Record types for immutable data

package com.example.demo.dto;

import java.time.LocalDateTime;
import java.util.List;

// Simple record
public record UserDTO(
    Long id,
    String name,
    String email
) {}

// Record with validation
public record CreateUserRequest(
    String name,
    String email,
    String password
) {
    // Compact constructor for validation
    public CreateUserRequest {
        if (name == null || name.isBlank()) {
            throw new IllegalArgumentException("Name cannot be blank");
        }
        if (email == null || !email.contains("@")) {
            throw new IllegalArgumentException("Invalid email format");
        }
        if (password == null || password.length() < 8) {
            throw new IllegalArgumentException("Password must be at least 8 characters");
        }
    }
}

// Record with computed fields
public record Money(double amount, String currency) {

    public Money add(Money other) {
        if (!currency.equals(other.currency)) {
            throw new IllegalArgumentException("Currency mismatch");
        }
        return new Money(amount + other.amount, currency);
    }

    public String formatted() {
        return String.format("%s %.2f", currency, amount);
    }
}

// Record implementing interface
public interface Identifiable {
    Long getId();
}

public record Post(
    Long id,
    Long userId,
    String title,
    String content,
    LocalDateTime createdAt
) implements Identifiable {

    @Override
    public Long getId() {
        return id;
    }

    public boolean isRecent() {
        return createdAt.isAfter(LocalDateTime.now().minusDays(7));
    }
}

// Nested records
public record Order(
    Long id,
    Customer customer,
    List<LineItem> items,
    Money total
) {
    public record Customer(String name, String email) {}
    public record LineItem(String product, int quantity, Money price) {}
}

// Record with static factory method
public record ApiResponse<T>(
    boolean success,
    T data,
    String message,
    int statusCode
) {
    public static <T> ApiResponse<T> success(T data) {
        return new ApiResponse<>(true, data, "Success", 200);
    }

    public static <T> ApiResponse<T> error(String message, int statusCode) {
        return new ApiResponse<>(false, null, message, statusCode);
    }
}