wesnoth/data/ai/micro_ais/ais/mai_simple_attack_engine.lua

return {
    init = function(ai, existing_engine)

        local engine = existing_engine or {}

        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"

        function engine:mai_simple_attack_eval(cfg)

            -- Find all units that can attack and match the SUF
            local units = wesnoth.get_units {
                side = wesnoth.current.side,
                formula = '$this_unit.attacks_left > 0',
                { "and", cfg.filter }
            }

            -- Eliminate units without attacks
            for i = #units,1,-1 do
                if (not H.get_child(units[i].__cfg, 'attack')) then
                    table.remove(units, i)
                end
            end
            --print('#units', #units)
            if (not units[1]) then return 0 end

            -- Get all possible attacks
            local attacks = AH.get_attacks(units, { include_occupied = true })
            --print('#attacks', #attacks)
            if (not attacks[1]) then return 0 end

            -- If cfg.filter_second is set, set up a map (location set)
            -- of enemies that it is okay to attack
            local enemy_map
            if cfg.filter_second then
                local enemies = wesnoth.get_units {
                    { "filter_side", {{ "enemy_of", { side = wesnoth.current.side } }} },
                    { "and", cfg.filter_second }
                }
                --print('#enemies', #enemies)
                if (not enemies[1]) then return 0 end

                enemy_map = LS.create()
                for i,e in ipairs(enemies) do enemy_map:insert(e.x, e.y) end
            end

            -- Now find the best of the possible attacks
            local max_rating, best_attack = -9e99, {}
            for i, att in ipairs(attacks) do
                local valid_target = true
                if cfg.filter_second and (not enemy_map:get(att.target.x, att.target.y)) then
                    valid_target = false
                end

                if valid_target then
                    local attacker = wesnoth.get_unit(att.src.x, att.src.y)
                    local enemy = wesnoth.get_unit(att.target.x, att.target.y)
                    local dst = { att.dst.x, att.dst.y }

                    local rating = BC.attack_rating(attacker, enemy, dst)
                    --print('rating:', rating, attacker.id, enemy.id)

                    if (rating > max_rating) then
                        max_rating = rating
                        best_attack = att
                    end
                end
            end

            if (max_rating > -9e99) then
                self.data.attack = best_attack
                return cfg.ca_score
            end

            return 0
        end

        function engine:mai_simple_attack_exec()
            local attacker = wesnoth.get_unit(self.data.attack.src.x, self.data.attack.src.y)
            local defender = wesnoth.get_unit(self.data.attack.target.x, self.data.attack.target.y)

            AH.movefull_outofway_stopunit(ai, attacker, self.data.attack.dst.x, self.data.attack.dst.y)
            ai.attack(attacker, defender)
            self.data.attack = nil
        end

        return engine
    end
}