defmodule Bamboo.PostmarkAdapter do
  @moduledoc """
  Sends email using Postmarks's API.

  Use this adapter to send emails through Postmark's API. Requires that an API
  key is set in the config.

  ## Example config

      # In config/config.exs, or config.prod.exs, etc.
      config :my_app, MyApp.Mailer,
        adapter: Bamboo.PostmarkAdapter,
        api_key: "my_api_key" or {:system, "POSTMARK_API_KEY"}
  """

  @behaviour Bamboo.Adapter

  @default_base_uri "https://api.postmarkapp.com"
  @send_email_path "email"
  @send_email_template_path "email/withTemplate"

  import Bamboo.ApiError, only: [build_api_error: 1]

  def deliver(email, config) do
    api_key = get_key(config)
    params = email |> convert_to_postmark_params() |> json_library().encode!()
    uri = [base_uri(), "/", api_path(email)]

    case :hackney.post(uri, headers(api_key), params, options(config)) do
      {:ok, status, _headers, response} when status > 299 ->
        {:error, build_api_error(%{params: params, response: response})}

      {:ok, status, headers, response} ->
        {:ok, %{status_code: status, headers: headers, body: response}}

      {:error, reason} ->
        {:error, build_api_error(%{message: inspect(reason)})}
    end
  end

  def handle_config(config) do
    # build the api key - will raise if there are errors
    Map.merge(config, %{api_key: get_key(config)})
  end

  @doc false
  def supports_attachments?, do: true

  defp get_key(config) do
    api_key =
      case Map.get(config, :api_key) do
        {:system, var} -> System.get_env(var)
        key -> key
      end

    if api_key in [nil, ""] do
      raise_api_key_error(config)
    else
      api_key
    end
  end

  def json_library do
    Bamboo.json_library()
  end

  defp raise_api_key_error(config) do
    raise ArgumentError, """
    There was no API key set for the Postmark adapter.
    * Here are the config options that were passed in:
    #{inspect config}
    """
  end

  defp convert_to_postmark_params(email) do
    email
    |> email_params()
    |> maybe_put_template_params(email)
    |> maybe_put_tag_params(email)
    |> maybe_put_attachments(email)
  end

  def maybe_put_attachments(params, %{attachments: []}) do
    params
  end

  def maybe_put_attachments(params, %{attachments: attachments}) do
    params
    |> Map.put(:"Attachments", Enum.map(attachments, fn attachment ->
      %{
        Name: attachment.filename,
        Content: attachment.data |> Base.encode64(),
        ContentType: attachment.content_type,
        ContentId: attachment.content_id
      }
    end))
  end

  defp maybe_put_template_params(params, %{private:
    %{template_id: template_name, template_model: template_model}}) do
    params
    |> Map.put(:"TemplateId", template_name)
    |> Map.put(:"TemplateModel", template_model)
    |> Map.put(:"InlineCss", true)
  end

  defp maybe_put_template_params(params, _) do
    params
  end

  defp maybe_put_tag_params(params, %{private: %{tag: tag}}) do
    Map.put(params, :"Tag", tag)
  end

  defp maybe_put_tag_params(params, _) do
    params
  end

  defp email_params(email) do
    recipients = recipients(email)
    add_message_params(%{
                         "From": email_from(email),
                         "To": recipients_to_string(recipients, "To"),
                         "Cc": recipients_to_string(recipients, "Cc"),
                         "Bcc": recipients_to_string(recipients, "Bcc"),
                         "Subject": email.subject,
                         "TextBody": email.text_body,
                         "HtmlBody": email.html_body,
                         "Headers": email_headers(email),
                         "TrackOpens": true
                       }, email)
  end

  defp add_message_params(params, %{private: %{message_params: message_params}}) do
    Enum.reduce(message_params, params, fn({key, value}, params) ->
      Map.put(params, key, value)
    end)
  end
  defp add_message_params(params, _), do: params

  defp email_from(email) do
    name = elem(email.from, 0)
    email = elem(email.from, 1)
    if name do
      String.trim("#{name} <#{email}>")
    else
      String.trim(email)
    end
  end

  defp email_headers(email) do
    Enum.map(email.headers,
              fn {header, value} -> %{"Name": header, "Value": value} end)
  end

  defp recipients(email) do
    []
    |> add_recipients(email.to, type: "To")
    |> add_recipients(email.cc, type: "Cc")
    |> add_recipients(email.bcc, type: "Bcc")
  end

  defp add_recipients(recipients, new_recipients, type: recipient_type) do
    Enum.reduce(new_recipients, recipients, fn(recipient, recipients) ->
      recipients ++ [%{
        name: elem(recipient, 0),
        email: elem(recipient, 1),
        type: recipient_type
      }]
    end)
  end

  defp recipients_to_string(recipients, type) do
    recipients
    |> Enum.filter(fn(recipient) -> recipient[:type] == type end)
    |> Enum.map_join(",", fn(rec) -> "#{rec[:name]} <#{rec[:email]}>" end)
  end

  defp headers(api_key) do
    [{"accept", "application/json"},
     {"content-type", "application/json"},
     {"x-postmark-server-token", api_key}]
  end

  defp api_path(%{private: %{template_id: _}}), do: @send_email_template_path
  defp api_path(_), do: @send_email_path

  defp base_uri do
    Application.get_env(:bamboo, :postmark_base_uri) || @default_base_uri
  end

  defp options(config) do
    Keyword.merge(config[:request_options] || [], [with_body: true])
  end

end