Add support for AI candidate actions written in lua.

patch LuaW_pcall to support LUA_MULTRET. Patch #1558 by Darkas.

changelog

@@ -2,6 +2,7 @@ Version 1.7.15+svn:
  * AI:
    * Fixed bug #14247: Make formula AI behave correctly if the side has only 1
      potential recruit.
+   * Added support for candidate actions written in lua.
  * Campaigns:
    * Legend of Wesmere:
      * Fixed bug #15631: Scenario 3: arrival of Kalenz failed

data/ai/scenarios/scenario-lua-ai.cfg

@@ -205,11 +205,32 @@ local my_ai = { }
 local ai_stdlib = wesnoth.require('ai/lua/stdlib.lua');
 ai_stdlib.init(ai)
 
-function my_ai:execute()
-       ai.say_hello()
+function my_ai:stage_hello()
+       wesnoth.message('hello from stage!')
+end
+
+function my_ai:candidate_action_evaluation_hello()
+       wesnoth.message('hello from candidate action evaluation!')
+       return 42, {test=123}
+end
+
+function my_ai:candidate_action_execution_hello(cfg)
+       wesnoth.message('hello from candidate action execution!')
+       wesnoth.message('test value is ' .. cfg.test)
        self:do_moves()
 end
 
+function my_ai:candidate_action_evaluation_hello2()
+       wesnoth.message('hello from second candidate action evaluation!')
+       return 99
+end
+
+function my_ai:candidate_action_execution_hello2()
+       wesnoth.message('hello from second candidate action execution!')
+       self:do_moves()
+end
+
+
 function my_ai:do_moves()
        my_leader = wesnoth.get_units({canrecruit = true, side = ai.side})[1]
        --! move (partial move)
@@ -237,9 +258,24 @@ return my_ai
 --! ==============================================================
 >>
             [/engine]
+            [stage]
+                name=testing_ai_default::candidate_action_evaluation_loop
+                [candidate_action]
+                     engine=lua
+                     name=first
+                     evaluation="return (...):candidate_action_evaluation_hello()"
+                     execution="local ai, cfg = ...; ai:candidate_action_execution_hello(cfg)"
+                [/candidate_action]
+                [candidate_action]
+                     engine=lua
+                     name=second
+                     evaluation="return (...):candidate_action_evaluation_hello2()"
+                     execution="(...):candidate_action_execution_hello2()"
+                [/candidate_action]
+            [/stage]
             [stage]
                 engine="lua"
-                code= "(...):execute()"
+                code= "(...):stage_hello()"
             [/stage]
         [/ai]
     [/side]

data/core/about.cfg

@@ -799,6 +799,9 @@
     [entry]
         name = "Alesis Novik"
     [/entry]
+    [entry]
+        name = "André Knispel"
+    [/entry]
     [entry]
         name = "Andrea Palmatè (afxgroup)"
     [/entry]

src/ai/composite/engine_lua.cpp

@@ -55,7 +55,7 @@ public:
 	{
 		serialized_evaluation_state_ = config();
 		if (evaluation_action_handler_) {
-			evaluation_action_handler_->handle(serialized_evaluation_state_);
+			evaluation_action_handler_->handle(serialized_evaluation_state_, true);
 		} else {
 			return BAD_SCORE;
 		}

src/scripting/lua.cpp

@@ -364,6 +364,8 @@ static bool luaW_pcall(lua_State *L
 	lua_rawget(L, LUA_REGISTRYINDEX);
 	lua_insert(L, -2 - nArgs);
 
+	int error_handler_index = lua_gettop(L) - nArgs - 1;
+
 	// Call the function.
 	int res = lua_pcall(L, nArgs, nRets, -2 - nArgs);
 	if (res)
@@ -382,7 +384,13 @@ static bool luaW_pcall(lua_State *L
 	}
 
 	// Remove the error handler.
-	lua_remove(L, -1 - nRets);
+
+	if(nRets == LUA_MULTRET) {
+		lua_remove(L, error_handler_index);
+	} else {
+		lua_remove(L, -1 - nRets);
+	}
+
 	return true;
 }
 
@@ -2735,19 +2743,38 @@ lua_ai_context::~lua_ai_context()
 	lua_pop(L, 1);
 }
 
-/**
- * handling of config in-out parameter will be done later
- */
-void lua_ai_action_handler::handle(config &/*cfg*/)
+void lua_ai_action_handler::handle(config &cfg, bool configOut)
 {
+	int initial_top = lua_gettop(L);//get the old stack size
+
 	// Load the user function from the registry.
 	lua_pushlightuserdata(L, (void *)&aisKey);//stack size is now 1 [-1: ais_table key]
 	lua_rawget(L, LUA_REGISTRYINDEX);//stack size is still 1 [-1: ais_table]
 	lua_rawgeti(L, -1, num_);//stack size is 2 [-1: ai_action  -2: ais_table]
-	lua_remove(L,-2);//stack size is 1 [-1: ai_action]
+	lua_remove(L, -2);//stack size is 1 [-1: ai_action]
 	//load the lua ai context as a parameter
 	context_.load();//stack size is 2 [-1: ai_context -2: ai_action]
-	luaW_pcall(L, 1, 0, true);
+
+	if (!configOut)
+	{
+		lua_newtable(L);//stack size is 3 [-1: table -2: ai_context -3: ai_action]
+		table_of_wml_config(L, cfg);//the new table now contains the config
+		luaW_pcall(L, 2, LUA_MULTRET, true);
+	}
+	else if (lua_gettop(L) > initial_top)
+	{
+		if (luaW_pcall(L, 1, LUA_MULTRET, true)) {
+			int score = lua_tonumber(L, initial_top + 1);//get score
+
+			if (lua_gettop(L) >= initial_top + 2) {//check if we also have config
+				luaW_toconfig(L, initial_top + 2, cfg);//get config
+			}
+
+			cfg["score"] = str_cast(score);//write score to the config
+		}
+	}
+
+	lua_settop(L, initial_top);//empty stack
 }
 
 lua_ai_action_handler::~lua_ai_action_handler()

src/scripting/lua.hpp

@@ -51,7 +51,7 @@ public:
 	{
 	}
 	~lua_ai_action_handler();
-	void handle(config &);
+	void handle(config &, bool configOut = false);
 };