Goto MAI: add avoid_enemies= parameter

data/ai/micro_ais/ais/mai_goto_engine.lua

@@ -5,8 +5,19 @@ return {
 
         local H = wesnoth.require "lua/helper.lua"
         local AH = wesnoth.require "ai/lua/ai_helper.lua"
+        local BC = wesnoth.require "ai/lua/battle_calcs.lua"
         local LS = wesnoth.require "lua/location_set.lua"
 
+        local function custom_cost(x, y, u, enemy_map, enemy_attack_map, multiplier)
+            local terrain = wesnoth.get_terrain(x, y)
+            local move_cost = wesnoth.unit_movement_cost(u, terrain)
+
+            move_cost = move_cost + (enemy_map:get(x,y) or 0)
+            move_cost = move_cost + (enemy_attack_map.units:get(x,y) or 0) * multiplier
+
+            return move_cost
+        end
+
         function engine:mai_goto_eval(cfg)
 
             -- If cfg.release_all_units_at_goal is set, check
@@ -75,6 +86,28 @@ return {
         function engine:mai_goto_exec(cfg)
             local units, locs = self.data.units, self.data.locs  -- simply for convenience
 
+            -- Need the enemy map and enemy attack map if avoid_enemies is set
+            local enemy_map, enemy_attack_map
+            if cfg.avoid_enemies then
+                if (type(cfg.avoid_enemies) ~= 'number') then
+                    H.wml_error("Goto AI avoid_enemies= requires a number as argument")
+                elseif (cfg.avoid_enemies <= 0) then
+                    H.wml_error("Goto AI avoid_enemies= argument must be >0")
+                end
+
+                local enemies = wesnoth.get_units {  { "filter_side", { {"enemy_of", {side = wesnoth.current.side} } } } }
+
+                enemy_map = LS.create()
+                for i,e in ipairs(enemies) do
+                    enemy_map:insert(e.x, e.y, (enemy_map:get(e.x, e.y) or 0) + 1000)
+                    for x, y in H.adjacent_tiles(e.x, e.y) do
+                        enemy_map:insert(x, y, (enemy_map:get(x, y) or 0) + 10)
+                    end
+                end
+
+                enemy_attack_map = BC.get_attack_map(enemies)
+            end
+
             local closest_hex, best_unit, max_rating = {}, {}, -9e99
             for i,u in ipairs(units) do
                 for i,l in ipairs(locs) do
@@ -95,7 +128,15 @@ return {
                             closest_hex, best_unit = hex, u
                         end
                     else  -- Otherwise find the best path to take
-                        local path, cost = wesnoth.find_path(u, l[1], l[2])
+                        local path, cost
+                        if cfg.avoid_enemies then
+                            path, cost = wesnoth.find_path(u, l[1], l[2],
+                                function(x, y, current_cost)
+                                return custom_cost(x, y, u, enemy_map, enemy_attack_map, cfg.avoid_enemies)
+                            end)
+                        else
+                            path, cost = wesnoth.find_path(u, l[1], l[2])
+                        end
 
                         -- Make all hexes within the unit's current MP equaivalent
                         if (cost <= u.moves) then cost = 0 end
@@ -118,8 +159,6 @@ return {
             end
             --print(best_unit.id, best_unit.x, best_unit.y, closest_hex[1], closest_hex[2], max_rating)
 
-            AH.movefull_outofway_stopunit(ai, best_unit, closest_hex[1], closest_hex[2])
-
             -- If 'unique_goals' is set, mark this location as being taken
             if cfg.unique_goals then
                 local str = 'goals_taken_' .. wesnoth.current.turn
@@ -127,6 +166,30 @@ return {
                 self.data[str]:insert(closest_hex[1], closest_hex[2])
             end
 
+            -- If avoid_enemies is set, we need to pick farthest reachable hex along that path
+            if cfg.avoid_enemies then
+                local path, cost = wesnoth.find_path(best_unit, closest_hex[1], closest_hex[2],
+                    function(x, y, current_cost)
+                    return custom_cost(x, y, best_unit, enemy_map, enemy_attack_map, cfg.avoid_enemies)
+                end)
+
+                -- Now go through the hexes along that path, use normal path finding
+                closest_hex = path[1]
+                for i = 2,#path do
+                    local sub_path, sub_cost = wesnoth.find_path(best_unit, path[i][1], path[i][2], cfg)
+                    if sub_cost <= best_unit.moves then
+                        local unit_in_way = wesnoth.get_unit(path[i][1], path[i][2])
+                        if not unit_in_way then
+                            closest_hex = path[i]
+                        end
+                    else
+                        break
+                    end
+                end
+            end
+
+            AH.movefull_outofway_stopunit(ai, best_unit, closest_hex[1], closest_hex[2])
+
             -- If release_unit_at_goal= or release_all_units_at_goal= key is set:
             -- Check if the unit made it to one of the goal hexes
             -- This needs to be done for the original goal hexes, not checking the SLF again,

data/ai/micro_ais/ais/micro_ais_wml_tags.lua

@@ -457,7 +457,7 @@ function wesnoth.wml_actions.micro_ai(cfg)
     --------- Goto Micro AI - side-wide AI ------------------------------------
     elseif (cfg.ai_type == 'goto') then
         required_keys = { "filter", "filter_location" }
-        optional_keys = { "release_all_units_at_goal", "release_unit_at_goal", "unique_goals", "use_straight_line" }
+        optional_keys = { "avoid_enemies", "release_all_units_at_goal", "release_unit_at_goal", "unique_goals", "use_straight_line" }
         CA_parms = { { ca_id = 'mai_goto', score = cfg.ca_score or 300000 } }
 
     --------- Hang Out Micro AI - side-wide AI ------------------------------------