const loaded: { [key: string]: Promise<void> } = {}

function loadScript(url) {
  if (!loaded[url]) {
    loaded[url] = new Promise((resolve, reject) => {

      const script = document.createElement('script')
      script.onload = () => resolve()
      script.onerror = reject
      script.src = url

      document.head.appendChild(script)
    })
  }
  return loaded[url]
}

type Message = any

interface IProfile {
  userId: string
  displayName: string
  pictureUrl: string
  statusMessage: string
}

export interface ILiff {
  init(
    config: { liffId: string },
    successCallback?: () => void,
    errorCallback?: () => void,
  )
  getOS (): string
  getLanguage (): string
  getVersion(): string
  isInClient(): boolean

  // plugins
  initPlugins(pluginList: string[]): Promise<void>

  // authentication
  isLoggedIn(): boolean
  login(
    loginConfig?: {
      redirectUri?: string
    }
  )
  logout()
  getAccessToken(): string

  // profile
  getProfile(): Promise<IProfile>
  sendMessages(messages: Message[])

  // utils
  openWindow(params: {
    url: string,
    external?: boolean
  })
  scanCode(): string
  closeWindow()
}

export async function initLIFF(liffId): Promise<ILiff> {
  await loadScript('https://static.line-scdn.net/liff/edge/2.1/sdk.js')
  const liff: ILiff = (window as any).liff
  await new Promise((resolve, _) => {
    liff.init({ liffId }, resolve)
  })
  return liff
}