defmodule MessengerBot.Webhook.Callback do
  @moduledoc """
  MessengerBot webhook for all callbacks
  """

  alias MessengerBot.Model.{Entry, Sender, Recipient, AccountLinking,
    Delivery, Message, Optin, Postback, Read, Referral}
  alias MessengerBot.Payload.Process, as: ProcessPayload
  alias MessengerBot.Payload.Webhook, as: WebhookPayload

  @decoder %WebhookPayload{entry: [%Entry{}]}

  @spec process(String.t) :: {:ok, String.t}
  def process(payload) do
    EventBus.notify({:mb_webhook_received, payload})
    webhook_payload = Poison.decode!(payload, as: @decoder, keys: :atoms)
    Enum.each(webhook_payload.entry, fn(entry) -> process_entry(entry) end)
    {:ok, "ok"}
  end

  defp process_entry(%Entry{} = entry) do
    Enum.each(entry.messaging, fn(messaging) ->
      process_messaging(entry.id, entry.time, messaging)
    end)
  end

  defp process_messaging(page_id, time, messaging) do
    {topic, data} = fetch_topic_and_data(messaging)
    payload = %ProcessPayload{page_id: page_id, data: data, time: time,
      sender: struct(Sender, messaging.sender || %{}),
      recipient: struct(Recipient, messaging.recipient || %{})}
    EventBus.notify({topic, payload})
  end

  defp fetch_topic_and_data(%{delivery: delivery})
    when not is_nil(delivery) do
    {:mb_delivery_received, struct(Delivery, delivery)}
  end
  defp fetch_topic_and_data(%{read: read})
    when not is_nil(read) do
    {:mb_read_received, struct(Read, read)}
  end
  defp fetch_topic_and_data(%{message: %{is_echo: true}} = messaging) do
    {:mb_message_echo_received, struct(Message, messaging.message)}
  end
  defp fetch_topic_and_data(%{message: %{attachments: attachments}} = messaging)
    when not is_nil(attachments) do
    {:mb_message_attachments_received, struct(Message, messaging.message)}
  end
  defp fetch_topic_and_data(%{message: %{quick_reply: quick_reply}} = messaging)
    when not is_nil(quick_reply) do
    {:mb_message_quick_reply_received, struct(Message, messaging.message)}
  end
  defp fetch_topic_and_data(%{message: message})
    when not is_nil(message) do
    {:mb_message_received, struct(Message, message)}
  end
  defp fetch_topic_and_data(%{optin: optin})
    when not is_nil(optin) do
    {:mb_optin_received, struct(Optin, optin)}
  end
  defp fetch_topic_and_data(%{postback: postback})
    when not is_nil(postback) do
    {:mb_postback_received, struct(Postback, postback)}
  end
  defp fetch_topic_and_data(%{referral: referral})
    when not is_nil(referral) do
    {:mb_referral_received, struct(Referral, referral)}
  end
  defp fetch_topic_and_data(%{payment: payment})
    when not is_nil(payment) do
    {:mb_payment_received, payment}
  end
  defp fetch_topic_and_data(%{checkout_update: checkout_update})
    when not is_nil(checkout_update) do
    {:mb_checkout_update_received, checkout_update}
  end
  defp fetch_topic_and_data(%{pre_checkout: pre_checkout})
    when not is_nil(pre_checkout) do
    {:mb_pre_checkout_received, pre_checkout}
  end
  defp fetch_topic_and_data(%{account_linking: account_linking})
    when not is_nil(account_linking) do
    {:mb_account_linking_received,
      struct(AccountLinking, account_linking)}
  end
  defp fetch_topic_and_data(%{policy_enforcement: policy_enforcement})
    when not is_nil(policy_enforcement) do
    {:mb_policy_enforcement_received, policy_enforcement}
  end
  defp fetch_topic_and_data(%{app_roles: app_roles})
    when not is_nil(app_roles) do
    {:mb_app_roles_received, app_roles}
  end
  defp fetch_topic_and_data(%{standby: standby})
    when not is_nil(standby) do
    {:mb_standby_received, standby}
  end
  defp fetch_topic_and_data(%{pass_thread_control: pass_thread_control})
    when not is_nil(pass_thread_control) do
    {:mb_pass_thread_control_received, pass_thread_control}
  end
  defp fetch_topic_and_data(%{take_thread_control: take_thread_control})
    when not is_nil(take_thread_control) do
    {:mb_take_thread_control_received, take_thread_control}
  end
  defp fetch_topic_and_data(data) do
    {:mb_na_received, data}
  end
end