From 0c091b3a27a74918e9715b1f316452ec98cc8ee7 Mon Sep 17 00:00:00 2001
From: TheXamlGuy <dan_clark@outlook.com>
Date: Thu, 3 Oct 2024 22:39:56 +0100
Subject: [PATCH] Add Config locking and caching

---
 Toolkit.Foundation/ConfigurationCache.cs      |  26 ++
 Toolkit.Foundation/ConfigurationLock.cs       |  36 +++
 Toolkit.Foundation/ConfigurationMonitor.cs    |  15 +-
 Toolkit.Foundation/ConfigurationSource.cs     | 222 +++++++++---------
 .../ConfigurationValueViewModel.cs            |  57 +++--
 Toolkit.Foundation/IConfigurationSource.cs    |   4 +-
 Toolkit.Foundation/IHostBuilderExtension.cs   |  12 +-
 Toolkit.Foundation/IRemovable.cs              |   4 +
 8 files changed, 235 insertions(+), 141 deletions(-)
 create mode 100644 Toolkit.Foundation/ConfigurationCache.cs
 create mode 100644 Toolkit.Foundation/ConfigurationLock.cs
 create mode 100644 Toolkit.Foundation/IRemovable.cs

diff --git a/Toolkit.Foundation/ConfigurationCache.cs b/Toolkit.Foundation/ConfigurationCache.cs
new file mode 100644
index 0000000..e96cbd2
--- /dev/null
+++ b/Toolkit.Foundation/ConfigurationCache.cs
@@ -0,0 +1,26 @@
+using System.Collections.Concurrent;
+
+namespace Toolkit.Foundation;
+
+public static class ConfigurationCache
+{
+    private static readonly ConcurrentDictionary<string, object?> cache = new();
+
+    public static void Set<TConfiguration>(string section,
+        TConfiguration configuration) => cache[section] = configuration;
+
+    public static bool Remove(string section) => cache.TryRemove(section, out _);
+
+    public static bool TryGet<TConfiguration>(string section,
+        out TConfiguration? configuration)
+    {
+        if (cache.TryGetValue(section, out object? cachedValue))
+        {
+            configuration = (TConfiguration?)cachedValue;
+            return true;
+        }
+
+        configuration = default;
+        return false;
+    }
+}
diff --git a/Toolkit.Foundation/ConfigurationLock.cs b/Toolkit.Foundation/ConfigurationLock.cs
new file mode 100644
index 0000000..20929e5
--- /dev/null
+++ b/Toolkit.Foundation/ConfigurationLock.cs
@@ -0,0 +1,36 @@
+namespace Toolkit.Foundation;
+
+public static class ConfigurationLock
+{
+    private static readonly ReaderWriterLockSlim readerWriterLock = new();
+
+    public static IDisposable EnterRead()
+    {
+        readerWriterLock.EnterReadLock();
+        return new ConfigurationReaderLockDisposer(readerWriterLock);
+    }
+
+    public static IDisposable EnterWrite()
+    {
+        readerWriterLock.EnterWriteLock();
+        return new ConfigurationWriterLockDisposer(readerWriterLock);
+    }
+
+    private class ConfigurationWriterLockDisposer(ReaderWriterLockSlim lockSlim) : 
+        IDisposable
+    {
+        public void Dispose()
+        {
+            lockSlim.ExitWriteLock();
+        }
+    }
+
+    private class ConfigurationReaderLockDisposer(ReaderWriterLockSlim lockSlim) :
+        IDisposable
+    {
+        public void Dispose()
+        {
+            lockSlim.ExitReadLock();
+        }
+    }
+}
diff --git a/Toolkit.Foundation/ConfigurationMonitor.cs b/Toolkit.Foundation/ConfigurationMonitor.cs
index ca86ea6..20add1a 100644
--- a/Toolkit.Foundation/ConfigurationMonitor.cs
+++ b/Toolkit.Foundation/ConfigurationMonitor.cs
@@ -1,7 +1,10 @@
-namespace Toolkit.Foundation;
+using Microsoft.Extensions.DependencyInjection;
 
