I'm trying to create a java application. I am in the system design phase following DDD principles. Can you provide an system design for the app? The app should be similar to Uber, but instead of selling rides, you sell parking spot (public parking spot). It means that if you are leaving you can signal on the app that you are leaving a parking spot, and the estimated time you leave, so another person can go there (if they are trying to find a spot) and take your place. You should be rewarded for this (maybe a variable amount)
System Design for a Parking Spot Exchange Application Using Domain-Driven Design (DDD)

Overview
You are designing a Java application that facilitates the exchange of public parking spots between users. By following Domain-Driven Design (DDD) principles, we'll structure the system into well-defined domains and bounded contexts to manage complexity and ensure scalability.

Core Requirements
User Actions:
Leaving User: Signals they are leaving a parking spot and provides an estimated departure time.
Arriving User: Searches for available spots, reserves one, and goes to take the spot.
Rewards System:
Leaving users are rewarded (variable amount) when their spot is successfully taken by an arriving user.
Additional Considerations:
Real-time notifications.
Handling cancellations and no-shows.
User ratings and feedback.

High-Level Architecture
Frontend:
Mobile applications (iOS/Android) for user interaction.
Backend:
Microservices or modular monolith built with Spring Boot.
Database:
Relational database (e.g., PostgreSQL) or NoSQL database (e.g., MongoDB) for persistence.
External Services:
Mapping and geolocation services.
Payment gateway for processing rewards.

Domain-Driven Design Components
1. Ubiquitous Language
User: An individual using the app.
Leaving User: A user vacating a parking spot.
Arriving User: A user seeking a parking spot.
Parking Spot Availability: The state indicating a spot will be free.
Reservation: An arriving user's claim to an available spot.
Reward: Compensation given to the leaving user.
Notification: Messages sent to users regarding spot availability or status changes.
2. Bounded Contexts
User Context
Manages user profiles, authentication, and ratings.
Parking Context
Handles parking spot availability, reservations, and status updates.
Reward Context
Manages the reward mechanism and transactions.
Notification Context
Takes care of all user notifications.
Mapping Context
Interacts with external mapping services for geolocation.
3. Entities, Value Objects, and Aggregates

User Context
Entity: User
Attributes:
userId (unique identifier)
name
email
phoneNumber
paymentInfo (value object)
rating
Aggregate Root: User
Repository: UserRepository
Service: UserService

Parking Context
Entity: Availability
Attributes:
availabilityId (unique identifier)
leavingUserId
location (value object with latitude and longitude)
estimatedLeavingTime
status (Available, Reserved, Taken, Canceled)
reservedByUserId
timestamps (createdAt, updatedAt)
Entity: Reservation
Attributes:
reservationId
availabilityId
arrivingUserId
status (Active, Completed, Canceled)
timestamps
Aggregate Root: Availability
Repository: AvailabilityRepository
Service: ParkingService

Reward Context
Entity: Reward
Attributes:
rewardId
fromUserId (leaving user)
toUserId (arriving user)
amount
timestamp
status (Pending, Completed, Failed)
Aggregate Root: Reward
Repository: RewardRepository
Service: RewardService

Notification Context
Entity: Notification
Attributes:
notificationId
userId
message
type (SpotAvailable, ReservationConfirmed, etc.)
status (Sent, Read)
timestamp
Aggregate Root: Notification
Service: NotificationService

Mapping Context
Value Object: Location
Attributes:
latitude
longitude
address (optional)
Service: MappingService
Interacts with external APIs to convert between addresses and coordinates.

Domain Services and Interactions
UserService
Methods:
registerUser()
authenticateUser()
updateUserProfile()
getUserDetails(userId)
calculateUserRating(userId)
ParkingService
Methods:
reportAvailability(leavingUserId, location, estimatedLeavingTime)
getAvailableSpots(location, radius)
reserveSpot(availabilityId, arrivingUserId)
confirmSpotTaken(availabilityId, arrivingUserId)
cancelAvailability(availabilityId, userId)
handleNoShow(reservationId)
RewardService
Methods:
calculateReward(availabilityId, reservationId)
The amount can be variable based on factors like demand, location, time.
processReward(rewardId)
handleFailedReward(rewardId)
NotificationService
Methods:
sendNotification(userId, message, type)
broadcastAvailability(availabilityId, location)
notifyReservationStatus(reservationId)
MappingService
Methods:
getCoordinates(address)
getAddress(latitude, longitude)
calculateDistance(location1, location2)

Domain Events
SpotAvailableEvent
Triggered when a leaving user reports availability.
Handled by NotificationService to alert nearby users.
SpotReservedEvent
Triggered when an arriving user reserves a spot.
Updates the status in ParkingService and notifies the leaving user.
SpotTakenEvent
Triggered when the arriving user confirms they've taken the spot.
Initiates reward processing in RewardService.
ReservationCanceledEvent
Triggered when a reservation is canceled.
Frees up the availability for other users.
NoShowEvent
Triggered when the arriving user fails to show up.
May impact user ratings and handle potential penalties.

