import { describe, expect, it } from 'vitest'
import { scrollRatio, scrollTopForRatio } from '../src/scrollsync'

describe('scrollsync', () => {
  it('没有溢出时不同步', () => {
    expect(scrollRatio({ scrollTop: 0, scrollHeight: 100, clientHeight: 100 })).toBeNull()
    expect(scrollTopForRatio({ scrollHeight: 80, clientHeight: 80 }, 0.5)).toBeNull()
  })

  it('按可滚动范围的比例映射，并夹在 0 到 1', () => {
    expect(scrollRatio({ scrollTop: 50, scrollHeight: 200, clientHeight: 100 })).toBe(0.5)
    expect(scrollTopForRatio({ scrollHeight: 300, clientHeight: 100 }, 0.5)).toBe(100)
    expect(scrollTopForRatio({ scrollHeight: 300, clientHeight: 100 }, 2)).toBe(200)
    expect(scrollTopForRatio({ scrollHeight: 300, clientHeight: 100 }, -1)).toBe(0)
  })
})