Implement library support for Angular-style single page applications

handler.go

@@ -72,6 +72,7 @@ type Handler struct {
 	dir       map[string]*packed.File
 	headers   map[string]string
 	startTime time.Time
+	notFound  *packed.File
 }
 
 // SetHeader allows a custom header to be set on HTTP responses. These are
@@ -110,6 +111,28 @@ func (h *Handler) SetIndex(filename string) {
 	}
 }
 
+// SetNotFound allows overriding the returned resource when a request is made
+// for a resource that does not exist. The default behaviour would be to return
+// a standard HTTP 404 Not Found response; calling this function with an empty
+// string will restore that behaviour.
+//
+// This function will return an error if the named resource is not present in
+// the packfile.
+func (h *Handler) SetNotFound(notFound string) error {
+	if notFound == "" {
+		h.notFound = nil
+		return nil
+	}
+
+	notFound = path.Clean(notFound)
+	dir := h.dir[path.Clean(notFound)]
+	if dir == nil {
+		return fmt.Errorf("no such resource %q", notFound)
+	}
+	h.notFound = dir
+	return nil
+}
+
 // ServeHTTP handles requests for files. It supports GET and HEAD methods, with
 // anything else returning a 405. Exact path matches are required, else a 404 is
 // returned.
@@ -130,8 +153,11 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 
 	info := h.dir[path.Clean(req.URL.Path)]
 	if info == nil {
-		http.NotFound(w, req)
-		return
+		if h.notFound == nil {
+			http.NotFound(w, req)
+			return
+		}
+		info = h.notFound
 	}
 
 	// set standard headers