refactor(base64-to-file): clean validation to convert base64 to file

src/composable/downloadBase64.ts

@@ -1,16 +1,35 @@
 import { extension as getExtensionFromMime } from 'mime-types';
 import type { Ref } from 'vue';
 
+function getFileExtensionFromBase64({
+  base64String,
+  defaultExtension = 'txt',
+}: {
+  base64String: string;
+  defaultExtension?: string;
+}) {
+  const hasMimeType = base64String.match(/data:(.*?);base64/i);
+
+  if (hasMimeType) {
+    return getExtensionFromMime(hasMimeType[1]) || defaultExtension;
+  }
+
+  return defaultExtension;
+}
+
 export function useDownloadFileFromBase64({ source, filename }: { source: Ref<string>; filename?: string }) {
   return {
     download() {
-      const base64 = source.value;
-      const mimeType = base64.match(/data:(.*?);base64/i)?.[1] ?? 'text/plain';
-      console.log({ mimeType });
-      const cleanFileName = filename ?? `file.${getExtensionFromMime(mimeType)}`;
+      const base64String = source.value;
+
+      if (base64String === '') {
+        throw new Error('Base64 string is empty');
+      }
+
+      const cleanFileName = filename ?? `file.${getFileExtensionFromBase64({ base64String })}`;
 
       const a = document.createElement('a');
-      a.href = source.value;
+      a.href = base64String;
       a.download = cleanFileName;
       a.click();
     },