Feature/json parser (#18)

* chore(model/json-parser): Added maven dependency
* chore(model): Removed old test JSON file
* refactor(model/GameState): List better then map, entities should be able
to overlap

* feat(Pacman): Added GameState builder to initiate GameState with given
paramters.

Added a short example JSON-file, more key-value pairs needs to be added
as the game progresses.
Likewise the builder won't parse for any other key-value pair
automatically.

3 files changed, 125 insertions, 43 deletions

diff --git a/pacman/model/src/main/java/com/gr15/pacman/model/GameState.java b/pacman/model/src/main/java/com/gr15/pacman/model/GameState.java
index ef33488..609bfc0 100644
--- a/pacman/model/src/main/java/com/gr15/pacman/model/GameState.java
+++ b/pacman/model/src/main/java/com/gr15/pacman/model/GameState.java
@@ -1,5 +1,6 @@
 package com.gr15.pacman.model;
 
+import java.util.List;
 import java.util.Map;
 
 import com.gr15.pacman.model.entities.Entity;
@@ -15,15 +16,15 @@ public class GameState {
     private Board board;
 
     private Pacman pacman;
-    private Map<Position, Entity> entities;
+    private List<Entity> entities;
     private Map<Position, Items> items;
 
     private int score = 0;
     private int lives = 3;
     private double powerModeDuration = 0;
 
-    public GameState(Board board, Pacman pacman, 
-            Map<Position, Entity> entities, Map<Position, Items> items) {
+    protected GameState(Board board, Pacman pacman, 
+            List<Entity> entities, Map<Position, Items> items) {
         this.board = board;
         this.entities = entities;
         this.items = items;
@@ -42,7 +43,7 @@ public class GameState {
         powerModeDuration = Math.max(powerModeDuration, 0);
 
         /* updating and checking collisions with entities */
-        entities.forEach((pos, entity) -> { 
+        for (Entity entity : entities) {
             entity.move(board, deltaSeconds);
             if (EntityUtils.hasCollided(pacman, entity)
                 && powerModeDuration == 0) {
@@ -50,7 +51,7 @@ public class GameState {
             } else if (EntityUtils.hasCollided(pacman, entity)) {
                 score += 100;
             }
-        });
+        }
 
