stacker.news/components/snow.js

import React, { useCallback, useContext, useState } from 'react'
import { randInRange } from '@/lib/rand'

export const SnowContext = React.createContext(() => {})

// maximum amount of flakes that can get rendered at the same time
const MAX_FLAKES = 1024

export const SnowProvider = ({ children }) => {
  const [startIndex, setStartIndex] = useState(0)
  const [flakes, setFlakes] = useState(Array(1024))

  const snow = useCallback(() => {
    const should = window.localStorage.getItem('lnAnimate') || 'yes'
    if (should === 'yes') {
      // amount of flakes to add
      const n = Math.floor(randInRange(5, 30))
      const newFlakes = [...flakes]
      let i
      for (i = startIndex; i < (startIndex + n); ++i) {
        const key = startIndex + i
        newFlakes[i % MAX_FLAKES] = <Snow key={key} />
      }
      setStartIndex(i % MAX_FLAKES)
      setFlakes(newFlakes)
      return true
    }
    return false
  }, [setFlakes, startIndex])

  return (
    <SnowContext.Provider value={snow}>
      {flakes}
      {children}
    </SnowContext.Provider>
  )
}

function Snow () {
  return <div className='snow' />
}

export const SnowConsumer = SnowContext.Consumer

export function useSnow () {
  return useContext(SnowContext)
}