Move React server-side rendering into more general SpaServices package

src/Microsoft.AspNet.SpaServices/Webpack/WebpackDevMiddleware.cs

@@ -0,0 +1,73 @@
+using System;
+using System.IO;
+using System.Threading.Tasks;
+using Microsoft.AspNet.NodeServices;
+using Microsoft.AspNet.Proxy;
+using Microsoft.AspNet.SpaServices.Webpack;
+using Microsoft.Extensions.PlatformAbstractions;
+using Newtonsoft.Json;
+
+// Putting in this namespace so it's always available whenever MapRoute is
+namespace Microsoft.AspNet.Builder
+{
+    public static class WebpackDevMiddleware
+    {
+        const string WebpackDevMiddlewareHostname = "localhost";
+        const string WebpackHotMiddlewareEndpoint = "/__webpack_hmr";
+
+        static INodeServices fallbackNodeServices; // Used only if no INodeServices was registered with DI
+
+        public static void UseWebpackDevMiddleware(this IApplicationBuilder appBuilder, WebpackDevMiddlewareOptions options = null) {
+            // Validate options
+            if (options != null) {
+                if (options.ReactHotModuleReplacement && !options.HotModuleReplacement) {
+                    throw new ArgumentException("To enable ReactHotModuleReplacement, you must also enable HotModuleReplacement.");
+                }
+            }
+
+            // Get the NodeServices instance from DI
+            var nodeServices = (INodeServices)appBuilder.ApplicationServices.GetService(typeof (INodeServices)) ?? fallbackNodeServices;
+            
+            // Consider removing the following. Having it means you can get away with not putting app.AddNodeServices()
+            // in your startup file, but then again it might be confusing that you don't need to.
+            var appEnv = (IApplicationEnvironment)appBuilder.ApplicationServices.GetService(typeof(IApplicationEnvironment));
+            if (nodeServices == null) {
+                nodeServices = fallbackNodeServices = Configuration.CreateNodeServices(NodeHostingModel.Http, appEnv.ApplicationBasePath);
+            }
+            
+            // Get a filename matching the middleware Node script
+            var script = EmbeddedResourceReader.Read(typeof (WebpackDevMiddleware), "/Content/Node/webpack-dev-middleware.js");
+            var nodeScript = new StringAsTempFile(script); // Will be cleaned up on process exit
+
+            // Tell Node to start the server hosting webpack-dev-middleware
+            var devServerOptions = new {
+                webpackConfigPath = Path.Combine(appEnv.ApplicationBasePath, "webpack.config.js"),
+                suppliedOptions = options ?? new WebpackDevMiddlewareOptions()
+            };
+            var devServerInfo = nodeServices.InvokeExport<WebpackDevServerInfo>(nodeScript.FileName, "createWebpackDevServer", JsonConvert.SerializeObject(devServerOptions)).Result;
+
+            // Proxy the corresponding requests through ASP.NET and into the Node listener 
+            appBuilder.Map(devServerInfo.PublicPath, builder => {
+                builder.RunProxy(new ProxyOptions {
+                    Host = WebpackDevMiddlewareHostname,
+                    Port = devServerInfo.Port.ToString()
+                });
+            });
+            
+            // While it would be nice to proxy the /__webpack_hmr requests too, these return an EventStream,
+            // and the Microsoft.Aspnet.Proxy code doesn't handle that entirely - it throws an exception after
+            // a while. So, just serve a 302 for those.
+            appBuilder.Map(WebpackHotMiddlewareEndpoint, builder => {
+                builder.Use(next => async ctx => {
+                    ctx.Response.Redirect($"http://localhost:{ devServerInfo.Port.ToString() }{ WebpackHotMiddlewareEndpoint }");
+                    await Task.Yield();
+                });
+            });
+        }
+        
+        class WebpackDevServerInfo {
+            public int Port;
+            public string PublicPath;
+        }
+    }
+}