defmodule Pushest do
  @moduledoc ~S"""
  Pushest is a Pusher library leveraging Elixir/OTP to combine server and client-side Pusher features.
  Abstracts un/subscription, client-side triggers, private/presence channel authorizations.
  Keeps track of subscribed channels and users presence when subscribed to presence channel.
  Pushest is meant to be used in your module where you can define callbacks for
  events you're interested in.

  A simple implementation in an OTP application would be:
  ```
  # Add necessary pusher configuration to your application config:
  # simple_client/config/config.exs
  config :simple_client, SimpleClient,
    pusher_app_id: System.get_env("PUSHER_APP_ID"),
    pusher_key: System.get_env("PUSHER_APP_KEY"),
    pusher_secret: System.get_env("PUSHER_SECRET"),
    pusher_cluster: System.get_env("PUSHER_CLUSTER"),
    pusher_encrypted: true

  # simple_client/simple_client.ex
  defmodule SimpleClient do
    use Pushest, otp_app: :simple_client

    def handle_event({:ok, "public-channel", "some-event"}, frame) do
      # do something with public frame
    end

    def handle_event({:ok, "private-channel", "some-other-event"}, frame) do
      # do something with private frame
    end
  end

  # Now you can start your application with Pushest as a part of your supervision tree:
  # simple_client/lib/simple_client/application.ex
  def start(_type, _args) do
    children = [
      {SimpleClient, []}
    ]

    opts = [strategy: :one_for_one, name: Sup.Supervisor]
    Supervisor.start_link(children, opts)
  end
  ```

  You can also provide Pusher options directly via start_link/1 (without using OTP app configuration):
  ```
  config = %{
    app_id:  System.get_env("PUSHER_APP_ID"),
    key: System.get_env("PUSHER_APP_KEY"),
    secret: System.get_env("PUSHER_SECRET"),
    cluster: System.get_env("PUSHER_CLUSTER"),
    encrypted: true
  }

  {:ok, pid} = SimpleClient.start_link(config)
  ```

  Now you can interact with Pusher:
  ```
  SimpleClient.trigger("private-channel", "event", %{message: "via api"}) 
  SimpleClient.channels()
  # => %{"channels" => %{"public-channel" => %{}}}
  SimpleClient.subscribe("private-channel")
  SimpleClient.trigger("private-channel", "event", %{message: "via ws"}) 
  SimpleClient.trigger("private-channel", "event", %{message: "via api"}, force_api: true) 
  # ...
  ```
  """

  alias Pushest.Router

  @doc ~S"""
  Invoked when the Pusher event occurs (e.g. other client sends a message).
  """
  @callback handle_event({atom, String.t(), String.t()}, term) :: term

  defmacro __using__(opts) do
    quote bind_quoted: [opts: opts] do
      @typedoc ~S"""
      Options for Pushest to properly communicate with Pusher server.

      - `:app_id` - Pusher Application ID.
      - `:key` - Pusher Application key.
      - `:secret` - Necessary to subscribe to private/presence channels and trigger events.
      - `:cluster` - Cluster where your Pusher app is configured.
      - `:encrypted` - When set to true communication with Pusher is fully encrypted.
      """
      @type pusher_opts :: %{
              app_id: String.t(),
              secret: String.t(),
              key: String.t(),
              cluster: String.t(),
              encrypted: boolean
            }

      @typedoc ~S"""
      Optional options for trigger function.

      - `:force_api` - Always triggers via Pusher REST API endpoint when set to `true`
      """
      @type trigger_opts :: [force_api: boolean]

      @behaviour Pushest

      @config Pushest.Supervisor.config(__MODULE__, opts)

      @doc ~S"""
      Starts a Pushest Supervisor process linked to current process.
      Can be started as a part of host application supervision tree.
      Pusher options can be passed as an argument or can be provided in an OTP
      application config.

      For available pusher_opts values see `t:pusher_opts/0`.
      """
      @spec start_link(pusher_opts) :: {:ok, pid} | {:error, term}
      def start_link(pusher_opts) when is_map(pusher_opts) do
        Pushest.Supervisor.start_link(pusher_opts, __MODULE__)
      end

      def start_link(_) do
        Pushest.Supervisor.start_link(@config, __MODULE__)
      end

      def child_spec(opts) do
        %{
          id: __MODULE__,
          start: {__MODULE__, :start_link, [opts]},
          type: :supervisor
        }
      end

      @doc ~S"""
      Subscribe to a channel with user_data as a map. When subscribing to a
      presence- channel user_id key with unique identifier as a value has to be
      provided in the user_data map. user_info key can contain a map with optional
      informations about user.
      E.g.: %{user_id: "1", user_info: %{name: "Tomas Koutsky"}}
      """
      @spec subscribe(String.t(), map) :: term
      def subscribe(channel, user_data) do
        Router.cast({:subscribe, channel, user_data})
      end

      @doc ~S"""
      Subscribe to a channel without any user data, like any public channel.
      """
      @spec subscribe(String.t()) :: term
      def subscribe(channel) do
        Router.cast({:subscribe, channel, %{}})
      end

      @doc ~S"""
      Trigger on given channel/event combination - sends given data to Pusher.
      data has to be a map.
      """
      @spec trigger(String.t(), String.t(), map) :: term
      def trigger(channel, event, data) do
        Router.cast({:trigger, channel, event, data})
      end

      @doc ~S"""
      Same as trigger/3 but adds a possiblity to enforce triggering via API endpoint.
      For enforced API trigger provide `force_api: true` as an `opts`.
      E.g.: `Mod.trigger("channel", "event", %{message: "m"}, force_api: true)`

      For trigger_opts values see `t:trigger_opts/0`.
      """
      @spec trigger(String.t(), String.t(), map, trigger_opts) :: term
      def trigger(channel, event, data, opts) do
        Router.cast({:trigger, channel, event, data}, opts)
      end

      @doc ~S"""
      Returns all the channels anyone is using, calls Pusher via REST API.
      """
      def channels do
        Router.call(:channels)
      end

      @doc ~S"""
      Returns only the channels this client is subscribed to.
      """
      def subscribed_channels do
        Router.call(:subscribed_channels)
      end

      @doc ~S"""
      Returns information about all the users subscribed to a presence channels
      this client is subscribed to.
      """
      def presence do
        Router.call(:presence)
      end

      @doc ~S"""
      Unsubscribes from a channel
      """
      def unsubscribe(channel) do
        Router.cast({:unsubscribe, channel})
      end

      @doc ~S"""
      Function meant to be overwritten in user module, e.g.:
      ```
      defmodule MyMod do
        use Pushest, otp_app: :my_mod

        handle_event({:ok, "my-channel, "my-event"}, frame) do
          # Do something with a frame here.
        end
      end
      ```
      """
      def handle_event({status, channel, event}, frame) do
        require Logger

        Logger.error(
          "No #{inspect(status)} handle_event/2 clause in #{__MODULE__} provided for #{
            inspect(event)
          }"
        )
      end

      defoverridable handle_event: 2
    end
  end
end