puyopuyotetr.is/app/javascript/mastodon/features/status/components/card.js

import React from 'react';
import ImmutablePropTypes from 'react-immutable-proptypes';

const hostStyle = {
  display: 'block',
  marginTop: '5px',
  fontSize: '13px'
};

const getHostname = url => {
  const parser = document.createElement('a');
  parser.href = url;
  return parser.hostname;
};

class Card extends React.PureComponent {

  renderLink () {
    const { card } = this.props;

    let image    = '';
    let provider = card.get('provider_name');

    if (card.get('image')) {
      image = (
        <div className='status-card__image'>
          <img src={card.get('image')} alt={card.get('title')} className='status-card__image-image' />
        </div>
      );
    }

    if (provider.length < 1) {
      provider = getHostname(card.get('url'))
    }

    return (
      <a href={card.get('url')} className='status-card' target='_blank' rel='noopener'>
        {image}

        <div className='status-card__content'>
          <strong className='status-card__title' title={card.get('title')}>{card.get('title')}</strong>
          <p className='status-card__description'>{(card.get('description') || '').substring(0, 50)}</p>
          <span className='status-card__host' style={hostStyle}>{provider}</span>
        </div>
      </a>
    );
  }

  renderPhoto () {
    const { card } = this.props;

    return (
      <a href={card.get('url')} className='status-card-photo' target='_blank' rel='noopener'>
        <img src={card.get('url')} alt={card.get('title')} width={card.get('width')} height={card.get('height')} />
      </a>
    );
  }

  renderVideo () {
    const { card } = this.props;
    const content  = { __html: card.get('html') };

    return (
      <div
        className='status-card-video'
        dangerouslySetInnerHTML={content}
      />
    );
  }

  render () {
    const { card } = this.props;

    if (card === null) {
      return null;
    }

    switch(card.get('type')) {
    case 'link':
      return this.renderLink();
    case 'photo':
      return this.renderPhoto();
    case 'video':
      return this.renderVideo();
    case 'rich':
    default:
      return null;
    }
  }
}

Card.propTypes = {
  card: ImmutablePropTypes.map
};

export default Card;