react/components/button/button.drip.tsx

import React, { useEffect, useRef } from 'react'
import withDefaults from '../utils/with-defaults'

interface Props {
  x: number
  y: number
  onCompleted: () => void
  color: string
}

const defaultProps = {
  x: 0,
  y: 0,
}

export type ButtonDrip = Props & typeof defaultProps

const ButtonDrip: React.FC<ButtonDrip> = ({ x, y, color, onCompleted }) => {
  const dripRef = useRef<HTMLDivElement>(null)
  /* istanbul ignore next */
  const top = Number.isNaN(+y) ? 0 : y - 10
  /* istanbul ignore next */
  const left = Number.isNaN(+x) ? 0 : x - 10

  useEffect(() => {
    /* istanbul ignore next */
    if (!dripRef.current) return
    dripRef.current.addEventListener('animationend', onCompleted)
    return () => {
      /* istanbul ignore next */
      if (!dripRef.current) return
      dripRef.current.removeEventListener('animationend', onCompleted)
    }
  })

  return (
    <div ref={dripRef} className="drip">
      <svg width="20" height="20" viewBox="0 0 20 20" style={{ top, left }}>
        <g stroke="none" strokeWidth="1" fill="none" fillRule="evenodd">
          <g fill={color}>
            <rect width="100%" height="100%" rx="10" />
          </g>
        </g>
      </svg>

      <style jsx>{`
        .drip {
          position: absolute;
          left: 0;
          right: 0;
          top: 0;
          bottom: 0;
        }

        svg {
          position: absolute;
          animation: 400ms ease-in expand;
          animation-fill-mode: forwards;
          width: 20px;
          height: 20px;
        }

        @keyframes expand {
          0% {
            opacity: 0;
            transform: scale(1);
          }
          30% {
            opacity: 1;
          }
          80% {
            opacity: 0.5;
          }
          100% {
            transform: scale(25);
            opacity: 0;
          }
        }
      `}</style>
    </div>
  )
}

const MemoButtonDrip = React.memo<ButtonDrip>(ButtonDrip)

export default withDefaults(MemoButtonDrip, defaultProps)