Workflow Scenarios
1. Leaving User Reports Availability
Action:
Leaving user opens the app and signals they are leaving a spot.
Provides estimated leaving time and confirms location.
Process:
ParkingService.reportAvailability() creates a new Availability with status Available.
SpotAvailableEvent is triggered.
Outcome:
NotificationService broadcasts the availability to nearby users.
2. Arriving User Searches and Reserves a Spot
Action:
Arriving user searches for available spots within a radius.
Process:
ParkingService.getAvailableSpots() returns a list of Availability instances.
User selects a spot and calls ParkingService.reserveSpot().
Status of Availability changes to Reserved, and reservedByUserId is set.
SpotReservedEvent is triggered.
Outcome:
NotificationService notifies the leaving user of the reservation.
The spot is marked as reserved for a specific time window.
3. Arriving User Confirms Spot Taken
Action:
Arriving user reaches the spot and confirms it's taken via ParkingService.confirmSpotTaken().
Process:
Status of Availability changes to Taken.
SpotTakenEvent is triggered.
Outcome:
RewardService.calculateReward() determines the reward amount.
RewardService.processReward() handles payment to the leaving user.
NotificationService updates both users about the successful transaction.
4. Handling Cancellations or No-Shows
Cancellation:
User cancels via ParkingService.cancelAvailability() or ParkingService.cancelReservation().
Status changes accordingly, and ReservationCanceledEvent is triggered.
No-Show:
If the arriving user doesn't confirm within a time window, NoShowEvent is triggered.
ParkingService updates status, and UserService may adjust user ratings.

Data Model Examples
User Entity
public class User {
    private UUID userId;
    private String name;
    private String email;
    private String phoneNumber;
    private PaymentInfo paymentInfo;
    private double rating;
    // Getters and setters omitted for brevity
}


Availability Entity
public class Availability {
    private UUID availabilityId;
    private UUID leavingUserId;
    private Location location;
    private LocalDateTime estimatedLeavingTime;
    private AvailabilityStatus status;
    private UUID reservedByUserId;
    private LocalDateTime createdAt;
    private LocalDateTime updatedAt;
    // Getters and setters omitted for brevity
}


Reward Entity
public class Reward {
    private UUID rewardId;
    private UUID fromUserId;
    private UUID toUserId;
    private BigDecimal amount;
    private RewardStatus status;
    private LocalDateTime timestamp;
    // Getters and setters omitted for brevity
}



Technical Considerations
Concurrency and Consistency:
Use optimistic locking or transactions to handle concurrent reservations.
Scalability:
Implement caching strategies for frequently accessed data.
Use asynchronous messaging (e.g., RabbitMQ, Kafka) for events.
Security:
Implement authentication and authorization (e.g., JWT tokens).
Secure sensitive data like payment info.
Performance:
Optimize database queries.
Use indexing on location data for efficient searches.
Reliability:
Implement retry mechanisms for external service calls.
Validate data at every layer.

Example Sequence Diagram
Scenario: Arriving user reserves and takes a parking spot.
Arriving User searches for spots.
Calls ParkingService.getAvailableSpots().
Receives available spots list.
Selects one and calls ParkingService.reserveSpot().
ParkingService updates the Availability status.
SpotReservedEvent is triggered.
NotificationService notifies the leaving user.
Arriving user goes to the spot and calls ParkingService.confirmSpotTaken().
ParkingService updates the status to Taken.
SpotTakenEvent is triggered.
RewardService processes the reward.
NotificationService notifies both users of the successful transaction.

Conclusion
By following DDD principles, we've structured the parking spot exchange application into clear bounded contexts, each managing its specific domain logic. Entities, value objects, aggregates, and domain events are defined to encapsulate the business rules and workflows.
This modular design promotes scalability, maintainability, and a clear separation of concerns, which are essential for the complex interactions in an application akin to Uber but for parking spots.

Next Steps:
Prototyping: Begin implementing the core services, starting with the UserService and ParkingService.
Integration: Set up the infrastructure for domain events and ensure services can communicate effectively.
Testing: Write unit and integration tests for each service.
Feedback Loop: Continuously gather user feedback to refine the reward system and user experience.

Feel free to ask if you need more detailed explanations on any of the components or further assistance with the implementation strategy.
I would also integrate a review system, maybe similar to bla bla car to avoid users from both sides to perform badly on the platform
Integrating a Review System into the Parking Spot Exchange Application

Absolutely, adding a review system is an excellent way to promote positive behavior and accountability on the platform. By enabling users to rate and review each other after transactions, you can encourage punctuality, honesty, and overall good conduct, similar to platforms like BlaBlaCar.
Here's how you can integrate a review system into the existing Domain-Driven Design (DDD) architecture we previously discussed.

Modifications to the System Design
1. Updates to the Ubiquitous Language
Review: A feedback provided by one user about another after a completed transaction.
Rating: A numerical value reflecting the user's performance (e.g., 1 to 5 stars).
Feedback: Written comments accompanying a rating.
Reviewer: The user who provides the review.
Reviewee: The user being reviewed.
2. Updates to Bounded Contexts
User Context
Manages user profiles, authentication, ratings, and reviews.
Review Context (New Bounded Context)
Purpose: Handles creation, storage, and retrieval of user reviews and ratings.
Entities:
Review
Services:
ReviewService
Repositories:
ReviewRepository

Entities, Value Objects, and Aggregates
User Context
Entity: User
Attributes:
userId (unique identifier)
name
email
phoneNumber
paymentInfo (value object)
averageRating (calculated from reviews)
reviews (collection of received Review objects)
Aggregate Root: User
Repository: UserRepository
Service: UserService

Review Context
Entity: Review
Attributes:
reviewId (unique identifier)
transactionId (link to the associated parking spot transaction)
reviewerId (user who writes the review)
revieweeId (user being reviewed)
rating (numerical score)
comments (optional feedback text)
timestamp
Aggregate Root: Review
Repository: ReviewRepository
Service: ReviewService

Domain Services and Interactions
ReviewService
Methods:
submitReview(transactionId, reviewerId, revieweeId, rating, comments)
Validates the transaction has taken place.
Ensures a user can only review once per transaction.
Saves the new Review.
Triggers an event to update the User's average rating.
getUserReviews(userId)
Retrieves all reviews for a specific user.
calculateUserRating(userId)
Calculates and updates the user's average rating based on received reviews.

