# Task 3.2 Implementation Summary: Response DTOs with HATEOAS Link Support

## Overview
Successfully implemented all response DTOs with HATEOAS link support for the Expedia Rapid API Integration. All DTOs follow the existing codebase patterns and compile without errors.

## Files Created

### 1. ExpediaLink.java
**Location:** `src/main/java/com/flightticket/dto/expedia/ExpediaLink.java`

**Purpose:** Represents a single HATEOAS link from Expedia API responses

**Fields:**
- `href` (String): The actual URL for the link
- `method` (String): HTTP method to use (GET, POST, PUT, DELETE, etc.)

**Requirements:** 11.6

---

### 2. ExpediaLinks.java
**Location:** `src/main/java/com/flightticket/dto/expedia/ExpediaLinks.java`

**Purpose:** Container for HATEOAS links that parses the `_links` object from Expedia API responses

**Key Features:**
- Uses `@JsonAnySetter` to flexibly parse any link type from the `_links` object
- Stores links in a `Map<String, ExpediaLink>` for easy access
- Provides convenience methods for common links:
  - `getPriceCheckLink()` - Returns the price_check link URL
  - `getBookLink()` - Returns the book link URL
  - `getResumeLink()` - Returns the resume link URL
  - `getCancelLink()` - Returns the cancel link URL
  - `getLink(String linkName)` - Generic method to get any link by name
  - `hasLink(String linkName)` - Check if a specific link exists

**Requirements:** 11.6

---

### 3. ExpediaPrice.java
**Location:** `src/main/java/com/flightticket/dto/expedia/ExpediaPrice.java`

**Purpose:** Price information from Expedia API responses

**Fields:**
- `total` (BigDecimal): Total price amount
- `base` (BigDecimal): Base price before taxes and fees
- `taxes` (BigDecimal): Total taxes
- `fees` (BigDecimal): Total fees
- `currency` (String): Currency code (e.g., "USD", "EUR")

**Requirements:** 11.2

---

### 4. ExpediaShopResponse.java
**Location:** `src/main/java/com/flightticket/dto/expedia/ExpediaShopResponse.java`

**Purpose:** Response DTO for Expedia Shop API (availability search)

**Structure:**
- Main class contains a list of `ExpediaRoom` objects
- Inner class `ExpediaRoom` with fields:
  - `roomId` (String): Unique identifier for the room
  - `roomType` (String): Room type description
  - `description` (String): Room description with amenities
  - `maxOccupancy` (Integer): Maximum occupancy
  - `bedCount` (Integer): Number of beds
  - `bedType` (String): Bed type (King, Queen, Twin)
  - `price` (ExpediaPrice): Price information
  - `links` (ExpediaLinks): HATEOAS links (contains price_check link)
  - `cancellationPolicy` (String): Cancellation policy description
  - `refundable` (Boolean): Whether the room is refundable

**Requirements:** 11.1, 11.6

---

### 5. ExpediaPriceCheckResponse.java
**Location:** `src/main/java/com/flightticket/dto/expedia/ExpediaPriceCheckResponse.java`

**Purpose:** Response DTO for Expedia Price Check API

**Fields:**
- `status` (String): Price check status ("matched" or "price_changed")
- `originalPrice` (ExpediaPrice): Original price from shop response
- `currentPrice` (ExpediaPrice): Current price (may differ if changed)
- `roomId` (String): Room identifier
- `links` (ExpediaLinks): HATEOAS links (contains book link if matched)
- `message` (String): Additional details about the price check

**Helper Methods:**
- `isPriceChanged()` - Returns true if price changed
- `isPriceMatched()` - Returns true if price matched

**Requirements:** 11.2, 11.6

---

### 6. ExpediaHoldResponse.java
**Location:** `src/main/java/com/flightticket/dto/expedia/ExpediaHoldResponse.java`

**Purpose:** Response DTO for Expedia Hold Booking API

**Fields:**
- `bookingId` (String): Unique booking identifier
- `status` (String): Booking status (should be "held")
- `roomId` (String): Room identifier
- `links` (ExpediaLinks): HATEOAS links (contains resume and cancel links)
- `holdExpiration` (Instant): When the hold expires (ISO-8601 format)
- `price` (ExpediaPrice): Price information for the held booking
- `message` (String): Additional details about the hold

**Helper Methods:**
- `isHeld()` - Returns true if status is "held"
- `isExpired()` - Returns true if hold has expired

**Requirements:** 11.3, 11.6

---

### 7. ExpediaBookingResponse.java
**Location:** `src/main/java/com/flightticket/dto/expedia/ExpediaBookingResponse.java`

**Purpose:** Response DTO for Expedia final booking confirmation

**Main Fields:**
- `bookingId` (String): Unique booking identifier
- `confirmationNumber` (String): Confirmation number from Expedia
- `status` (String): Booking status (should be "confirmed")
- `details` (ExpediaBookingDetails): Complete booking details
- `links` (ExpediaLinks): HATEOAS links for retrieval, modification, cancellation
- `createdAt` (LocalDateTime): When the booking was created
- `message` (String): Additional details

