# Implementation Plan

- [x] 1. Create ScheduleService with core scheduling functionality

  - Implement datetime parsing and validation methods
  - Add delay calculation logic for scheduling operations
  - Create countdown display functionality with user-friendly formatting
  - _Requirements: 1.1, 1.4, 4.1, 4.2, 4.3_

- [x] 2. Implement scheduling wait logic with cancellation support

  - Add waitUntilScheduledTime method with Promise-based timing
  - Implement graceful cancellation handling during wait period
  - Create status display updates during countdown period
  - _Requirements: 2.2, 3.1, 3.2_

- [x] 3. Update environment configuration to support scheduling

  - Add SCHEDULED_EXECUTION_TIME as optional environment variable to loadEnvironmentConfig
  - Implement validation logic for datetime format when scheduling is provided
  - Ensure backward compatibility when scheduling parameter is not set
  - _Requirements: 1.1, 4.1, 4.2, 4.3, 4.4_

- [x] 4. Integrate scheduling into main application flow

  - Modify main execution function to check for scheduled execution time
  - Add scheduling confirmation display before entering wait period
  - Implement scheduled operation execution with existing ShopifyPriceUpdater logic
  - _Requirements: 1.2, 2.1, 2.3_

- [x] 5. Enhance signal handlers for scheduled operation cancellation

  - Update SIGINT and SIGTERM handlers to support cancellation during wait period
  - Add clear cancellation confirmation messages for scheduled operations
  - Ensure cancellation does not interrupt operations once price updates begin
  - _Requirements: 3.1, 3.2, 3.3_

- [x] 6. Add comprehensive error handling for scheduling scenarios

  - Implement error handling for invalid datetime formats with clear messages
  - Add validation for past datetime values with helpful error messages
  - Create warning system for distant future dates (>7 days)
  - _Requirements: 1.4, 4.3, 4.4_

- [x] 7. Update .env.example with scheduling configuration

  - Add SCHEDULED_EXECUTION_TIME example with proper ISO 8601 format
  - Include comments explaining scheduling functionality and format requirements
  - Provide examples for different timezone specifications
  - _Requirements: 4.1, 4.2_

- [x] 8. Implement logging integration for scheduled operations

  - Add scheduling event logging to existing Logger class methods
  - Log scheduling confirmation, countdown updates, and execution start
  - Integrate scheduled operation context into existing error logging
  - _Requirements: 2.1, 2.3, 5.3, 5.4_

- [x] 9. Create unit tests for ScheduleService functionality

  - Write tests for datetime parsing with various valid and invalid formats
  - Test delay calculation accuracy and edge cases
  - Create tests for cancellation handling during wait periods
  - _Requirements: 1.1, 1.4, 3.1, 4.1, 4.2, 4.3_

- [x] 10. Write integration tests for scheduled execution workflow

  - Test complete scheduling workflow with both update and rollback modes
  - Create tests for cancellation scenarios during countdown period
  - Verify backward compatibility when scheduling is not used
  - _Requirements: 1.2, 2.1, 3.1, 3.2, 5.1, 5.2_

- [x] 11. Add error handling tests for scheduling edge cases

  - Test invalid datetime format handling with clear error messages
  - Create tests for past datetime validation and error responses
  - Test system behavior with distant future dates and warning display
  - _Requirements: 1.4, 4.3, 4.4, 5.3_

- [x] 12. Update package.json scripts for scheduled operations

  - Add npm scripts for common scheduling scenarios (e.g., schedule-update, schedule-rollback)
  - Include examples in script comments for typical scheduling use cases
  - Ensure existing scripts continue to work without scheduling
  - _Requirements: 1.1, 1.2_