defmodule ExRollbar do
  @moduledoc """
  Error handling for RollBar.
  """

  alias ExRollbar.RestAPI
  alias RestAPI.Payload.Data
  alias Data.Body

  @doc """
  Sets up ExRollbar
  args must contain at least these keys:
    `access_token`
    `environment`

  args may also contain:
    * Person Object
        * `person_id`, (Required to use the Person object)
        * `person_email`
        * `person_username`
    * Custom Object
        * `custom` a (jsonable) map of custom data.
    * Logger
        * `enable_logger` (boolean) enable logger backend
    * Framework
        * `framework` IE "Nerves"
    * Code Version
        * `code_version` a git sha or similar.
  """
  @spec setup(Keyword.t) :: :ok | {:error, term}
  def setup(args) do
    # Token
    token = Keyword.get(args, :access_token) || raise ArgumentError, "Please supply a token when setting up ExRollbar"
    Application.put_env(:ex_rollbar, :access_token, token)

    # Environment
    env = Keyword.get(args, :environment) || raise ArgumentError, "Please supply an environment when setting up ExRollbar"
    Application.put_env(:ex_rollbar, :environment, env)

    # Custom
    custom = Keyword.get(args, :custom, %{})
    Application.put_env(:ex_rollbar, :custom, custom)

    code_version = Keyword.get(args, :code_version, %{})
    Application.put_env(:ex_rollbar, :code_version, code_version)

    framework = Keyword.get(args, :framework)
    Application.put_env(:ex_rollbar, :framework, framework)

    # Person
    person_id = Keyword.get(args, :person_id)
    if person_id do
      Application.put_env(:ex_rollbar, :person_id, person_id)

      person_email = Keyword.get(args, :person_email)
      person_username = Keyword.get(args, :person_username)
      Application.put_env(:ex_rollbar, :person_email, person_email)
      Application.put_env(:ex_rollbar, :person_username, person_username)
    end

    # Logger
    if Keyword.get(args, :enable_logger, false) do
      Logger.add_backend(Logger.Backends.ExRollbar)
    end
    :ok
  end

  @doc false
  defdelegate uuid, to: UUID, as: :generate

  @doc """
  Reports an item to RollBar.
  * `level` can be one of :error, :warn, :info, :debug
  * `value` can be a Exception struct or a string
  * `stack_trace` is the result of `System.stack_trace()`
  * `meta` is a bucket of extra key/value data.

  ## Meta
  Can contain any of:
  * `uuid` - a uuid (generated automatically)
  * `timstamp` - a unix timestamp (generated automatically)
  * `context` - a context object.
  * `custom` - any jsonable map of extra data
  * `request_meta` - A request object from the rollbar docs
  * `server_meta` - A server object from the rollbar docs
  * `client_meta` - A client object from the rollbar docs
  """
  @spec report(Data.level, Exception.t | binary, Exception.stack_trace, Keyword.t) :: no_return
  def report(level, value, stack_trace, meta \\ []) do
    level = parse_level(level)
    %Data{
      # will change frequently
      level: level,

      # Should exist, but could be user provided.
      uuid: Keyword.get(meta, :uuid, uuid()),
      timestamp: Keyword.get(meta, :timestamp, :os.system_time(:seconds)),

      context: Keyword.get(meta, :context),
      custom: get_custom(meta),

      # These should not change at runtime.
      environment: from_env(:environment),
      code_version: from_env(:code_version),
      framework: from_env(:framework),

      # Body.
      body: generate_body(value, stack_trace, meta),

      person:   generate_person(),
      request: generate_request(Keyword.get(meta, :request_meta)),
      server:   generate_server(Keyword.get(meta, :server_meta)),
      client:   generate_client(Keyword.get(meta, :client_meta))
    }
    |> RestAPI.emit()
  end

  defp get_custom(meta) do
    env_custom = from_env(:custom, %{})
    meta_custom = Keyword.get(meta, :custom, %{})
    Map.merge(env_custom, meta_custom)
  end

  defp parse_level(_), do: :error

  defp generate_body(value, stack_trace, metadata)

  defp generate_body(%{message: message}, stack_trace, meta),
    do: generate_body(message, stack_trace, meta)

  defp generate_body(value, [stack_item | _] = stack_trace, meta) do
    case stack_item do
      {module, _function, _arity, _file_and_line} ->
        %{
          trace: %Body.Trace{
            frames: Enum.map(stack_trace, fn(item) ->
              {item_module, item_function, _item_arity, item_file_and_line} = item
              %Body.Trace.Frame{
                filename: fn() ->

                  # FIXME
                  thing = Keyword.get(item_file_and_line, :file)
                  if thing do
                    thing |> to_string()
                  else
                    raise(ArgumentError, "Could not find filename for: #{inspect value}")
                  end
                end.(),

                lineno: Keyword.get(item_file_and_line, :line),
                method: item_function,
                class_name: item_module
              }
            end),
            exception: %Body.Trace.Exception{
              class: module,
              message: value,
              description: Keyword.get(meta, :description)
            }
          }
        }
      _ -> generate_body(value, [], meta)
    end
  end

  defp generate_body(value, [], _m), do: %{message: %Body.Message{body: value}}

  @spec generate_person() :: map | nil
  defp generate_person() do
    id = from_env(:person_id)
    if id do
      %Data.Person{
        id: id,
        username: from_env(:person_username),
        email: from_env(:person_email)
      }
    else
      nil
    end
  end

  @spec generate_request(nil | Keyword.t) :: map
  defp generate_request(nil), do: nil
  defp generate_request(_meta) do
    #TODO(Connor) Fixme
    %{}
  end

  @spec generate_server(nil | Keyword.t) :: map
  defp generate_server(nil), do: nil
  defp generate_server(_meta) do
    %{}
  end

  @spec generate_client(nil | Keyword.t) :: map
  defp generate_client(nil), do: nil
  defp generate_client(_client) do
    %{}
  end

  @spec from_env(atom, any) :: any
  defp from_env(key, default \\ nil) do
    Application.get_env(:ex_rollbar, key, default)
  end
end