-public class ConfigurationMonitor<TConfiguration>(IConfigurationFile<TConfiguration> file,
-    IConfigurationReader<TConfiguration> reader,
+namespace Toolkit.Foundation;
+
+public class ConfigurationMonitor<TConfiguration>(string section,
+    IConfigurationFile<TConfiguration> file, 
+    IServiceProvider serviceProvider,
     IPublisher publisher) :
     IConfigurationMonitor<TConfiguration>
     where TConfiguration :
@@ -14,9 +17,11 @@ public class ConfigurationMonitor<TConfiguration>(IConfigurationFile<TConfigurat
         void ChangedHandler(object sender,
             FileSystemEventArgs args)
         {
-            if (reader.Read() is { } configuration)
+            if (serviceProvider.GetRequiredKeyedService<IConfigurationDescriptor<TConfiguration>>(section) is 
+                IConfigurationDescriptor<TConfiguration> configuration)
             {
-                publisher.PublishUI(new ChangedEventArgs<TConfiguration>(configuration));
+                ConfigurationCache.Remove(section);
+                publisher.PublishUI(new ChangedEventArgs<TConfiguration>(configuration.Value));
             }
         }
 
diff --git a/Toolkit.Foundation/ConfigurationSource.cs b/Toolkit.Foundation/ConfigurationSource.cs
index 9932602..142f10b 100644
--- a/Toolkit.Foundation/ConfigurationSource.cs
+++ b/Toolkit.Foundation/ConfigurationSource.cs
@@ -13,7 +13,7 @@ public class ConfigurationSource<TConfiguration>(IConfigurationFile<TConfigurati
     where TConfiguration :
     class
 {
-    private static readonly Func<JsonSerializerOptions> defaultSerializerOptions = new(() =>
+    private static readonly Func<JsonSerializerOptions> defaultSerializerOptions = () =>
     {
         return new JsonSerializerOptions
         {
@@ -26,133 +26,82 @@ public class ConfigurationSource<TConfiguration>(IConfigurationFile<TConfigurati
                 new DictionaryStringObjectJsonConverter()
             }
         };
-    });
-
-    private readonly object lockingObject = new();
+    };
 
     public void Set(TConfiguration value) => Set((object)value);
 
     public void Set(object value)
     {
-        lock (lockingObject)
+        using (ConfigurationLock.EnterWrite())
         {
             IFileInfo fileInfo = configurationFile.FileInfo;
-            if (!File.Exists(fileInfo.PhysicalPath))
-            {
-                string? fileDirectoryPath = Path.GetDirectoryName(fileInfo.PhysicalPath);
-                if (!string.IsNullOrEmpty(fileDirectoryPath))
-                {
-                    Directory.CreateDirectory(fileDirectoryPath);
-                }
+            EnsureFileExists(fileInfo.PhysicalPath);
 
-                File.WriteAllText(fileInfo.PhysicalPath!, "{}");
+            string? content;
+            JsonNode? rootNode;
+
+            using (Stream stream = new FileStream(fileInfo.PhysicalPath!, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite))
+            using (StreamReader reader = new(stream))
+            {
+                content = reader.ReadToEnd();
+                stream.Seek(0, SeekOrigin.Begin);
+
+                rootNode = JsonNode.Parse(content);
             }
 
-            using Stream stream = fileInfo.PhysicalPath is not null
-                    ? new FileStream(fileInfo.PhysicalPath, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite)
-                    : fileInfo.CreateReadStream();
+            JsonNode? valueNode = JsonNode.Parse(JsonSerializer.SerializeToUtf8Bytes(value, serializerOptions ?? defaultSerializerOptions()));
 
-            using StreamReader? reader = new(stream);
+            ApplyConfigurationUpdates(ref rootNode, valueNode, section);
 
-            string? content = reader.ReadToEnd();
-            stream.Seek(0, SeekOrigin.Begin);
+            using Stream stream2 = new FileStream(fileInfo.PhysicalPath!, FileMode.Create, FileAccess.ReadWrite, FileShare.ReadWrite);
+            JsonSerializer.Serialize(stream2, rootNode, serializerOptions ?? defaultSerializerOptions());
 
