Add the ability to intercept web requests

Author: mattleibow

src/Controls/src/Core/Controls.Core.csproj

@@ -40,6 +40,10 @@
     <ProjectReference Include="..\..\..\Core\src\Core.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <Compile Include="..\..\..\Essentials\src\Types\Shared\WebUtils.shared.cs" />
+  </ItemGroup>
+
   <ItemGroup Condition=" '$(_MauiDesignDllBuild)' == 'True' and '$(TargetFramework)' == '$(_MauiDotNetTfm)'">
     <ProjectReference Include="..\..\..\Controls\src\Core.Design\Controls.Core.Design.csproj" ReferenceOutputAssembly="false" />
   </ItemGroup>

src/Controls/src/Core/HybridWebView/HybridWebView.cs

@@ -66,6 +66,26 @@ void IHybridWebView.RawMessageReceived(string rawMessage)
 		/// </summary>
 		public event EventHandler<HybridWebViewRawMessageReceivedEventArgs>? RawMessageReceived;
 
+		bool IHybridWebView.WebResourceRequested(WebResourceRequestedEventArgs args)
+		{
+			var platformArgs = new PlatformHybridWebViewWebResourceRequestedEventArgs(args);
+			var e = new HybridWebViewWebResourceRequestedEventArgs(platformArgs);
+			WebResourceRequested?.Invoke(this, e);
+			return e.Handled;
+		}
+
+		/// <summary>
+		/// Raised when a web resource is requested. This event allows the application to intercept the request and provide a
+		/// custom response.
+		/// The event handler can set the <see cref="HybridWebViewWebResourceRequestedEventArgs.Handled"/> property to true
+		/// to indicate that the request has been handled and no further processing is needed. If the event handler does set this
+		/// property to true, it must also call the
+		/// <see cref="HybridWebViewWebResourceRequestedEventArgs.SetResponse(int, string, System.Collections.Generic.IReadOnlyDictionary{string, string}?, System.IO.Stream?)"/>
+		/// or <see cref="HybridWebViewWebResourceRequestedEventArgs.SetResponse(int, string, System.Collections.Generic.IReadOnlyDictionary{string, string}?, System.Threading.Tasks.Task{System.IO.Stream?})"/>
+		/// method to provide a response to the request.
+		/// </summary>
+		public event EventHandler<HybridWebViewWebResourceRequestedEventArgs>? WebResourceRequested;
+
 		/// <summary>
 		/// Sends a raw message to the code running in the web view. Raw messages have no additional processing.
 		/// </summary>

src/Controls/src/Core/HybridWebView/HybridWebViewWebResourceRequestedEventArgs.cs

