# Task 4 Implementation Summary: Authorization and Role-Based Access Control

## Overview
Successfully implemented comprehensive authorization and role-based access control (RBAC) for the B2B Flight Ticketing Platform, including Spring Security configuration, JWT authentication, custom permission checking, and agency-level data isolation.

## Completed Sub-tasks

### 4.1 Spring Security Configuration ✅
**Requirements: 1.4, 1.6, 2.1**

#### Implemented Components:

1. **Enhanced SecurityConfig.java**
   - Configured security filter chain with stateless session management
   - Defined role-based endpoint access rules:
     - Public: `/api/v1/auth/**`, health endpoints
     - Super Admin only: `/api/v1/admin/**`, agency verification, wallet approvals
     - Agency Admin: User management endpoints
     - Finance User: Wallet and reporting endpoints
     - Agent: Flight, booking, and ticketing endpoints
   - Integrated JWT authentication with OAuth 2.0 resource server
   - Added custom JWT authentication filter

2. **JwtAuthenticationFilter.java**
   - Custom filter for JWT token validation
   - Extracts Bearer token from Authorization header
   - Decodes and validates JWT using JwtDecoder
   - Sets authentication context in SecurityContextHolder
   - Handles JWT validation errors gracefully

3. **Role Hierarchy**
   - Configured hierarchical role structure:
     - SUPER_ADMIN > AGENCY_ADMIN
     - AGENCY_ADMIN > HR_USER, FINANCE_USER, AGENT
   - Higher roles automatically inherit permissions from lower roles

4. **Method-Level Security**
   - Enabled `@PreAuthorize` annotations for fine-grained access control
   - Supports SpEL expressions for complex authorization rules

### 4.2 Custom Authorization Logic ✅
**Requirements: 1.4, 2.5, 2.6, 2.7, 3.3**

#### Implemented Components:

1. **PermissionService.java**
   - Comprehensive permission checking service with methods:
     - `hasRole()`, `hasAnyRole()`, `hasAllRoles()` - Role checking
     - `getCurrentUserAgencyId()` - Extract agency ID from JWT
     - `getCurrentUserId()`, `getCurrentUsername()` - User identification
     - `getCurrentUserRoles()` - Get all user roles
     - `isSuperAdmin()`, `isAgencyAdmin()`, `isHRUser()`, `isFinanceUser()`, `isAgent()` - Role-specific checks
     - `canAccessAgency()` - Agency-level access validation
     - `canManageUsers()`, `canManageFinances()`, `canPerformFlightOperations()` - Permission checks
     - `canAssignRole()` - Role assignment validation
     - `validateAgencyAccess()` - Throws exception if access denied

2. **Custom Annotations**
   Created role-based access control annotations:
   - `@RequiresSuperAdmin` - Super Admin only access
   - `@RequiresAgencyAdmin` - Agency Admin or Super Admin
   - `@RequiresHRUser` - HR User, Agency Admin, or Super Admin
   - `@RequiresFinanceUser` - Finance User or Super Admin
   - `@RequiresAgent` - Agent or Super Admin
   - `@RequiresAgencyAccess` - Enforces agency-level data isolation

3. **AgencyDataIsolationAspect.java**
   - AOP aspect for automatic agency access validation
   - Intercepts methods annotated with `@RequiresAgencyAccess`
   - Validates user can access specified agency before method execution
   - Logs access attempts and denials

4. **AgencyDataFilter.java**
   - Utility class for filtering data by agency ID
   - Methods:
     - `getAgencyFilterId()` - Returns agency ID for filtering (null for Super Admin)
     - `shouldFilterByAgency()` - Check if filtering is needed
     - `applyAgencyFilter()` - Apply agency filter to query parameters
     - `validateAgencyId()` - Validate agency ID matches user's agency

## Key Features Implemented

### 1. Multi-Tenant Data Isolation
- Super Admin can access all agencies
- Other users restricted to their own agency data
- Automatic filtering applied at service layer
- Validation enforced through aspects and filters

### 2. Role-Based Access Control
- Five distinct roles: SUPER_ADMIN, AGENCY_ADMIN, HR_USER, FINANCE_USER, AGENT
- Hierarchical role structure with permission inheritance
- Fine-grained endpoint protection
- Method-level security with custom annotations

