feat: add core utility functions for date formatting, validation, and UI helpers

js/utils.js

@@ -202,6 +202,41 @@ const Utils = (() => {
         return dateStr; // Fallback: return original if not recognized
     };
 
+    /**
+     * Convert a date string from DD/MM/YYYY to YYYY-MM-DD (ISO).
+     * @param {string} uiDate - Date in DD/MM/YYYY
+     * @returns {string} - Date in YYYY-MM-DD
+     */
+    const toISODate = (uiDate) => {
+        if (!uiDate) return '';
+        const parts = uiDate.match(/^(\d{1,2})\/(\d{1,2})\/(\d{4})$/);
+        if (parts) {
+            const day = String(parts[1]).padStart(2, '0');
+            const month = String(parts[2]).padStart(2, '0');
+            const year = parts[3];
+            return `${year}-${month}-${day}`;
+        }
+        // If already in ISO format, return as is
+        if (/^\d{4}-\d{2}-\d{2}$/.test(uiDate)) return uiDate;
+        return uiDate;
+    };
+
+    /**
+     * Convert a date string from YYYY-MM-DD (ISO) to DD/MM/YYYY for UI.
+     * @param {string} isoDate - Date in YYYY-MM-DD
+     * @returns {string} - Date in DD/MM/YYYY
+     */
+    const toUIDate = (isoDate) => {
+        if (!isoDate) return '';
+        const parts = isoDate.match(/^(\d{4})-(\d{2})-(\d{2})$/);
+        if (parts) {
+            return `${parts[3]}/${parts[2]}/${parts[1]}`;
+        }
+        // If already in UI format, return as is
+        if (/^\d{1,2}\/\d{1,2}\/\d{4}$/.test(isoDate)) return isoDate;
+        return isoDate;
+    };
+
     return {
         formatDate,
         getTodayDate,
@@ -211,6 +246,7 @@ const Utils = (() => {
         calculateWeightStats,
         copyToClipboard,
         sanitizeHTML,
-        uiDateToISO // Export the new function
+        toISODate,
+        toUIDate
     };
 })();