defmodule FabricaMail do
  @moduledoc """
  Drop-in Swoosh adapter for Fabrica Mail. Copy this file into your application's
  `lib/` directory. Requires the existing `:swoosh` and `:req` dependencies.

      config :my_app, MyApp.Mailer,
        adapter: FabricaMail,
        base_url: System.fetch_env!("FABRICA_URL"),
        token: System.fetch_env!("FABRICA_TOKEN")

  Use the Fabrica origin as `base_url`, without `/api/v1`. Supports to/cc/bcc,
  reply-to, HTML/text, custom headers and attachments (including inline images).
  `put_provider_option(:tag, "welcome")` and `put_provider_option(:metadata, %{})` are
  forwarded. Delivery is a single attempt: check Postmark before retrying an
  ambiguous timeout. `{:ok, %{id: id}}` means provider acceptance, not delivery.
  """
  use Swoosh.Adapter, required_config: [:base_url, :token]

  @impl true
  def deliver(%Swoosh.Email{} = email, config) do
    payload =
      %{
        from: address(email.from),
        to: Enum.map(email.to, &address/1),
        cc: Enum.map(email.cc, &address/1),
        bcc: Enum.map(email.bcc, &address/1),
        reply_to: address(email.reply_to),
        subject: email.subject,
        html_body: email.html_body,
        text_body: email.text_body,
        tag: email.provider_options[:tag],
        metadata: email.provider_options[:metadata],
        headers: Enum.map(email.headers, fn {name, value} -> %{name: name, value: value} end),
        attachments: Enum.map(email.attachments, &attachment/1)
      }
      |> Map.reject(fn {_, value} -> is_nil(value) end)

    options = [
      url: String.trim_trailing(Keyword.fetch!(config, :base_url), "/") <> "/api/v1/emails",
      auth: {:bearer, Keyword.fetch!(config, :token)},
      json: payload,
      retry: false,
      redirect: false,
      receive_timeout: 30_000
    ]

    # :req_options supports Req.Test in the consuming application's tests.
    case Req.post(Keyword.merge(options, Keyword.get(config, :req_options, []))) do
      {:ok, %{status: 200, body: %{"message_id" => id, "status" => "accepted"}}} ->
        {:ok, %{id: id}}

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

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

  defp address(nil), do: nil
  defp address({"", email}), do: email

  defp address({name, email}) do
    # Quoted display names allow ordinary punctuation; Fabrica accepts a list
    # of individual addresses so commas within names aren't split.
    escaped = name |> String.replace("\\", "\\\\") |> String.replace("\"", "\\\"")
    "\"#{escaped}\" <#{email}>"
  end

  defp attachment(attachment) do
    %{
      name: attachment.filename,
      content_type: attachment.content_type,
      content: Swoosh.Attachment.get_content(attachment, :base64)
    }
    |> then(fn item ->
      if attachment.type == :inline and attachment.cid,
        do: Map.put(item, :content_id, "cid:" <> String.trim_leading(attachment.cid, "cid:")),
        else: item
    end)
  end
end