Feature Specification: Leave Management Workflow

1. Overview & Vision

The Leave Management system handles the submission, approval, and tracking of employee time off. It aims to eliminate spreadsheet-based tracking, ensure legal compliance, and provide visibility into team availability for managers.

2. Personas & Stakeholders

Persona	Goal
Employee	Request time off, track remaining balances, and plan vacations.
Manager	Review team leave requests and manage department coverage.
HR Admin	Configure leave policies, carry-forward limits, and accruals.

3. User Stories

• As an employee, I want to know my annual leave balance so I can plan my year-end trip.
• As a manager, I want to see a team calendar so I don't approve too many leaves during a peak period.
• As an HR Admin, I want to credit sick leave to all employees automatically each year.

4. Functional Requirements (FR)

• REQ-LV-001: Support for multiple leave types (Annual, Sick, Unpaid, etc.).
• REQ-LV-002: Automated balance deduction upon request approval.
• REQ-LV-003: Multi-level approval workflow — Team Lead → Manager → HR, each level configurable per policy.
• REQ-LV-004: Business day calculation (excluding weekends/public holidays).
• REQ-LV-005: Leave Policy Engine — HR configures auto-accrual schedules, carry-forward limits, and eligibility rules per leave type.
• REQ-LV-006: Probation block — employees in Probation status cannot submit leave requests.
• REQ-LV-007: In-app notifications to approvers on submission; to employee on decision.

5. Non-Functional Requirements (NFR)

• Accuracy: Balance updates must be atomic (Database transactions).
• Consistency: Leave status must always reflect the manager's decision in real-time.

6. Business Logic & Rules

• Accrual: Standard annual leave is 12 days/year (accrued at 1 day per month); configurable per policy.
• Carry-forward: Maximum 5 days can be carried over to the next calendar year (configurable).
• Validation: Annual leave cannot be submitted if the balance is insufficient.
• Probation Block: Employees in Probation lifecycle state are blocked from submitting any leave request.
• Approval Chain: Policy defines the approval chain depth; each approver can approve/reject independently; rejection at any level closes the request.

7. User Interface (UI/UX)

• Dashboard: Balance cards (Total, Used, Remaining).
• Request Form: Date-range picker with auto-calculated duration.
• Manager Inbox: List of pending requests with "Approve" and "Reject" buttons.

8. Information Architecture

• "My Leave" section for employees.
• "Team Calendar" and "Approvals" for managers.

9. Data Model & Persistence

• Tables: leave_balances, leave_requests.
• Constraint: Unique constraint on overlapping leave dates per employee.

10. API & Service Layer

• POST /leave-requests
• POST /leave-requests/:id/approve
• LeaveService handles complex overlap validation.

11. Integration Patterns

• Notifications: Sends in-app notifications to managers via the Shell bus.
• Calendar: Syncs approved leaves to the "Team Calendar" (FullCalendar).

12. Security & Permissions

• RBAC: leave_requests:create for all; leave_requests:approve for managers.
• Ownership: Users can only view and cancel their own requests.

13. Error Handling & Resilience

• Insufficient Balance: Block submission with a clear explanation.
• Overlap Detection: Prevent double-booking same dates.

14. Performance & Scalability

• Balance lookups are indexed for sub-10ms response times.
• Background jobs handle year-end accrual resets for large organizations.

15. Globalization & i18n

• Support for organization-specific public holidays.
• Multi-language support for leave type names.

16. Accessibility (a11y)

• Accessible date pickers (keyboard friendly).
• Color-coded leave status (Approved = Green, Pending = Yellow, Rejected = Red).

17. Observability & Analytics

• Tracking of "Absenteeism Rates" per department.
• Analytics on "Top Leave Months" for resource planning.

18. Testing & Quality

• Unit tests for the working-day calculation logic.
• Integration tests for the atomic balance deduction flow.

19. Constraints & Assumptions

• Assumes organizations operate on a standard Monday-Friday work week (configurable in v1.2).

20. Future Enhancements

• Half-day leave support.
• Leave calendar integration with Google Calendar / Outlook.
• Leave request on behalf of (HR submits for employee).