UserService Modifications
Methods:
updateUserRating(userId)
Invokes ReviewService.calculateUserRating(userId).
Updates the averageRating in the User entity.
getUserProfile(userId)
Now includes averageRating and recent reviews.

Workflow Scenarios
1. After a Successful Transaction
Trigger:
Once a parking spot transaction is completed, both the leaving and arriving users are prompted to review each other.
Process:
Each user submits a review via ReviewService.submitReview().
The service validates the transaction and saves the review.
An event is triggered to update the reviewee's average rating.
Outcome:
The review is stored and associated with the user.
The reviewee's profile is updated with the new average rating.

2. Viewing User Ratings and Reviews
Users can view other users' ratings and reviews when:
Searching for available parking spots.
Viewing profiles of users they are interacting with.

Data Model Examples
Review Entity
public class Review {
    private UUID reviewId;
    private UUID transactionId;
    private UUID reviewerId;
    private UUID revieweeId;
    private int rating; // e.g., 1 to 5 stars
    private String comments;
    private LocalDateTime timestamp;
    // Getters and setters omitted for brevity
}



User Entity (Updated)
public class User {
    private UUID userId;
    private String name;
    private String email;
    private String phoneNumber;
    private PaymentInfo paymentInfo;
    private double averageRating;
    private List<Review> reviews; // Reviews received
    // Getters and setters omitted for brevity
}



Domain Events
ReviewSubmittedEvent
Triggered when a new review is submitted.
Handled by UserService to update the user's average rating.
Handled by NotificationService to inform users about new reviews.

Integration with Other Contexts
Notification Context:
Sends notifications to users when:
They receive a new review.
They are prompted to submit a review after a transaction.
Parking Context:
Ensures that reviews can only be made post-transaction.
Associates reviews with their respective transactions.

Technical Considerations
Data Integrity and Validation
Transaction Verification:
Ensure that a user can only review another user if they have completed a transaction together.
One Review per Transaction:
Prevent users from submitting multiple reviews for the same transaction.
Rating Calculation
Average Rating:
Calculate the average rating based on all received reviews.
Optionally, you may weigh recent reviews more heavily.
Moderation and Reporting
Content Moderation:
Implement mechanisms to detect and handle inappropriate or offensive content in comments.
Dispute Resolution:
Provide a process for users to dispute unfair reviews.
Support team can mediate and remove unjust reviews if necessary.
Review Visibility:
Determine if reviews are public or only visible to users involved in a transaction.
Privacy and Compliance
Data Protection:
Ensure reviews comply with privacy laws and regulations.
Anonymity:
Decide whether to display reviewer identities or keep them anonymous.

User Interface Implications
Review Submission:
Design intuitive interfaces for users to submit ratings and comments post-transaction.
User Profiles:
Display average ratings and a selection of recent reviews.
Search Results:
Show user ratings next to their parking spot availability listings.

Example Sequence Diagram
Scenario: User Submits a Review After Transaction
Transaction Completed:
ParkingService marks the transaction as completed.
Triggers TransactionCompletedEvent.
Prompt to Review:
NotificationService sends notifications to both users to submit reviews.
Review Submission:
User submits review via the app.
App calls ReviewService.submitReview().
ReviewService validates and saves the review.
Triggers ReviewSubmittedEvent.
Update User Rating:
UserService handles ReviewSubmittedEvent.
Calls ReviewService.calculateUserRating(revieweeId).
Updates the averageRating in the User entity.
Notification of New Review:
NotificationService notifies the reviewee about the new review.

Benefits of the Review System
Enhanced Trust:
Users can make informed decisions based on others' experiences.
Accountability:
Encourages users to adhere to community guidelines and standards.
Improved Quality of Service:
Highlights exemplary users and identifies those who may need to improve.

Handling Negative Reviews
Fairness and Objectivity
Encourage users to provide constructive feedback focusing on the transaction experience.
Dispute Mechanism
Reporting Inaccurate Reviews:
Users can report reviews they believe are unfair or violate guidelines.
Review Moderation:
Establish clear policies on what constitutes acceptable reviews.
Moderators can assess reported reviews and take appropriate action.

Policy and Guidelines
Review Guidelines:
Provide clear instructions on how to write appropriate reviews.
Prohibit offensive language, personal attacks, and irrelevant content.
Community Standards:
Outline the expected behavior of users within the platform.

Security Considerations
Data Security:
Protect review data from unauthorized access or manipulation.
Authentication:
Ensure only authenticated users can submit or view reviews.

Next Steps
Define ReviewService API:
Specify endpoints for submitting and retrieving reviews.
Update Database Schema:
Add tables/collections for Review entities.
Modify User entity to include averageRating and a list of Review references.
Develop User Interfaces:
Design screens for review submission and display.
Implement Moderation Tools:
Build interfaces and processes for administrators to manage reviews.
Testing:
Conduct unit and integration tests for the review system.
Test scenarios for both positive and negative reviews.

Summary
Integrating a review system into your application enhances the overall user experience by fostering trust and accountability. By carefully designing this feature within the DDD framework, you can maintain a clean architecture while adding valuable functionality.

Feel free to let me know if you need further details on implementing specific components, or if you'd like to discuss other features or considerations for your application.
Thanks, now let's start from wherever you want, using spring boot to write all the services necessary for one bounded context
Implementing the Parking Context Using Spring Boot

Now, let's proceed to implement one of the bounded contexts using Spring Boot. We'll focus on the Parking Context, which is central to the application's functionality.
The Parking Context handles:
Reporting parking spot availability by leaving users.
Searching for available spots by arriving users.
Managing reservations and status updates of parking spots.

