Discord notifs (#14)

* Add role id to config

* Add discord notifications for games

* Fix discord discriminant tests

1 files changed, 129 insertions, 0 deletions

diff --git a/lib/chessh/discord/notifier.ex b/lib/chessh/discord/notifier.ex
new file mode 100644
index 0000000..09c4ec0
--- /dev/null
+++ b/lib/chessh/discord/notifier.ex
@@ -0,0 +1,129 @@
+defmodule Chessh.DiscordNotifier do
+  use GenServer
+
+  @name :discord_notifier
+
+  alias Chessh.{Game, Player, Repo}
+
+  def start_link(state \\ []) do
+    GenServer.start_link(__MODULE__, state, name: @name)
+  end
+
+  @impl true
+  def init(state) do
+    {:ok, state}
+  end
+
+  @impl true
+  def handle_cast(x, state), do: handle_info(x, state)
+
+  @impl true
+  def handle_info({:attempt_notification, notification} = body, state) do
+    [discord_notification_rate, discord_notification_rate_ms] =
+      Application.get_env(:chessh, RateLimits)
+      |> Keyword.take([:discord_notification_rate, :discord_notification_rate_ms])
+      |> Keyword.values()
+
+    reschedule_delay = Application.get_env(:chessh, RateLimits)[:reschedule_delay]
+
+    case Hammer.check_rate_inc(
+           :redis,
+           "discord-webhook-message-rate",
+           discord_notification_rate_ms,
+           discord_notification_rate,
+           1
+         ) do
+      {:allow, _count} ->
+        send_notification(notification)
+
+      {:deny, _limit} ->
+        Process.send_after(self(), body, reschedule_delay)
+    end
+
+    {:noreply, state}
+  end
+
+  @impl true
+  def handle_info({:schedule_notification, notification, delay}, state) do
+    Process.send_after(self(), {:attempt_notification, notification}, delay)
+    {:noreply, state}
+  end
+
+  defp send_notification({:move_reminder, game_id}) do
+    [min_delta_t, discord_game_move_notif_webhook] =
+      Application.get_env(:chessh, DiscordNotifications)
+      |> Keyword.take([:game_move_notif_delay_ms, :discord_game_move_notif_webhook])
+      |> Keyword.values()
+
+    case Repo.get(Game, game_id) do
+      nil ->
+        nil
+
+      game ->
+        %Game{
+          dark_player: %Player{discord_id: dark_player_discord_id},
+          light_player: %Player{discord_id: light_player_discord_id},
+          turn: turn,
+          updated_at: last_updated,
+          moves: move_count
+        } = Repo.preload(game, [:dark_player, :light_player])
+
+        delta_t = NaiveDateTime.diff(NaiveDateTime.utc_now(), last_updated, :millisecond)
+
+        if delta_t >= min_delta_t do
+          post_discord(
+            discord_game_move_notif_webhook,
+            "<@#{if turn == :light, do: light_player_discord_id, else: dark_player_discord_id}> it is your move in Game #{game_id} (move #{move_count})."
+          )
+        end
+    end
+  end
+
+  defp send_notification({:game_created, game_id}) do
+    [pingable_mention, discord_game_created_notif_webhook] =
+      Application.get_env(:chessh, DiscordNotifications)
+      |> Keyword.take([:looking_for_games_role_mention, :discord_new_game_notif_webhook])
+      |> Keyword.values()
+
+    case Repo.get(Game, game_id) do
+      nil ->
+        nil
+
+      game ->
+        %Game{
+          dark_player: dark_player,
+          light_player: light_player
+        } = Repo.preload(game, [:dark_player, :light_player])
+
+        message =
+          case {is_nil(light_player), is_nil(dark_player)} do
+            {true, false} ->
+              "#{pingable_mention}, <@#{dark_player.discord_id}> is looking for an opponent to play as light in Game #{game_id}"
+
+            {false, true} ->
+              "#{pingable_mention}, <@#{light_player.discord_id}> is looking for an opponent to play as dark in Game #{game_id}"
+
+            _ ->
+              false
+          end
+
+        if message do
+          post_discord(discord_game_created_notif_webhook, message)
+        end
+    end
+  end
+
+  defp post_discord(webhook, message) do
+    :httpc.request(
+      :post,
+      {
+        String.to_charlist(webhook),
+        [],
+        'application/json',
+        %{content: message} |> Jason.encode!() |> String.to_charlist()
+      },
+      [],
+      []
+    )
+  end
+end