import { TestBed } from '@angular/core/testing';
import { NgDropdownPanelService } from './ng-dropdown-panel.service';

describe('NgDropdownPanelService', () => {

    let service: NgDropdownPanelService;

    beforeEach(() => {
        TestBed.configureTestingModule({
            providers: [NgDropdownPanelService]
        });

        service = TestBed.inject(NgDropdownPanelService);
    });

    describe('calculate items', () => {
        it('should calculate items from start', () => {
            const itemsLength = 100;
            const buffer = 4;

            service.setDimensions(25, 100);
            const res = service.calculateItems(0, itemsLength, buffer);

            expect(res).toEqual({
                start: 0,
                end: 9,
                topPadding: 0,
                scrollHeight: 2500
            })
        });

        it('should calculate items when scrolled', () => {
            const itemsLength = 100;
            const buffer = 4;

            service.setDimensions(25, 100);
            const res = service.calculateItems(1250, itemsLength, buffer);

            expect(res).toEqual({
                start: 46,
                end: 59,
                topPadding: 1150,
                scrollHeight: 2500
            })
        });
    });

    describe('scroll to', () => {
        beforeEach(() => {
            service.setDimensions(40, 240);
        });

        it('should not scroll if item is in visible area', () => {
            expect(service.getScrollTo(0, 40, 0)).toBeNull();
            expect(service.getScrollTo(200, 40, 0)).toBeNull();
        });

        it('should not scroll if item is inside panel height', () => {
            expect(service.getScrollTo(40, 40, 40)).toBeNull();
        });

        it('should scroll by item height', () => {
            expect(service.getScrollTo(240, 40, 0)).toBe(40);
        });

        it('should start from top when reached bottom', () => {
            expect(service.getScrollTo(0, 40, 400)).toBe(0);
        });

        it('should move to bottom when reached top', () => {
            expect(service.getScrollTo(600, 40, 0)).toBe(400);
        });
    });
});