make lang check overridable add nonconfigured engine shim

init.lua

@@ -5,8 +5,24 @@ dofile(modpath.."/http.lua" )
 dofile(modpath.."/chat.lua" )
 local engine = minetest.setting_get("babelfish.engine") or "yandex"
 babel.key = minetest.setting_get("babelfish.key")
+
+-- ========================== Language engine and overridable validation
+
+function babel.validate_lang(self,langstring)
+	for target, langname in pairs(babel.langcodes) do
+		if target == langstring then
+			return true
+		end
+	end
+
+	return langstring.." is not a recognized language"
+end
+
+if not babel.key then engine = "none" end
 dofile(modpath.."/"..engine.."_engine.lua")
 
+-- =====================================================================/
+
 local chat_history = {}
 
 minetest.register_on_chat_message(function(player, message)
@@ -21,16 +37,6 @@ local function components(mystring)
 	return targetlang, targetphrase
 end
 
-local function validate_lang(langstring)
-	for target, langname in pairs(babel.langcodes) do
-		if target == langstring then
-			return true
-		end
-	end
-
-	return false
-end
-
 local function validate_player(playername)
 	if minetest.get_player_by_name(playername) then
 		return true
@@ -45,8 +51,9 @@ end
 local function f_babel(player, argstring)
 	local targetplayer, targetlang = components(argstring)
 
-	if not validate_lang(targetlang) then
-		babel.chat_send_player(player, targetlang.." is not a recognized language")
+	local validation = babel:validate_lang(targetlang)
+	if validation ~= true then
+		babel.chat_send_player(player, validation)
 		return
 	end
 
@@ -63,8 +70,9 @@ end
 function f_babelshout(player, argstring)
 	local targetlang, targetphrase = components(argstring)
 
-	if not validate_lang(targetlang) then
-		babel.chat_send_player(player, targetlang.." is not a recognized language")
+	local validation = babel:validate_lang(targetlang)
+	if validation ~= true then
+		babel.chat_send_player(player, validation)
 		return
 	end
 
@@ -78,8 +86,9 @@ function f_babelmsg(player, argstring)
 	local targetlang, targetphrase = components(argstring)
 	local targetplayer, targetphrase = components(targetphrase)
 
-	if not validate_lang(targetlang) then
-		babel.chat_send_player(player, targetlang.." is not a recognized language")
+	local validation = babel:validate_lang(targetlang)
+	if validation ~= true then
+		babel.chat_send_player(player, validation)
 		return
 	end
 

none_engine.lua

@@ -0,0 +1,13 @@
+babel.engine = "none"
+
+babel.langcodes = {}
+
+local serviceurl = "https://example.com"
+
+function babel.validate_lang()
+	return "Not configured"
+end
+
+function babel.translate(self,phrase,lang)
+	return "Not configured"
+end