const shadowEl = document.querySelector('.shadow-host');
const shadow = shadowEl.attachShadow({mode: 'open'});

// 폴백 요소에 트위터 아이콘을 추가하여 새로 생성한 shadow DOM
const link = document.createElement('a');
link.href= shadowEl.querySelector('a').href;
link.innerHTML = `
  <span aria-label="Twitter icon"></span>
  ${shadowEl.querySelector('a').textContent}
`;

shadow.appendChild(link);

// 로컬 스타일 적용
const styles = document.createElement('style');
styles.textContent = `
a, span {
  vertical-align: top;
  display: inline-block;
  box-sizing: border-box;
}

a {
    height: 20px;
    padding: 1px 8px 1px 6px;
    background-color: #1b95e0;
    color: #fff;
    border-radius: 3px;
    font-weight: 500;
    font-size: 11px;
    font-family:'Helvetica Neue', Arial, sans-serif;
    line-height: 18px;
    text-decoration: none;   
}

a:hover {  background-color: #0c7abf; }

span {
    position: relative;
    top: 2px;
    width: 14px;
    height: 14px;
    margin-right: 3px;
    background: transparent 0 0 no-repeat;
    background-image: url(data:image/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20viewBox%3D%220%200%2072%2072%22%3E%3Cpath%20fill%3D%22none%22%20d%3D%22M0%200h72v72H0z%22%2F%3E%3Cpath%20class%3D%22icon%22%20fill%3D%22%23fff%22%20d%3D%22M68.812%2015.14c-2.348%201.04-4.87%201.744-7.52%202.06%202.704-1.62%204.78-4.186%205.757-7.243-2.53%201.5-5.33%202.592-8.314%203.176C56.35%2010.59%2052.948%209%2049.182%209c-7.23%200-13.092%205.86-13.092%2013.093%200%201.026.118%202.02.338%202.98C25.543%2024.527%2015.9%2019.318%209.44%2011.396c-1.125%201.936-1.77%204.184-1.77%206.58%200%204.543%202.312%208.552%205.824%2010.9-2.146-.07-4.165-.658-5.93-1.64-.002.056-.002.11-.002.163%200%206.345%204.513%2011.638%2010.504%2012.84-1.1.298-2.256.457-3.45.457-.845%200-1.666-.078-2.464-.23%201.667%205.2%206.5%208.985%2012.23%209.09-4.482%203.51-10.13%205.605-16.26%205.605-1.055%200-2.096-.06-3.122-.184%205.794%203.717%2012.676%205.882%2020.067%205.882%2024.083%200%2037.25-19.95%2037.25-37.25%200-.565-.013-1.133-.038-1.693%202.558-1.847%204.778-4.15%206.532-6.774z%22%2F%3E%3C%2Fsvg%3E);
}
`;

shadow.appendChild(styles);