Project Setup
Initialize a Spring Boot Project:
Use Spring Initializr to create a new project with the following dependencies:
Spring Web
Spring Data JPA
H2 Database (for simplicity; can be replaced with PostgreSQL or another DB)
Lombok (optional, for reducing boilerplate code)
Project Structure:
src/main/java/
└── com.example.parking
    ├── ParkingApplication.java
    ├── controller
    ├── entity
    ├── repository
    ├── service
    └── dto



Entities
1. Availability
Represents a parking spot that is becoming available.
// src/main/java/com/example/parking/entity/Availability.java

package com.example.parking.entity;

import javax.persistence.*;
import java.time.LocalDateTime;
import java.util.UUID;

@Entity
public class Availability {

    @Id
    @GeneratedValue
    private UUID availabilityId;

    private UUID leavingUserId;

    @Embedded
    private Location location;

    private LocalDateTime estimatedLeavingTime;

    @Enumerated(EnumType.STRING)
    private AvailabilityStatus status;

    private UUID reservedByUserId;

    private LocalDateTime createdAt;

    private LocalDateTime updatedAt;

    // Constructors, Getters, Setters omitted for brevity
}


2. Location (Embeddable Value Object)
Represents geographical coordinates.
// src/main/java/com/example/parking/entity/Location.java

package com.example.parking.entity;

import javax.persistence.Embeddable;

@Embeddable
public class Location {

    private double latitude;
    private double longitude;

    // Constructors, Getters, Setters omitted for brevity
}


3. AvailabilityStatus (Enum)
Represents the status of a parking spot availability.
// src/main/java/com/example/parking/entity/AvailabilityStatus.java

package com.example.parking.entity;

public enum AvailabilityStatus {
    AVAILABLE,
    RESERVED,
    TAKEN,
    CANCELED
}



Repositories
AvailabilityRepository
Handles data access for Availability entities.
// src/main/java/com/example/parking/repository/AvailabilityRepository.java

package com.example.parking.repository;

import com.example.parking.entity.Availability;
import com.example.parking.entity.AvailabilityStatus;
import org.springframework.data.jpa.repository.JpaRepository;

import java.util.List;
import java.util.UUID;

public interface AvailabilityRepository extends JpaRepository<Availability, UUID> {

    List<Availability> findByStatus(AvailabilityStatus status);

    // Additional query methods can be added as needed
}



Services
ParkingService
Contains the business logic for parking functionalities.
// src/main/java/com/example/parking/service/ParkingService.java

package com.example.parking.service;

import com.example.parking.entity.Availability;
import com.example.parking.entity.AvailabilityStatus;
import com.example.parking.repository.AvailabilityRepository;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;
import java.util.UUID;

@Service
public class ParkingService {

    private final AvailabilityRepository availabilityRepository;

    public ParkingService(AvailabilityRepository availabilityRepository) {
        this.availabilityRepository = availabilityRepository;
    }

    @Transactional
    public Availability reportAvailability(Availability availability) {
        availability.setStatus(AvailabilityStatus.AVAILABLE);
        availability.setCreatedAt(java.time.LocalDateTime.now());
        availability.setUpdatedAt(java.time.LocalDateTime.now());
        return availabilityRepository.save(availability);
    }

    public List<Availability> getAvailableSpots() {
        return availabilityRepository.findByStatus(AvailabilityStatus.AVAILABLE);
    }

    @Transactional
    public Availability reserveSpot(UUID availabilityId, UUID arrivingUserId) {
        Availability availability = availabilityRepository.findById(availabilityId)
                .orElseThrow(() -> new IllegalArgumentException("Availability not found"));

        if (availability.getStatus() != AvailabilityStatus.AVAILABLE) {
            throw new IllegalStateException("Spot is not available");
        }

        availability.setStatus(AvailabilityStatus.RESERVED);
        availability.setReservedByUserId(arrivingUserId);
        availability.setUpdatedAt(java.time.LocalDateTime.now());

        return availabilityRepository.save(availability);
    }

    @Transactional
    public Availability confirmSpotTaken(UUID availabilityId, UUID arrivingUserId) {
        Availability availability = availabilityRepository.findById(availabilityId)
                .orElseThrow(() -> new IllegalArgumentException("Availability not found"));

        if (!availability.getReservedByUserId().equals(arrivingUserId)) {
            throw new IllegalStateException("This spot is not reserved by you");
        }

        availability.setStatus(AvailabilityStatus.TAKEN);
        availability.setUpdatedAt(java.time.LocalDateTime.now());

        return availabilityRepository.save(availability);
    }

    @Transactional
    public Availability cancelAvailability(UUID availabilityId, UUID userId) {
        Availability availability = availabilityRepository.findById(availabilityId)
                .orElseThrow(() -> new IllegalArgumentException("Availability not found"));

        if (!availability.getLeavingUserId().equals(userId) &&
            !availability.getReservedByUserId().equals(userId)) {
            throw new IllegalStateException("You do not have permission to cancel this availability");
        }

        availability.setStatus(AvailabilityStatus.CANCELED);
        availability.setUpdatedAt(java.time.LocalDateTime.now());

        return availabilityRepository.save(availability);
    }

    // Additional methods can be added as needed
}



Controllers
Exposes RESTful endpoints for clients to interact with the Parking Service.
// src/main/java/com/example/parking/controller/ParkingController.java

package com.example.parking.controller;

import com.example.parking.dto.AvailabilityRequest;
import com.example.parking.dto.AvailabilityResponse;
import com.example.parking.entity.Availability;
import com.example.parking.service.ParkingService;
import org.modelmapper.ModelMapper;
import org.springframework.web.bind.annotation.*;

import java.util.List;
import java.util.UUID;
import java.util.stream.Collectors;

