Use HTMX fragements on the fitness dashboard

main.go

@@ -64,6 +64,14 @@ type pageTypeHandler interface {
 	redirect(root, fsPath, urlPath string, r *http.Request) (target string, ok bool)
 }
 
+// fragmentHandler is optionally implemented by a pageTypeHandler whose page
+// updates part of itself over htmx (e.g. one chart of a dashboard). It
+// answers only htmx GETs outside the editor and returns false when the
+// request is not for one of its fragments, so the full page renders.
+type fragmentHandler interface {
+	serveFragment(w http.ResponseWriter, r *http.Request, root, fsPath, urlPath string) bool
+}
+
 // pageTypeHandlers is the registry. Each type registers itself via init().
 var pageTypeHandlers []pageTypeHandler
 
@@ -306,6 +314,14 @@ func (h *handler) serveDir(w http.ResponseWriter, r *http.Request, urlPath, fsPa
 		return
 	}
 
+	if isHX(r) && !editMode {
+		for _, ph := range pageTypeHandlers {
+			if fh, ok := ph.(fragmentHandler); ok && fh.serveFragment(w, r, h.root, fsPath, urlPath) {
+				return
+			}
+		}
+	}
+
 	for _, ph := range pageTypeHandlers {
 		if target, ok := ph.redirect(h.root, fsPath, urlPath, r); ok {
 			http.Redirect(w, r, target, http.StatusFound)