defmodule Bamboo.SentEmailApiPlug do
  use Plug.Router
  alias Bamboo.SentEmail

  @moduledoc """
  A plug that exposes delivered emails over a JSON API.

  This is useful for an integration test runner that doesn't have
  access to the `Bamboo.Test` helpers, but needs to be able to assert that
  emails have been delivered.

  You must use the `Bamboo.LocalAdapter` or no emails will be available.

  ## Using with Plug or Phoenix

      # Make sure you are using Bamboo.LocalAdapter in your config
      config :my_app, MyApp.Mailer,
        adapter: Bamboo.LocalAdapter

      # In your Router
      defmodule MyApp.Router do
        use Phoenix.Router # or use Plug.Router if you're not using Phoenix

        if Mix.env == :e2e do
          # If using Phoenix
          forward "/sent_emails_api", Bamboo.SentEmailApiPlug

          # If using Plug.Router, make sure to add the `to`
          forward "/sent_emails_api", to: Bamboo.SentEmailApiPlug
        end
      end

  ## API endpoints

  There are two endpoints:

  * `GET /emails.json` exposes the list of sent emails
  * `POST /reset.json` resets the sent emails back to an empty list

  Usually, you would `POST` to `/reset.json` at the beginning of a test run,
  and `GET` from `/emails.json` as you need to during an integration test to
  make assertions. The details of how you make assertions is left up to your
  integration test runner.

  ## Email response JSON

  Sent emails are returned in the following format:

  ```json
  {
    "to": [[null, "to@example.com"], ["Alice", "alice@example.com"]],
    "text_body": "hello world",
    "subject": "This is a test email",
    "html_body": "<p>hello world</p>",
    "headers": {},
    "from": [null, "from@example.com"],
    "cc": [[null, "cc@example.com"]],
    "bcc": [["Bob", "bob@example.com"]],
    "attachments": []
  }
  ```

  Email addresses are returned in array pairs, with the first element as the
  name, and the second as the email address. The first element can be `null`
  if the address didn't specify a name. The `to`, `cc` and `bcc` fields are
  returned as arrays of these pairs.
  """

  plug(:match)
  plug(:dispatch)

  get "/emails.json" do
    data =
      SentEmail.all()
      |> Enum.map(&format_json_email/1)

    conn
    |> send_json(:ok, data)
  end

  post "/reset.json" do
    SentEmail.reset()

    conn
    |> send_json(:ok, %{ok: true})
  end

  defp send_json(conn, status, data) do
    body = data |> Bamboo.json_library().encode!()

    conn
    |> Plug.Conn.put_resp_content_type("application/json")
    |> send_resp(status, body)
  end

  defp format_json_email(email) do
    email
    |> Map.take([:from, :to, :cc, :bcc, :subject, :text_body, :html_body, :headers, :attachments])
    |> Map.update(:from, nil, &format_json_email_address/1)
    |> Map.update(:to, nil, &format_json_email_addresses/1)
    |> Map.update(:cc, nil, &format_json_email_addresses/1)
    |> Map.update(:bcc, nil, &format_json_email_addresses/1)
  end

  defp format_json_email_addresses(addresses) do
    addresses |> Enum.map(&format_json_email_address/1)
  end

  defp format_json_email_address({name, address}) do
    [name, address]
  end
end