Phase 3 Step 7: Scan Comparison Features & UX Improvements

Implemented comprehensive scan comparison functionality with historical
analysis and improved user experience for scan triggering.

Features Added:
- Scan comparison engine with ports, services, and certificates analysis
- Drift score calculation (0.0-1.0 scale) for infrastructure changes
- Side-by-side comparison UI with color-coded changes (added/removed/changed)
- Historical trend charts showing port counts over time
- "Compare with Previous" button on scan detail pages
- Scan history API endpoint for trending data

API Endpoints:
- GET /api/scans/<id1>/compare/<id2> - Compare two scans
- GET /api/stats/scan-history/<id> - Historical scan data for charts

UI Improvements:
- Replaced config file text inputs with dropdown selectors
- Added config file selection to dashboard and scans pages
- Improved delete scan confirmation with proper async handling
- Enhanced error messages with detailed validation feedback
- Added 2-second delay before redirect to ensure deletion completes

Comparison Features:
- Port changes: tracks added, removed, and unchanged ports
- Service changes: detects version updates and service modifications
- Certificate changes: monitors SSL/TLS certificate updates
- Interactive historical charts with clickable data points
- Automatic detection of previous scan for comparison

Bug Fixes:
- Fixed scan deletion UI alert appearing on successful deletion
- Prevented config file path duplication (configs/configs/...)
- Improved error handling for failed API responses
- Added proper JSON response parsing with fallback handling

Testing:
- Created comprehensive test suite for comparison functionality
- Tests cover comparison API, service methods, and drift scoring
- Added edge case tests for identical scans and missing data

web/api/scans.py

@@ -165,10 +165,12 @@ def trigger_scan():
 
     except ValueError as e:
         # Config file validation error
-        logger.warning(f"Invalid config file: {str(e)}")
+        error_message = str(e)
+        logger.warning(f"Invalid config file: {error_message}")
+        logger.warning(f"Request data: config_file='{config_file}'")
         return jsonify({
             'error': 'Invalid request',
-            'message': str(e)
+            'message': error_message
         }), 400
     except SQLAlchemyError as e:
         logger.error(f"Database error triggering scan: {str(e)}")
@@ -276,20 +278,48 @@ def compare_scans(scan_id1, scan_id2):
     """
     Compare two scans and show differences.
 
+    Compares ports, services, and certificates between two scans,
+    highlighting added, removed, and changed items.
+
     Args:
-        scan_id1: First scan ID
-        scan_id2: Second scan ID
+        scan_id1: First (older) scan ID
+        scan_id2: Second (newer) scan ID
 
     Returns:
-        JSON response with comparison results
+        JSON response with comparison results including:
+        - scan1, scan2: Metadata for both scans
+        - ports: Added, removed, and unchanged ports
+        - services: Added, removed, and changed services
+        - certificates: Added, removed, and changed certificates
+        - drift_score: Overall drift metric (0.0-1.0)
     """
-    # TODO: Implement in Phase 4
-    return jsonify({
-        'scan_id1': scan_id1,
-        'scan_id2': scan_id2,
-        'diff': {},
-        'message': 'Scan comparison endpoint - to be implemented in Phase 4'
-    })
+    try:
+        # Compare scans using service
+        scan_service = ScanService(current_app.db_session)
+        comparison = scan_service.compare_scans(scan_id1, scan_id2)
+
+        if not comparison:
+            logger.warning(f"Scan comparison failed: one or both scans not found ({scan_id1}, {scan_id2})")
+            return jsonify({
+                'error': 'Not found',
+                'message': 'One or both scans not found'
+            }), 404
+
+        logger.info(f"Compared scans {scan_id1} and {scan_id2}: drift_score={comparison['drift_score']}")
+        return jsonify(comparison), 200
+
+    except SQLAlchemyError as e:
+        logger.error(f"Database error comparing scans {scan_id1} and {scan_id2}: {str(e)}")
+        return jsonify({
+            'error': 'Database error',
+            'message': 'Failed to compare scans'
+        }), 500
+    except Exception as e:
+        logger.error(f"Unexpected error comparing scans {scan_id1} and {scan_id2}: {str(e)}", exc_info=True)
+        return jsonify({
+            'error': 'Internal server error',
+            'message': 'An unexpected error occurred'
+        }), 500
 
 
 # Health check endpoint