add WASM blazor-like thing

go/wasmruntime/router.go

@@ -0,0 +1,38 @@
+//go:build js && wasm
+
+package wasmruntime
+
+import (
+	"syscall/js"
+
+	"kjol/vdom"
+)
+
+// Router holds the current path in a signal, so reading Path() during render
+// re-renders on navigation (and browser back/forward).
+type Router struct {
+	path *vdom.Signal[string]
+}
+
+func NewRouter() *Router {
+	r := &Router{path: vdom.NewSignal(currentPath())}
+	popstate := js.FuncOf(func(this js.Value, args []js.Value) any {
+		r.path.Set(currentPath())
+		return nil
+	})
+	js.Global().Call("addEventListener", "popstate", popstate)
+	return r
+}
+
+func currentPath() string {
+	return js.Global().Get("location").Get("pathname").String()
+}
+
+// Path returns the current route (reactive when read during render).
+func (r *Router) Path() string { return r.path.Get() }
+
+// Navigate pushes a history entry and re-renders (client-side SPA navigation).
+func (r *Router) Navigate(path string) {
+	js.Global().Get("history").Call("pushState", nil, "", path)
+	r.path.Set(path)
+}