Prevent duplicate URL additions in NewGuru component

Enhance URL input handling by filtering out duplicate URLs before adding them to the editor. Ensure only unique URLs are appended to the existing list, improving the user experience and preventing redundant entries.

src/gurubase-frontend/src/components/NewGuru.jsx

@@ -155,18 +155,26 @@ export default function NewGuru({ guruData, isProcessing }) {
         .split("\n")
         .filter((url) => url.trim());
 
-      // Add new URLs line by line
-      const updatedContent =
-        currentContent +
-        (currentContent && newUrls.length > 0 ? "\n" : "") +
-        newUrls.join("\n");
-
-      // Update editor content
-      setUrlEditorContent(updatedContent);
-
-      // Update form value
-      const allUrls = [...existingUrls, ...newUrls];
-      form.setValue("websiteUrls", allUrls);
+      // Filter out URLs that already exist in the editor
+      const uniqueNewUrls = newUrls.filter(
+        (url) => !existingUrls.includes(url)
+      );
+
+      // Only proceed if there are new unique URLs to add
+      if (uniqueNewUrls.length > 0) {
+        // Add new URLs line by line
+        const updatedContent =
+          currentContent +
+          (currentContent ? "\n" : "") +
+          uniqueNewUrls.join("\n");
+
+        // Update editor content
+        setUrlEditorContent(updatedContent);
+
+        // Update form value with all unique URLs
+        const allUrls = [...existingUrls, ...uniqueNewUrls];
+        form.setValue("websiteUrls", allUrls);
+      }
     }
   );