@RestController
@RequestMapping("/api/parking")
public class ParkingController {

    private final ParkingService parkingService;
    private final ModelMapper modelMapper;

    public ParkingController(ParkingService parkingService, ModelMapper modelMapper) {
        this.parkingService = parkingService;
        this.modelMapper = modelMapper;
    }

    @PostMapping("/availability")
    public AvailabilityResponse reportAvailability(@RequestBody AvailabilityRequest request) {
        Availability availability = modelMapper.map(request, Availability.class);
        Availability savedAvailability = parkingService.reportAvailability(availability);
        return modelMapper.map(savedAvailability, AvailabilityResponse.class);
    }

    @GetMapping("/spots")
    public List<AvailabilityResponse> getAvailableSpots() {
        List<Availability> spots = parkingService.getAvailableSpots();
        return spots.stream()
                .map(spot -> modelMapper.map(spot, AvailabilityResponse.class))
                .collect(Collectors.toList());
    }

    @PostMapping("/reserve/{availabilityId}")
    public AvailabilityResponse reserveSpot(@PathVariable UUID availabilityId,
                                            @RequestParam UUID arrivingUserId) {
        Availability availability = parkingService.reserveSpot(availabilityId, arrivingUserId);
        return modelMapper.map(availability, AvailabilityResponse.class);
    }

    @PostMapping("/confirm/{availabilityId}")
    public AvailabilityResponse confirmSpotTaken(@PathVariable UUID availabilityId,
                                                 @RequestParam UUID arrivingUserId) {
        Availability availability = parkingService.confirmSpotTaken(availabilityId, arrivingUserId);
        return modelMapper.map(availability, AvailabilityResponse.class);
    }

    @PostMapping("/cancel/{availabilityId}")
    public AvailabilityResponse cancelAvailability(@PathVariable UUID availabilityId,
                                                   @RequestParam UUID userId) {
        Availability availability = parkingService.cancelAvailability(availabilityId, userId);
        return modelMapper.map(availability, AvailabilityResponse.class);
    }

    // Additional endpoints can be added as needed
}



DTOs (Data Transfer Objects)
Used to transfer data between layers without exposing the entity directly.
1. AvailabilityRequest
// src/main/java/com/example/parking/dto/AvailabilityRequest.java

package com.example.parking.dto;

import com.example.parking.entity.Location;
import java.time.LocalDateTime;
import java.util.UUID;

public class AvailabilityRequest {

    private UUID leavingUserId;

    private Location location;

    private LocalDateTime estimatedLeavingTime;

    // Getters and setters omitted for brevity
}


2. AvailabilityResponse
// src/main/java/com/example/parking/dto/AvailabilityResponse.java

package com.example.parking.dto;

import com.example.parking.entity.AvailabilityStatus;
import com.example.parking.entity.Location;
import java.time.LocalDateTime;
import java.util.UUID;

public class AvailabilityResponse {

    private UUID availabilityId;

    private UUID leavingUserId;

    private Location location;

    private LocalDateTime estimatedLeavingTime;

    private AvailabilityStatus status;

    private UUID reservedByUserId;

    private LocalDateTime createdAt;

    private LocalDateTime updatedAt;

    // Getters and setters omitted for brevity
}



Model Mapper Configuration
Configure ModelMapper to convert between entities and DTOs.
// src/main/java/com/example/parking/ParkingApplication.java

package com.example.parking;

import org.modelmapper.ModelMapper;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class ParkingApplication {

    @Bean
    public ModelMapper modelMapper() {
        return new ModelMapper();
    }

    // Main method and other configurations
}



Exception Handling
Implement global exception handling to return meaningful error responses.
// src/main/java/com/example/parking/exception/GlobalExceptionHandler.java

package com.example.parking.exception;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

@RestControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(IllegalArgumentException.class)
    public ResponseEntity<String> handleIllegalArgs(IllegalArgumentException ex) {
        return ResponseEntity.badRequest().body(ex.getMessage());
    }

    @ExceptionHandler(IllegalStateException.class)
    public ResponseEntity<String> handleIllegalState(IllegalStateException ex) {
        return ResponseEntity.status(HttpStatus.CONFLICT).body(ex.getMessage());
    }

    // Additional exception handlers can be added as needed
}



Testing the API
Sample Requests Using cURL
Report Availability
curl -X POST http://localhost:8080/api/parking/availability \
-H 'Content-Type: application/json' \
-d '{
  "leavingUserId": "user-uuid-1",
  "location": {
    "latitude": 37.7749,
    "longitude": -122.4194
  },
  "estimatedLeavingTime": "2023-10-01T15:30:00"
}'


Get Available Spots
curl http://localhost:8080/api/parking/spots


Reserve a Spot
curl -X POST "http://localhost:8080/api/parking/reserve/{availabilityId}?arrivingUserId=user-uuid-2"


Confirm Spot Taken
curl -X POST "http://localhost:8080/api/parking/confirm/{availabilityId}?arrivingUserId=user-uuid-2"


Cancel Availability
curl -X POST "http://localhost:8080/api/parking/cancel/{availabilityId}?userId=user-uuid-1"


Replace {availabilityId} with the actual UUID obtained from previous responses.

Notes and Considerations
Timestamp Handling:
Ensure consistent use of time zones (e.g., UTC) across the application.
Entity Relationships:
The Availability entity can be linked to User entities if the User context is integrated.
Data Validation:
Use validation annotations (e.g., @NotNull, @Future) on DTOs and entities to enforce data integrity.
Security:
Implement security measures (e.g., authentication, authorization) to protect endpoints.
Asynchronous Processing:
For sending notifications or handling events, consider using asynchronous messaging (e.g., Spring Events, message queues).
Error Handling:
Provide meaningful error messages to the client and handle exceptions gracefully.

