Add short gallery URL toggle and token support (#38)

backend/src/utils/shareLinkUtils.js

@@ -0,0 +1,63 @@
+const SHARE_TOKEN_REGEX = /^[0-9a-fA-F]{32}$/;
+
+/**
+ * Extracts the share token portion from a stored share link.
+ * Supports full URLs, absolute paths, and legacy slug/token formats.
+ * @param {string|null|undefined} shareLink
+ * @returns {string|null}
+ */
+function extractShareToken(shareLink) {
+  if (!shareLink) {
+    return null;
+  }
+
+  const trimmed = String(shareLink).trim();
+  if (!trimmed) {
+    return null;
+  }
+
+  // Remove protocol + host when a full URL is stored
+  const path = trimmed.replace(/^https?:\/\/[^/]+/i, '');
+  const segments = path.split('/').filter(Boolean);
+  if (segments.length === 0) {
+    return null;
+  }
+
+  const candidate = segments[segments.length - 1];
+  return candidate || null;
+}
+
+/**
+ * Returns true if the provided identifier looks like a generated share token.
+ * @param {string|null|undefined} identifier
+ * @returns {boolean}
+ */
+function isPotentialShareToken(identifier) {
+  if (!identifier) {
+    return false;
+  }
+  return SHARE_TOKEN_REGEX.test(String(identifier).trim());
+}
+
+/**
+ * Builds the gallery share path depending on whether short URLs are enabled.
+ * @param {string} slug
+ * @param {string} shareToken
+ * @param {boolean} useShort
+ * @returns {string}
+ */
+function buildSharePath(slug, shareToken, useShort) {
+  if (!shareToken) {
+    throw new Error('shareToken is required to build share path');
+  }
+  if (useShort || !slug) {
+    return `/gallery/${shareToken}`;
+  }
+  return `/gallery/${slug}/${shareToken}`;
+}
+
+module.exports = {
+  extractShareToken,
+  isPotentialShareToken,
+  buildSharePath
+};