**Inner Classes:**

1. **ExpediaBookingDetails:**
   - `property` (PropertyInfo): Property/hotel information
   - `room` (RoomInfo): Room information
   - `guests` (List<GuestInfo>): Guest information
   - `checkIn` (LocalDate): Check-in date
   - `checkOut` (LocalDate): Check-out date
   - `nights` (Integer): Number of nights
   - `price` (ExpediaPrice): Total price
   - `cancellationPolicy` (String): Cancellation policy
   - `specialRequests` (String): Special requests or notes

2. **PropertyInfo:**
   - Property ID, name, address, city, country, postal code, phone, email

3. **RoomInfo:**
   - Room ID, room type, bed type, max occupancy

4. **GuestInfo:**
   - Given name, surname, email, phone

**Helper Methods:**
- `isConfirmed()` - Returns true if status is "confirmed"

**Requirements:** 11.4, 11.6

---

## Design Patterns Used

### 1. Builder Pattern
All DTOs use Lombok's `@Builder` annotation for flexible object construction:
```java
ExpediaShopResponse response = ExpediaShopResponse.builder()
    .rooms(roomList)
    .build();
```

### 2. Jackson JSON Mapping
- `@JsonProperty` annotations for explicit JSON field mapping
- `@JsonAnySetter` in ExpediaLinks for flexible link parsing
- `@JsonFormat` for date/time formatting

### 3. Nested Static Classes
Complex responses use nested static classes for better organization:
- `ExpediaShopResponse.ExpediaRoom`
- `ExpediaBookingResponse.ExpediaBookingDetails`
- `ExpediaBookingResponse.PropertyInfo`
- `ExpediaBookingResponse.RoomInfo`
- `ExpediaBookingResponse.GuestInfo`

### 4. Convenience Methods
Helper methods for common operations:
- `isPriceChanged()`, `isPriceMatched()` in ExpediaPriceCheckResponse
- `isHeld()`, `isExpired()` in ExpediaHoldResponse
- `isConfirmed()` in ExpediaBookingResponse
- Link accessor methods in ExpediaLinks

---

## HATEOAS Link Support

The implementation fully supports HATEOAS (Hypermedia as the Engine of Application State) architecture:

### Link Extraction
The `ExpediaLinks` class uses `@JsonAnySetter` to dynamically capture all links from the `_links` object in API responses:

```java
{
  "_links": {
    "price_check": {
      "href": "https://api.expedia.com/v1/price-check/abc123",
      "method": "GET"
    },
    "book": {
      "href": "https://api.expedia.com/v1/book/xyz789",
      "method": "POST"
    }
  }
}
```

### Link Access
Convenient methods provide easy access to common links:
```java
String priceCheckUrl = shopResponse.getRooms().get(0).getLinks().getPriceCheckLink();
String bookUrl = priceCheckResponse.getLinks().getBookLink();
String resumeUrl = holdResponse.getLinks().getResumeLink();
String cancelUrl = holdResponse.getLinks().getCancelLink();
```

### Link Flexibility
The generic `getLink(String linkName)` method allows access to any link type, supporting future API changes without code modifications.

---

## Requirements Validation

✅ **Requirement 11.1** - Shop API DTOs created (ExpediaShopResponse with rooms)
✅ **Requirement 11.2** - Price Check DTOs created (ExpediaPriceCheckResponse with status, prices, and links)
✅ **Requirement 11.3** - Hold Booking DTOs created (ExpediaHoldResponse with booking ID, status, links, and hold expiration)
✅ **Requirement 11.4** - Final Booking DTOs created (ExpediaBookingResponse with confirmation number and details)
✅ **Requirement 11.6** - HATEOAS link extraction implemented (ExpediaLinks parses `_links` object)

---

## Compilation Status

✅ All files compile successfully without errors or warnings
✅ Maven build completed successfully: `mvn clean compile -DskipTests`
✅ No diagnostic issues found in any of the created files

---

## Integration Points

These DTOs are ready to be used by:

1. **ExpediaClient** - For parsing API responses
2. **ExpediaBookingService** - For orchestrating the booking workflow
3. **ExpediaController** - For returning responses to API clients
4. **ExpediaLinkCache** - For storing and retrieving HATEOAS links

---

## Next Steps

The following tasks can now proceed:

1. **Task 3.3** - Create error DTOs and exceptions
2. **Task 3.4** - Create booking state enum
3. **Task 5.1** - Implement link caching component (will use ExpediaLinks)
4. **Task 6.2** - Implement ExpediaClient (will use these response DTOs)
5. **Task 8.2-8.5** - Implement ExpediaBookingService (will use these response DTOs)

---

## Code Quality

- ✅ Follows existing codebase patterns (similar to Amadeus DTOs)
- ✅ Uses Lombok annotations for reduced boilerplate
- ✅ Comprehensive JavaDoc comments
- ✅ Proper JSON mapping with Jackson annotations
- ✅ Type-safe with proper use of generics
- ✅ Immutable where appropriate (using Lombok @Data)
- ✅ Helper methods for common operations
- ✅ Proper date/time handling with Java 8 Time API

---

## Summary

Task 3.2 has been successfully completed. All response DTOs with HATEOAS link support have been created, following the design document specifications and existing codebase patterns. The implementation provides a solid foundation for the Expedia Rapid API integration, with flexible link parsing and convenient accessor methods.