Implement library support for Angular-style single page applications

README.md

@@ -28,3 +28,35 @@ else will be ignored.
 The interaction between range handling and compression also seems a little
 ill-defined; as we have pre-compressed data, however, we can consistently
 serve the exact same byte data for compressed files.
+
+## Angular-style single-page application handling
+
+If you wish to support an angular.js-style single page application, in which
+a Javascript application uses the browser's history API to create a set of
+virtual paths ("routes"), it is necessary to somehow intercept HTTP 404 errors
+being returned from the handler and instead return an HTTP 200 with an HTML
+document.
+
+This can be achieved with a number of methods.
+
+If you have an nginx instance reverse proxying in front of `htpack`, then you
+can use a couple of extra directives, for example:
+
+	# prevent page loaded at "http://server.example/my-application" from
+	# requesting resources at "/*" when it should request them at
+	# "/my-application/*" instead
+	location = /my-application {
+		return 308 /my-application/;
+	}
+
+	location /my-application/ {
+		proxy_to http://htpack-addr:8080/;
+		proxy_intercept_errors on;
+		error_page 404 =200 /my-application/;
+	}
+
+If you are using the handler as a library, then you may call
+`handler.SetNotFound(filename)` to select a resource to return (with HTTP 200)
+if a request is made for a resource that is not found. The filename must match
+a packed resource, so it will be preceded with a `/` (for example it may be
+`"/index.html"`).