Filter a list of invalid image urls using coroutines and Glide

MultiGlide.kt

/**
 * From the given list of urls, returns a list of urls that were successfully downloaded by Glide
 * and cached.
 *
 * @param imageUrls List of image urls.
 * @return 
 */
suspend fun Activity.tryImageUrls(imageUrls: List<String>): List<String> {
    return imageUrls.map {
        try {
            tryImageUrl(this, it)
        } catch (e: Exception) {
            null
        }
    }.mapNotNull { it }
}

private suspend fun tryImageUrl(activity: Activity, imageUrl: String): String {
    val response = CompletableDeferred<String>()
    Glide.with(activity)
            .asBitmap()
            .load(imageUrl)
            .diskCacheStrategy(DiskCacheStrategy.ALL)
            .into(object : CustomTarget<Bitmap>() {
                override fun onResourceReady(resource: Bitmap, transition: Transition<in Bitmap>?) {
                    response.complete(imageUrl)
                }

                override fun onLoadCleared(placeholder: Drawable?) {

                }

                override fun onLoadFailed(errorDrawable: Drawable?) {
                    super.onLoadFailed(errorDrawable)
                    response.completeExceptionally(Exception("Url failed."))
                }
            })
    return response.await()
}