-            JsonNode? rootNode = JsonNode.Parse(content);
-            JsonNode? valueNode = JsonNode.Parse(JsonSerializer.SerializeToUtf8Bytes(value,
-                serializerOptions ?? defaultSerializerOptions()));
-
-            string[] segments = section.Split(':');
-            JsonNode? currentNode = rootNode;
-            int lastIndex = segments.Length - 1;
-
-            for (int i = 0; i < lastIndex; i++)
-            {
-                if (currentNode is null)
-                {
-                    return;
-                }
-
-                string currentKey = segments[i];
-                if (currentNode[currentKey] is null)
-                {
-                    currentNode[currentKey] = new JsonObject();
-                }
-
-                currentNode = currentNode[currentKey];
-            }
-
-            if (currentNode is not null)
-            {
-                string lastKey = segments[lastIndex];
-                if (currentNode is JsonArray array && int.TryParse(lastKey, out int index))
-                {
-                    if (array.Count <= index)
-                    {
-                        array.Add(value);
-                    }
-                    else
-                    {
-                        array[index] = MergeNodes(array[index], valueNode);
-                    }
-                }
-                else
-                {
-                    currentNode[lastKey] = MergeNodes(currentNode[lastKey], valueNode);
-                }
-            }
-
-            using Stream stream2 = fileInfo.PhysicalPath is not null
-                    ? new FileStream(fileInfo.PhysicalPath, FileMode.Create, FileAccess.ReadWrite, FileShare.ReadWrite)
-                    : fileInfo.CreateReadStream();
-
-            JsonSerializer.Serialize(stream, rootNode, serializerOptions ?? defaultSerializerOptions());
+            ConfigurationCache.Set(section, value);
         }
     }
 
     public bool TryGet(out TConfiguration? value)
     {
-        lock (lockingObject)
+        if (ConfigurationCache.TryGet(section, out value))
+        {
+            return true;
+        }
+
+        using (ConfigurationLock.EnterRead())
         {
             IFileInfo fileInfo = configurationFile.FileInfo;
-            if (File.Exists(fileInfo.PhysicalPath))
+
+            if (!File.Exists(fileInfo.PhysicalPath))
             {
-                static Stream OpenRead(IFileInfo fileInfo)
+                value = default;
+                return false;
+            }
+
+            using Stream stream = new FileStream(fileInfo.PhysicalPath!, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite);
+            using StreamReader reader = new(stream);
+            string content = reader.ReadToEnd();
+            JsonNode? rootNode = JsonNode.Parse(content);
+
+            string[] segments = section.Split(':');
+            JsonNode? currentNode = rootNode;
+
+            int lastIndex = segments.Length - 1;
+            for (int i = 0; i < lastIndex; i++)
+            {
+                if (currentNode is null)
                 {
-                    return fileInfo.PhysicalPath is not null
-                        ? new FileStream(fileInfo.PhysicalPath, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite)
-                        : fileInfo.CreateReadStream();
+                    value = default;
+                    return false;
                 }
 
-                using Stream stream = OpenRead(fileInfo);
-                using StreamReader? reader = new(stream);
+                currentNode = currentNode[segments[i]];
+            }
 
-                string? content = reader.ReadToEnd();
-                JsonNode? rootNode = JsonNode.Parse(content);
-
-                string[] segments = section.Split(':');
-                JsonNode? currentNode = rootNode;
-                int lastIndex = segments.Length - 1;
-
-                for (int i = 0; i < lastIndex; i++)
-                {
-                    if (currentNode is null)
-                    {
-                        value = default;
-                        return false;
-                    }
-
-                    currentNode = currentNode[segments[i]];
-                }
-
-                if (currentNode is not null)
-                {
-                    if (currentNode[segments[lastIndex]] is JsonNode sectionNode)
-                    {
-                        value = JsonSerializer.Deserialize<TConfiguration>(sectionNode,
-                            serializerOptions ?? defaultSerializerOptions());
-                        return true;
-                    }
-                }
+            if (currentNode != null && currentNode[segments[lastIndex]] is JsonNode sectionNode)
+            {
+                value = JsonSerializer.Deserialize<TConfiguration>(sectionNode, serializerOptions ?? defaultSerializerOptions());
+                ConfigurationCache.Set(section, value);
+                return true;
             }
 
             value = default;
@@ -160,6 +109,49 @@ public class ConfigurationSource<TConfiguration>(IConfigurationFile<TConfigurati
         }
     }
 
