defmodule Coherence.ControllerHelpers do
  @moduledoc """
  Common helper functions for Coherence Controllers.
  """
  alias Coherence.Config
  require Logger
  import Phoenix.Controller, only: [put_flash: 3]

  @lockable_failure "Failed to update lockable attributes "

  @doc """
  Get the MyProject.Router.Helpers module.

  Returns the projects Router.Helpers module.
  """
  def router_helpers do
    Module.concat(Config.module, Router.Helpers)
  end

  @doc """
  Get the configured logged_out_url.
  """
  def logged_out_url(conn) do
    Config.logged_out_url || Module.concat(Config.module, Router.Helpers).session_path(conn, :new)
  end

  @doc """
  Get a random string of given length.

  Returns a random url safe encoded64 string of the given length.
  Used to generate tokens for the various modules that require unique tokens.
  """
  def random_string(length) do
    :crypto.strong_rand_bytes(length)
    |> Base.url_encode64
    |> binary_part(0, length)
  end

  @doc """
  Test if a datetime has expired.

  Convert the datetime from Ecto.DateTime format to Timex format to do
  the comparison given the time during in opts.

  ## Examples

      expired?(user.expire_at, days: 5)
      expired?(user.expire_at, minutes: 10)
  """
  def expired?(datetime, opts) do
    expire_on? = datetime
    |> Ecto.DateTime.to_erl
    |> Timex.DateTime.from_erl
    |> Timex.shift(opts)
    not Timex.before?(Timex.DateTime.now, expire_on?)
  end

  @doc """
  Log an error message when lockable update fails.
  """
  def lockable_failure(changeset) do
    Logger.error @lockable_failure <> inspect(changeset.errors)
  end

  @doc """
  Send a user email.

  Sends a user email given the module, model, and url. Logs the email for
  debug purposes.

  Note: This function uses an apply to avoid compile warnings if the
  mailer is not selected as an option.
  """
  def send_user_email(fun, model, url) do
    email = apply(Module.concat(Config.module, Coherence.UserEmail), fun, [model, url])
    Logger.debug fn -> "#{fun} email: #{inspect email}" end
    apply(Module.concat(Config.module, Coherence.Mailer), :deliver, [email])
  end

  @doc """
  Send confirmation email with token.

  If the user supports confirmable, generate a token and send the email.
  """
  def send_confirmation(conn, user, user_schema) do
    if user_schema.confirmable? do
      token = random_string 48
      url = router_helpers.confirmation_url(conn, :edit, token)
      Logger.debug "confirmation email url: #{inspect url}"
      dt = Ecto.DateTime.utc
      user_schema.changeset(user,
        %{confirmation_token: token, confirmation_send_at: dt})
      |> Config.repo.update!

      send_user_email :confirmation, user, url
      conn
      |> put_flash(:info, "Confirmation email sent.")
    else
      conn
      |> put_flash(:info, "Registration created successfully.")
    end
  end
end