defmodule Receivex do
  @moduledoc """
  Package to deal with inbound email webhooks for several providers. Right now
  Mailgun and Mandrill are supported.


  ## Installation

  If [available in Hex](https://hex.pm/docs/publish), the package can be installed
  by adding `receivex` to your list of dependencies in `mix.exs`:

  ```elixir
  def deps do
  [
    {:receivex, "~> 0.8.0"}
  ]
  end
  ```


  Example configuration for Mandrill with the Plug router
  ```elixir
  forward("_incoming", to: Receivex, init_opts: [
  adapter: Receivex.Adapter.Mandrill,
  adapter_opts: [
    secret: "i8PTcm8glMgsfaWf75bS1FQ",
    url: "http://example.com"
  ],
  handler: Example.Processor]
  )
  ```

  Example configuration for Mandrill with the Phoenix router
  ```elixir
  forward("_incoming", Receivex, [
  adapter: Receivex.Adapter.Mandrill,
  adapter_opts: [
    secret: "i8PTcm8glMgsfaWf75bS1FQ",
    url: "http://example.com"
  ],
  handler: Example.Processor]
  )
  ```

  Example configuration for Mailgun with the Plug router
  ```elixir
  forward("_incoming", to: Receivex, init_opts: [
  adapter: Receivex.Adapter.Mailgun,
  adapter_opts: [
    api_key: "some-key"
  ],
  handler: Example.Processor]
  )
  ```

  Example processor
  ```elixir
  defmodule Example.Processor do
    @behaviour Receivex.Handler

    def process(%Receivex.Email{} = mail) do
      IO.inspect(mail)
    end
  end

  ```

  """

  import Plug.Conn
  @behaviour Plug

  @impl true
  def init(opts) do
    handler = Keyword.fetch!(opts, :handler)

    adapter = Keyword.fetch!(opts, :adapter)
    adapter_opts = Keyword.fetch!(opts, :adapter_opts)

    {adapter, adapter_opts, handler}
  end

  @impl true
  def call(conn, opts) do
    {adapter, adapter_opts, handler} = opts

    case adapter.handle_webhook(conn, handler, adapter_opts) do
      {:ok, conn} ->
        conn |> send_resp(:ok, "ok") |> halt()

      {:error, conn, message} ->
        conn |> send_resp(:forbidden, "bad signature") |> halt()
    end
  end
end