Small achievements cleanup (#7368)

* Move logic into lua engine code.
* Don't let use of limit decrease an achievement's progress.

data/lua/wml-tags.lua

@@ -1013,12 +1013,7 @@ function wml_actions.remove_trait(cfg)
 end
 
 function wml_actions.set_achievement(cfg)
-	local achievement = wesnoth.achievements.get(cfg.content_for, cfg.id)
-	-- don't show the achievement popup for an achievement they already have
-	if not achievement.achieved then
-		wesnoth.achievements.set(cfg.content_for, cfg.id)
-		gui.show_popup(achievement.name_completed, achievement.description_completed, achievement.icon_completed)
-	end
+	wesnoth.achievements.set(cfg.content_for, cfg.id)
 end
 
 function wml_actions.progress_achievement(cfg)
@@ -1027,9 +1022,5 @@ function wml_actions.progress_achievement(cfg)
 		return
 	end
 
-	local pcfg = wesnoth.achievements.progress(cfg.content_for, cfg.id, cfg.amount, tonumber(cfg.limit) or 999999999)
-	-- if this update completes the achievement, mark it as complete and show the popup
-	if pcfg.progress ~= -1 and pcfg.max_progress > 0 and pcfg.progress >= pcfg.max_progress then
-		wml_actions.set_achievement(cfg)
-	end
+	wesnoth.achievements.progress(cfg.content_for, cfg.id, cfg.amount, tonumber(cfg.limit) or 999999999)
 end

src/preferences/general.cpp

@@ -1085,7 +1085,13 @@ int progress_achievement(const std::string& content_for, const std::string& id,
 			{
 				if(in_progress["id"].str() == id)
 				{
-					in_progress["progress_at"] = std::clamp(in_progress["progress_at"].to_int() + amount, 0, std::min(limit, max_progress));
+					// don't let using 'limit' decrease the achievement's current progress
+					int starting_progress = in_progress["progress_at"].to_int();
+					if(starting_progress >= limit) {
+						return starting_progress;
+					}
+
+					in_progress["progress_at"] = std::clamp(starting_progress + amount, 0, std::min(limit, max_progress));
 					return in_progress["progress_at"].to_int();
 				}
 			}

src/scripting/game_lua_kernel.cpp

@@ -3078,6 +3078,10 @@ int game_lua_kernel::intf_set_achievement(lua_State *L)
 		if(group.content_for_ == content_for) {
 			for(achievement& achieve : group.achievements_) {
 				if(achieve.id_ == id) {
+					// already achieved
+					if(achieve.achieved_) {
+						return 0;
+					}
 					// found the achievement - mark it as completed
 					preferences::set_achievement(content_for, id);
 					achieve.achieved_ = true;
@@ -3088,6 +3092,12 @@ int game_lua_kernel::intf_set_achievement(lua_State *L)
 					if(achieve.sound_path_ != "") {
 						sound::play_sound(achieve.sound_path_, sound::SOUND_FX);
 					}
+					// show the achievement popup
+					luaW_getglobal(L, "gui", "show_popup");
+					luaW_pushtstring(L, achieve.name_completed_);
+					luaW_pushtstring(L, achieve.description_completed_);
+					lua_pushstring(L, achieve.icon_completed_.c_str());
+					luaW_pcall(L, 3, 0, 0);
 					return 0;
 				}
 			}
@@ -3173,47 +3183,56 @@ int game_lua_kernel::intf_get_achievement(lua_State *L)
  * - Arg 2: string - id.
  * - Arg 3: int - the amount to progress the achievement.
  * - Arg 4: int - the limit the achievement can progress by
- * - Ret 1: WML table returned by the function.
+ * - Ret 1: int - the achievement's current progress after adding amount, -2 if not found, -1 not a progressable achievement (including if it's already achieved)
+ * - Ret 2: int - the achievement's max progress, -2 if not found, or -1 not a progressable achievement
  */
 int game_lua_kernel::intf_progress_achievement(lua_State *L)
 {
 	const char *content_for = luaL_checkstring(L, 1);
 	const char *id = luaL_checkstring(L, 2);
 	int amount = luaL_checkinteger(L, 3);
-	int limit = luaL_checkinteger(L, 4);
-
-	config cfg;
-	cfg["progress"] = 0;
-	cfg["max_progress"] = 0;
+	int limit = luaL_optinteger(L, 4, 999999999);
 
 	for(achievement_group& group : game_config_manager::get()->get_achievements()) {
 		if(group.content_for_ == content_for) {
 			for(achievement& achieve : group.achievements_) {
 				if(achieve.id_ == id) {
-					// found the achievement
+					// check that this is a progressable achievement
+					if(achieve.max_progress_ == 0) {
+						ERR_LUA << "Attempted to progress achievement " << id << " for achievement group " << content_for << ", which does not have max_progress set.";
+						lua_pushinteger(L, -1);
+						lua_pushinteger(L, -1);
+						return 2;
+					}
+
 					if(!achieve.achieved_) {
 						int progress = preferences::progress_achievement(content_for, id, limit, achieve.max_progress_, amount);
-						cfg["progress"] = progress;
-						achieve.current_progress_ = progress;
+						if(progress >= achieve.max_progress_) {
+							intf_set_achievement(L);
+							achieve.current_progress_ = -1;
+						}
+						lua_pushinteger(L, progress);
 					} else {
-						cfg["progress"] = -1;
+						lua_pushinteger(L, -1);
 					}
-					cfg["max_progress"] = achieve.max_progress_;
-					luaW_pushconfig(L, cfg);
-					return 1;
+					lua_pushinteger(L, achieve.max_progress_);
+
+					return 2;
 				}
 			}
 			// achievement not found - existing achievement group but non-existing achievement id
 			ERR_LUA << "Achievement " << id << " not found for achievement group " << content_for;
-			luaW_pushconfig(L, cfg);
-			return 1;
+			lua_pushinteger(L, -2);
+			lua_pushinteger(L, -2);
+			return 2;
 		}
 	}
 
 	// achievement group not found
 	ERR_LUA << "Achievement group " << content_for << " not found";
-	luaW_pushconfig(L, cfg);
-	return 1;
+	lua_pushinteger(L, -2);
+	lua_pushinteger(L, -2);
+	return 2;
 }
 
 /**