Lua AIs: do not use engine's 'data' variable unless necessary

Now that all the AIs use external CAs, there is no need to use the persistent 'data' variable any more, unless information is to be exchanged between different CAs or is supposed to be persistent across save/load cycles.

data/ai/lua/ca_castle_switch.lua

@@ -3,6 +3,9 @@
 local AH = wesnoth.require "ai/lua/ai_helper.lua"
 local M = wesnoth.map
 
+local CS_leader_score
+-- Note that leader_target is also needed by the recruiting CA, so it must be stored in 'data'
+
 local function get_reachable_enemy_leaders(unit)
 	-- We're cheating a little here and also find hidden enemy leaders. That's
 	-- because a human player could make a pretty good educated guess as to where
@@ -51,7 +54,7 @@ function ca_castle_switch:evaluation(cfg, data)
 		local next_hop = AH.next_hop(leader, data.leader_target[1], data.leader_target[2])
 		if next_hop and next_hop[1] == data.leader_target[1]
 		and next_hop[2] == data.leader_target[2] then
-			return data.leader_score
+			return CS_leader_score
 		end
 	end
 
@@ -158,7 +161,7 @@ function ca_castle_switch:evaluation(cfg, data)
 		data.leader_target = next_hop
 
 		-- if we're on a keep, wait until there are no movable units on the castle before moving off
-		data.leader_score = 290000
+		CS_leader_score = 290000
 		if wesnoth.get_terrain_info(wesnoth.get_terrain(leader.x, leader.y)).keep then
 			local castle = wesnoth.get_locations {
 				x = "1-"..width, y = "1-"..height,
@@ -178,12 +181,12 @@ function ca_castle_switch:evaluation(cfg, data)
 				end
 			end
 			if should_wait then
-				data.leader_score = 15000
+				CS_leader_score = 15000
 			end
 		end
 
 		if AH.print_eval() then AH.done_eval_messages(start_time, ca_name) end
-		return data.leader_score
+		return CS_leader_score
 	end
 
 	if AH.print_eval() then AH.done_eval_messages(start_time, ca_name) end

data/ai/lua/ca_grab_villages.lua

@@ -4,6 +4,8 @@ local AH = wesnoth.require "ai/lua/ai_helper.lua"
 local BC = wesnoth.require "ai/lua/battle_calcs.lua"
 local M = wesnoth.map
 
+local GV_unit, GV_village
+
 local ca_grab_villages = {}
 
 function ca_grab_villages:evaluation(cfg, data)
@@ -116,7 +118,7 @@ function ca_grab_villages:evaluation(cfg, data)
     end
 
     if best_village then
-        data.unit, data.village = best_unit, best_village
+        GV_unit, GV_village = best_unit, best_village
         if (max_rating >= 1000) then
             if AH.print_eval() then AH.done_eval_messages(start_time, ca_name) end
             return return_value
@@ -131,10 +133,10 @@ end
 
 function ca_grab_villages:execution(cfg, data)
     if AH.print_exec() then AH.print_ts('   Executing grab_villages CA') end
-    if AH.show_messages() then wesnoth.wml_actions.message { speaker = data.unit.id, message = 'Grab villages' } end
+    if AH.show_messages() then wesnoth.wml_actions.message { speaker = GV_unit.id, message = 'Grab villages' } end
 
-    AH.movefull_stopunit(ai, data.unit, data.village)
-    data.unit, data.village = nil, nil
+    AH.movefull_stopunit(ai, GV_unit, GV_village)
+    GV_unit, GV_village = nil, nil
 end
 
 return ca_grab_villages

data/ai/lua/ca_high_xp_attack.lua

@@ -26,6 +26,8 @@ local M = wesnoth.map
 --    so that we can follow up with stronger units. In addition, use of poison or
 --    slow attacks is strongly discouraged. See code for exact equations.
 
+local XP_attack
+
 local ca_attack_highxp = {}
 
 function ca_attack_highxp:evaluation(cfg, data)
@@ -284,15 +286,15 @@ function ca_attack_highxp:evaluation(cfg, data)
     end
 
     if best_attack then
-        data.XP_attack = best_attack
+        XP_attack = best_attack
     end
 
     return max_ca_score
 end
 
 function ca_attack_highxp:execution(cfg, data)
-    AH.robust_move_and_attack(ai, data.XP_attack.src, data.XP_attack.dst, data.XP_attack.target, { weapon = data.XP_attack.attack_num })
-    data.XP_attack = nil
+    AH.robust_move_and_attack(ai, XP_attack.src, XP_attack.dst, XP_attack.target, { weapon = XP_attack.attack_num })
+    XP_attack = nil
 end
 
 return ca_attack_highxp

data/ai/lua/ca_move_to_any_enemy.lua

@@ -5,6 +5,8 @@
 
 local AH = wesnoth.require "ai/lua/ai_helper.lua"
 
+local MTAE_unit, MTAE_destination
+
 local ca_move_to_any_enemy = {}
 
 function ca_move_to_any_enemy:evaluation(cfg, data)
@@ -45,16 +47,17 @@ function ca_move_to_any_enemy:evaluation(cfg, data)
         return 0
     end
 
