export const TAB_DRAG_MIME = 'application/x-farmcontrol-tab'
export const TAB_DRAG_TEXT_PREFIX = 'farmcontrol-tab:'

export const hasExternalTabDrag = (event) => {
  const types = event?.dataTransfer?.types
  if (!types) return false
  const list = Array.from(types)
  return (
    list.includes(TAB_DRAG_MIME) ||
    list.includes('text/plain') ||
    list.includes('text/uri-list')
  )
}

export const writeTabDragData = (event, payload) => {
  const serialized = JSON.stringify(payload)
  try {
    event.dataTransfer.setData(TAB_DRAG_MIME, serialized)
  } catch {
    // Some engines only allow text/plain during dragstart.
  }
  event.dataTransfer.setData('text/plain', `${TAB_DRAG_TEXT_PREFIX}${serialized}`)
}

export const readTabDragData = (event) => {
  const transfer = event?.dataTransfer
  if (!transfer) return null

  const custom = (() => {
    try {
      return transfer.getData(TAB_DRAG_MIME)
    } catch {
      return ''
    }
  })()
  const plain = (() => {
    try {
      return transfer.getData('text/plain')
    } catch {
      return ''
    }
  })()

  const raw = custom
    ? custom
    : plain.startsWith(TAB_DRAG_TEXT_PREFIX)
      ? plain.slice(TAB_DRAG_TEXT_PREFIX.length)
      : ''

  if (!raw) return null

  try {
    const parsed = JSON.parse(raw)
    if (!parsed?.tab?.id) return null
    return parsed
  } catch {
    return null
  }
}