:sparkles: Add additional errors for other cases.

2 files changed, 8 insertions, 2 deletions

diff --git a/lib/src/lustre.ffi.mjs b/lib/src/lustre.ffi.mjs
index 2d07394..c7008ed 100644
--- a/lib/src/lustre.ffi.mjs
+++ b/lib/src/lustre.ffi.mjs
@@ -1,6 +1,8 @@
 import {
-  ElementNotFound,
+  AppAlreadyStarted,
+  AppNotYetStarted,
   ComponentAlreadyRegistered,
+  ElementNotFound,
   NotABrowser,
 } from "./lustre.mjs";
 import { from } from "./lustre/effect.mjs";
@@ -31,7 +33,7 @@ export class App {
 
   start(selector, flags) {
     if (!is_browser()) return new Error(new NotABrowser());
-    if (this.#root) return this;
+    if (this.#root) return new Error(new AppAlreadyStarted());
 
     const el = document.querySelector(selector);
 
@@ -65,6 +67,8 @@ export class App {
   }
 
   destroy() {
+    if (!this.#root) return new Error(new AppNotYetStarted());
+
     this.#root.remove();
     this.#state = null;
     this.#queue = [];
diff --git a/lib/src/lustre.gleam b/lib/src/lustre.gleam
index dcfe76a..ec04f3e 100644
--- a/lib/src/lustre.gleam
+++ b/lib/src/lustre.gleam
@@ -50,6 +50,8 @@ import lustre/element.{Element}
 pub type App(flags, model, msg)
 
 pub type Error {
+  AppAlreadyStarted
+  AppNotYetStarted
   ComponentAlreadyRegistered
   ElementNotFound
   NotABrowser