aa.exs

defmodule KVServer.Command do
  @doc ~S"""
  Parses a line into a command.

  ## Examples

      iex> KVServer.Command.parse "CREATE shopping\r\n"
      {:ok, {:create, "shopping"}}

      iex> KVServer.Command.parse "CREATE  shopping  \r\n"
      {:ok, {:create, "shopping"}}

      iex> KVServer.Command.parse "PUT shopping milk 1\r\n"
      {:ok, {:put, "shopping", "milk", "1"}}

      iex> KVServer.Command.parse "GET shopping milk\r\n"
      {:ok, {:get, "shopping", "milk"}}

      iex> KVServer.Command.parse "DELETE shopping eggs\r\n"
      {:ok, {:delete, "shopping", "eggs"}}

  Unknown commands or commands with the wrong number of
  arguments return an error:

      iex> KVServer.Command.parse "UNKNOWN shopping eggs\r\n"
      {:error, :unknown_command}

      iex> KVServer.Command.parse "GET shopping\r\n"
      {:error, :unknown_command}
  """
  def parse(line) do
    case String.split(line) do
      ["CREATE", bucket] ->
        {:ok, {:create, bucket}}
      ["PUT", bucket, name, value] ->
        {:ok, {:put, bucket, name, value}}
      ["GET", bucket, name] ->
        {:ok, {:get, bucket, name}}
      ["DELETE", bucket, name] ->
        {:ok, {:delete, bucket, name}}
      _ ->
        {:error, :unknown_command}
    end
  end
end