byGalax
58 lines
1.8 KiB
TypeScript
58 lines
1.8 KiB
TypeScript
import { describe, expect, it } from 'vitest';
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import { isNearBottom, isNearTop, resolveInitialAnchor } from './scrollController';
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const m = (scrollTop: number, scrollHeight: number, clientHeight: number) => ({
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scrollTop,
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scrollHeight,
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clientHeight,
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});
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describe('isNearBottom', () => {
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it('true exactly at the bottom', () => {
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expect(isNearBottom(m(900, 1000, 100), 64)).toBe(true);
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});
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it('true within threshold', () => {
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expect(isNearBottom(m(860, 1000, 100), 64)).toBe(true);
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});
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it('false beyond threshold', () => {
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expect(isNearBottom(m(800, 1000, 100), 64)).toBe(false);
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});
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});
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describe('isNearTop', () => {
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it('true at top', () => {
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expect(isNearTop(m(0, 1000, 100), 64)).toBe(true);
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});
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it('false past threshold', () => {
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expect(isNearTop(m(200, 1000, 100), 64)).toBe(false);
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});
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});
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describe('resolveInitialAnchor', () => {
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it('anchors to last row at end by default (no saved position)', () => {
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expect(resolveInitialAnchor(null, 50)).toEqual({ index: 49, align: 'end' });
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});
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it('anchors to bottom when saved position stuck to bottom', () => {
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expect(resolveInitialAnchor({ topmostIndex: 10, stickToBottom: true }, 50)).toEqual({
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index: 49,
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align: 'end',
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});
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});
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it('restores the saved row at the top when scrolled up', () => {
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expect(resolveInitialAnchor({ topmostIndex: 12, stickToBottom: false }, 50)).toEqual({
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index: 12,
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align: 'start',
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});
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});
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it('clamps a stale saved index to the current row count', () => {
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expect(resolveInitialAnchor({ topmostIndex: 999, stickToBottom: false }, 50)).toEqual({
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index: 49,
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align: 'start',
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});
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});
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it('handles an empty list', () => {
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expect(resolveInitialAnchor(null, 0)).toEqual({ index: 0, align: 'end' });
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});
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});
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