🏄‍♂️ fix: Handle SSE Stream Edge Case (#8556)

* refactor: Move draft-related utilities to a new `drafts.ts` file

* refactor: auto-save draft logic to use new get/set functions

* fix: Ensure `getDraft` properly decodes stored draft values

* fix: Handle edge case where stream is cancelled before any response, which creates a blank page

client/src/utils/drafts.ts

@@ -0,0 +1,39 @@
+import debounce from 'lodash/debounce';
+import { LocalStorageKeys } from 'librechat-data-provider';
+
+export const clearDraft = debounce((id?: string | null) => {
+  localStorage.removeItem(`${LocalStorageKeys.TEXT_DRAFT}${id ?? ''}`);
+}, 2500);
+
+export const encodeBase64 = (plainText: string): string => {
+  try {
+    const textBytes = new TextEncoder().encode(plainText);
+    return btoa(String.fromCharCode(...textBytes));
+  } catch {
+    return '';
+  }
+};
+
+export const decodeBase64 = (base64String: string): string => {
+  try {
+    const bytes = atob(base64String);
+    const uint8Array = new Uint8Array(bytes.length);
+    for (let i = 0; i < bytes.length; i++) {
+      uint8Array[i] = bytes.charCodeAt(i);
+    }
+    return new TextDecoder().decode(uint8Array);
+  } catch {
+    return '';
+  }
+};
+
+export const setDraft = ({ id, value }: { id: string; value?: string }) => {
+  if (value && value.length > 1) {
+    localStorage.setItem(`${LocalStorageKeys.TEXT_DRAFT}${id}`, encodeBase64(value));
+    return;
+  }
+  localStorage.removeItem(`${LocalStorageKeys.TEXT_DRAFT}${id}`);
+};
+
+export const getDraft = (id?: string): string | null =>
+  decodeBase64((localStorage.getItem(`${LocalStorageKeys.TEXT_DRAFT}${id ?? ''}`) ?? '') || '');