, 26 Sep 2024 10:32:38 +0200
Subject: [PATCH] Implement value caches

---
 .../SystemExtensions.NetCore.csproj           |  2 +-
 .../Cache/AsyncValueCache.cs                  | 36 +++++++++++++++++++
 .../Cache/ValueCache.cs                       | 35 ++++++++++++++++++
 .../SystemExtensions.NetStandard.csproj       |  2 +-
 4 files changed, 73 insertions(+), 2 deletions(-)
 create mode 100644 SystemExtensions.NetStandard/Cache/AsyncValueCache.cs
 create mode 100644 SystemExtensions.NetStandard/Cache/ValueCache.cs

diff --git a/SystemExtensions.NetCore/SystemExtensions.NetCore.csproj b/SystemExtensions.NetCore/SystemExtensions.NetCore.csproj
index cd68814..a2411e2 100644
--- a/SystemExtensions.NetCore/SystemExtensions.NetCore.csproj
+++ b/SystemExtensions.NetCore/SystemExtensions.NetCore.csproj
@@ -8,7 +8,7 @@
     <RootNamespace>System</RootNamespace>
 	  <PackageLicenseFile>LICENSE</PackageLicenseFile>
 	  <PackageRequireLicenseAcceptance>true</PackageRequireLicenseAcceptance>
-	  <Version>1.6.8</Version>
+	  <Version>1.6.9</Version>
 	  <Authors>Alexandru Macocian</Authors>
 	  <RepositoryUrl>https://github.com/AlexMacocian/SystemExtensions</RepositoryUrl>
 	  <Description>Extensions for the System namespace</Description>
diff --git a/SystemExtensions.NetStandard/Cache/AsyncValueCache.cs b/SystemExtensions.NetStandard/Cache/AsyncValueCache.cs
new file mode 100644
index 0000000..c901cad
--- /dev/null
+++ b/SystemExtensions.NetStandard/Cache/AsyncValueCache.cs
@@ -0,0 +1,36 @@
+using System.Extensions;
+using System.Threading.Tasks;
+
+namespace System.Cache;
+public sealed class AsyncValueCache<T>(Func<Task<T>> cacheRefreshOperation, TimeSpan cacheDuration)
+    where T : class
+{
+    private readonly Func<Task<T>> cacheRefreshOperation = cacheRefreshOperation.ThrowIfNull(nameof(cacheRefreshOperation));
+    private readonly TimeSpan cacheDuration = cacheDuration;
+
+    private T? value;
+    private DateTime lastCacheRefresh = DateTime.MinValue;
+
+    public async Task<T> GetValue()
+    {
+        if (DateTime.Now - this.lastCacheRefresh < this.cacheDuration &&
+            this.value is not null)
+        {
+            return this.value;
+        }
+
+        return await this.PerformCacheRefresh();
+    }
+
+    public async Task<T> ForceCacheRefresh()
+    {
+        return await this.PerformCacheRefresh();
+    }
+
+    private async Task<T> PerformCacheRefresh()
+    {
+        this.value = await this.cacheRefreshOperation();
+        this.lastCacheRefresh = DateTime.Now;
+        return this.value;
+    }
+}
diff --git a/SystemExtensions.NetStandard/Cache/ValueCache.cs b/SystemExtensions.NetStandard/Cache/ValueCache.cs
new file mode 100644
index 0000000..1f8df85
--- /dev/null
+++ b/SystemExtensions.NetStandard/Cache/ValueCache.cs
@@ -0,0 +1,35 @@
+using System.Extensions;
+
+namespace System.Cache;
+public sealed class ValueCache<T>(Func<T> cacheRefreshOperation, TimeSpan cacheDuration)
+    where T : class
+{
+    private readonly Func<T> cacheRefreshOperation = cacheRefreshOperation.ThrowIfNull(nameof(cacheRefreshOperation));
+    private readonly TimeSpan cacheDuration = cacheDuration;
+
+    private T? value;
+    private DateTime lastCacheRefresh = DateTime.MinValue;
+
+    public T GetValue()
+    {
+        if (DateTime.Now - this.lastCacheRefresh < this.cacheDuration &&
+            this.value is not null)
+        {
+            return this.value;
+        }
+
+        return this.PerformCacheRefresh();
+    }
+
+    public T ForceCacheRefresh()
+    {
+        return this.PerformCacheRefresh();
+    }
+
+    private T PerformCacheRefresh()
+    {
+        this.value = this.cacheRefreshOperation();
+        this.lastCacheRefresh = DateTime.Now;
+        return this.value;
+    }
+}
diff --git a/SystemExtensions.NetStandard/SystemExtensions.NetStandard.csproj b/SystemExtensions.NetStandard/SystemExtensions.NetStandard.csproj
index 6e1456a..91eb33b 100644
--- a/SystemExtensions.NetStandard/SystemExtensions.NetStandard.csproj
+++ b/SystemExtensions.NetStandard/SystemExtensions.NetStandard.csproj
@@ -7,7 +7,7 @@
     <PackageLicenseFile>LICENSE</PackageLicenseFile>
     <PackageRequireLicenseAcceptance>true</PackageRequireLicenseAcceptance>
     <RootNamespace>System</RootNamespace>
-    <Version>1.6.8</Version>
+    <Version>1.6.9</Version>
     <Authors>Alexandru Macocian</Authors>
     <RepositoryUrl>https://github.com/AlexMacocian/SystemExtensions</RepositoryUrl>
     <Description>Extensions for the System namespace</Description>