defmodule NLdoc.S3 do
  @moduledoc """
  Helper functions for S3.
  """

  @type response() :: {:ok, term()} | {:error, term()}

  @doc """
  Upload a specific file as a stream.
  """
  @spec stream_upload(
          path :: String.t(),
          bucket :: String.t(),
          key :: String.t(),
          opts :: ExAws.S3.upload_opts()
        ) :: {:ok, term()} | {:error, term()}
  def stream_upload(path, bucket, key, opts) do
    with stream = %File.Stream{} <- ExAws.S3.Upload.stream_file(path),
         operation = %ExAws.S3.Upload{} <- ExAws.S3.upload(stream, bucket, key, opts) do
      ExAws.request(operation)
    end
  end

  @doc """
  Download a specific file as a stream
  """
  @spec stream_download!(bucket :: String.t(), key :: String.t()) :: Enumerable.t()
  def stream_download!(bucket, key) do
    with download = %ExAws.S3.Download{} <- ExAws.S3.download_file(bucket, key, :memory) do
      ExAws.stream!(download)
    end
  end

  @doc """
  Head an object in a bucket.
  """
  @spec head_object(bucket :: String.t(), key :: String.t()) :: response()
  def head_object(bucket, key) do
    with operation = %ExAws.Operation.S3{} <- ExAws.S3.head_object(bucket, key) do
      ExAws.request(operation)
    end
  end

  @doc """
  Check if bucket exists. Create it if it does not.
  """
  @spec upsert_bucket(bucket :: String.t(), region :: String.t()) :: response()
  def upsert_bucket(bucket, region) do
    case bucket |> ExAws.S3.head_bucket() |> ExAws.request() do
      {:ok, _} = ok ->
        ok

      {:error, {:http_error, 404, _}} ->
        bucket
        |> ExAws.S3.put_bucket(region)
        |> ExAws.request()
        |> handle_put_bucket_conflicts()

      {:error, other} ->
        {:error, other}
    end
  end

  defp handle_put_bucket_conflicts(ok = {:ok, _}), do: ok

  # If the name is taken globally but owned by us, treat as success.
  defp handle_put_bucket_conflicts({:error, {:http_error, 409, _}}),
    do: {:ok, :exists}

  defp handle_put_bucket_conflicts(other),
    do: other
end