+    private void ApplyConfigurationUpdates(ref JsonNode? rootNode, JsonNode? valueNode, string section)
+    {
+        string[] segments = section.Split(':');
+        JsonNode? currentNode = rootNode;
+        int lastIndex = segments.Length - 1;
+
+        for (int i = 0; i < lastIndex; i++)
+        {
+            if (currentNode is null)
+            {
+                return;
+            }
+
+            string currentKey = segments[i];
+            if (currentNode[currentKey] is null)
+            {
+                currentNode[currentKey] = new JsonObject();
+            }
+
+            currentNode = currentNode[currentKey];
+        }
+
+        if (currentNode is not null)
+        {
+            string lastKey = segments[lastIndex];
+            if (currentNode is JsonArray array && int.TryParse(lastKey, out int index))
+            {
+                if (array.Count <= index)
+                {
+                    array.Add(valueNode);
+                }
+                else
+                {
+                    array[index] = MergeNodes(array[index], valueNode);
+                }
+            }
+            else
+            {
+                currentNode[lastKey] = MergeNodes(currentNode[lastKey], valueNode);
+            }
+        }
+    }
+
     private JsonNode? CloneNode(JsonNode? node)
     {
         if (node is null)
@@ -171,15 +163,29 @@ public class ConfigurationSource<TConfiguration>(IConfigurationFile<TConfigurati
         return JsonNode.Parse(serialized);
     }
 
+    private void EnsureFileExists(string? filePath)
+    {
+        if (filePath == null || File.Exists(filePath))
+        {
+            return;
+        }
+
+        string? directoryPath = Path.GetDirectoryName(filePath);
+        if (!string.IsNullOrEmpty(directoryPath))
+        {
+            Directory.CreateDirectory(directoryPath);
+        }
+
+        File.WriteAllText(filePath, "{}");
+    }
+
     private JsonNode? MergeNodes(JsonNode? existingNode, JsonNode? newNode)
     {
-        newNode = CloneNode(newNode);
-
         if (existingNode is JsonObject existingObject && newNode is JsonObject newObject)
         {
             foreach (KeyValuePair<string, JsonNode?> property in newObject)
             {
-                existingObject[property.Key] = MergeNodes(existingObject[property.Key], property.Value);
+                existingObject[property.Key] = MergeNodes(existingObject[property.Key], CloneNode(property.Value));
             }
 
             return existingObject;
@@ -188,7 +194,7 @@ public class ConfigurationSource<TConfiguration>(IConfigurationFile<TConfigurati
         {
             foreach (JsonNode? item in newArray)
             {
-                existingArray.Add(item);
+                existingArray.Add(CloneNode(item));
             }
 
             return existingArray;
@@ -198,4 +204,4 @@ public class ConfigurationSource<TConfiguration>(IConfigurationFile<TConfigurati
             return newNode;
         }
     }
-}
\ No newline at end of file
+}
diff --git a/Toolkit.Foundation/ConfigurationValueViewModel.cs b/Toolkit.Foundation/ConfigurationValueViewModel.cs
index 358d084..d95ef04 100644
--- a/Toolkit.Foundation/ConfigurationValueViewModel.cs
+++ b/Toolkit.Foundation/ConfigurationValueViewModel.cs
@@ -15,22 +15,29 @@ public partial class ConfigurationValueViewModel<TConfiguration, TValue>(IServic
     INotificationHandler<ChangedEventArgs<TConfiguration>>
     where TConfiguration : class
 {
-    public Task Handle(ChangedEventArgs<TConfiguration> args)
+    public async Task Handle(ChangedEventArgs<TConfiguration> args)
     {
-        throw new NotImplementedException();
+        if (args.Sender is TConfiguration configuration)
+        {
+           // await Task.Run(() => Value = read(configuration));
+        }
     }
 
-    protected override void OnChanged(TValue? value)
+    public override async Task OnActivated()
     {
-        writer.Write(args => write(value, args));
+        await Task.Run(() => Value = read(configuration));
+        await base.OnActivated();
+    }
+
+    protected override async void OnChanged(TValue? value)
+    {
+        if (IsActivated)
+        {
+            await Task.Run(() => writer.Write(args => write(value, args)));
+        }
+
         base.OnChanged(value);
     }
-
-    public override Task OnActivated()
-    {
-        Value = read(configuration);
-        return base.OnActivated();
-    }
 }
 
 public partial class ConfigurationValueViewModel<TConfiguration, TValue, TItem> :
@@ -41,10 +48,9 @@ public partial class ConfigurationValueViewModel<TConfiguration, TValue, TItem>
     IDisposable
 {
     private readonly TConfiguration configuration;
-    private readonly IWritableConfiguration<TConfiguration> writer;
     private readonly Func<TConfiguration, TValue?> read;
     private readonly Action<TValue?, TConfiguration> write;
-
+    private readonly IWritableConfiguration<TConfiguration> writer;
     public ConfigurationValueViewModel(IServiceProvider provider, 
         IServiceFactory factory, 
         IMediator mediator, 
@@ -86,20 +92,27 @@ public partial class ConfigurationValueViewModel<TConfiguration, TValue, TItem>
         Value = value;
     }
 
