Separate captcha implementation into a behaviour and use it

lib/pleroma/captcha/kocaptcha.ex

@@ -0,0 +1,37 @@
+defmodule Pleroma.Captcha.Kocaptcha do
+  alias Pleroma.Captcha.Service
+  @behaviour Service
+
+  @ets __MODULE__.Ets
+
+  @impl Service
+  def new() do
+    endpoint = Pleroma.Config.get!([__MODULE__, :endpoint])
+    case HTTPoison.get(endpoint <> "/new") do
+      {:error, _} ->
+        %{error: "Kocaptcha service unavailable"}
+      {:ok, res} ->
+        json_resp = Poison.decode!(res.body)
+
+        token = json_resp["token"]
+
+        true = :ets.insert(@ets, {token, json_resp["md5"]})
+
+        %{type: :kocaptcha, token: token, url: endpoint <> json_resp["url"]}
+    end
+  end
+
+  @impl Service
+  def validate(token, captcha) do
+    with false <- is_nil(captcha),
+         [{^token, saved_md5}] <- :ets.lookup(@ets, token),
+         true <- (:crypto.hash(:md5, captcha) |> Base.encode16) == String.upcase(saved_md5) do
+      # Clear the saved value
+      :ets.delete(@ets, token)
+
+      true
+    else
+      _ -> false
+    end
+  end
+end