defmodule Baiji do
  @moduledoc """
  Baiji provides an interface for interacting with the AWS API. Baiji is 
  typically used by invoking a service function to generate an operation which 
  is then passed to Baiji.run to make the request.

  ## Examples

    iex> Baiji.EC2.describe_instances
    ...> |> Baiji.run
    {:ok, %{reservations: ...}}
  """
  alias Baiji.{
    Operation,
    Config,
    Auth,
    Request,
    Response
  }

  @doc """
  Perform an operation
  """
  def perform(%Operation{} = operation, opts \\ []) do
    try do
      %{operation | options: Keyword.merge(operation.options, opts)}
      |> Config.merge
      |> Operation.debug("Populating Authentication Parameters...")
      |> Auth.populate
      |> Operation.debug("Making Request...")
      |> Request.make
      |> Response.parse(operation)
    rescue
      e -> {:error, e.message}
    end
  end

  @doc """
  Perform an operation, raises an exception if the operation fails
  """
  def perform!(%Operation{} = operation, opts \\ []) do
    case perform(operation, opts) do
      {:ok, response} -> 
        response
      {:error, error} ->
        raise error
    end
  end
end