add more preconditions

src/ch/epfl/chacun/ActionEncoder.java

@@ -2,6 +2,7 @@
 
 import java.util.Comparator;
 import java.util.List;
+import java.util.Objects;
 
 /**
  * A utility class that offers methods
@@ -91,6 +92,7 @@ private static List<Occupant> sortedOccupants(GameState gameState) {
      * @return the new game state resulting from the action and the encoded action
      */
     public static StateAction withPlacedTile(GameState gameState, PlacedTile tile) {
+        Objects.requireNonNull(tile);
         List<Pos> fringeIndexes = fringeIndexes(gameState);
         int indexToEncode = fringeIndexes.indexOf(tile.pos()); // a number between 0 and 189
         int rotationToEncode = tile.rotation().ordinal(); // a number between 0 and 3

src/ch/epfl/chacun/gui/ImageLoader.java

@@ -1,5 +1,6 @@
 package ch.epfl.chacun.gui;
 
+import ch.epfl.chacun.Preconditions;
 import javafx.scene.image.Image;
 
 import java.util.FormatProcessor;
@@ -62,6 +63,7 @@ private static Image imageForTile(int tileId, int pixelSize) {
      * @return the normal image for the tile with the given tile id
      */
     public static Image normalImageForTile(int tileId) {
+        Preconditions.checkArgument(tileId >= 0);
         return imageForTile(tileId, NORMAL_TILE_PIXEL_SIZE);
     }
 
@@ -72,6 +74,7 @@ public static Image normalImageForTile(int tileId) {
      * @return the large image for the tile with the given tile id
      */
     public static Image largeImageForTile(int tileId) {
+        Preconditions.checkArgument(tileId >= 0);
         return imageForTile(tileId, LARGE_TILE_PIXEL_SIZE);
     }