@@ -0,0 +1,301 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Microsoft.Maui.Controls;
+
+/// <summary>
+/// Event arguments for the <see cref="HybridWebView.WebResourceRequested"/> event.
+/// </summary>
+public class HybridWebViewWebResourceRequestedEventArgs
+{
+	IReadOnlyDictionary<string, string>? _headers;
+	IReadOnlyDictionary<string, string>? _queryParams;
+
+	internal HybridWebViewWebResourceRequestedEventArgs(PlatformHybridWebViewWebResourceRequestedEventArgs platformArgs)
+	{
+		PlatformArgs = platformArgs;
+		Uri = platformArgs.GetRequestUri() is string uri ? new Uri(uri) : throw new InvalidOperationException("Platform web request did not have a request URI.");
+		Method = platformArgs.GetRequestMethod() ?? throw new InvalidOperationException("Platform web request did not have a request METHOD.");
+	}
+
+	/// <summary>
+	/// Initializes a new instance of the <see cref="HybridWebViewWebResourceRequestedEventArgs"/> class
+	/// with the specified URI and method.
+	/// </summary>
+	public HybridWebViewWebResourceRequestedEventArgs(Uri uri, string method)
+	{
+		Uri = uri;
+		Method = method;
+	}
+
+	/// <summary>
+	/// Gets the platform-specific event arguments.
+	/// </summary>
+	public PlatformHybridWebViewWebResourceRequestedEventArgs? PlatformArgs { get; }
+
+	/// <summary>
+	/// Gets the URI of the requested resource.
+	/// </summary>
+	public Uri Uri { get; }
+
+	/// <summary>
+	/// Gets the HTTP method used for the request (e.g., GET, POST).
+	/// </summary>
+	public string Method { get; }
+
+	/// <summary>
+	/// Gets the headers associated with the request.
+	/// </summary>
+	public IReadOnlyDictionary<string, string> Headers =>
+		_headers ??= PlatformArgs?.GetRequestHeaders() ?? new Dictionary<string, string>();
+
+	/// <summary>
+	/// Gets the query parameters from the URI.
+	/// </summary>
+	public IReadOnlyDictionary<string, string> QueryParameters =>
+		_queryParams ??= WebUtils.ParseQueryString(Uri, false) ?? new Dictionary<string, string>();
+
+	/// <summary>
+	/// Gets or sets a value indicating whether the request has been handled.
+	/// 
+	/// If set to true, the web view will not process the request further and a response
+	/// must be provided using the 
+	/// <see cref="SetResponse(int, string, System.Collections.Generic.IReadOnlyDictionary{string, string}?, System.IO.Stream?)"/> 
+	/// or <see cref="SetResponse(int, string, System.Collections.Generic.IReadOnlyDictionary{string, string}?, System.Threading.Tasks.Task{System.IO.Stream?})"/> method.
+	/// If set to false, the web view will continue processing the request as normal.
+	/// </summary>
+	public bool Handled { get; set; }
+
+	/// <summary>
+	/// Sets the response for the web resource request. 
+	/// 
+	/// This method must be called if the <see cref="Handled"/> property is set to true.
+	/// </summary>
+	/// <param name="code">The HTTP status code for the response.</param>
+	/// <param name="reason">The reason phrase for the response.</param>
+	/// <param name="headers">The headers to include in the response.</param>
+	/// <param name="content">The content of the response as a stream.</param>
+	public void SetResponse(int code, string reason, IReadOnlyDictionary<string, string>? headers, Stream? content)
+	{
+		_ = PlatformArgs ?? throw new InvalidOperationException("Platform web request was not valid.");
+
+#if WINDOWS
+
+		// create the response
+		PlatformArgs.RequestEventArgs.Response = PlatformArgs.Sender.Environment.CreateWebResourceResponse(
+			content?.AsRandomAccessStream(),
+			code,
+			reason,
+			PlatformHeaders(headers));
+
+#elif IOS || MACCATALYST
+
+		// iOS and MacCatalyst will just wait until DidFinish is called
+		var task = PlatformArgs.UrlSchemeTask;
+
+		// create and send the response headers
+		task.DidReceiveResponse(new Foundation.NSHttpUrlResponse(
+			PlatformArgs.Request.Url,
+			code,
+			"HTTP/1.1",
+			PlatformHeaders(headers)));
+
+		// send the data
+		if (content is not null && Foundation.NSData.FromStream(content) is { } nsdata)
+		{
+			task.DidReceiveData(nsdata);
+		}
+
+		// let the webview know
+		task.DidFinish();
+
+#elif ANDROID
+
+		// Android requires that we return immediately, even if the data is coming later
+
+		// create and send the response headers
+		var platformHeaders = PlatformHeaders(headers, out var contentType);
+		PlatformArgs.Response = new global::Android.Webkit.WebResourceResponse(
+			contentType,
+			"UTF-8",
+			code,
+			reason,
+			platformHeaders,
+			content);
+
+#endif
+	}
+
+	/// <summary>
+	/// Sets the asynchronous response for the web resource request.
+	/// 
+	/// This method must be called if the <see cref="Handled"/> property is set to true.
+	/// </summary>
+	/// <param name="code">The HTTP status code for the response.</param>
+	/// <param name="reason">The reason phrase for the response.</param>
+	/// <param name="headers">The headers to include in the response.</param>
+	/// <param name="contentTask">A task that represents the asynchronous operation of getting the response content.</param>
+	/// <remarks>
+	/// This method is not asynchronous and will return immediately. The actual response will be sent when the content task completes.
+	/// </remarks>
+	public void SetResponse(int code, string reason, IReadOnlyDictionary<string, string>? headers, Task<Stream?> contentTask) =>
+		SetResponseAsync(code, reason, headers, contentTask).FireAndForget();
+
