1 files changed, 32 insertions, 0 deletions
diff --git a/lib/irc/parser/mode.ex b/lib/irc/parser/mode.ex
new file mode 100644
index 0000000..d4c0a16
--- /dev/null
+++ b/lib/irc/parser/mode.ex
@@ -0,0 +1,32 @@
+defmodule Irc.Parser.Mode do
+  @moduledoc """
+  Mode change parser
+  """
+
+  def changes(string, previous) do
+    list = to_charlist(string)
+    acc_changes(list, nil, previous)
+  end
+
+  defp acc_changes([?+ | rest], _, acc) do
+    acc_changes(rest, true, acc)
+  end
+
+  defp acc_changes([?- | rest], _, acc) do
+    acc_changes(rest, false, acc)
+  end
+
+  defp acc_changes([0x20 | _], _, acc), do: acc
+
+  defp acc_changes([char | rest], action, acc) do
+    acc = if action do
+      [char | acc]
+    else
+      List.delete(acc, char)
+    end
+    acc_changes(rest, action, acc)
+  end
+
+  defp acc_changes([], _, acc), do: acc
+
+end