Add a buffer for slowing message output to avoid flooding out the bot

lib/nulform/buffer.ex

@@ -0,0 +1,79 @@
+defmodule Nulform.Buffer do
+    use GenServer.Behaviour
+    @moduledoc """
+        A buffer takes outgoing messages from the bot and sends them to the
+        given connection process with a delay to prevent the bot from flooding
+        itself out of the network.
+
+        The algorithm is as follows (reasonable values are t = 2, m = 10):
+        1. Read messages from input
+        2. Insert messages into queue
+        3. Set timer to be current time, if lower
+        4. For each message
+            4.1. Raise timer value by t
+            4.2. If timer value is higher than current time + m, next send is
+                 at current time + t, otherwise send message immediately
+    """
+
+    defrecord Data,
+        connection: nil,
+        buffer: [] :: list,
+        waiting: :false,
+        timer: 0 :: integer
+
+    def init(pid) do
+        data = Data.new(connection: pid)
+        {:ok, data}
+    end
+
+    def handle_cast(msg, data) do
+        data = data.buffer data.buffer ++ [msg]
+
+        data = handle_buffer data
+        {:noreply, data}
+    end
+
+    def handle_info(msg, data) do
+        case msg do
+            {:send_message} ->
+                data = send_message data
+                data = handle_buffer data
+        end
+        {:noreply, data}
+    end
+
+
+    defp handle_buffer(data) do
+        {_, time, _} = :erlang.now()
+        if data.timer < time do
+            data = data.timer time
+        end
+
+        if (data.timer - time) <= 10 do
+            if not Enum.empty? data.buffer do
+                data = send_message data
+                data = data.waiting :false
+            end
+        else
+            if (not Enum.empty? data.buffer) and not data.waiting do
+                {:ok, timer} = :timer.send_after 2000, {:send_message}
+                data = data.waiting :true
+            end
+        end
+
+        data
+    end
+
+    defp send_message(data) do
+        data = data.waiting :false
+
+        if not Enum.empty? data.buffer do
+            [msg | tail] = data.buffer
+            data = data.buffer tail
+            data.connection <- {:nulform, :msg_out, msg}
+            data = data.timer data.timer + 2
+        else
+            data
+        end
+    end
+end