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import React, { useRef, useEffect } from 'react'
import { Canvas, useFrame } from 'react-three-fiber'
import create from 'zustand'
import { Controls, useControl } from 'react-three-gui'

const rpi = () => Math.random() * Math.PI
const [useStore, api] = create(set => ({
  amount: 0,
  boxes: [],
  coords: [],
  create(amount) {
    const ids = new Array(parseInt(amount)).fill().map((_, i) => i)
    set({
      amount,
      boxes: ids,
      coords: ids.reduce((acc, id) => ({ ...acc, [id]: [rpi(), rpi(), rpi()] }), 0),
    })
  },
  advance(state) {
    set(state => {
      const coords = {}
      for (let i = 0; i < state.boxes.length; i++) {
        const id = state.boxes[i]
        const [x, y, z] = state.coords[id]
        coords[id] = [x + 0.01, y + 0.01, z + 0.01]
      }
      return { ...state, coords }
    })
  },
}))

function ItemSlow({ id }) {
  const coords = useStore(state => state.coords[id])
  if (!coords) return null
  return (
    <mesh rotation={coords}>
      <boxBufferGeometry args={[2, 2, 2]} attach="geometry" />
      <meshNormalMaterial attach="material" />
    </mesh>
  )
}

function ItemFast({ id }) {
  const mesh = useRef()
  const coords = useRef([0, 0, 0])
  useEffect(() =>
    api.subscribe(
      xyz => (coords.current = xyz),
      state => state.coords[id]
    )
  )
  useFrame(() => mesh.current && mesh.current.rotation.set(...coords.current))
  return (
    <mesh ref={mesh}>
      <boxBufferGeometry args={[2, 2, 2]} attach="geometry" />
      <meshNormalMaterial attach="material" />
    </mesh>
  )
}

export default function App() {
  const ref = useRef()
  const boxes = useStore(state => state.boxes)
  const amount = useControl('Amount️', { type: 'select', items: [20, 100, 200, 500, 1000, 2000] })
  const root = useControl('React', {
    type: 'select',
    group: 'performance',
    items: ['legacy (slow)', 'concurrent (fast)'],
  })
  const flux = useControl('Zustand', {
    type: 'select',
    group: 'performance',
    items: ['reactive (slow)', 'transient (fast)'],
  })
  const concurrent = root === 'concurrent (fast)'
  const transient = flux === 'transient (fast)'
  const Component = transient ? ItemFast : ItemSlow

  useEffect(() => {
    let frame = undefined
    api.getState().create(amount)
    let lastCalledTime = Date.now()
    let fps = 0
    function renderLoop() {
      let delta = (Date.now() - lastCalledTime) / 1000
      lastCalledTime = Date.now()
      fps = 1 / delta
      ref.current.innerText = 'fps ' + fps.toFixed()
      // Change state every frame
      api.getState().advance()
      frame = requestAnimationFrame(renderLoop)
    }
    renderLoop()
    return () => cancelAnimationFrame(frame)
  }, [amount, concurrent, transient])

  return (
    <div style={{ background: transient || concurrent ? '#272737' : 'indianred', width: '100%', height: '100%' }}>
      <Canvas concurrent={concurrent} key={amount + root + flux}>
        {boxes.map(id => (
          <Component key={id} id={id} />
        ))}
      </Canvas>
      <div ref={ref} style={{ position: 'absolute', bottom: 350, right: 50, color: 'white' }} />
      <Description amount={amount} concurrent={concurrent} transient={transient} />
      <Controls />
    </div>
  )
}

function Description({ amount, transient, concurrent }) {
  const mode = concurrent ? 'Concurrent' : 'Legacy'
  const flux = transient ? 'Transient' : 'Reactive'
  return (
    <div style={{ position: 'absolute', bottom: 100, right: 50, color: 'white', maxWidth: 600 }}>
      <span>
        {amount} connected components update <b>{transient ? 'transiently' : 'reactively'}</b> 60 times/second in{' '}
        <b>{concurrent ? 'concurrent' : 'legacy'} mode</b>
      </span>
      <hr />
      <span>
        <b>{mode} mode</b>{' '}
        {concurrent
          ? 'means that React renders asynchroneously. It will now batch updates and schedule render passes. If you give it an impossible amount of load, so many render requests that it must choke, it will start to manage these requests to establish a stable 60/fps, by updating components virtually and letting them retain their visual state, using back buffers, etc.'
          : 'means that React renders synchroneously. This is how frameworks usually fare, despite micro-optimizations and good benchmarks. The renderer will eventually crumble under load, which in the web is easy, given that we only have more or less 20ms per frame on the javascript mainthread before we face jank.'}
      </span>
      <p>
        <b>{flux} updates</b>{' '}
        {transient
          ? 'means that the state manager informs components of changes without re-rendering them. This is a Zustand feature, a Redux-like flux state manager.'
          : 'means that the state manager informs components of changes by re-rendering them with fresh props. This is how most state managers, like Redux, usually work.'}
      </p>
    </div>
  )
}