Steps 1-11, still need to do 12

docs/enhanced-signal-handling.md

@@ -0,0 +1,123 @@
+# Enhanced Signal Handling for Scheduled Operations
+
+## Overview
+
+The enhanced signal handling system provides intelligent cancellation support for scheduled price update operations. It distinguishes between different phases of execution and responds appropriately to interrupt signals (SIGINT/SIGTERM).
+
+## Features
+
+### 1. Phase-Aware Cancellation
+
+The system recognizes three distinct phases:
+
+- **Scheduling Wait Period**: Cancellation is allowed and encouraged
+- **Price Update Operations**: Cancellation is prevented to avoid data corruption
+- **Normal Operations**: Standard graceful shutdown behavior
+
+### 2. Clear User Feedback
+
+When users press Ctrl+C during different phases, they receive clear, contextual messages:
+
+#### During Scheduling Wait Period
+
+```
+🛑 Received SIGINT during scheduled wait period.
+📋 Cancelling scheduled operation...
+✅ Scheduled operation cancelled successfully. No price updates were performed.
+```
+
+#### During Price Update Operations
+
+```
+⚠️  Received SIGINT during active price update operations.
+🔒 Cannot cancel while price updates are in progress to prevent data corruption.
+⏳ Please wait for current operations to complete...
+💡 Tip: You can cancel during the countdown period before operations begin.
+```
+
+### 3. State Coordination
+
+The system uses state management to coordinate between the main application and the ScheduleService:
+
+- `schedulingActive`: Indicates if the system is in the scheduling wait period
+- `operationInProgress`: Indicates if price update operations are running
+
+## Implementation Details
+
+### Main Application Signal Handlers
+
+Located in `src/index.js`, the enhanced signal handlers:
+
+1. Check the current phase (scheduling vs. operations)
+2. Provide appropriate user feedback
+3. Coordinate with the ScheduleService for cleanup
+4. Prevent interruption during critical operations
+
+### ScheduleService Integration
+
+The `ScheduleService` (`src/services/schedule.js`) has been updated to:
+
+1. Remove its own signal handling (delegated to main application)
+2. Support external cancellation through the `cleanup()` method
+3. Provide proper resource cleanup and state management
+
+### State Management Functions
+
+The main application provides state management functions to the ShopifyPriceUpdater instance:
+
+- `setSchedulingActive(boolean)`: Updates scheduling phase state
+- `setOperationInProgress(boolean)`: Updates operation phase state
+
+## Usage Examples
+
+### Scheduled Operation with Cancellation
+
+```bash
+# Set scheduled execution time
+export SCHEDULED_EXECUTION_TIME="2025-08-07T15:30:00"
+
+# Run the application
+npm start
+
+# During countdown, press Ctrl+C to cancel
+# Result: Clean cancellation with confirmation message
+```
+
+### Scheduled Operation During Updates
+
+```bash
+# Same setup, but let the countdown complete
+# Once price updates begin, press Ctrl+C
+# Result: Cancellation is prevented with explanation
+```
+
+## Testing
+
+The enhanced signal handling is thoroughly tested in:
+
+- `tests/services/schedule-signal-handling.test.js`: Unit tests for all requirements
+- Tests cover all three requirements:
+  - 3.1: Cancellation during wait period
+  - 3.2: Clear cancellation confirmation messages
+  - 3.3: No interruption once operations begin
+
+## Requirements Compliance
+
+### Requirement 3.1: Cancellation Support
+
+✅ **IMPLEMENTED**: System responds to SIGINT and SIGTERM during wait period
+
+### Requirement 3.2: Clear Confirmation Messages
+
+✅ **IMPLEMENTED**: Contextual messages inform users about cancellation status
+
+### Requirement 3.3: Operation Protection
+
+✅ **IMPLEMENTED**: Price updates cannot be interrupted to prevent data corruption
+
+## Benefits
+
+1. **Data Integrity**: Prevents partial updates that could corrupt pricing data
+2. **User Experience**: Clear feedback about what's happening and what's possible
+3. **Flexibility**: Users can cancel during planning phase but not during execution
+4. **Reliability**: Proper resource cleanup and state management