import { act, render } from '@testing-library/react'

import LoadMoreTrigger from '@/components/home/LoadMoreTrigger'

type ObserverCallback = IntersectionObserverCallback

class IntersectionObserverMock {
  static instances: IntersectionObserverMock[] = []

  callback: ObserverCallback
  observe = jest.fn()
  disconnect = jest.fn()
  unobserve = jest.fn()
  takeRecords = jest.fn(() => [])
  root = null
  rootMargin = ''
  thresholds = [0]

  constructor(callback: ObserverCallback) {
    this.callback = callback
    IntersectionObserverMock.instances.push(this)
  }

  trigger(isIntersecting: boolean) {
    this.callback([{ isIntersecting } as IntersectionObserverEntry], this as unknown as IntersectionObserver)
  }
}

describe('LoadMoreTrigger', () => {
  beforeEach(() => {
    IntersectionObserverMock.instances = []
    window.IntersectionObserver = IntersectionObserverMock as unknown as typeof IntersectionObserver
  })

  test('筛选刷新期间不启动懒加载，刷新结束后恢复观察', () => {
    const onLoadMore = jest.fn()
    const { rerender } = render(
      <LoadMoreTrigger
        hasMore
        isLoading={false}
        disabled
        onLoadMore={onLoadMore}
      />,
    )

    expect(IntersectionObserverMock.instances).toHaveLength(0)

    rerender(
      <LoadMoreTrigger
        hasMore
        isLoading={false}
        disabled={false}
        onLoadMore={onLoadMore}
      />,
    )

    expect(IntersectionObserverMock.instances).toHaveLength(1)
    act(() => IntersectionObserverMock.instances[0].trigger(true))
    expect(onLoadMore).toHaveBeenCalledTimes(1)
  })

  test('筛选刷新开始时断开已有的懒加载观察器', () => {
    const onLoadMore = jest.fn()
    const { rerender } = render(
      <LoadMoreTrigger
        hasMore
        isLoading={false}
        onLoadMore={onLoadMore}
      />,
    )
    const observer = IntersectionObserverMock.instances[0]

    rerender(
      <LoadMoreTrigger
        hasMore
        isLoading={false}
        disabled
        onLoadMore={onLoadMore}
      />,
    )

    expect(observer.disconnect).toHaveBeenCalledTimes(1)
  })
})