From 27490e4eb16304aaa5c0c1071ce020e4a207e72c Mon Sep 17 00:00:00 2001
From: Yuriy Durov <u.a.durov@gmail.com>
Date: Tue, 23 Apr 2024 13:49:19 +0400
Subject: [PATCH] Add QueryStringParameterAttribute

---
 .../QueryStringParameterAttribute.cs          | 27 +++++++++
 .../BitzArt.Blazor.MVVM.csproj                |  1 +
 .../Components/PageBase.cs                    | 18 +++++-
 .../QueryStringParameterExtensions.cs         | 56 +++++++++++++++++++
 4 files changed, 101 insertions(+), 1 deletion(-)
 create mode 100644 src/BitzArt.Blazor.MVVM/Attributes/QueryStringParameterAttribute.cs
 create mode 100644 src/BitzArt.Blazor.MVVM/Extensions/QueryStringParameterExtensions.cs

diff --git a/src/BitzArt.Blazor.MVVM/Attributes/QueryStringParameterAttribute.cs b/src/BitzArt.Blazor.MVVM/Attributes/QueryStringParameterAttribute.cs
new file mode 100644
index 0000000..bde9d4f
--- /dev/null
+++ b/src/BitzArt.Blazor.MVVM/Attributes/QueryStringParameterAttribute.cs
@@ -0,0 +1,27 @@
+namespace BitzArt.Blazor.MVVM;
+
+/// <summary>
+/// Attribute to decorate properties that should be read from the query string.
+/// </summary>
+[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
+public sealed class QueryStringParameterAttribute : Attribute
+{
+    /// <summary>Name of the query string parameter. It uses the property name by default.</summary>
+    public string? Name { get; }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="QueryStringParameterAttribute"/> class.
+    /// </summary>
+    public QueryStringParameterAttribute()
+    {
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="QueryStringParameterAttribute"/> class.
+    /// </summary>
+    /// <param name="name"></param>
+    public QueryStringParameterAttribute(string name)
+    {
+        Name = name;
+    }
+}
diff --git a/src/BitzArt.Blazor.MVVM/BitzArt.Blazor.MVVM.csproj b/src/BitzArt.Blazor.MVVM/BitzArt.Blazor.MVVM.csproj
index 37a00aa..526624b 100644
--- a/src/BitzArt.Blazor.MVVM/BitzArt.Blazor.MVVM.csproj
+++ b/src/BitzArt.Blazor.MVVM/BitzArt.Blazor.MVVM.csproj
@@ -28,6 +28,7 @@
 
 	<ItemGroup>
 	  <PackageReference Include="Microsoft.AspNetCore.Components.Web" Version="8.*" />
+	  <PackageReference Include="Microsoft.AspNetCore.WebUtilities" Version="8.*" />
 	</ItemGroup>
 
 </Project>
diff --git a/src/BitzArt.Blazor.MVVM/Components/PageBase.cs b/src/BitzArt.Blazor.MVVM/Components/PageBase.cs
index a3b0777..b5299dc 100644
--- a/src/BitzArt.Blazor.MVVM/Components/PageBase.cs
+++ b/src/BitzArt.Blazor.MVVM/Components/PageBase.cs
@@ -3,7 +3,7 @@
 namespace BitzArt.Blazor.MVVM;
 
 /// <summary>
-/// Blazor component base class with view model support.
+/// Blazor page base class with view model support.
 /// </summary>
 /// <typeparam name="TViewModel">Type of this component's ViewModel</typeparam>
 public abstract class PageBase<TViewModel> : ComponentBase, IPersistentComponent
@@ -21,6 +21,12 @@ public abstract class PageBase<TViewModel> : ComponentBase, IPersistentComponent
     [Inject]
     protected TViewModel ViewModel { get; set; } = null!;
 
+    /// <summary>
+    /// Navigation manager.
+    /// </summary>
+    [Inject]
+    protected NavigationManager NavigationManager { get; set; } = null!;
+
     /// <summary>
     /// Method invoked when the component is ready to start, having received its initial
     /// parameters from its parent in the render tree. Override this method if you will
@@ -45,4 +51,14 @@ void IPersistentComponent.StateHasChanged()
     {
         StateHasChanged();
     }
+
+    /// <summary>
+    /// Set the parameters from the query string.
+    /// </summary>
+    public override Task SetParametersAsync(ParameterView parameters)
+    {
+        ViewModel.SetParametersFromQueryString(NavigationManager);
+
+        return base.SetParametersAsync(parameters);
+    }
 }
diff --git a/src/BitzArt.Blazor.MVVM/Extensions/QueryStringParameterExtensions.cs b/src/BitzArt.Blazor.MVVM/Extensions/QueryStringParameterExtensions.cs
new file mode 100644
index 0000000..79b02b4
--- /dev/null
+++ b/src/BitzArt.Blazor.MVVM/Extensions/QueryStringParameterExtensions.cs
@@ -0,0 +1,56 @@
+using Microsoft.AspNetCore.Components;
+using Microsoft.AspNetCore.WebUtilities;
+using Microsoft.Extensions.Primitives;
+using System.Globalization;
+using System.Reflection;
+
+namespace BitzArt.Blazor.MVVM;
+
+internal static class QueryStringParameterExtensions
+{
+    // Apply the values from the query string to the current component
+    public static void SetParametersFromQueryString<T>(this T component, NavigationManager navigationManager)
+        where T : class
+    {
+        if (!Uri.TryCreate(navigationManager.Uri, UriKind.RelativeOrAbsolute, out var uri))
+            throw new InvalidOperationException("The current url is not a valid URI. Url: " + navigationManager.Uri);
+
+        // Parse the query string
+        Dictionary<string, StringValues> queryString = QueryHelpers.ParseQuery(uri.Query);
+
+        // Enumerate all properties of the component
+        foreach (var property in GetProperties<T>())
+        {
+            // Get the name of the parameter to read from the query string
+            var parameterName = GetQueryStringParameterName(property);
+            if (parameterName == null)
+                continue; // The property is not decorated by [QueryStringParameterAttribute]
+
+            if (queryString.TryGetValue(parameterName, out var value))
+            {
+                // Convert the value from string to the actual property type
+                var convertedValue = ConvertValue(value, property.PropertyType);
+                property.SetValue(component, convertedValue);
+            }
+        }
+    }
+
+    private static object ConvertValue(StringValues value, Type type)
+    {
+        return Convert.ChangeType(value[0], type, CultureInfo.InvariantCulture)!;
+    }
+
+    private static PropertyInfo[] GetProperties<T>()
+    {
+        return typeof(T).GetProperties(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
+    }
+
+    private static string? GetQueryStringParameterName(PropertyInfo property)
+    {
+        var attribute = property.GetCustomAttribute<QueryStringParameterAttribute>();
+        if (attribute == null)
+            return null;
+
+        return attribute.Name ?? property.Name;
+    }
+}