import { renderHook } from '@testing-library/react-native'
import { FlatList, LayoutChangeEvent, NativeScrollEvent, NativeSyntheticEvent } from 'react-native'
import { useRestAwayFromDismissEdge } from '../../hooks/use_rest_away_from_dismiss_edge'

const VIEWPORT_HEIGHT = 800
const LIST_WIDTH = 390

const layoutEvent = (height: number) =>
  ({ nativeEvent: { layout: { x: 0, y: 0, width: LIST_WIDTH, height } } }) as LayoutChangeEvent

const settledEvent = (y: number) =>
  ({ nativeEvent: { contentOffset: { x: 0, y } } }) as NativeSyntheticEvent<NativeScrollEvent>

const renderEnabledHook = () => {
  const scrollToOffset = jest.fn()
  const listRef = { current: { scrollToOffset } as unknown as FlatList }
  const { result } = renderHook(() => useRestAwayFromDismissEdge({ listRef, enabled: true }))
  return { scrollToOffset, handlers: result.current }
}

describe('useRestAwayFromDismissEdge', () => {
  test('leaves a list that fits in its viewport alone', () => {
    const { scrollToOffset, handlers } = renderEnabledHook()

    handlers.onLayout(layoutEvent(VIEWPORT_HEIGHT))
    handlers.onContentSizeChange(LIST_WIDTH, VIEWPORT_HEIGHT / 2)
    handlers.onMomentumScrollEnd(settledEvent(0))
    handlers.onScrollEndDrag(settledEvent(0))

    expect(scrollToOffset).not.toHaveBeenCalled()
  })

  test('leaves a list with less than 1pt of overflow alone', () => {
    const { scrollToOffset, handlers } = renderEnabledHook()

    handlers.onLayout(layoutEvent(VIEWPORT_HEIGHT))
    handlers.onContentSizeChange(LIST_WIDTH, VIEWPORT_HEIGHT + 0.5)
    handlers.onMomentumScrollEnd(settledEvent(0.333))

    expect(scrollToOffset).not.toHaveBeenCalled()
  })

  test('rests a scrollable list 1pt off the dismiss edge on open and after it settles there', () => {
    const { scrollToOffset, handlers } = renderEnabledHook()

    handlers.onLayout(layoutEvent(VIEWPORT_HEIGHT))
    handlers.onContentSizeChange(LIST_WIDTH, VIEWPORT_HEIGHT * 2)
    expect(scrollToOffset).toHaveBeenCalledTimes(1)
    expect(scrollToOffset).toHaveBeenCalledWith({ animated: false, offset: 1 })

    handlers.onMomentumScrollEnd(settledEvent(0))
    expect(scrollToOffset).toHaveBeenCalledTimes(2)

    handlers.onMomentumScrollEnd(settledEvent(1))
    handlers.onMomentumScrollEnd(settledEvent(-20))
    expect(scrollToOffset).toHaveBeenCalledTimes(2)
  })

  test('applies the initial offset once a short list grows past its viewport', () => {
    const { scrollToOffset, handlers } = renderEnabledHook()

    handlers.onLayout(layoutEvent(VIEWPORT_HEIGHT))
    handlers.onContentSizeChange(LIST_WIDTH, VIEWPORT_HEIGHT / 2)
    expect(scrollToOffset).not.toHaveBeenCalled()

    handlers.onContentSizeChange(LIST_WIDTH, VIEWPORT_HEIGHT * 2)
    handlers.onContentSizeChange(LIST_WIDTH, VIEWPORT_HEIGHT * 3)
    expect(scrollToOffset).toHaveBeenCalledTimes(1)
  })
})