Fix scroll on reload (#1015)

* fix scroll on reload

* fix comment

packages/webawesome/docs/assets/scripts/scroll.js

@@ -1,3 +1,19 @@
+import { allDefined } from '/dist/webawesome.js';
+
+/**
+ * Determines how the page was loaded. Possible return values include "reload", "navigate", "back_forward", "prerender",
+ * and "unknown".
+ */
+function getNavigationType() {
+  if (performance.getEntriesByType) {
+    const navEntries = performance.getEntriesByType('navigation');
+    if (navEntries.length > 0) {
+      return navEntries[0].type;
+    }
+  }
+  return 'unknown';
+}
+
 // Smooth links
 document.addEventListener('click', event => {
   const link = event.target.closest('a');
@@ -31,3 +47,26 @@ function updateScrollClass() {
 window.addEventListener('scroll', updateScrollClass);
 window.addEventListener('turbo:render', updateScrollClass);
 updateScrollClass();
+
+// Restore scroll position after components are defined
+allDefined().then(() => {
+  const navigationType = getNavigationType();
+  const key = `wa-scroll-y-[${location.pathname}]`;
+  const scrollY = sessionStorage.getItem(key);
+
+  // Only restore when reloading, otherwise clear it
+  if (navigationType === 'reload' && scrollY) {
+    window.scrollTo(0, scrollY);
+  } else {
+    sessionStorage.removeItem(key);
+  }
+
+  // After restoring, keep tabs on the page's scroll position for next reload
+  window.addEventListener(
+    'scroll',
+    () => {
+      sessionStorage.setItem(key, window.scrollY);
+    },
+    { passive: true },
+  );
+});