parallel-programming/src/test/java/business/ConcurrentCurrencyExchangeTest.java

package business;

import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import ru.lionarius.api.CurrencyExchange;
import ru.lionarius.api.client.Client;
import ru.lionarius.api.currency.Currency;
import ru.lionarius.api.currency.CurrencyPair;
import ru.lionarius.api.order.OrderType;

import java.util.ArrayList;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.*;
import java.util.stream.Stream;

import static org.junit.jupiter.api.Assertions.*;

public abstract class ConcurrentCurrencyExchangeTest {
    protected abstract CurrencyExchange createExchange(Set<CurrencyPair> pairs);
    protected abstract void shutdownExchange(CurrencyExchange exchange);

    private CurrencyExchange exchange;
    private CurrencyPair RUB_CNY;
    private ExecutorService executorService;

    @BeforeEach
    void setUp() {
        Currency RUB = new Currency("RUB");
        Currency CNY = new Currency("CNY");
        RUB_CNY = new CurrencyPair(RUB, CNY);

        exchange = createExchange(Set.of(RUB_CNY));

        executorService = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());
    }

    @Test
    void testConcurrentClientCreation() throws InterruptedException {
        int numClients = 100;
        var latch = new CountDownLatch(numClients);
        var futures = new ArrayList<CompletableFuture<Client>>();

        for (int i = 0; i < numClients; i++) {
            var future = CompletableFuture.supplyAsync(() -> {
                try {
                    return exchange.createClient("Client " + UUID.randomUUID()).join();
                } finally {
                    latch.countDown();
                }
            }, executorService);
            futures.add(future);
        }

        latch.await(30, TimeUnit.SECONDS);
        CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();

        assertEquals(numClients, futures.stream().map(CompletableFuture::join).distinct().count(),
                "All created clients should be unique");
    }


    @Test
    void testConcurrentOrderPlacement() throws InterruptedException {
        var numSellers = 10;
        var numBuyers = 10;
        var ordersPerClient = 20;
        var latch = new CountDownLatch(numSellers + numBuyers);

        var sellers = new ArrayList<Client>();
        for (int i = 0; i < numSellers; i++) {
            var seller = exchange.createClient("Seller " + i).join();
            sellers.add(seller);
        }

        var buyers = new ArrayList<Client>();
        for (int i = 0; i < numBuyers; i++) {
            var buyer = exchange.createClient("Buyer " + i).join();
            buyers.add(buyer);
        }

        var sellerFutures = sellers.stream()
                .map(seller -> CompletableFuture.runAsync(() -> {
                    try {
                        for (int i = 0; i < ordersPerClient; i++) {
                            exchange.placeOrder(seller.id(), RUB_CNY, OrderType.SELL, 10.0, 10.0).join();
                            Thread.sleep(10);
                        }
                    } catch (InterruptedException e) {
                        Thread.currentThread().interrupt();
                    } finally {
                        latch.countDown();
                    }
                }, executorService))
                .toList();

        var buyerFutures = buyers.stream()
                .map(buyer -> CompletableFuture.runAsync(() -> {
                    try {
                        for (int i = 0; i < ordersPerClient; i++) {
                            exchange.placeOrder(buyer.id(), RUB_CNY, OrderType.BUY, 1.2, 10.0).join();
                            Thread.sleep(10);
                        }
                    } catch (InterruptedException e) {
                        Thread.currentThread().interrupt();
                    } finally {
                        latch.countDown();
                    }
                }, executorService))
                .toList();

        latch.await(30, TimeUnit.SECONDS);
        CompletableFuture.allOf(
                Stream.concat(sellerFutures.stream(), buyerFutures.stream())
                        .toArray(CompletableFuture[]::new)
        ).join();

        for (var seller : sellers) {
            assertTrue((long) exchange.getOrders(seller.id()).join().size() <= ordersPerClient);
        }

        for (var buyer : buyers) {
            assertTrue((long) exchange.getOrders(buyer.id()).join().size() <= ordersPerClient);
        }
    }

    @Test
    void testConcurrentOrderMatchingWithDifferentPrices() throws InterruptedException {
        var numOrders = 50;
        var latch = new CountDownLatch(2);

        var seller = exchange.createClient("Seller").join();
        var buyer = exchange.createClient("Buyer").join();

        var sellerFuture = CompletableFuture.runAsync(() -> {
            try {
                for (int i = 0; i < numOrders; i++) {
                    var price = 1.0 + (i * 0.01);
                    exchange.placeOrder(seller.id(), RUB_CNY, OrderType.SELL, price, 10.0).join();
                    Thread.sleep(5);
                }
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            } finally {
                latch.countDown();
            }
        }, executorService);

        var buyerFuture = CompletableFuture.runAsync(() -> {
            try {
                for (var i = 0; i < numOrders; i++) {
                    var price = 2.0 - (i * 0.01);
                    exchange.placeOrder(buyer.id(), RUB_CNY, OrderType.BUY, price, 10.0).join();
                    Thread.sleep(5);
                }
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            } finally {
                latch.countDown();
            }
        }, executorService);

        latch.await(30, TimeUnit.SECONDS);
        CompletableFuture.allOf(sellerFuture, buyerFuture).join();

        var sellerOrders = exchange.getOrders(seller.id()).join();
        var buyerOrders = exchange.getOrders(buyer.id()).join();

        var remainingSellerOrders = sellerOrders.stream().filter(order -> !order.closed()).count();
        var remainingBuyerOrders = buyerOrders.stream().filter(order -> !order.closed()).count();

        assertTrue(remainingSellerOrders + remainingBuyerOrders < numOrders * 2,
                "Some orders should have been matched");
    }

