remove variable substitution from leadership and backstab abilities

data/core/macros/abilities.cfg

@@ -112,7 +112,7 @@ Adjacent own units of lower level will do more damage in battle. When a unit adj
         affect_self=no
         [affect_adjacent]
             [filter]
-                level=$($other_unit.level - 5)
+                lua_function="leadership_receiver_filter_5"
             [/filter]
         [/affect_adjacent]
     [/leadership]
@@ -123,7 +123,7 @@ Adjacent own units of lower level will do more damage in battle. When a unit adj
         affect_self=no
         [affect_adjacent]
             [filter]
-                level=$($other_unit.level - 4)
+                lua_function="leadership_receiver_filter_4"
             [/filter]
         [/affect_adjacent]
     [/leadership]
@@ -134,7 +134,7 @@ Adjacent own units of lower level will do more damage in battle. When a unit adj
         affect_self=no
         [affect_adjacent]
             [filter]
-                level=$($other_unit.level - 3)
+                lua_function="leadership_receiver_filter_3"
             [/filter]
         [/affect_adjacent]
     [/leadership]
@@ -145,7 +145,7 @@ Adjacent own units of lower level will do more damage in battle. When a unit adj
         affect_self=no
         [affect_adjacent]
             [filter]
-                level=$($other_unit.level - 2)
+                lua_function="leadership_receiver_filter_2"
             [/filter]
         [/affect_adjacent]
     [/leadership]
@@ -156,7 +156,7 @@ Adjacent own units of lower level will do more damage in battle. When a unit adj
         affect_self=no
         [affect_adjacent]
             [filter]
-                level=$($other_unit.level - 1)
+                lua_function="leadership_receiver_filter_1"
             [/filter]
         [/affect_adjacent]
     [/leadership]
@@ -349,13 +349,7 @@ Enemy units cannot see this unit while it is in deep water, except if they have
         multiply=2
         active_on=offense
         [filter_opponent]
-            [filter_adjacent]
+            lua_function="backstab_defender_filter"
-                adjacent=$other_unit.facing
-                is_enemy=yes
-                [not]
-                    status=petrified
-                [/not]
-            [/filter_adjacent]
         [/filter_opponent]
     [/damage]
 #enddef

data/lua/teleport_filter.lua

@@ -13,3 +13,46 @@ function teleport_target_filter(x, y)
 	local blocking_unit = wesnoth.get_unit(x, y)
 	return not blocking_unit
 end
+
+function backstab_defender_filter(defender)
+
+	local attacker_x = wesnoth.get_variable("other_unit.x")
+	local attacker_y = wesnoth.get_variable("other_unit.y")
+	
+	local defender_x = defender.x
+	local defender_y = defender.y
+	
+	local adjacent = {wesnoth.map.get_adjacent_tiles(x, y)}
+
+	local attacker_pos_index = nil
+	for i,v in ipairs(adjacent) do
+		if v[1] == attacker_x and v[2] == attacker_y then
+			attacker_pos_index = i
+		end
+	end
+	
+	if attacker_pos_index == nil then
+		-- Attack not from adjacent location
+		return false
+	end
+	
+	local opposite_pos_index = (((attacker_pos_index + 3) - 1) % 6) + 1
+	local opposite_unit = wesnoth.get_unit(adjacent[opposite_pos_index][1], adjacent[opposite_pos_index][2])
+
+	if not opposite_unit then
+		-- No opposite unit
+		return false
+	end
+
+	if opposite_unit.status.petrified then
+		return false
+	end
+	
+	return wesnoth.is_enemy(opposite_unit.side, defender.side)
+end
+
+for i = 1, 5 do
+	_G["leadership_receiver_filter_" .. i] = function(receiver)
+		return receiver.level == wesnoth.get_variable("other_unit.level") - i
+	end
+end