Extending the Implementation
To fully realize the Parking Context, additional features and integrations can be developed:
Location-Based Search:
Implement a method in ParkingService to find available spots within a certain radius of a given location.
Integration with User Context:
Fetch user details (e.g., ratings) when displaying available spots.
Notification Service Integration:
Trigger notifications to users upon certain events (e.g., spot reserved).
Domain Events:
Publish and handle domain events (e.g., SpotAvailableEvent, SpotReservedEvent) using Spring's event mechanism or a message broker.
Reservation Expiry:
Implement logic to expire reservations if the arriving user does not confirm within a certain time frame.

Conclusion
We've implemented the core components of the Parking Context using Spring Boot, including entities, repositories, services, controllers, and DTOs. This provides a solid foundation for handling parking spot availability and reservations within the application.

Next Steps:
Implement Other Contexts:
Continue building out the other bounded contexts (User, Reward, Notification, Review) using similar approaches.
Integrate Contexts:
Connect the Parking Context with other contexts for a cohesive application.
Testing and Validation:
Write unit and integration tests to ensure the functionality works as intended.
Performance Optimization:
Optimize database queries, especially for location-based searches.
Deployment:
Prepare the application for deployment, considering scalability and high availability.

Feel free to ask if you need further assistance with implementing other contexts or integrating additional features into the Parking Context.
How would you handle the fact that a user may or may not accept a reservation from another user? Maybe based on reputation. So a used doesn't have the ability to directly reserve a spot
Handling Reservation Requests with Acceptance Based on User Reputation

Understanding the New Requirement
You want to modify the reservation process so that:
Arriving Users cannot directly reserve a parking spot.
Instead, they send a reservation request to the leaving user.
Leaving Users can accept or reject reservation requests.
Leaving users may base their decision on the reputation (ratings/reviews) of the arriving user.
This feature introduces a more controlled reservation flow and adds an extra layer of trust and accountability between users.

Modifying the System Design
To incorporate this new requirement, we'll need to:
Introduce a Reservation Request mechanism in the Parking Context.
Integrate User Reputation from the User Context.
Update Entities, Services, and Workflows to reflect the new process.
Ensure Seamless Integration with existing features like notifications and reviews.

Updates to the Domain Model
New Entities
ReservationRequest
Attributes:
requestId (unique identifier)
availabilityId (reference to the parking spot availability)
arrivingUserId (user who wants to reserve)
leavingUserId (owner of the availability)
status (Pending, Accepted, Rejected, Canceled)
requestedAt (timestamp)
respondedAt (timestamp)
message (optional message from arriving user)
Updates to Existing Entities
Availability
Modify status to handle the new flow.
Possible statuses: Available, RequestPending, Reserved, Taken, Canceled.

Domain Services and Interactions
ParkingService Modifications
Methods:
requestReservation(availabilityId, arrivingUserId, optionalMessage)
Creates a new ReservationRequest with status set to Pending.
Updates Availability status to RequestPending.
respondToReservation(requestId, leavingUserId, accepted)
Leaving user accepts or rejects the reservation request.
If accepted:
Update ReservationRequest status to Accepted.
Update Availability status to Reserved.
Set reservedByUserId in Availability.
If rejected:
Update ReservationRequest status to Rejected.
Update Availability status back to Available.
confirmSpotTaken(availabilityId, arrivingUserId)
Remains largely the same.
UserService (from User Context)
Provide method to get user reputation:
getUserReputation(userId)

Workflow Scenarios
1. Arriving User Requests a Reservation
Action:
Arriving user selects an available spot and sends a reservation request.
Process:
ParkingService.requestReservation() creates a ReservationRequest.
Availability status is updated to RequestPending.
NotificationService notifies the leaving user of the new reservation request.
Outcome:
Leaving user receives a notification with details including the arriving user's reputation.
2. Leaving User Responds to Reservation Request
Action:
Leaving user reviews the request and accepts or rejects it.
Process:
ParkingService.respondToReservation() updates ReservationRequest and Availability statuses.
NotificationService notifies the arriving user of the response.
Outcome:
If accepted, the spot is reserved for the arriving user.
If rejected, the spot becomes available again.
3. Arriving User Confirms Spot Taken
Same as before:
Arriving user confirms they have taken the spot.
ParkingService.confirmSpotTaken() updates the status.
Initiates reward processing, etc.

Updated Entities and Relationships
ReservationRequest Entity
// src/main/java/com/example/parking/entity/ReservationRequest.java

package com.example.parking.entity;

import javax.persistence.*;
import java.time.LocalDateTime;
import java.util.UUID;

@Entity
public class ReservationRequest {

    @Id
    @GeneratedValue
    private UUID requestId;

    private UUID availabilityId;

    private UUID arrivingUserId;

    private UUID leavingUserId;

    @Enumerated(EnumType.STRING)
    private RequestStatus status;

    private LocalDateTime requestedAt;

    private LocalDateTime respondedAt;

    private String message;

    // Constructors, Getters, Setters omitted for brevity
}


RequestStatus Enum
// src/main/java/com/example/parking/entity/RequestStatus.java

package com.example.parking.entity;

public enum RequestStatus {
    PENDING,
    ACCEPTED,
    REJECTED,
    CANCELED
}


Updates to Availability Entity
Add Statuses:
REQUEST_PENDING, RESERVED remain, but their use is slightly adjusted.
Adjust Transitions:
public enum AvailabilityStatus {
    AVAILABLE,
    REQUEST_PENDING,
    RESERVED,
    TAKEN,
    CANCELED
}



