import { Scroller } from '../src/scroller';
import { Descriptor } from '../src/descriptor';
import { ScrollDetector } from '../src/scroll-detector';
import { IElementsManager } from '../src/elements-manager';

describe('Scroller', function () {
    let scopeMock: jasmine.SpyObj<ng.IScope>;
    let scrollDetectorMock: jasmine.SpyObj<ScrollDetector>;
    let descriptorMock: Descriptor;

    beforeEach(function () {
        scrollDetectorMock = jasmine.createSpyObj<ScrollDetector>('scrollDetectorMock', ['SubscribeToElement']);
        scopeMock = jasmine.createSpyObj<ng.IScope>('scopeMock', ['$watchCollection', '$apply']);

        descriptorMock = {
            Scope: scopeMock as ng.IScope,
        } as Descriptor;
    });

    describe('watcher', function () {
        it('alerts element manager on collection change', function () {
            // Arrange
            let watchHandler;
            const elementsManagerMock = jasmine.createSpyObj<IElementsManager>('elementsManagerMock', ['UpdateCollection']);
            scopeMock.$watchCollection.and.callFake(function (_collection, callback) {
                watchHandler = callback;
            });

            const scroller = new Scroller(descriptorMock, scrollDetectorMock, elementsManagerMock);
            scroller.Subscribe();

            // Act
            watchHandler([1, 2, 3]);

            // Assert
            expect(elementsManagerMock.UpdateCollection).toHaveBeenCalledWith([1, 2, 3]);
        });
    });

    describe('on scrolling', function () {
        it('instruments element manager on scroll down', function () {
            // Arrange
            const elementsManagerMock = jasmine.createSpyObj<IElementsManager>('elementsManagerMock', ['AddBottom', 'RemoveTop', 'AddTop', 'RemoveBottom']);
            expect(new Scroller(descriptorMock, scrollDetectorMock, elementsManagerMock)).toBeDefined();
            scopeMock.$apply.and.callFake(callback => callback());

            // Act
            scrollDetectorMock.OnScrollDown();

            // Assert
            expect(scopeMock.$apply).toHaveBeenCalled();
            expect(elementsManagerMock.AddBottom).toHaveBeenCalled();
            expect(elementsManagerMock.RemoveTop).toHaveBeenCalled();
        });

        it('instruments element manager on scroll up', function () {
            // Arrange
            const elementsManagerMock = jasmine.createSpyObj<IElementsManager>('elementsManagerMock', ['AddBottom', 'RemoveTop', 'AddTop', 'RemoveBottom']);
            expect(new Scroller(descriptorMock, scrollDetectorMock, elementsManagerMock)).toBeDefined();
            scopeMock.$apply.and.callFake(callback => callback());

            // Act
            scrollDetectorMock.OnScrollUp();

            // Assert
            expect(scopeMock.$apply).toHaveBeenCalled();
            expect(elementsManagerMock.AddTop).toHaveBeenCalled();
            expect(elementsManagerMock.RemoveBottom).toHaveBeenCalled();
        });
    });

});