checkViaImgSrc.ts

// import { Log } from './Log'

// const log = new Log('checkViaImgSrc')

async function checkViaImgSrc (imgUrl: string | URL): Promise<void> {
  // we check if gateway is up by loading 1x1 px image:
  // this is more robust check than loading js, as it won't be blocked
  // by privacy protections present in modern browsers or in extensions such as Privacy Badger
  const imgCheckTimeout = 15000
  return await new Promise((resolve, reject) => {
    const img = new Image()
    const timer: ReturnType<typeof setTimeout> = setTimeout(() => {
      // clearTimeout(timer)
      reject(new Error(`Timeout when attempting to load img from '${img.src}`))
    }, imgCheckTimeout)
    // const timeout = () => {
    //   if (timer == null) {
    //     return false
    //   }
    //   clearTimeout(timer)
    //   // timer = null
    //   return true
    // }
    const onImageError: OnErrorEventHandler = (event, source, lineno, colno, error) => {
      clearTimeout(timer)

      if (error == null) {
        reject(new Error(`Unknown Error when attempting to load img from '${img.src}`))
      } else {
        reject(error)
      }
    }
    img.onerror = onImageError
    img.onload = () => {
      // subdomain works
      // timeout()
      clearTimeout(timer)
      resolve()
    }
    img.src = imgUrl.toString()
  })
}

export { checkViaImgSrc }