/*
 * Copyright (c) 2016-present, RxJava Contributors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
 * the License for the specific language governing permissions and limitations under the License.
 */

package io.reactivex.rxjava4.internal.operators.maybe;

import static org.junit.Assert.*;
import static org.mockito.ArgumentMatchers.any;
import static org.mockito.Mockito.*;

import java.util.List;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicInteger;

import org.junit.Test;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.stubbing.Answer;

import io.reactivex.rxjava4.core.*;
import io.reactivex.rxjava4.disposables.Disposable;
import io.reactivex.rxjava4.functions.Supplier;
import io.reactivex.rxjava4.observers.TestObserver;
import io.reactivex.rxjava4.plugins.RxJavaPlugins;
import io.reactivex.rxjava4.schedulers.Schedulers;
import io.reactivex.rxjava4.testsupport.TestHelper;

public class MaybeFromSupplierTest extends RxJavaTest {

    @Test
    public void fromSupplier() {
        final AtomicInteger atomicInteger = new AtomicInteger();

        Maybe.fromSupplier(new Supplier<Object>() {
            @Override
            public Object get() throws Exception {
                atomicInteger.incrementAndGet();
                return null;
            }
        })
            .test()
            .assertResult();

        assertEquals(1, atomicInteger.get());
    }

    @Test
    public void fromSupplierTwice() {
        final AtomicInteger atomicInteger = new AtomicInteger();

        Supplier<Object> supplier = new Supplier<Object>() {
            @Override
            public Object get() throws Exception {
                atomicInteger.incrementAndGet();
                return null;
            }
        };

        Maybe.fromSupplier(supplier)
            .test()
            .assertResult();

        assertEquals(1, atomicInteger.get());

        Maybe.fromSupplier(supplier)
            .test()
            .assertResult();

        assertEquals(2, atomicInteger.get());
    }

    @Test
    public void fromSupplierInvokesLazy() {
        final AtomicInteger atomicInteger = new AtomicInteger();

        Maybe<Object> completable = Maybe.fromSupplier(new Supplier<Object>() {
            @Override
            public Object get() throws Exception {
                atomicInteger.incrementAndGet();
                return null;
            }
        });

        assertEquals(0, atomicInteger.get());

        completable
            .test()
            .assertResult();

        assertEquals(1, atomicInteger.get());
    }

    @Test
    public void fromSupplierThrows() {
        Maybe.fromSupplier(new Supplier<Object>() {
            @Override
            public Object get() throws Exception {
                throw new UnsupportedOperationException();
            }
        })
            .test()
            .assertFailure(UnsupportedOperationException.class);
    }

    @SuppressWarnings("unchecked")
    @Test
    public void supplier() throws Throwable {
        final int[] counter = { 0 };

        Maybe<Integer> m = Maybe.fromSupplier(new Supplier<Integer>() {
            @Override
            public Integer get() throws Exception {
                counter[0]++;
                return 0;
            }
        });

        assertTrue(m.getClass().toString(), m instanceof Supplier);

        assertEquals(0, ((Supplier<Void>)m).get());

        assertEquals(1, counter[0]);
    }

    @Test
    public void noErrorLoss() throws Exception {
        List<Throwable> errors = TestHelper.trackPluginErrors();
        try {
            final CountDownLatch cdl1 = new CountDownLatch(1);
            final CountDownLatch cdl2 = new CountDownLatch(1);

            TestObserver<Integer> to = Maybe.fromSupplier(new Supplier<Integer>() {
                @Override
                public Integer get() throws Exception {
                    cdl1.countDown();
                    cdl2.await(5, TimeUnit.SECONDS);
                    return 1;
                }
            }).subscribeOn(Schedulers.single()).test();

            assertTrue(cdl1.await(5, TimeUnit.SECONDS));

            to.dispose();

            int timeout = 10;

            while (timeout-- > 0 && errors.isEmpty()) {
                Thread.sleep(100);
            }

            TestHelper.assertUndeliverable(errors, 0, InterruptedException.class);
        } finally {
            RxJavaPlugins.reset();
        }
    }

    @SuppressWarnings("unchecked")
    @Test
    public void shouldNotDeliverResultIfSubscriberUnsubscribedBeforeEmission() throws Throwable {
        Supplier<String> func = mock(Supplier.class);

        final CountDownLatch funcLatch = new CountDownLatch(1);
        final CountDownLatch observerLatch = new CountDownLatch(1);

        when(func.get()).thenAnswer(new Answer<String>() {
            @Override
            public String answer(InvocationOnMock invocation) throws Throwable {
                observerLatch.countDown();

                try {
                    funcLatch.await();
                } catch (InterruptedException e) {
                    // It's okay, unsubscription causes Thread interruption

                    // Restoring interruption status of the Thread
                    Thread.currentThread().interrupt();
                }

                return "should_not_be_delivered";
            }
        });

        Maybe<String> fromSupplierObservable = Maybe.fromSupplier(func);

        Observer<Object> observer = TestHelper.mockObserver();

        TestObserver<String> outer = new TestObserver<>(observer);

        fromSupplierObservable
                .subscribeOn(Schedulers.computation())
                .subscribe(outer);

        // Wait until func will be invoked
        observerLatch.await();

        // Unsubscribing before emission
        outer.dispose();

        // Emitting result
        funcLatch.countDown();

        // func must be invoked
        verify(func).get();

        // Observer must not be notified at all
        verify(observer).onSubscribe(any(Disposable.class));
        verifyNoMoreInteractions(observer);
    }

    @Test
    public void success() {
        Maybe.fromSupplier(() -> 1)
        .test()
        .assertResult(1);
    }

    @Test
    public void disposeUpfront() throws Throwable {
        @SuppressWarnings("unchecked")
        Supplier<Integer> supplier = mock(Supplier.class);

        Maybe.fromSupplier(supplier)
        .test(true)
        .assertEmpty();

        verify(supplier, never()).get();
    }
}