    @Test
    void testBalanceConsistencyWithConcurrentTradesSamePrices() throws InterruptedException {
        var numTraders = 100;
        var numOrders = 1000;
        var latch = new CountDownLatch(numTraders * 2);

        var sellers = new ArrayList<Client>();
        var buyers = new ArrayList<Client>();
        var sellAmount = 100.0;
        var buyAmount = 100.0;

        for (var i = 0; i < numTraders; i++) {
            var seller = exchange.createClient("Seller " + i).join();
            var buyer = exchange.createClient("Buyer " + i).join();

            sellers.add(seller);
            buyers.add(buyer);
        }

        var futures = new ArrayList<CompletableFuture<Void>>();

        for (var seller : sellers) {
            var future = CompletableFuture.runAsync(() -> {
                try {
                    for (var i = 0; i < numOrders; i++) {
                        exchange.placeOrder(seller.id(), RUB_CNY, OrderType.SELL, buyAmount, sellAmount).join();
                    }
                } finally {
                    latch.countDown();
                }
            }, executorService);
            futures.add(future);
        }

        for (var buyer : buyers) {
            var future = CompletableFuture.runAsync(() -> {
                try {
                    for (var i = 0; i < numOrders; i++) {
                        exchange.placeOrder(buyer.id(), RUB_CNY, OrderType.BUY, sellAmount, buyAmount).join();
                    }
                } finally {
                    latch.countDown();
                }
            }, executorService);
            futures.add(future);
        }

        latch.await(30, TimeUnit.SECONDS);
        CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
        var totalRubMoney = 0.0;
        var totalCnyMoney = 0.0;

        for (var seller : sellers) {
            var orders = exchange.getOrders(seller.id()).join();

            totalCnyMoney += orders.stream().mapToDouble(order -> order.originalData().quantity() - order.lastData().quantity()).sum();
            totalRubMoney += orders.stream().mapToDouble(order -> order.originalData().price() - order.lastData().price()).sum();
        }

        assertEquals(numOrders * numTraders * sellAmount, totalCnyMoney, 0.001);
        assertEquals(numOrders * numTraders * buyAmount, totalRubMoney, 0.001);

        for (var buyer : buyers) {
            var orders = exchange.getOrders(buyer.id()).join();

            totalCnyMoney -= orders.stream().mapToDouble(order -> order.originalData().quantity() - order.lastData().quantity()).sum();
            totalRubMoney -= orders.stream().mapToDouble(order -> order.originalData().price() - order.lastData().price()).sum();
        }

        assertEquals(0.0, totalRubMoney, 0.001);
        assertEquals(0.0, totalCnyMoney, 0.001);
    }

    @Test
    void testBalanceConsistencyWithConcurrentTrades() throws InterruptedException {
        var numTraders = 100;
        var numOrders = 1000;
        var latch = new CountDownLatch(numTraders * 3);

        var sellers = new ArrayList<Client>();
        var buyers = new ArrayList<Client>();
        var sellAmount = 100.0;
        var buyAmount = 50.0;

        for (var i = 0; i < numTraders; i++) {
            var seller = exchange.createClient("Seller " + i).join();
            var buyer = exchange.createClient("Buyer " + i).join();
            var buyer2 = exchange.createClient("Buyer " + i).join();

            sellers.add(seller);
            buyers.add(buyer);
            buyers.add(buyer2);
        }

        var futures = new ArrayList<CompletableFuture<Void>>();

        for (var seller : sellers) {
            var future = CompletableFuture.runAsync(() -> {
                try {
                    for (var i = 0; i < numOrders; i++) {
                        exchange.placeOrder(seller.id(), RUB_CNY, OrderType.SELL, buyAmount, sellAmount).join();
                    }
                } finally {
                    latch.countDown();
                }
            }, executorService);
            futures.add(future);
        }

        for (var buyer : buyers) {
            var future = CompletableFuture.runAsync(() -> {
                try {
                    for (var i = 0; i < numOrders; i++) {
                        exchange.placeOrder(buyer.id(), RUB_CNY, OrderType.BUY, sellAmount, buyAmount).join();
                    }
                } finally {
                    latch.countDown();
                }
            }, executorService);
            futures.add(future);
        }

        latch.await(30, TimeUnit.SECONDS);
        CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
        var totalRubMoney = 0.0;
        var totalCnyMoney = 0.0;

        for (var seller : sellers) {
            var orders = exchange.getOrders(seller.id()).join();

            totalCnyMoney += orders.stream().mapToDouble(order -> order.originalData().quantity() - order.lastData().quantity()).sum();
            totalRubMoney += orders.stream().mapToDouble(order -> order.originalData().price() - order.lastData().price()).sum();
        }

        assertEquals(numOrders * numTraders * sellAmount, totalCnyMoney, 0.001);
        assertEquals(numOrders * numTraders * buyAmount, totalRubMoney, 0.001);

        for (var buyer : buyers) {
            var orders = exchange.getOrders(buyer.id()).join();

            totalCnyMoney -= orders.stream().mapToDouble(order -> order.originalData().quantity() - order.lastData().quantity()).sum();
            totalRubMoney -= orders.stream().mapToDouble(order -> order.originalData().price() - order.lastData().price()).sum();
        }

        assertEquals(0.0, totalCnyMoney, 0.001);
        assertEquals(0.0, totalRubMoney, 0.001);
    }

    @AfterEach
    void tearDown() {
        executorService.shutdown();
        try {
            if (!executorService.awaitTermination(5, TimeUnit.SECONDS)) {
                executorService.shutdownNow();
            }
        } catch (InterruptedException e) {
            executorService.shutdownNow();
        }

        shutdownExchange(exchange);
    }
}