Fix bugs in DotsAndBoxesGrid

src/main/java/dotsandboxes/DotsAndBoxesGrid.java

 package dotsandboxes;
 
-
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.function.Consumer;
 
-/**
- * The state of a dots and boxes grid.
- *
- * A (4, 3) dots and boxes grid looks like this:
- *
- * *-*-*-*
- * | | | |
- * *-*-*-*
- * | | | |
- * *-*-*-*
- *
- * Notice that:
- *
- * - for each row, there is one less horizontal than the number of corner dots
- * - for each row, there are as many verticals as there are corner dots
- * - for each row, there is one less box than the number of corner dots
- * - for each column, there is one less vertical than the number of corner dots.
- * - for each column, there are as many horizontals as there are corner dots.
- * - for each column, there is one less box than the number of corner dots
- *
- * For example, in this (4, 3) grid, there are (3, 3) horizontal lines, and (4, 2) vertical lines, and (3, 2) boxes.
- *
- * We number all lines and boxes by their top-left coordinate.
- *
- * In Java 14+, we might use a Record class for this, but we're using 11+ as an LTS version, so we don't have that yet.
- */
 public class DotsAndBoxesGrid {
 
     final int width;
     final int height;
 
-    /** The horizontal lines in the grid. True if drawn. */
     private boolean[][] horizontals;
-
-    /** The vertical lines in the grid. True if drawn. */
     private boolean[][] verticals;
-
-    /** Which owner (if any) claimed any given box. */
     private int[][] boxOwners;
 
-    /** A list of functions to notify when there is an update */
     private ArrayList<Consumer<DotsAndBoxesGrid>> watchers = new ArrayList<>();
-
     final int players;
     private int player = 1;
+
     public int getPlayer() {
         return player;
     }
 
-    /** Moves to the next player */
     private void nextPlayer() {
         player++;
         if (player > players) {
@@ -78,44 +44,30 @@ public class DotsAndBoxesGrid {
         }
     }
 
-    /** Listens to this grid for changes */
     public void addConsumer(Consumer<DotsAndBoxesGrid> consumer) {
         watchers.add(consumer);
     }
 
-    /** Returns whether a horizontal line has been drawn */
     public boolean getHorizontal(int x, int y) {
         return horizontals[x][y];
     }
 
-    /** Returns whether a vertical line has been drawn */
     public boolean getVertical(int x, int y) {
         return verticals[x][y];
     }
 
-    /** Returns which player owns a box. By convention, 0 is unowned. */
     public int getBoxOwner(int x, int y) {
         return boxOwners[x][y];
     }
 
-
-    /**
-     * Checks whether a box has been fully drawn (all four sides)
-     * @param x coordinate of the left side of the box
-     * @param y coordinate of the top of the box
-     * @return true if all four sides have been drawn.
-     */
     public boolean boxComplete(int x, int y) {
         if (x >= width - 1 || x < 0 || y >= height - 1 || y < 0) {
             return false;
         }
 
-        // A box is complete if the north and south horizontals and the east and west verticals have all been drawn.
-        // FIXME: You'll need to fix this code (after writing a test first).
-        return true;
+        return horizontals[x][y] && horizontals[x][y+1] && verticals[x][y] && verticals[x+1][y];
     }
 
-    /** Tries to claim a box for a player. If the box is complete, sets the ownership and returns true. */
     private boolean claimBox(int x, int y, int p) {
         if (boxComplete(x, y)) {
             boxOwners[x][y] = player;
@@ -125,12 +77,6 @@ public class DotsAndBoxesGrid {
         }
     }
 
-    /**
-     * "Draws" a horizontal line, from grid point (x, y) to (x + 1, y). (i.e. sets that line to true)
-     * @param x
-     * @param y
-     * @return true if it completes a box
-     */
     public boolean drawHorizontal(int x, int y, int player) {
         if (x >= width - 1 || x < 0) {
             throw new IndexOutOfBoundsException(String.format("x was %d, which is out of range. Range is 0 to %d", x, width - 1));
@@ -139,11 +85,12 @@ public class DotsAndBoxesGrid {
             throw new IndexOutOfBoundsException(String.format("y was %d, which is out of range. Range is 0 to %d", y, height));
         }
 
-        // FIXME: You need to throw an exception if the line was already drawn.
+        if (horizontals[x][y]) {
+            throw new IllegalStateException("This line has already been drawn.");
+        }
 
         this.horizontals[x][y] = true;
 
-        // Try to claim the north or south boxes
         boolean claimN = claimBox(x, y-1, player);
         boolean claimS = claimBox(x, y, player);
         if (claimN || claimS) {
@@ -156,12 +103,6 @@ public class DotsAndBoxesGrid {
         }
     }
 
-    /**
-     * "Draws" a vertical line, from grid point (x, y) to (x, y + 1). (i.e. sets that line to true)
-     * @param x
-     * @param y
-     * @return true if it completes a box
-     */
     public boolean drawVertical(int x, int y, int player) {
         if (x >= width || x < 0) {
             throw new IndexOutOfBoundsException(String.format("x was %d, which is out of range. Range is 0 to %d", x, width));
@@ -170,10 +111,12 @@ public class DotsAndBoxesGrid {
             throw new IndexOutOfBoundsException(String.format("y was %d, which is out of range. Range is 0 to %d", y, height - 1));
         }
 
-        // You need to throw an exception if the line was already drawn.
+        if (verticals[x][y]) {
+            throw new IllegalStateException("This line has already been drawn.");
+        }
 
         this.verticals[x][y] = true;
-        // Try to claim the north or south boxes
+
         boolean claimE = claimBox(x, y, player);
         boolean claimW = claimBox(x-1, y, player);
         if (claimE || claimW) {
@@ -184,14 +127,10 @@ public class DotsAndBoxesGrid {
             notifyObservers();
             return false;
         }
-
     }
 
     public boolean gameComplete() {
-        // Students who took COSC250 might recognise this style of code. This is Java's version of higher order functions.
-        // The grid is complete if "for all rows, all the boxes in that row have a non-zero owner"
         return Arrays.stream(boxOwners).allMatch((row) -> Arrays.stream(row).allMatch((owner) -> owner > 0));
     }
-
-
 }
+