DefenderAI that makes octs follow units (#4757)

core/src/mindustry/ai/types/DefenderAI.java

@@ -0,0 +1,34 @@
+package mindustry.ai.types;
+
+import arc.math.*;
+import mindustry.entities.*;
+import mindustry.entities.Units.*;
+import mindustry.entities.units.*;
+import mindustry.gen.*;
+import mindustry.world.meta.*;
+
+public class DefenderAI extends AIController{
+
+    @Override
+    public void updateMovement(){
+        if(target != null){
+            moveTo(target, unit.range(), 5f);
+            unit.lookAt(target);
+        }else{
+            Teamc block = targetFlag(unit.x, unit.y, BlockFlag.rally, false);
+            if(block == null) block = unit.closestCore();
+            moveTo(block, 60f);
+        }
+    }
+
+    @Override
+    protected void updateTargeting(){
+        if(retarget()) target = findTarget(unit.x, unit.y, 0f, true, true);
+    }
+    
+    @Override
+    protected Teamc findTarget(float x, float y, float range, boolean air, boolean ground){
+        //Sort by max health and closer target.
+        return Units.closest(unit.team, x, y, u -> !u.dead() && u.type != unit.type, (u, tx, ty) -> -u.maxHealth + Mathf.dst2(u.x, u.y, tx, ty) / 800f);
+    }
+}