defmodule MvWeb.Emails.JoinEmail do
  @moduledoc """
  Shared build/deliver skeleton for the join-flow emails (confirmation,
  already-a-member, already-pending).

  Each concrete join email supplies only its subject, template, and any
  email-specific assigns; this module builds the Swoosh email with the unified
  layout and delivers it via `Mailer.deliver/2` with `Mailer.smtp_config/0`,
  preserving the `{:ok, email}` / `{:error, reason}` contract.
  """
  use Phoenix.Swoosh,
    view: MvWeb.EmailsView,
    layout: {MvWeb.EmailLayoutView, "layout.html"}

  import Swoosh.Email

  alias Mv.Mailer

  @doc """
  Builds and delivers a join-flow email.

  - `email_address` - recipient address
  - `template` - the EmailsView template to render (e.g. `"join_confirmation.html"`)
  - `subject` - already-translated subject line
  - `extra_assigns` - email-specific assigns merged on top of the common ones
    (`subject`, `app_name`, `locale`)

  Returns `{:ok, email}` on success, `{:error, reason}` on delivery failure.
  """
  @spec deliver(String.t(), String.t(), String.t(), map()) ::
          {:ok, Swoosh.Email.t()} | {:error, term()}
  def deliver(email_address, template, subject, extra_assigns \\ %{})
      when is_binary(email_address) and is_binary(template) and is_binary(subject) do
    assigns =
      Map.merge(
        %{
          subject: subject,
          app_name: Mailer.mail_from() |> elem(0),
          locale: Gettext.get_locale(MvWeb.Gettext)
        },
        extra_assigns
      )

    email =
      new()
      |> from(Mailer.mail_from())
      |> to(email_address)
      |> subject(subject)
      |> put_view(MvWeb.EmailsView)
      |> render_body(template, assigns)

    Mailer.deliver(email, Mailer.smtp_config())
  end
end