-    data.destination = destination
-    data.unit = unit
+    MTAE_destination = destination
+    MTAE_unit = unit
 
     if AH.print_eval() then AH.done_eval_messages(start_time, ca_name) end
     return 1
 end
 
 function ca_move_to_any_enemy:execution(cfg, data)
     if AH.print_exec() then AH.print_ts('   Executing move_to_any_enemy CA') end
-    AH.checked_move(ai, data.unit, data.destination[1], data.destination[2])
+    AH.checked_move(ai, MTAE_unit, MTAE_destination[1], MTAE_destination[2])
+    MTAE_unit, MTAE_destination = nil,nil
 end
 
 return ca_move_to_any_enemy

data/ai/lua/ca_retreat_injured.lua

@@ -3,6 +3,8 @@
 local AH = wesnoth.require "ai/lua/ai_helper.lua"
 local R = wesnoth.require "ai/lua/retreat.lua"
 
+local retreat_unit, retreat_loc
+
 local ca_retreat_injured = {}
 
 function ca_retreat_injured:evaluation(cfg, data)
@@ -15,8 +17,8 @@ function ca_retreat_injured:evaluation(cfg, data)
     }
     local unit, loc = R.retreat_injured_units(units)
     if unit then
-        data.retreat_unit = unit
-        data.retreat_loc = loc
+        retreat_unit = unit
+        retreat_loc = loc
 
         -- First check if attacks are possible for any unit
         -- If one with > 50% chance of kill is possible, set return_value to lower than combat CA
@@ -36,9 +38,9 @@ end
 
 function ca_retreat_injured:execution(cfg, data)
     if AH.print_exec() then AH.print_ts('   Executing retreat_injured CA') end
-    AH.robust_move_and_attack(ai, data.retreat_unit, data.retreat_loc)
-    data.retreat_unit = nil
-    data.retreat_loc = nil
+    AH.robust_move_and_attack(ai, retreat_unit, retreat_loc)
+    retreat_unit = nil
+    retreat_loc = nil
 end
 
 return ca_retreat_injured

data/ai/lua/ca_spread_poison.lua

@@ -2,6 +2,8 @@
 
 local AH = wesnoth.require "ai/lua/ai_helper.lua"
 
+local SP_attack
+
 local ca_spread_poison = {}
 
 function ca_spread_poison:evaluation(cfg, data)
@@ -78,7 +80,7 @@ function ca_spread_poison:evaluation(cfg, data)
     end
 
     if best_attack then
-        data.attack = best_attack
+        SP_attack = best_attack
         if AH.print_eval() then AH.done_eval_messages(start_time, ca_name) end
         return 190000
     end
@@ -87,16 +89,16 @@ function ca_spread_poison:evaluation(cfg, data)
 end
 
 function ca_spread_poison:execution(cfg, data)
-    local attacker = wesnoth.get_unit(data.attack.src.x, data.attack.src.y)
+    local attacker = wesnoth.get_unit(SP_attack.src.x, SP_attack.src.y)
     -- If several attacks have poison, this will always find the last one
     local is_poisoner, poison_weapon = AH.has_weapon_special(attacker, "poison")
 
     if AH.print_exec() then AH.print_ts('   Executing spread_poison CA') end
     if AH.show_messages() then wesnoth.wml_actions.message { speaker = attacker.id, message = 'Poison attack' } end
 
-    AH.robust_move_and_attack(ai, attacker, data.attack.dst, data.attack.target, { weapon = poison_weapon })
+    AH.robust_move_and_attack(ai, attacker, SP_attack.dst, SP_attack.target, { weapon = poison_weapon })
 
-    data.attack = nil
+    SP_attack = nil
 end
 
 return ca_spread_poison

data/ai/micro_ais/cas/ca_bottleneck_attack.lua

@@ -1,5 +1,7 @@
 local AH = wesnoth.require "ai/lua/ai_helper.lua"
 
+local BD_attacker, BD_target, BD_weapon, BD_bottleneck_attacks_done
+
 local ca_bottleneck_attack = {}
 
 function ca_bottleneck_attack:evaluation(cfg, data)
@@ -48,29 +50,29 @@ function ca_bottleneck_attack:evaluation(cfg, data)
 
     if (not best_attacker) then
         -- In this case we take attacks away from all units
-        data.BD_bottleneck_attacks_done = true
+        BD_bottleneck_attacks_done = true
     else
-        data.BD_bottleneck_attacks_done = false
-        data.BD_attacker = best_attacker
-        data.BD_target = best_target
-        data.BD_weapon = best_weapon
+        BD_bottleneck_attacks_done = false
+        BD_attacker = best_attacker
+        BD_target = best_target
+        BD_weapon = best_weapon
     end
 
     return cfg.ca_score
 end
 
 function ca_bottleneck_attack:execution(cfg, data)
-    if data.BD_bottleneck_attacks_done then
+    if BD_bottleneck_attacks_done then
         local units = AH.get_units_with_attacks { side = wesnoth.current.side }
         for _,unit in ipairs(units) do
             AH.checked_stopunit_attacks(ai, unit)
         end
     else
-        AH.checked_attack(ai, data.BD_attacker, data.BD_target, data.BD_weapon)
+        AH.checked_attack(ai, BD_attacker, BD_target, BD_weapon)
     end
 
-    data.BD_attacker, data.BD_target, data.BD_weapon = nil, nil, nil
-    data.BD_bottleneck_attacks_done = nil
+    BD_attacker, BD_target, BD_weapon = nil, nil, nil
+    BD_bottleneck_attacks_done = nil
 end
 
 return ca_bottleneck_attack