+#pragma warning disable CS1998 // Android implememntation does not use async/await
+	async Task SetResponseAsync(int code, string reason, IReadOnlyDictionary<string, string>? headers, Task<Stream?> contentTask)
+#pragma warning restore CS1998
+	{
+		_ = PlatformArgs ?? throw new InvalidOperationException("Platform web request was not valid.");
+
+#if WINDOWS
+
+		// Windows uses a deferral to let the webview know that we are going to be async
+		using var deferral = PlatformArgs.RequestEventArgs.GetDeferral();
+
+		// get the actual content
+		var data = await contentTask;
+
+		// create the response
+		PlatformArgs.RequestEventArgs.Response = PlatformArgs.Sender.Environment.CreateWebResourceResponse(
+			data?.AsRandomAccessStream(),
+			code,
+			reason,
+			PlatformHeaders(headers));
+
+		// let the webview know
+		deferral.Complete();
+
+#elif IOS || MACCATALYST
+
+		// iOS and MacCatalyst will just wait until DidFinish is called
+		var task = PlatformArgs.UrlSchemeTask;
+
+		// create and send the response headers
+		task.DidReceiveResponse(new Foundation.NSHttpUrlResponse(
+			PlatformArgs.Request.Url,
+			code,
+			"HTTP/1.1",
+			PlatformHeaders(headers)));
+
+		// get the actual content
+		var data = await contentTask;
+
+		// send the data
+		if (data is not null && Foundation.NSData.FromStream(data) is { } nsdata)
+		{
+			task.DidReceiveData(nsdata);
+		}
+
+		// let the webview know
+		task.DidFinish();
+
+#elif ANDROID
+
+		// Android requires that we return immediately, even if the data is coming later
+
+		// get the actual content
+		var stream = new AsyncStream(contentTask, null);
+
+		// create and send the response headers
+		var platformHeaders = PlatformHeaders(headers, out var contentType);
+		PlatformArgs.Response = new global::Android.Webkit.WebResourceResponse(
+			contentType,
+			"UTF-8",
+			code,
+			reason,
+			platformHeaders,
+			stream);
+
+#endif
+	}
+
+#if WINDOWS
+	static string? PlatformHeaders(IReadOnlyDictionary<string, string>? headers)
+	{
+		if (headers?.Count > 0)
+		{
+			var sb = new StringBuilder();
+			foreach (var header in headers)
+			{
+				sb.AppendLine($"{header.Key}: {header.Value}");
+			}
+			return sb.ToString();
+		}
+		return null;
+	}
+#elif IOS || MACCATALYST
+	static Foundation.NSMutableDictionary? PlatformHeaders(IReadOnlyDictionary<string, string>? headers)
+	{
+		if (headers?.Count > 0)
+		{
+			var dic = new Foundation.NSMutableDictionary();
+			foreach (var header in headers)
+			{
+				dic.Add((Foundation.NSString)header.Key, (Foundation.NSString)header.Value);
+			}
+			return dic;
+		}
+		return null;
+	}
+#elif ANDROID
+	static global::Android.Runtime.JavaDictionary<string, string>? PlatformHeaders(IReadOnlyDictionary<string, string>? headers, out string contentType)
+	{
+		contentType = "application/octet-stream";
+		if (headers?.Count > 0)
+		{
+			var dic = new global::Android.Runtime.JavaDictionary<string, string>();
+			foreach (var header in headers)
+			{
+				if ("Content-Type".Equals(header.Key, StringComparison.OrdinalIgnoreCase))
+				{
+					contentType = header.Value;
+				}
+
+				dic.Add(header.Key, header.Value);
+			}
+			return dic;
+		}
+		return null;
+	}
+#endif
+}
+
+/// <summary>
+/// Extension methods for the <see cref="HybridWebViewWebResourceRequestedEventArgs"/> class.
+/// </summary>
+public static class HybridWebViewWebResourceRequestedEventArgsExtensions
+{
+	/// <summary>
+	/// Sets the response for the web resource request with a status code and reason.
+	/// </summary>
+	/// <param name="e">The event arguments.</param>
+	/// <param name="code">The HTTP status code for the response.</param>
+	/// <param name="reason">The reason phrase for the response.</param>
+	public static void SetResponse(this HybridWebViewWebResourceRequestedEventArgs e, int code, string reason) =>
+		e.SetResponse(code, reason, null, (Stream?)null);
+
+	/// <summary>
+	/// Sets the response for the web resource request with a status code, reason, and content type.
+	/// </summary>
+	/// <param name="e">The event arguments.</param>
+	/// <param name="code">The HTTP status code for the response.</param>
+	/// <param name="reason">The reason phrase for the response.</param>
+	/// <param name="contentType">The content type of the response.</param>
+	/// <param name="content">The content of the response as a stream.</param>
+	public static void SetResponse(this HybridWebViewWebResourceRequestedEventArgs e, int code, string reason, string contentType, Stream? content) =>
+		e.SetResponse(code, reason, new Dictionary<string, string> { ["Content-Type"] = contentType }, content);
+
+	/// <summary>
+	/// Sets the response for the web resource request with a status code, reason, and content type.
+	/// </summary>
+	/// <param name="e">The event arguments.</param>
+	/// <param name="code">The HTTP status code for the response.</param>
+	/// <param name="reason">The reason phrase for the response.</param>
+	/// <param name="contentType">The content type of the response.</param>
+	/// <param name="contentTask">A task that represents the asynchronous operation of getting the response content.</param>
+	public static void SetResponse(this HybridWebViewWebResourceRequestedEventArgs e, int code, string reason, string contentType, Task<Stream?> contentTask) =>
+		e.SetResponse(code, reason, new Dictionary<string, string> { ["Content-Type"] = contentType }, contentTask);
+}