From 8d42e6ecb38c5ed67dc4cb32c42b422aaaabf2e1 Mon Sep 17 00:00:00 2001
From: Alek Ratzloff <alekratz@gmail.com>
Date: Wed, 12 Aug 2020 15:33:04 -0700
Subject: [PATCH] Add ping watcher to Omnibot.Core

Core module now pings the server and attempts to reconnect if a
respective pong has not been received in a certain amount of time.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>
---
 lib/core.ex | 66 +++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 62 insertions(+), 4 deletions(-)

diff --git a/lib/core.ex b/lib/core.ex
index 261c970..229c431 100644
--- a/lib/core.ex
+++ b/lib/core.ex
@@ -1,8 +1,20 @@
 defmodule Omnibot.Core do
+  require Logger
   use Omnibot.Plugin
-  alias Omnibot.{Config, Irc}
+  alias Omnibot.{Config, Irc, Util}
 
-  @default_config channels: :all
+  @default_config ping_every: 60, ping_after: 60, channels: :all
+
+  @impl true
+  def children(_cfg) do
+    [{Task.Supervisor, name: Omnibot.Core.PingWatchers}]
+  end
+
+  @impl true
+  def on_connect(irc) do
+    Logger.info("Starting ping watcher")
+    Task.Supervisor.async(Omnibot.Core.PingWatchers, fn -> ping_watcher(irc) end)
+  end
 
   @impl true
   def on_join(irc, channel, nick) do
@@ -36,18 +48,27 @@ defmodule Omnibot.Core do
     end
   end
 
+  @impl true
+  def on_msg(irc, :connect) do
+    on_connect(irc)
+  end
+
   @impl true
   def on_msg(irc, msg) do
     case String.upcase(msg.command) do
       "001" -> sync_channels(irc)
-      "PING" -> Irc.send_msg(irc, "PONG", msg.params)
+      "PING" ->
+        Irc.send_msg(irc, "PONG", msg.params)
+        update_last_ping(Util.now_unix())
+        update_last_pong(Util.now_unix()) # also update pong because we ponged
+      "PONG" -> update_last_pong(Util.now_unix())
       _ -> route_msg(irc, msg)
     end
   end
 
   @impl true
   def on_init(_cfg) do
-    %{channels: MapSet.new()}
+    %{channels: MapSet.new(), last_pong: Util.now_unix(), last_ping: Util.now_unix()}
   end
 
   defp sync_channels(irc) do
@@ -71,5 +92,42 @@ defmodule Omnibot.Core do
   defp remove_channel(channel) do
     update_state(fn cfg = %{channels: channels} -> %{cfg | channels: MapSet.delete(channels, channel)} end)
   end
+
+  defp last_pong() do
+    state().last_pong
+  end
+
+  defp update_last_pong(last_pong) do
+    update_state(fn cfg -> %{cfg | last_pong: last_pong} end)
+  end
+
+  defp last_ping() do
+    state().last_ping
+  end
+
+  defp update_last_ping(last_ping) do
+    update_state(fn cfg -> %{cfg | last_ping: last_ping} end)
+  end
+
+  defp ping_watcher(irc) do
+    since_pong = Util.now_unix() - last_pong()
+    since_ping = Util.now_unix() - last_ping()
+    ping_every = cfg(:ping_every)
+    ping_after = cfg(:ping_after)
+    cond do
+      # Kill IRC instance
+      since_pong >= (3 * ping_every) ->
+        Logger.error("IRC has not replied in #{3 * ping_every}")
+        Process.exit(irc, :ping_timeout)
+
+      # Send ping message
+      since_pong >= ping_every and ping_after >= since_ping ->
+        Irc.send_msg(irc, "PING", "omnibot")
+
+      true -> nil
+    end
+    Process.sleep(1000)
+    ping_watcher(irc)
+  end
 end