/** copy code block to clipboard
 * @todo better transition animate
 * @todo remove dummy code
 * @todo typecheck
 */
export const copyCode = () => {
  const codeBlocks = document.querySelectorAll('pre')
  const copyText = 'Copy'
  const copiedText = 'Copied!'

  //copy funciton
  const copy = async (el: HTMLElement, btn: HTMLElement) => {
    //select code
    const range = document.createRange()
    const end = el.childNodes.length
    range.setStart(el, 2)
    range.setEnd(el, end)
    const selection = window.getSelection()
    if (!selection) return
    selection.removeAllRanges()
    selection.addRange(range)

    // copy to clipboard
    document.execCommand('copy', false)
    const clip = async () => navigator.clipboard.writeText(selection.toString())

    if (!clip) return
    btn.textContent = copiedText
    setTimeout(() => {
      btn.textContent = copyText
    }, 1000)
    selection.removeRange(range)
  }

  codeBlocks.forEach((block: HTMLElement) => {
    // add copy button
    const copyBtn: HTMLElement = document.createElement('button')
    copyBtn.textContent = copyText
    copyBtn.classList.add('btn', 'btn-secondary', 'btn-xs', 'absolute', 'right-2', 'top-3', 'hidden')
    block.prepend(copyBtn)

    block.addEventListener('mouseenter', () => {
      copyBtn.classList.remove('hidden')
    })

    block.addEventListener('mouseleave', () => {
      copyBtn.classList.add('hidden')
    })

    copyBtn.addEventListener('click', e => {
      e.preventDefault()
      copy(block, copyBtn)
    })
  })
}