### 3. JWT Token Integration
- Extracts user information from Keycloak JWT tokens
- Validates token signature and expiration
- Extracts roles from `realm_access.roles` claim
- Extracts agency ID from custom claim

### 4. Security Best Practices
- Stateless authentication (no server-side sessions)
- Bearer token authentication
- Comprehensive error handling
- Detailed security logging
- Fail-secure defaults (deny by default)

## Files Created/Modified

### Created Files:
1. `src/main/java/com/flightticket/security/JwtAuthenticationFilter.java`
2. `src/main/java/com/flightticket/security/PermissionService.java`
3. `src/main/java/com/flightticket/security/AgencyDataFilter.java`
4. `src/main/java/com/flightticket/security/aspect/AgencyDataIsolationAspect.java`
5. `src/main/java/com/flightticket/security/annotation/RequiresSuperAdmin.java`
6. `src/main/java/com/flightticket/security/annotation/RequiresAgencyAdmin.java`
7. `src/main/java/com/flightticket/security/annotation/RequiresHRUser.java`
8. `src/main/java/com/flightticket/security/annotation/RequiresFinanceUser.java`
9. `src/main/java/com/flightticket/security/annotation/RequiresAgent.java`
10. `src/main/java/com/flightticket/security/annotation/RequiresAgencyAccess.java`

### Modified Files:
1. `src/main/java/com/flightticket/config/SecurityConfig.java` - Enhanced with comprehensive security rules
2. `pom.xml` - Added spring-boot-starter-aop dependency

## Usage Examples

### Using Custom Annotations in Controllers:

```java
@RestController
@RequestMapping("/api/v1/agencies")
public class AgencyController {
    
    @RequiresSuperAdmin
    @PostMapping("/{agencyId}/verify")
    public ResponseEntity<Agency> verifyAgency(@PathVariable String agencyId) {
        // Only Super Admin can verify agencies
    }
    
    @RequiresAgencyAccess
    @GetMapping("/{agencyId}/bookings")
    public ResponseEntity<List<Booking>> getAgencyBookings(@PathVariable String agencyId) {
        // Automatically validates user can access this agency
    }
}
```

### Using PermissionService in Services:

```java
@Service
public class BookingService {
    
    private final PermissionService permissionService;
    private final AgencyDataFilter agencyDataFilter;
    
    public List<Booking> getBookings(String requestedAgencyId) {
        // Apply agency filter based on user permissions
        String agencyId = agencyDataFilter.applyAgencyFilter(requestedAgencyId);
        
        if (agencyId != null) {
            return bookingRepository.findByAgencyId(agencyId);
        } else {
            // Super Admin - return all bookings
            return bookingRepository.findAll();
        }
    }
}
```

### Using Method-Level Security:

```java
@Service
public class UserService {
    
    @PreAuthorize("@permissionService.canAssignRole(#role)")
    public User assignRole(String userId, String role) {
        // Method only executes if user can assign the specified role
    }
}
```

## Requirements Validation

✅ **Requirement 1.4**: JWT token validation and role permission verification implemented  
✅ **Requirement 1.6**: Authorization errors returned for insufficient permissions  
✅ **Requirement 2.1**: Five distinct roles supported with proper hierarchy  
✅ **Requirement 2.5**: HR_User role restricted to employee management functions  
✅ **Requirement 2.6**: Finance_User role restricted to financial operations  
✅ **Requirement 2.7**: Agent role restricted to flight operations  
✅ **Requirement 3.3**: Complete data isolation between agencies implemented  

## Testing Recommendations

The following tests should be implemented in future tasks:

1. **Unit Tests**:
   - Test PermissionService methods with different roles
   - Test AgencyDataFilter filtering logic
   - Test custom annotation behavior

2. **Integration Tests**:
   - Test endpoint access with different roles
   - Test JWT token extraction and validation
   - Test agency data isolation across endpoints

3. **Property-Based Tests**:
   - Property 3: Authorization enforces role permissions
   - Property 5: Role-based access control isolation
   - Property 10: Data isolation between agencies

## Build Status

✅ **Compilation**: Successful  
✅ **Dependencies**: All resolved  
✅ **Code Quality**: No compilation errors or warnings

## Next Steps

The authorization infrastructure is now complete and ready for use in:
- Task 5: User management service
- Task 6: Agency management service
- Task 7: Subscription management service
- All subsequent service implementations

Controllers and services can now use the custom annotations and PermissionService to enforce proper authorization and data isolation.