New Entry page improvements on link detection

frontend/static/new-entry.js

@@ -11,8 +11,9 @@
   const existingTagsEl = document.getElementById('existing-tags');
   const mastodonPublishing = document.getElementById('mastodon-publishing');
   const mastodonEnabledCheckbox = document.getElementById('mastodon-enabled');
-  const scrapeButton = document.getElementById('scrape-button');
   const scrapeStatus = document.getElementById('scrape-status');
+  const duplicateStatus = document.getElementById('duplicate-status');
+  const refetchTitleButton = document.getElementById('refetch-title-button');
   const submitButton = document.getElementById('submit-button');
   const submitStatus = document.getElementById('submit-status');
 
@@ -21,9 +22,14 @@
   let selectedTags = new Set();
   let currentUser = null;
 
-  // Utility function to add status messages
+  // Utility function to add status messages; splits on \n into real <br> line breaks without using innerHTML.
   function setStatus(statusEl, message, isError = false) {
-    statusEl.textContent = message;
+    const lines = message.split('\n');
+    statusEl.replaceChildren(
+      ...lines.flatMap((line, index) => (
+        index === 0 ? [document.createTextNode(line)] : [document.createElement('br'), document.createTextNode(line)]
+      )),
+    );
     statusEl.className = `status ${isError ? 'error' : 'success'}`;
     statusEl.classList.remove('hidden');
     if (!isError) {
@@ -106,17 +112,29 @@
     });
   }
 
-  // Scrape URL for title
-  scrapeButton.addEventListener('click', async (e) => {
-    e.preventDefault();
-    const url = urlInput.value.trim();
-    if (!url) {
-      setStatus(scrapeStatus, 'Please enter a URL', true);
-      return;
+  // Strip known tracking parameters so duplicate detection and scraping ignore them, mirroring the browser extension.
+  function removeKnownTrackingParams(urlString) {
+    try {
+      const url = new URL(urlString);
+      const known = new Set([
+        'utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
+        'utm_id', 'utm_name', 'gclid', 'fbclid', 'dclid', 'msclkid',
+      ]);
+      for (const key of known) {
+        url.searchParams.delete(key);
+      }
+      return url.toString();
+    } catch (error) {
+      return urlString;
     }
+  }
 
-    scrapeButton.disabled = true;
-    setStatus(scrapeStatus, 'Scraping...', false);
+  // Fetch the page title for the given URL and fill it in, unless the user already typed one.
+  let lastScrapedUrl = null;
+  async function fetchTitle(url, { force = false } = {}) {
+    if (!url || (!force && (titleInput.value.trim() || url === lastScrapedUrl))) return;
+
+    setStatus(scrapeStatus, 'Looking up title...', false);
 
     try {
       const response = await fetch(`/api/scrape?url=${encodeURIComponent(url)}`, {
@@ -132,6 +150,7 @@
         throw new Error(`HTTP ${response.status}`);
       }
 
+      lastScrapedUrl = url;
       const data = await response.json();
       if (data.title) {
         titleInput.value = data.title;
@@ -142,16 +161,64 @@
     } catch (error) {
       console.error('Scrape error:', error);
       setStatus(scrapeStatus, `Error: ${error.message}`, true);
-    } finally {
-      scrapeButton.disabled = false;
     }
+  }
+
+  urlInput.addEventListener('blur', async () => {
+    await fetchTitle(removeKnownTrackingParams(urlInput.value.trim()));
+    checkDuplicate();
   });
 
+  refetchTitleButton.addEventListener('click', (e) => {
+    e.preventDefault();
+    const url = removeKnownTrackingParams(urlInput.value.trim());
+    if (!url) {
+      setStatus(scrapeStatus, 'Please enter a URL', true);
+      return;
+    }
+    titleInput.value = '';
+    fetchTitle(url, { force: true });
+  });
+
+  // Warn when the URL/title combination already exists for this user, mirroring the browser extension.
+  titleInput.addEventListener('blur', checkDuplicate);
+
+  urlInput.addEventListener('input', () => duplicateStatus.classList.add('hidden'));
+  titleInput.addEventListener('input', () => duplicateStatus.classList.add('hidden'));
+
+  async function checkDuplicate() {
+    const url = removeKnownTrackingParams(urlInput.value.trim());
+    const title = titleInput.value.trim();
+    if (!url || !title) return;
+
+    try {
+      const response = await fetch(`/api/links/check?${new URLSearchParams({ title, url })}`, {
+        headers: { Authorization: `Bearer ${token}` },
+      });
+      if (!response.ok) return;
+      const data = await response.json();
+      if (data.exists) {
+        let message = 'This link already exists. ';
+        if (!data.url_matches) {
+          message += 'But, the stored link has a different URL (missing or different parameters).';
+          message += '\nWhen you save the entry you risk a duplicate entry.';
+        } else {
+          message += '\nYou can still save the entry, which will update the existing entry\'s comment and or tags.';
+        }
+        setStatus(duplicateStatus, message, true);
+      } else {
+        duplicateStatus.classList.add('hidden');
+      }
+    } catch (error) {
+      // Duplicate checking is advisory; submission remains available.
+    }
+  }
+
   // Handle form submission
   entryForm.addEventListener('submit', async (e) => {
     e.preventDefault();
 
-    const url = urlInput.value.trim();
+    const url = removeKnownTrackingParams(urlInput.value.trim());
     const title = titleInput.value.trim();
     const comment = commentInput.value.trim();
     const newTags = newTagsInput.value.trim();