# Task 24.1 Implementation Summary: Queue Management Service

## Overview
Successfully implemented the Amadeus queue management service for handling after-sales operations including schedule changes, cancellations, and refunds.

## Requirements Addressed
- **19.1**: Retrieve and display Amadeus queue messages for the Master_Agency
- **19.2**: Allow authorized users to process queue messages
- **19.3**: Categorize queue messages by type (schedule changes, cancellations, refunds)
- **19.4**: Route queue messages to appropriate Sub_Agencies based on PNR ownership
- **19.5**: Maintain a history of processed queue messages with actions taken

## Components Created

### 1. Enums
- **QueueMessageType.java**: Defines message categories
  - SCHEDULE_CHANGE
  - CANCELLATION
  - REFUND
  - TICKETING_TIME_LIMIT
  - GENERAL
  - UNKNOWN

- **QueueMessageStatus.java**: Defines processing status
  - PENDING
  - PROCESSED
  - FAILED
  - IGNORED

### 2. Entity
- **QueueMessage.java**: JPA entity for storing queue messages
  - Stores Amadeus message details
  - Links to agency via PNR routing
  - Tracks processing status and history
  - Includes audit fields (created_at, updated_at, processed_at, processed_by)

### 3. Repository
- **QueueMessageRepository.java**: Data access layer
  - Find by Amadeus message ID
  - Find by agency ID
  - Find by status
  - Find by PNR
  - Find by message type
  - Find by date range
  - Find pending messages by agency

### 4. DTOs
- **QueueMessageResponse.java**: Response DTO with enriched data
  - Includes agency name
  - Includes processed by username
  
- **ProcessQueueMessageRequest.java**: Request DTO for processing messages
  - Action taken
  - Notes

### 5. Service
- **QueueManagementService.java**: Service interface
- **QueueManagementServiceImpl.java**: Service implementation
  - Retrieves messages from Amadeus API
  - Categorizes messages based on content analysis
  - Routes messages to agencies based on PNR ownership
  - Processes messages with status tracking
  - Maintains complete message history

### 6. Database Migration
- **V3__create_queue_messages_table.sql**: Flyway migration script
  - Creates queue_messages table
  - Creates indexes for efficient querying
  - Adds foreign key constraints

## Key Features

### Message Retrieval
- Fetches messages from Amadeus API via AmadeusClient
- Prevents duplicate message storage
- Automatically categorizes messages
- Routes to appropriate agency

### Message Categorization (Requirement 19.3)
The service analyzes message content and category to classify messages:
- Keywords like "schedule change", "flight change" → SCHEDULE_CHANGE
- Keywords like "cancel" → CANCELLATION
- Keywords like "refund" → REFUND
- Keywords like "ticketing time limit", "ttl" → TICKETING_TIME_LIMIT
- Keywords like "general" → GENERAL
- Unknown patterns → UNKNOWN

### Message Routing (Requirement 19.4)
- Looks up booking by PNR
- Extracts agency ID from booking
- Associates message with correct agency
- Handles cases where PNR is not found

### Message Processing (Requirement 19.2, 19.5)
- Process message with action taken and notes
- Mark message as failed with reason
- Mark message as ignored with reason
- Track who processed the message and when
- Maintain complete audit trail

### Query Capabilities
- Get messages by agency
- Get messages by status
- Get messages by PNR
- Get messages by type
- Get pending messages by agency
- Get messages by date range
- Get single message by ID

## Database Schema

```sql
queue_messages (
    id UUID PRIMARY KEY,
    amadeus_message_id VARCHAR(255) NOT NULL,
    queue_number VARCHAR(50) NOT NULL,
    category VARCHAR(100),
    pnr VARCHAR(10),
    message_type VARCHAR(50) NOT NULL,
    message_content TEXT NOT NULL,
    priority VARCHAR(20),
    agency_id UUID REFERENCES agencies(id),
    status VARCHAR(20) NOT NULL,
    received_at TIMESTAMP NOT NULL,
    processed_at TIMESTAMP,
    processed_by UUID REFERENCES users(id),
    action_taken TEXT,
    notes TEXT,
    created_at TIMESTAMP NOT NULL,
    updated_at TIMESTAMP NOT NULL
)
```

### Indexes Created
- idx_queue_messages_agency (agency_id)
- idx_queue_messages_pnr (pnr)
- idx_queue_messages_status (status)
- idx_queue_messages_type (message_type)
- idx_queue_messages_received (received_at)
- idx_queue_messages_amadeus_id (amadeus_message_id)

## Integration Points

### Dependencies
- **AmadeusClient**: For retrieving queue messages from Amadeus API
- **BookingRepository**: For routing messages based on PNR
- **AgencyRepository**: For enriching responses with agency names
- **UserRepository**: For enriching responses with user names

### Transaction Management
- All write operations are transactional
- Read operations use read-only transactions for optimization

### Error Handling
- Comprehensive logging at all levels
- Graceful handling of missing data
- Exception handling with meaningful error messages

## Testing Considerations

The implementation supports the following property-based tests (optional tasks):
- **Property 78**: Queue messages retrieved and displayed
- **Property 79**: Queue messages categorized correctly
- **Property 80**: Queue messages routed to correct agency
- **Property 81**: Processed queue messages recorded

## Next Steps

To complete the queue management feature:
1. Implement REST API controllers (Task 28.11)
2. Add authorization checks for queue access
3. Implement property-based tests (Tasks 24.2-24.5)
4. Implement unit tests (Task 24.6)
5. Add notification integration for critical queue messages

## Compilation Status
✅ Code compiles successfully with no errors
✅ All dependencies resolved
✅ Ready for integration testing