Improve isAdjacent function

This also fixes a bug where an enemy unit might get selected multiple
times. The AI now checks if it's already adjacent to the closest unit,
to prevent it from unnecessarily moving.

core/src/com/redstrate/watersymbol/screens/GameScreen.java

@@ -95,6 +95,7 @@ public class GameScreen implements Screen {
         for(int i = currentUnitIndex; i < units.size(); i++) {
             if(units.get(i).team == currentTurnTeam) {
                 currentUnit = units.get(i);
+                currentUnitIndex = i;
                 return;
             }
         }
@@ -161,7 +162,22 @@ public class GameScreen implements Screen {
     }
 
     boolean isAdjacent(Unit a, Unit b) {
-        return Vector2.dst(a.positionX, a.positionY, b.positionX, b.positionY) <= 1.0;
+        ArrayList<Vector2> adjacentPositions = new ArrayList<>();
+        adjacentPositions.add(new Vector2(0, -1));
+        adjacentPositions.add(new Vector2(0, 1));
+        adjacentPositions.add(new Vector2(-1, 0));
+        adjacentPositions.add(new Vector2(1, 0));
+        adjacentPositions.add(new Vector2(-1, -1));
+        adjacentPositions.add(new Vector2(-1, 1));
+        adjacentPositions.add(new Vector2(1, -1));
+        adjacentPositions.add(new Vector2(1, 1));
+        for (Vector2 position : adjacentPositions) {
+            Vector2 newPosition = new Vector2(a.positionX + position.x, a.positionY + position.y);
+            if(b.positionX == newPosition.x && b.positionY == newPosition.y)
+                return true;
+        }
+
+        return false;
     }
 
     List<UnitAction> getAvailableActionsForPosition(int x, int y) {
@@ -316,6 +332,10 @@ public class GameScreen implements Screen {
                 }
             }
 
+            // if we're already next to them, why move?
+            if(isAdjacent(currentUnit, closestUnit)) {
+                currentlyAwaitingAuxilaryAction = true;
+            } else {
                 // now that we have the closest unit, let's path to it.
                 ArrayList<Vector2> path = AStar.path(new Vector2(currentUnit.positionX, currentUnit.positionY), new Vector2((float) closestUnit.positionX, (float) closestUnit.positionY), getCollision());
                 if (path != null) {
@@ -328,6 +348,7 @@ public class GameScreen implements Screen {
                     moveUnitTo((int) determinedPos.x, (int) determinedPos.y);
                 }
             }
+        }
 
         if(currentlyTakingAction) {
             if(!currentMovementList.isEmpty()) {
@@ -362,7 +383,6 @@ public class GameScreen implements Screen {
                 } else {
                     advanceTurn();
                 }
-
             } else {
                 Vector3 mousePos = new Vector3(Gdx.input.getX(), Gdx.input.getY(), 0);