extension Array {
  // TODO: When withoutActuallyEscaping() supports async closures, use withoutActuallyEscaping
  // on the group.spawnUnlessCancelled() closure, and then to remove the unnecessary @escaping decoration.
  func asyncMap<B>(_ transform: @escaping (Element) async throws -> B) async throws -> [B] {
    try await withThrowingTaskGroup(of: (Int, B).self) { group in
      for i in self.indices {
        _ = group.asyncUnlessCancelled {
          (i, try await transform(self[i]))
        }
      }
      var result = [B?](repeating: nil, count: count)
      while let (index, transformed) = try await group.next() {
        result[index] = transformed
      }
      return result.map { $0! }
    }
  }
}

func fetch(url: URL) async throws -> String {
  try await String(decoding: URLSession.shared.data(from:url).0, as: UTF8.self)
}

func scrapeHouseplants(url: URL) async throws -> HouseplantCategoryDictionary {
  return try reduceHouseplantInfos(
    infos: await scrapeListOfHouseplants(url: url, html: fetch(url: url))
      .asyncMap { ticket in
        (ticket.key, try scrapeHouseplantInfo(url: ticket.url,
                                              html:await fetch(url: ticket.url)))
      }
  )
}

func scrapeAsync() async {
  let url = URL(string:"https://en.wikipedia.org/wiki/Houseplant")!
  _ = try! await scrapeHouseplants(url:url)
}