Implement PuzzleModel class

src/main/java/me/taako/swt/prog2/model/PuzzleModel.java

@@ -1,4 +1,48 @@
 package me.taako.swt.prog2.model;
 
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.IntStream;
+
 public class PuzzleModel {
+    private final int size;
+    private final List<Integer> tiles;
+
+    public PuzzleModel(int rows, int cols) {
+        this.size = rows * cols;
+        this.tiles = new ArrayList<>(size);
+        initTiles();
+        shuffleTiles();
+    }
+
+    private void initTiles() {
+        IntStream.range(0, size)
+                .forEach(tiles::add);
+    }
+
+    private void shuffleTiles() {
+        Collections.shuffle(tiles);
+    }
+
+    public int getTile(int index) {
+        return tiles.get(index);
+    }
+
+    public int getSize() {
+        return size;
+    }
+
+    public boolean isTileCorrect(int index) {
+        return tiles.get(index) == index;
+    }
+
+    public boolean isSolved() {
+        return IntStream.range(0, size)
+                .allMatch(this::isTileCorrect);
+    }
+
+    public void swapTiles(int index1, int index2) {
+        Collections.swap(tiles, index1, index2);
+    }
 }