text: import React from 'react'
  import Fade from 'material-ui/transitions/Fade'
  import { withStyles } from 'material-ui/styles'
  import { CircularProgress } from 'material-ui/Progress'
  import PropTypes from 'prop-types'
  
  const styles = theme => ({
      root: {
        display: 'flex',
        flexDirection: 'column',
        alignItems: 'center',
      },
      button: {
        margin: theme.spacing.unit * 2,
      },
      placeholder: {
        height: 40,
      },
  });
  
  const Loader = (props) => {
      return (
          <div className={props.classes.placeholder}>
            <Fade in={props.loading}
              style={{ transitionDelay: props.loading ? '800ms' : '0ms' }} unmountOnExit>
              <CircularProgress />
            </Fade>
          </div>
      )
  }
  
  Loader.propTypes = {
      classes: PropTypes.object.isRequired,
      loading: PropTypes.bool.isRequired
  }
  
  export default withStyles(styles)(Loader)