Send email from Phoenix

defmodule MyApp.EmailsshAdapter do
  @moduledoc """
  Swoosh adapter for the emails.sh HTTP API.

  Implementing the behaviour rather than calling the API from a context means
  every existing Swoosh.Email in the app, including whatever a generator wrote,
  goes out over emails.sh with no other change.
  """

  use Swoosh.Adapter, required_config: [:api_key]

  @endpoint "https://emails.sh/v1/emails"

  @impl Swoosh.Adapter
  def deliver(%Swoosh.Email{} = email, config) do
    body =
      %{
        from: address(email.from),
        to: Enum.map(email.to, &address/1),
        subject: email.subject,
        html: email.html_body,
        text: email.text_body
      }
      |> put_unless_empty(:cc, Enum.map(email.cc || [], &address/1))
      |> put_unless_empty(:bcc, Enum.map(email.bcc || [], &address/1))
      |> put_unless_empty(:reply_to, email.reply_to && address(email.reply_to))
      |> Map.reject(fn {_key, value} -> is_nil(value) end)

    case Req.post(@endpoint,
           json: body,
           auth: {:bearer, Keyword.fetch!(config, :api_key)},
           receive_timeout: 15_000
         ) do
      {:ok, %{status: status, body: %{"id" => id}}} when status in 200..299 ->
        {:ok, %{id: id}}

      {:ok, %{status: status, body: body}} ->
        {:error, {status, body}}

      {:error, reason} ->
        {:error, reason}
    end
  end

  defp address({nil, email}), do: email
  defp address({name, email}), do: "#{name} <#{email}>"
  defp address(email) when is_binary(email), do: email

  defp put_unless_empty(map, _key, nil), do: map
  defp put_unless_empty(map, _key, []), do: map
  defp put_unless_empty(map, key, value), do: Map.put(map, key, value)
end

defmodule MyApp.Accounts.UserNotifier do
  import Swoosh.Email

  alias MyApp.Mailer

  def deliver_welcome(user) do
    new()
    |> to({user.name, user.email})
    |> from({"Acme", "hello@acme.com"})
    |> subject("Welcome to Acme")
    |> html_body("<p>Hi #{Phoenix.HTML.html_escape(user.name) |> Phoenix.HTML.safe_to_string()}, your Acme account is ready.</p>")
    |> text_body("Hi #{user.name}, your Acme account is ready.")
    |> Mailer.deliver()
  end

  @doc """
  Sends without holding up the caller. Task.Supervisor is already in the
  supervision tree of a generated Phoenix app as MyApp.TaskSupervisor.
  """
  def deliver_welcome_async(user) do
    Task.Supervisor.start_child(MyApp.TaskSupervisor, fn -> deliver_welcome(user) end)
  end
end