feat: implement DataManager module and enhance API error handling for empty files

js/dataManager.js

@@ -25,10 +25,16 @@ const DataManager = (() => {
             if (response.ok) {
                 const data = await response.json();
                 if (data && typeof data === 'object') {
-                    appData = data;
+                    // Merge loaded data with defaults to ensure all keys are present
-                    console.log('Successfully loaded data from API.');
+                    appData = {
-                    // Optionally, update localStorage for offline or quick display, but API is truth
+                        ...defaultData, // Start with defaults
-                    // saveDataToLocalStorage(); 
+                        ...data,        // Override with loaded data
+                        // Ensure critical arrays exist if not in loaded data or if they are not arrays
+                        weights: Array.isArray(data.weights) ? data.weights : defaultData.weights,
+                        meals: Array.isArray(data.meals) ? data.meals : defaultData.meals,
+                        version: data.version || defaultData.version // Ensure version is present
+                    };
+                    console.log('Successfully loaded and merged data from API.');
                 } else {
                     console.warn('Data from API was not valid JSON or empty. Using default data.');
                     appData = { ...defaultData };

server-api.js

@@ -32,12 +32,17 @@ app.get('/', (req, res) => {
             console.error('Error reading data file:', err);
             return res.status(500).send('Error reading data file');
         }
+        // If file is empty or just whitespace, treat as empty object
+        if (!data || data.trim() === '') {
+            console.log(`Data file at ${DATA_FILE_PATH} is empty, returning empty object.`);
+            return res.json({});
+        }
+
         try {
             res.json(JSON.parse(data));
         } catch (parseErr) {
-            console.error('Error parsing data file content:', parseErr);
+            console.error(`Error parsing data file content from ${DATA_FILE_PATH}:`, parseErr);
-            // If file content is not valid JSON, perhaps return empty or handle error
+            return res.status(500).json({ message: 'Error parsing data file content. File may be corrupted.', error: parseErr.message });
-            res.status(500).send('Error parsing data file content'); 
         }
     });
 });