Add improvements

services/training/app/ml/enhanced_features.py

@@ -157,8 +157,13 @@ class AdvancedFeatureEngineer:
         # Week of year
         df['week_of_year'] = df[date_column].dt.isocalendar().week
 
-        # Payday indicators (15th and last day of month - high bakery traffic)
-        df['is_payday'] = ((df['day_of_month'] == 15) | df[date_column].dt.is_month_end).astype(int)
+        # Payday indicators for Spain (high bakery traffic)
+        # Spain commonly pays on: 28th, 15th, or last day of month
+        df['is_payday'] = (
+            (df['day_of_month'] == 15) |  # Mid-month payday
+            (df['day_of_month'] == 28) |  # Common Spanish payday (28th)
+            df[date_column].dt.is_month_end  # End of month
+        ).astype(int)
 
         # Add to feature list
         for col in ['month', 'quarter', 'day_of_month', 'is_month_start', 'is_month_end',
@@ -319,24 +324,27 @@ class AdvancedFeatureEngineer:
         """Get list of all created feature column names."""
         return self.feature_columns.copy()
 
-    def fill_na_values(self, df: pd.DataFrame, strategy: str = 'forward_backward') -> pd.DataFrame:
+    def fill_na_values(self, df: pd.DataFrame, strategy: str = 'forward_mean') -> pd.DataFrame:
         """
         Fill NA values in lagged and rolling features.
 
+        IMPORTANT: Never uses backward fill to prevent data leakage in time series training.
+
         Args:
             df: DataFrame with potential NA values
-            strategy: 'forward_backward', 'zero', 'mean'
+            strategy: 'forward_mean', 'zero', 'mean'
 
         Returns:
             DataFrame with filled NA values
         """
         df = df.copy()
 
-        if strategy == 'forward_backward':
+        if strategy == 'forward_mean':
             # Forward fill first (use previous values)
             df = df.fillna(method='ffill')
-            # Backward fill remaining (beginning of series)
-            df = df.fillna(method='bfill')
+            # Fill remaining with mean (typically at beginning of series)
+            # NEVER use bfill as it leaks future information into training data
+            df = df.fillna(df.mean())
 
         elif strategy == 'zero':
             df = df.fillna(0)