BattleAI: check negative obstacles instead of moat.

This will work for fire walls too (and if someone will summon elementals
after placing land mines). But will not work for Tower's landmines.

AI/BattleAI/BattleAI.cpp

@@ -19,6 +19,7 @@
 #include "../../lib/spells/CSpellHandler.h"
 #include "../../lib/spells/ISpellMechanics.h"
 #include "../../lib/battle/BattleStateInfoForRetreat.h"
+#include "../../lib/battle/CObstacleInstance.h"
 #include "../../lib/CStack.h" // TODO: remove
                               // Eventually only IBattleInfoCallback and battle::Unit should be used,
                               // CUnitState should be private and CStack should be removed completely
@@ -309,25 +310,38 @@ BattleAction CBattleAI::goTowardsNearest(const CStack * stack, std::vector<Battl
 
 	if(stack->hasBonusOfType(Bonus::FLYING))
 	{
-		std::set<BattleHex> moatHexes;
+		std::set<BattleHex> obstacleHexes;
 
-		if(hb.battleGetSiegeLevel() >= BuildingID::CITADEL)
-		{
-			auto townMoat = hb.getDefendedTown()->town->moatHexes;
+		auto insertAffected = [](const CObstacleInstance* spellObst, std::set<BattleHex> obstacleHexes) {
+			auto affectedHexes = spellObst->getAffectedTiles();
+			obstacleHexes.insert(affectedHexes.cbegin(), affectedHexes.cend());
+		};
+
+		const auto & obstacles = hb.battleGetAllObstacles();
+
+		for (const auto & obst: obstacles) {
+			const auto * spellObst = dynamic_cast<const SpellCreatedObstacle*>(obst.get());
 
-			moatHexes = std::set<BattleHex>(townMoat.begin(), townMoat.end());
+			if(spellObst && spellObst->trigger)
+			{
+				auto triggerAbility =  VLC->spells()->getById(SpellID(spellObst->ID));
+				auto triggerIsNegative = triggerAbility->isNegative() || triggerAbility->isDamage();
+
+				if(triggerIsNegative)
+					insertAffected(spellObst, obstacleHexes);
+			}
 		}
 		// Flying stack doesn't go hex by hex, so we can't backtrack using predecessors.
 		// We just check all available hexes and pick the one closest to the target.
 		auto nearestAvailableHex = vstd::minElementByFun(avHexes, [&](BattleHex hex) -> int
 		{
-			const int MOAT_PENALTY = 100; // avoid landing on moat
+			const int NEGATIVE_OBSTACLE_PENALTY = 100; // avoid landing on negative obstacle (moat, fire wall, etc)
 			const int BLOCKED_STACK_PENALTY = 100; // avoid landing on moat
 
 			auto distance = BattleHex::getDistance(bestNeighbor, hex);
 
-			if(vstd::contains(moatHexes, hex))
-				distance += MOAT_PENALTY;
+			if(vstd::contains(obstacleHexes, hex))
+				distance += NEGATIVE_OBSTACLE_PENALTY;
 
 			return scoreEvaluator.checkPositionBlocksOurStacks(hb, stack, hex) ? BLOCKED_STACK_PENALTY + distance : distance;
 		});