package com.iluwatar.event.aggregator;

import org.junit.Test;

import java.util.Objects;
import java.util.function.Function;
import java.util.function.Supplier;

import static org.mockito.Matchers.eq;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.times;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.verifyZeroInteractions;
import static org.mockito.Mockito.verifyNoMoreInteractions;

/**
 * Date: 12/12/15 - 10:58 PM
 *
 * @author Jeroen Meulemeester
 */
public abstract class EventEmitterTest<E extends EventEmitter> {

  /**
   * Factory used to create a new instance of the test object with a default observer
   */
  private final Function<EventObserver, E> factoryWithDefaultObserver;

  /**
   * Factory used to create a new instance of the test object without passing a default observer
   */
  private final Supplier<E> factoryWithoutDefaultObserver;

  /**
   * The day of the week an event is expected
   */
  private final Weekday specialDay;

  /**
   * The expected event, emitted on the special day
   */
  private final Event event;

  /**
   * Create a new event emitter test, using the given test object factories, special day and event
   */
  EventEmitterTest(final Weekday specialDay, final Event event,
                   final Function<EventObserver, E> factoryWithDefaultObserver,
                   final Supplier<E> factoryWithoutDefaultObserver) {

    this.specialDay = specialDay;
    this.event = event;
    this.factoryWithDefaultObserver = Objects.requireNonNull(factoryWithDefaultObserver);
    this.factoryWithoutDefaultObserver = Objects.requireNonNull(factoryWithoutDefaultObserver);
  }

  /**
   * Go over every day of the month, and check if the event is emitted on the given day. This test
   * is executed twice, once without a default emitter and once with
   */
  @Test
  public void testAllDays() {
    testAllDaysWithoutDefaultObserver(specialDay, event);
    testAllDaysWithDefaultObserver(specialDay, event);
  }

  /**
   * Pass each week of the day, day by day to the event emitter and verify of the given observers
   * received the correct event on the special day.
   *
   * @param specialDay The special day on which an event is emitted
   * @param event      The expected event emitted by the test object
   * @param emitter    The event emitter
   * @param observers  The registered observer mocks
   */
  private void testAllDays(final Weekday specialDay, final Event event, final E emitter,
                           final EventObserver... observers) {

    for (final Weekday weekday : Weekday.values()) {
      // Pass each week of the day, day by day to the event emitter
      emitter.timePasses(weekday);

      if (weekday == specialDay) {
        // On a special day, every observer should have received the event
        for (final EventObserver observer : observers) {
          verify(observer, times(1)).onEvent(eq(event));
        }
      } else {
        // On any other normal day, the observers should have received nothing at all
        verifyZeroInteractions(observers);
      }
    }

    // The observers should not have received any additional events after the week
    verifyNoMoreInteractions(observers);
  }
  
  /**
   * Go over every day of the month, and check if the event is emitted on the given day. Use an
   * event emitter without a default observer
   *
   * @param specialDay The special day on which an event is emitted
   * @param event      The expected event emitted by the test object
   */
  private void testAllDaysWithoutDefaultObserver(final Weekday specialDay, final Event event) {
    final EventObserver observer1 = mock(EventObserver.class);
    final EventObserver observer2 = mock(EventObserver.class);

    final E emitter = this.factoryWithoutDefaultObserver.get();
    emitter.registerObserver(observer1);
    emitter.registerObserver(observer2);

    testAllDays(specialDay, event, emitter, observer1, observer2);
  }

  /**
   * Go over every day of the month, and check if the event is emitted on the given day.
   *
   * @param specialDay The special day on which an event is emitted
   * @param event      The expected event emitted by the test object
   */
  private void testAllDaysWithDefaultObserver(final Weekday specialDay, final Event event) {
    final EventObserver defaultObserver = mock(EventObserver.class);
    final EventObserver observer1 = mock(EventObserver.class);
    final EventObserver observer2 = mock(EventObserver.class);

    final E emitter = this.factoryWithDefaultObserver.apply(defaultObserver);
    emitter.registerObserver(observer1);
    emitter.registerObserver(observer2);

    testAllDays(specialDay, event, emitter, defaultObserver, observer1, observer2);
  }

}
