kfrancis · November 23, 2021 18:00 · Nov 23, 2021
diff --git a/LoopbackHttpListener.cs b/LoopbackHttpListener.cs
@@ -0,0 +1,169 @@
+/// <summary>
+///     The HTTP Loopback Listener used to receive commands via HTTP.
+/// </summary>
+internal class LoopbackHttpListener : IDisposable
+{
+    /// <summary>
+    ///     The <see cref="TaskCompletionSource{TResult}"/>.
+    /// </summary>
+    private readonly TaskCompletionSource<string> _completionSource = new TaskCompletionSource<string>();
+
+    /// <summary>
+    ///     The <see cref="IWebHost"/>.
+    /// </summary>
+    private readonly IWebHost _host;
+
+    /// <summary>
+    ///     Gets the default <see cref="TimeSpan"/> to wait before timing out.
+    /// </summary>
+    public static TimeSpan DefaultTimeOut => TimeSpan.FromMinutes(5);
+
+    /// <summary>
+    ///     Gets the URL which the current <see cref="LoopbackHttpListener"/> is listening on.
+    /// </summary>
+    public string Url { get; }
+
+    /// <summary>
+    ///     Initializes a new instance of the <see cref="LoopbackHttpListener"/> class.
+    /// </summary>
+    /// <param name="host">
+    ///     The hostname or IP address to use.
+    /// </param>
+    /// <param name="port">
+    ///     The port to use.
+    /// </param>
+    /// <param name="path">
+    ///     The URL path after the address and port (http://127.0.0.1:42069/{PATH}).
+    /// </param>
+    public LoopbackHttpListener(string host, int port, string path = null)
+    {
+        if (string.IsNullOrEmpty(host)) throw new ArgumentNullException(nameof(host));
+
+        // Assign the path to an empty string if nothing was provided
+        path ??= string.Empty;
+
+        // Trim any excess slashes from the path
+        if (path.StartsWith("/")) path = path.Substring(1);
+
+        // Build the URL
+        Url = $"http://{host}:{port}/{path}";
+
+        // Build and start the web host
+        _host = new WebHostBuilder()
+            .UseKestrel()
+            .UseUrls(Url)
+            .Configure(Configure)
+            .Build();
+        _host.Start();
+    }
+
+    /// <summary>
+    ///     Waits until a callback has been received, then returns the result as an asynchronous operation.
+    /// </summary>
+    /// <param name="timeout">
+    ///     The <see cref="TimeSpan"/> to wait before timing out.
+    /// </param>
+    /// <returns>
+    ///     The <see cref="Task{T}"/> representing the asynchronous operation.
+    ///     The <see cref="Task{TResult}.Result"/> contains the result.
+    /// </returns>
+    public Task<string> WaitForCallbackAsync(TimeSpan? timeout = null)
+    {
+        if (timeout == null)
+        {
+            timeout = DefaultTimeOut;
+        }
+
+        Task.Run(async () =>
+        {
+            await Task.Delay(timeout.Value);
+            _completionSource.TrySetCanceled();
+        });
+
+        return _completionSource.Task;
+    }
+
+    /// <summary>
+    ///     Configures the current <see cref="LoopbackHttpListener"/>.
+    /// </summary>
+    /// <param name="app">
+    ///     The <see cref="IApplicationBuilder"/>.
+    /// </param>
+    private void Configure(IApplicationBuilder app)
+    {
+        app.Run(async ctx =>
+        {
+            var syncIoFeature = ctx.Features.Get<IHttpBodyControlFeature>();
+            if (syncIoFeature != null)
+            {
+                syncIoFeature.AllowSynchronousIO = true;
+            }
+
+            switch (ctx.Request.Method)
+            {
+                case "GET":
+                    await SetResult(ctx.Request.QueryString.Value, ctx);
+                    break;
+
+                case "POST" when !ctx.Request.ContentType.Equals("application/x-www-form-urlencoded", StringComparison.OrdinalIgnoreCase):
+                    ctx.Response.StatusCode = 415;
+                    break;
+
+                case "POST":
+                    {
+                        using var sr = new StreamReader(ctx.Request.Body, Encoding.UTF8);
+                        var body = await sr.ReadToEndAsync();
+                        await SetResult(body, ctx);
+
+                        break;
+                    }
+
+                default:
+                    ctx.Response.StatusCode = 405;
+                    break;
+            }
+        });
+    }
+
+    /// <summary>
+    ///     Disposes the current <see cref="LoopbackHttpListener"/> instance.
+    /// </summary>
+    public void Dispose()
+    {
+        Task.Run(async () =>
+        {
+            await Task.Delay(500);
+            _host.Dispose();
+        });
+    }
+
+    /// <summary>
+    ///     Sets the result to be returned by the <see cref="WaitForCallbackAsync"/> method.
+    /// </summary>
+    /// <param name="value">
+    ///     The value to set.
+    /// </param>
+    /// <param name="ctx">
+    ///     The <see cref="HttpContext"/>.
+    /// </param>
+    private async Task SetResult(string value, HttpContext ctx)
+    {
+        // Todo: Custom HTML page? Maybe make a request to the main site for a page to render? Or redirect if possible?
+        try
+        {
+            ctx.Response.StatusCode = 200;
+            ctx.Response.ContentType = "text/html";
+            await ctx.Response.WriteAsync("<h1>You can now return to the application.</h1>", Encoding.UTF8);
+            await ctx.Response.Body.FlushAsync();
+
+            _completionSource.TrySetResult(value);
+        }
+        catch
+        {
+            ctx.Response.StatusCode = 400;
+            ctx.Response.ContentType = "text/html";
+            await ctx.Response.WriteAsync("<h1>Invalid request.</h1>", Encoding.UTF8);
+            await ctx.Response.Body.FlushAsync();
+        }
+    }
+}
No results found