defmodule ExTus.Actions do
  import Plug.Conn
  alias ExTus.Utils
  alias ExTus.UploadInfo
  alias ExTus.UploadCache
  require Logger
 
  defp storage() do
    Application.get_env(:extus, :storage, ExTus.Storage.Local)
  end

  def options(conn)do
    conn
    |> handle_preflight_request
    |> put_resp_header("Tus-Resumable", ExTus.Config.tus_api_version)
    |> put_resp_header("Tus-Version", ExTus.Config.tus_api_version_supported)
    |> put_resp_header("Tus-Checksum-Algorithm", "sha1")
    |> put_resp_header("Tus-Max-Size", to_string(ExTus.Config.tus_max_file_size))
    |> put_resp_header("Tus-Extension", Enum.join(ExTus.Config.extensions, ","))
    |> resp(200, "")
  end

  def head(conn, identifier)do
    upload_info = UploadCache.get(identifier)
    if is_nil(upload_info) do
      conn
      |> Utils.set_base_resp
      |> resp(404, "")

    else
      upload_meta =
        %{
          size: upload_info.size,
          filename: upload_info.filename
        }

      upload_meta =
        upload_meta
        |> Enum.map(fn{k, v} ->  "#{k} #{Base.encode64(to_string(v))}" end)
        |> Enum.join(",")

      if not upload_meta in ["", nil] do
        put_resp_header(conn, "Upload-Metadata", upload_meta)
      else
        conn
      end
      |> Utils.set_base_resp
      |> Utils.put_cors_headers
      |> put_resp_header("Upload-Offset", "#{upload_info.offset}")
      |> put_resp_header("Upload-Length", "#{upload_info.size}")
      |> resp(200, "")
    end
  end

  def patch(conn, identifier, complete_cb)do
    headers = Utils.read_headers(conn)
    {offset, _} = Integer.parse(headers["upload-offset"])
    upload_info = UploadCache.get(identifier)

    [alg, checksum] = String.split(headers["upload-checksum"] || "_ _")
    if not is_nil(headers["upload-checksum"]) and not alg in ExTus.Config.hash_algorithms do
      conn
      |> Utils.set_base_resp
      |> resp(400, "Bad Request")
    else

      #%{size: current_offset} = File.stat!(file_path)
      if  offset != upload_info.offset do
        conn
        |> Utils.set_base_resp
        |> resp(409, "Conflict")
      else
        #read data Max chunk size is 8MB, if transferred data > 8MB, ignore it
        case read_body(conn) do
          {_, binary, conn} ->
            data_length = byte_size(binary)
            upload_info = Map.put(upload_info, :offset, data_length + upload_info.offset)

            # check Checksum if received a checksum digest
            if alg in ExTus.Config.hash_algorithms do
              alg = if alg == "sha1", do: "sha", else: alg
              hash_val = :crypto.hash(String.to_atom(alg), binary)
                |> Base.encode32()

              if checksum != hash_val do
                conn
                |> Utils.set_base_resp
                |> resp(460, "Checksum Mismatch")

              else
                write_append_data(conn, upload_info, binary, complete_cb)
              end
            else
              write_append_data(conn, upload_info, binary, complete_cb)
            end
          {:error, _term} ->
            conn
            |> Utils.set_base_resp
            |> resp(500, "Server error")
        end
      end

    end
  end

  defp write_append_data(conn, upload_info, binary, complete_cb \\ nil) do
    storage.append_data(upload_info, binary)
    |> case do
      {:ok, upload_info} ->
        UploadCache.update(upload_info)

        if upload_info.offset >= upload_info.size do
          rs = storage.complete_file(upload_info)

          # if upload fail remove uploaded file
          with {:error, err} <- rs do
            Logger.warn inspect err
            storage.abort_upload(upload_info)
          end
          
          # remove cache info
          UploadCache.delete(upload_info.identifier)

          if not is_nil(complete_cb) do
            complete_cb.(upload_info)
          end
        end

        conn
        |> Utils.set_base_resp
        |> Utils.put_cors_headers
        |> put_resp_header("Upload-Offset", "#{upload_info.offset}")
        |> resp(204, "")

      {:error, err} ->
        Logger.warn inspect err
        conn
        |> Utils.set_base_resp
        |> resp(404, "")
    end
  end

  def post(conn, create_cb)do
     headers = Utils.read_headers(conn)

     meta = Utils.parse_meta_data(headers["upload-metadata"])
     {upload_length, _} = Integer.parse(headers["upload-length"])

     if upload_length > ExTus.Config.tus_max_file_size do
       conn
       |> resp(413, "")
     else
       file_name =
         (meta["filename"] || "")
         |> Base.decode64!

       {:ok, {identifier, filename}} = storage.initiate_file(file_name)

       info = %UploadInfo{
         identifier: identifier,
         filename: filename,
         size: upload_length,
         started_at: DateTime.utc_now |> DateTime.to_iso8601
       }
       UploadCache.put(info)

       if create_cb do
         create_cb.(info)
       end

       location = ("#{conn.scheme}://#{conn.host }:#{conn.port}")
          |> URI.merge(Path.join(ExTus.Config.upload_url, identifier))
          |> to_string

       conn
       |> put_resp_header("Tus-Resumable", ExTus.Config.tus_api_version)
       |> put_resp_header("Location", location)
       |> Utils.put_cors_headers
       |> resp(201, "")
     end
  end


  def delete(conn, identifier) do
    upload_info = UploadCache.get(identifier)

    if is_nil(upload_info) do
      conn
      |> Utils.set_base_resp
      |> resp(404, "Not Found")
    else
      case storage.delete(upload_info) do
        :ok ->
          conn
          |> Utils.set_base_resp
          |> Utils.put_cors_headers
          |> resp(204, "No Content")
        _ ->
          conn
          |> Utils.set_base_resp
          |> resp(500, "Server Error")
      end
    end
  end

  def handle_preflight_request(conn) do
    headers = Enum.into(conn.req_headers, Map.new)
    if headers["access-control-request-method"] do
      conn
      |> put_resp_header("Access-Control-Allow-Methods", "POST, GET, HEAD, PATCH, DELETE, OPTIONS")
      |> put_resp_header("Access-Control-Allow-Origin", "null")
      |> put_resp_header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Upload-Length, Upload-Offset, Tus-Resumable, Upload-Metadata")
      |> put_resp_header("Access-Control-Max-Age", "86400")
    else
      conn
    end
  end
end