Service Layer Implementation
ParkingService Updates
// src/main/java/com/example/parking/service/ParkingService.java

package com.example.parking.service;

import com.example.parking.entity.*;
import com.example.parking.repository.AvailabilityRepository;
import com.example.parking.repository.ReservationRequestRepository;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.time.LocalDateTime;
import java.util.UUID;

@Service
public class ParkingService {

    private final AvailabilityRepository availabilityRepository;
    private final ReservationRequestRepository reservationRequestRepository;
    private final UserService userService; // From User Context

    public ParkingService(AvailabilityRepository availabilityRepository,
                          ReservationRequestRepository reservationRequestRepository,
                          UserService userService) {
        this.availabilityRepository = availabilityRepository;
        this.reservationRequestRepository = reservationRequestRepository;
        this.userService = userService;
    }

    @Transactional
    public ReservationRequest requestReservation(UUID availabilityId, UUID arrivingUserId, String message) {
        Availability availability = availabilityRepository.findById(availabilityId)
                .orElseThrow(() -> new IllegalArgumentException("Availability not found"));

        if (availability.getStatus() != AvailabilityStatus.AVAILABLE) {
            throw new IllegalStateException("Spot is not available for reservation");
        }

        ReservationRequest request = new ReservationRequest();
        request.setAvailabilityId(availabilityId);
        request.setArrivingUserId(arrivingUserId);
        request.setLeavingUserId(availability.getLeavingUserId());
        request.setStatus(RequestStatus.PENDING);
        request.setRequestedAt(LocalDateTime.now());
        request.setMessage(message);

        availability.setStatus(AvailabilityStatus.REQUEST_PENDING);
        availability.setUpdatedAt(LocalDateTime.now());

        // Save changes
        availabilityRepository.save(availability);
        ReservationRequest savedRequest = reservationRequestRepository.save(request);

        // Notify leaving user (not shown here)

        return savedRequest;
    }

    @Transactional
    public ReservationRequest respondToReservation(UUID requestId, UUID leavingUserId, boolean accepted) {
        ReservationRequest request = reservationRequestRepository.findById(requestId)
                .orElseThrow(() -> new IllegalArgumentException("Reservation request not found"));

        if (!request.getLeavingUserId().equals(leavingUserId)) {
            throw new IllegalStateException("You do not have permission to respond to this request");
        }

        if (request.getStatus() != RequestStatus.PENDING) {
            throw new IllegalStateException("Request has already been responded to");
        }

        request.setRespondedAt(LocalDateTime.now());

        Availability availability = availabilityRepository.findById(request.getAvailabilityId())
                .orElseThrow(() -> new IllegalArgumentException("Availability not found"));

        if (accepted) {
            request.setStatus(RequestStatus.ACCEPTED);

            availability.setStatus(AvailabilityStatus.RESERVED);
            availability.setReservedByUserId(request.getArrivingUserId());
        } else {
            request.setStatus(RequestStatus.REJECTED);

            availability.setStatus(AvailabilityStatus.AVAILABLE);
        }

        availability.setUpdatedAt(LocalDateTime.now());

        // Save changes
        availabilityRepository.save(availability);
        ReservationRequest savedRequest = reservationRequestRepository.save(request);

        // Notify arriving user (not shown here)

        return savedRequest;
    }

    // Existing methods remain
}


ReservationRequestRepository
// src/main/java/com/example/parking/repository/ReservationRequestRepository.java

package com.example.parking.repository;

import com.example.parking.entity.ReservationRequest;
import com.example.parking.entity.RequestStatus;
import org.springframework.data.jpa.repository.JpaRepository;

import java.util.List;
import java.util.UUID;

public interface ReservationRequestRepository extends JpaRepository<ReservationRequest, UUID> {

    List<ReservationRequest> findByLeavingUserIdAndStatus(UUID leavingUserId, RequestStatus status);

    // Additional query methods as needed
}



Controller Updates
ParkingController Modifications
// src/main/java/com/example/parking/controller/ParkingController.java

package com.example.parking.controller;

import com.example.parking.dto.*;
import com.example.parking.entity.ReservationRequest;
import com.example.parking.service.ParkingService;
import com.example.parking.service.UserService; // From User Context
import org.modelmapper.ModelMapper;
import org.springframework.web.bind.annotation.*;

import java.util.UUID;

@RestController
@RequestMapping("/api/parking")
public class ParkingController {

    private final ParkingService parkingService;
    private final UserService userService;
    private final ModelMapper modelMapper;

    public ParkingController(ParkingService parkingService, UserService userService, ModelMapper modelMapper) {
        this.parkingService = parkingService;
        this.userService = userService;
        this.modelMapper = modelMapper;
    }

    // Existing endpoints ...

    @PostMapping("/request/{availabilityId}")
    public ReservationRequestResponse requestReservation(@PathVariable UUID availabilityId,
                                                         @RequestBody ReservationRequestDto requestDto) {
        ReservationRequest request = parkingService.requestReservation(
                availabilityId,
                requestDto.getArrivingUserId(),
                requestDto.getMessage()
        );
        return modelMapper.map(request, ReservationRequestResponse.class);
    }

    @PostMapping("/respond/{requestId}")
    public ReservationRequestResponse respondToReservation(@PathVariable UUID requestId,
                                                           @RequestBody ReservationResponseDto responseDto) {
        ReservationRequest request = parkingService.respondToReservation(
                requestId,
                responseDto.getLeavingUserId(),
                responseDto.isAccepted()
        );
        return modelMapper.map(request, ReservationRequestResponse.class);
    }

