package com.helloaihub.core;

// Sealed Interface: Strict Algebraic Data Type hierarchy
public sealed interface PaymentEvent permits PaymentEvent.CreditCard, PaymentEvent.Crypto, PaymentEvent.BankWire {
    
    // Immutable Record: Auto-generates getters, equals, hashCode, and toString
    record CreditCard(String pan, double amount, String currency) implements PaymentEvent {}
    record Crypto(String txHash, double amount, String tokenSymbol) implements PaymentEvent {}
    record BankWire(String iban, double amount, String routingCode) implements PaymentEvent {}

    // Pattern Matching for Switch (Java 21+)
    static String processEvent(PaymentEvent event) {
        return switch (event) {
            case CreditCard(var pan, var amount, var curr) -> 
                "Charged " + curr + " " + amount + " to card ending in " + pan.substring(pan.length() - 4);
            case Crypto(var tx, var amount, var token) -> 
                "Verified blockchain settlement: " + amount + " " + token + " (Tx: " + tx + ")";
            case BankWire(var iban, var amount, var _) -> 
                "Initiated SEPA transfer of " + amount + " to IBAN " + iban;
        };
    }
}

// Launching 100,000 Concurrent Virtual Threads with StructuredTaskScope
import java.util.concurrent.StructuredTaskScope;

public class HighScaleService {
    
    public record AggregatedProfile(String userData, String creditScore) {}

    public AggregatedProfile fetchUserProfile(String userId) throws Exception {
        try (var scope = new StructuredTaskScope.ShutdownOnFailure()) {
            // Fork sub-tasks onto lightweight Virtual Threads (M:N user-space threads)
            var userSubtask = scope.fork(() -> fetchUserRestApi(userId));
            var creditSubtask = scope.fork(() -> fetchCreditScoreGrpc(userId));

            // Wait for all subtasks to complete or fail fast if any throw an exception
            scope.join().throwIfFailed();

            return new AggregatedProfile(userSubtask.get(), creditSubtask.get());
        }
    }
}