-    public Task Handle(ChangedEventArgs<TConfiguration> args)
+    public async Task Handle(ChangedEventArgs<TConfiguration> args)
     {
-        throw new NotImplementedException();
+        if (args.Sender is TConfiguration configuration)
+        {
+           // await Task.Run(() => Value = read(configuration));
+        }
     }
 
-    protected override void OnChanged(TValue? value)
+    public override async Task OnActivated()
     {
-        writer.Write(args => write(value, args));
+        await Task.Run(() => Value = read(configuration));
+        await base.OnActivated();
+    }
+
+    protected override async void OnChanged(TValue? value)
+    {
+        if (IsActivated)
+        {
+            await Task.Run(() => writer.Write(args => write(value, args)));
+        }
+
         base.OnChanged(value);
     }
-
-    public override Task OnActivated()
-    {
-        Value = read(configuration);
-        return base.OnActivated();
-    }
 }
\ No newline at end of file
diff --git a/Toolkit.Foundation/IConfigurationSource.cs b/Toolkit.Foundation/IConfigurationSource.cs
index 08da464..13d46f1 100644
--- a/Toolkit.Foundation/IConfigurationSource.cs
+++ b/Toolkit.Foundation/IConfigurationSource.cs
@@ -9,6 +9,4 @@ public interface IConfigurationSource<TConfiguration>
     void Set(TConfiguration value);
 
     void Set(object value);
-}
-
-public interface IRemovable : IDisposable;
\ No newline at end of file
+}
\ No newline at end of file
diff --git a/Toolkit.Foundation/IHostBuilderExtension.cs b/Toolkit.Foundation/IHostBuilderExtension.cs
index 85afc5c..631f278 100644
--- a/Toolkit.Foundation/IHostBuilderExtension.cs
+++ b/Toolkit.Foundation/IHostBuilderExtension.cs
@@ -141,10 +141,10 @@ public static class IHostBuilderExtension
                     }
 
                     return new ConfigurationSource<TConfiguration>(provider.GetRequiredService<IConfigurationFile<TConfiguration>>(),
-                        section, defaultSerializer);
+                        section,
+                        defaultSerializer);
                 });
 
-                //services.AddHostedService<ConfigurationMonitor<TConfiguration>>();
                 services.TryAddKeyedTransient<IConfigurationReader<TConfiguration>>(section, (provider, key) =>
                     new ConfigurationReader<TConfiguration>(provider.GetRequiredKeyedService<IConfigurationSource<TConfiguration>>(key),
                         provider.GetRequiredKeyedService<IConfigurationFactory<TConfiguration>>(key)));
@@ -179,6 +179,12 @@ public static class IHostBuilderExtension
 
                 services.AddTransient(provider =>
                     provider.GetRequiredKeyedService<IConfigurationDescriptor<TConfiguration>>(section).Value);
+
+                services.AddHostedService(provider => 
+                    new ConfigurationMonitor<TConfiguration>(section, 
+                        provider.GetRequiredService<IConfigurationFile<TConfiguration>>(),
+                        provider.GetRequiredService<IServiceProvider>(), 
+                        provider.GetRequiredService<IPublisher>()));
             }
         });
 
@@ -186,7 +192,7 @@ public static class IHostBuilderExtension
     }
 
     public static IHostBuilder UseContentRoot(this IHostBuilder hostBuilder,
-                                        string contentRoot,
+        string contentRoot,
         bool createDirectory)
     {
         if (createDirectory)
diff --git a/Toolkit.Foundation/IRemovable.cs b/Toolkit.Foundation/IRemovable.cs
new file mode 100644
index 0000000..0c90d31
--- /dev/null
+++ b/Toolkit.Foundation/IRemovable.cs
@@ -0,0 +1,4 @@
+namespace Toolkit.Foundation;
+
+public interface IRemovable : 
+    IDisposable;
\ No newline at end of file