    // Additional endpoints as needed
}


DTOs for Reservation Requests
ReservationRequestDto
// src/main/java/com/example/parking/dto/ReservationRequestDto.java

package com.example.parking.dto;

import java.util.UUID;

public class ReservationRequestDto {

    private UUID arrivingUserId;
    private String message;

    // Getters and setters
}


ReservationResponseDto
// src/main/java/com/example/parking/dto/ReservationResponseDto.java

package com.example.parking.dto;

import java.util.UUID;

public class ReservationResponseDto {

    private UUID leavingUserId;
    private boolean accepted;

    // Getters and setters
}


ReservationRequestResponse
// src/main/java/com/example/parking/dto/ReservationRequestResponse.java

package com.example.parking.dto;

import com.example.parking.entity.RequestStatus;

import java.time.LocalDateTime;
import java.util.UUID;

public class ReservationRequestResponse {

    private UUID requestId;
    private UUID availabilityId;
    private UUID arrivingUserId;
    private UUID leavingUserId;
    private RequestStatus status;
    private LocalDateTime requestedAt;
    private LocalDateTime respondedAt;
    private String message;

    // Getters and setters
}



Integrating User Reputation
Fetching User Reputation
When the leaving user receives a reservation request, they should see the reputation of the arriving user.
Inside ParkingService or ParkingController:
Use UserService.getUserReputation(arrivingUserId) to fetch reputation data.
Example UserService Method
// src/main/java/com/example/user/service/UserService.java

package com.example.user.service;

import com.example.user.entity.User;
import com.example.user.repository.UserRepository;
import org.springframework.stereotype.Service;

import java.util.UUID;

@Service
public class UserService {

    private final UserRepository userRepository;

    // Constructor

    public double getUserReputation(UUID userId) {
        User user = userRepository.findById(userId)
                .orElseThrow(() -> new IllegalArgumentException("User not found"));
        return user.getAverageRating();
    }

    // Additional methods
}


Including Reputation in Notifications
When notifying the leaving user of a reservation request, include the arriving user's reputation in the message.

User Interface Implications
Leaving User's View:
When a reservation request arrives, the leaving user receives:
Notification of the request.
Details of the arriving user, including reputation (average rating) and reviews.
Option to accept or reject the request.
Arriving User's View:
After sending a reservation request, sees the status as Pending.
Receives notification when the request is accepted or rejected.

Adjustments to Workflows
State Transitions
Availability Status Transitions:
Available → RequestPending (when a reservation request is made)
RequestPending → Reserved (if request is accepted)
RequestPending → Available (if request is rejected)
ReservationRequest Status Transitions:
Pending → Accepted / Rejected / Canceled

Domain Events and Notifications
ReservationRequestCreatedEvent
Triggered when a reservation request is made.
Handled by NotificationService to inform the leaving user.
ReservationRequestRespondedEvent
Triggered when the leaving user responds to the request.
Handled by NotificationService to inform the arriving user.

Technical Considerations
Concurrency Control
Optimistic Locking:
Use versioning in entities to prevent race conditions.
Transaction Management:
Ensure that updates to Availability and ReservationRequest are atomic.
Data Validation
Ensure Valid User IDs:
Verify that user IDs exist and are active in the system.
Request Uniqueness:
Prevent multiple pending requests for the same Availability and arrivingUserId.
Security
Authentication and Authorization:
Verify that users are authenticated.
Ensure users can only perform actions they are authorized for.

Extending the Review System
Encourage users to leave reviews after transactions.
Use reviews to update user reputation.

Testing the New Flow
Sample API Calls
Request Reservation
curl -X POST "http://localhost:8080/api/parking/request/{availabilityId}" \
-H 'Content-Type: application/json' \
-d '{
  "arrivingUserId": "user-uuid-arriving",
  "message": "I will arrive in 10 minutes."
}'


Leaving User Responds to Request
curl -X POST "http://localhost:8080/api/parking/respond/{requestId}" \
-H 'Content-Type: application/json' \
-d '{
  "leavingUserId": "user-uuid-leaving",
  "accepted": true
}'



Advantages of the New Approach
Enhanced Control:
Leaving users have control over who reserves their spot.
Promotes Trust:
Reputations influence decisions, encouraging good behavior.
Prevents Abuse:
Reduces the likelihood of misuse by users with poor reputations.

Potential Challenges and Solutions
Increased Wait Times
Challenge:
The additional approval step may slow down the reservation process.
Solution:
Implement timely notifications to encourage quick responses.
Allow leaving users to set an auto-accept option based on minimum reputation thresholds.
User Experience
Challenge:
Users may find the process cumbersome.
Solution:
Simplify the interface.
Provide clear instructions and feedback.
Offer default settings for experienced users.

Enhancements and Additional Features
Reputation Thresholds
Auto-Accept Based on Reputation:
Leaving users can set a minimum reputation score.
Requests from users meeting the criteria are auto-accepted.
Batch Requests
Multiple Requests Handling:
Allow multiple users to send requests.
Leaving user can choose among several arriving users.
Timeouts
Request Expiry:
Reservation requests expire after a certain period.
Notifications sent if no response.

Conclusion
By introducing a reservation request mechanism and integrating user reputation, we add an extra layer of trust and control to the platform. This approach encourages users to maintain good reputations and enhances the overall quality of service.

Next Steps:
Update Documentation:
Reflect the new processes in API documentation and user guides.
Implement User Interface Changes:
Modify the app to accommodate new screens and workflows.
Integrate Notification Service:
Ensure timely notifications are sent during the reservation process.
Expand Testing:
Thoroughly test the new features for usability and reliability.

Feel free to ask if you need further details on any specific part of the implementation or if there's anything else you'd like to discuss.

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I want to start from the beginning, i have intellij open, what do i do