package com.baeldung.backpressure;

import org.junit.jupiter.api.Test;
import reactor.core.publisher.BaseSubscriber;
import reactor.core.publisher.Flux;
import reactor.test.StepVerifier;

public class BackpressureUnitTest {

    @Test
    public void whenLimitRateSet_thenSplitIntoChunks() throws InterruptedException {
        Flux<Integer> limit = Flux.range(1, 25);

        limit.limitRate(10);
        limit.subscribe(
          value -> System.out.println(value),
          err -> err.printStackTrace(),
          () -> System.out.println("Finished!!"),
          subscription -> subscription.request(15)
        );

        StepVerifier.create(limit)
          .expectSubscription()
          .thenRequest(15)
          .expectNext(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
          .expectNext(11, 12, 13, 14, 15)
          .thenRequest(10)
          .expectNext(16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
          .verifyComplete();
    }

    @Test
    public void whenRequestingChunks10_thenMessagesAreReceived() {
        Flux<Integer> request = Flux.range(1, 50);

        request.subscribe(
          System.out::println,
          err -> err.printStackTrace(),
          () -> System.out.println("All 50 items have been successfully processed!!!"),
          subscription -> {
              for (int i = 0; i < 5; i++) {
                  System.out.println("Requesting the next 10 elements!!!");
                  subscription.request(10);
              }
          }
        );

        StepVerifier.create(request)
          .expectSubscription()
          .thenRequest(10)
          .expectNext(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
          .thenRequest(10)
          .expectNext(11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
          .thenRequest(10)
          .expectNext(21, 22, 23, 24, 25, 26, 27 , 28, 29 ,30)
          .thenRequest(10)
          .expectNext(31, 32, 33, 34, 35, 36, 37 , 38, 39 ,40)
          .thenRequest(10)
          .expectNext(41, 42, 43, 44, 45, 46, 47 , 48, 49 ,50)
          .verifyComplete();
    }

    @Test
    public void whenCancel_thenSubscriptionFinished() {
        Flux<Integer> cancel = Flux.range(1, 10).log();

        cancel.subscribe(new BaseSubscriber<Integer>() {
            @Override
            protected void hookOnNext(Integer value) {
                request(3);
                System.out.println(value);
                cancel();
            }
        });

        StepVerifier.create(cancel)
          .expectNext(1, 2, 3)
          .thenCancel()
          .verify();
    }
}