         /* checking collisions with items */
         Items item = items.get(pacman.getPosition());
@@ -66,7 +67,7 @@ public class GameState {
     /* Getters and setters */
     public Board getBoard() { return this.board; }
     public Pacman getPacman() { return this.pacman; }
-    public Map<Position, Entity> getEntities() { return this.entities; }
+    public List<Entity> getEntities() { return this.entities; }
     public Map<Position, Items> getItems() { return this.items; }
     public int getScore() { return this.score; }
     public int getLives() { return this.lives; }
@@ -79,7 +80,7 @@ public class GameState {
     public void setItems(Map<Position, Items> newItems) { 
         this.items = newItems; 
     }
-    public void setEntities(Map<Position, Entity> newEntities) { 
+    public void setEntities(List<Entity> newEntities) { 
         this.entities = newEntities; 
     }
 }
diff --git a/pacman/model/src/main/java/com/gr15/pacman/model/GameStateBuilder.java b/pacman/model/src/main/java/com/gr15/pacman/model/GameStateBuilder.java
new file mode 100644
index 0000000..aab7dd9
--- /dev/null
+++ b/pacman/model/src/main/java/com/gr15/pacman/model/GameStateBuilder.java
@@ -0,0 +1,117 @@
+package com.gr15.pacman.model;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
+import org.json.JSONTokener;
+
+import com.gr15.pacman.model.Board.Direction;
+import com.gr15.pacman.model.Board.TileType;
+import com.gr15.pacman.model.entities.Entity;
+import com.gr15.pacman.model.entities.Ghost;
+import com.gr15.pacman.model.entities.Items;
+import com.gr15.pacman.model.entities.Pacman;
+
+/**
+ * Utility class to build a {@link GameState} object from a JSON configuration.
+ *
+ * <p>
+ * This class provides static methods to parse game data such as the board,
+ * entities, and items from a JSON input stream and use it to initialize
+ * a game state. It handles parsing logic and translates string representations
+ * into model objects used by the game engine.
+ * </p>
+ */
+public class GameStateBuilder {
+
+    /**
+     Parses a JSON input stream and constructs a {@link GameState} based on the configuration.
+     * <p>
+     * Expected JSON structure includes:
+     * <ul>
+     *  <li>{@code pacmanSpawnPoint}: an array of two integers 
+     *      representing the X and Y coordinates.</li>
+     *  <li>{@code board}: a 2D array of strings 
+     *      representing the board tiles ("W" for wall, "E" for empty).</li>
+     *  <li>{@code pacman}: a JSON object containing properties 
+     *      such as {@code x}, {@code y}, {@code speed}, and {@code radius}.</li>
+     * </ul>
+     *
+     * @param inputStream the input stream of the JSON file.
+     * @return a {@link GameState} object built from the JSON configuration.
+     * @throws RuntimeException if the JSON is invalid or the file cannot be read.
+     */
+    public static GameState fromJson(InputStream inputStream) {
+        /* Reader gets closed automatically, 
+         * because it's in the resources part of a try-with-resource statement.
+         * The InputStream gets closed by Reader */
+        try (InputStreamReader reader = new InputStreamReader(inputStream)) {
+            JSONTokener tokener = new JSONTokener(reader);
+            JSONObject jsonObject = new JSONObject(tokener);
+            return buildFromJsonObject(jsonObject);
+        } catch (JSONException jsonException) {
+            throw new RuntimeException("""
+                Failed to parse JSON content. 
+                Please ensure the file contains valid JSON.""", jsonException);
+        } catch (IOException ioException) {
+            throw new RuntimeException("""
+                Error reading JSON file. 
+                Ensure the file exists and is accessible""", ioException);
+        }
+    }
+
+    /**
+     * Internal helper method that constructs a {@link GameState} object
+     * from a given {@link JSONObject}.
+     *
+     * <p>
+     * This method extracts the board layout, Pacman parameters, 
+     * and initializes the entities and items.
+     *
+     * @param jsonObject the JSON object containing game configuration data.
+     * @return a fully constructed {@link GameState} object.
+     * @throws RuntimeException if required fields are missing or incorrectly formatted.
+
+     */
+    private static GameState buildFromJsonObject(JSONObject jsonObject) {
+        try {
+            JSONArray stringBoard = jsonObject.getJSONArray("board");
+            TileType[][] tileBoard = new TileType
+                [stringBoard.length()]
+                [stringBoard.getJSONArray(0).length()];
+            for (int y = 0; y < stringBoard.length(); y++) {
+                JSONArray row = stringBoard.getJSONArray(y);
+                for (int x = 0; x < row.length(); x++) {
+                    switch (row.getString(x)) {
+                        case "W" -> tileBoard[y][x] = TileType.WALL;
+                        case "E" -> tileBoard[y][x] = TileType.EMPTY;
+                        default -> {}
+                    }
+                }
+            }
+            Board board = new Board(tileBoard[0].length, tileBoard.length, tileBoard);
+            
+            JSONObject pacmanJsonObject = jsonObject.getJSONObject("pacman");
+            double speed = pacmanJsonObject.getDouble("speed");
+            double radius = pacmanJsonObject.getDouble("radius");
+            Position pacmanStartPos = new Position(
+                pacmanJsonObject.getInt("x"),
+                pacmanJsonObject.getInt("y"));
+            Pacman pacman = new Pacman(pacmanStartPos, speed, Direction.NONE, radius);
+
+            ArrayList<Entity> entities = new ArrayList<>();
+            Map<Position, Items> items = new HashMap<>();
+
+            return new GameState(board, pacman, entities, items);
+        } catch (JSONException jsonException) {
+            throw new RuntimeException("Failed to parse GameState json", jsonException);
+        }
+    }
+}
diff --git a/pacman/model/src/main/java/com/gr15/pacman/model/JsonParser.java b/pacman/model/src/main/java/com/gr15/pacman/model/JsonParser.java
deleted file mode 100644
index 990fb15..0000000
--- a/pacman/model/src/main/java/com/gr15/pacman/model/JsonParser.java
+++ /dev/null
@@ -1,36 +0,0 @@
-package com.gr15.pacman.model;
-
-import java.util.HashMap;
-import java.util.Map;
-
-import com.gr15.pacman.model.entities.Entity.Direction;
-import com.gr15.pacman.model.Board.TileType;
-import com.gr15.pacman.model.entities.Entity;
-import com.gr15.pacman.model.entities.Pacman;
-import com.gr15.pacman.model.entities.Items;
-
-/**
- * jsonParser
- */
-public final class JsonParser {
-
-    public static GameState getGameState(String path) {
-        TileType[][] tileBoard = {
-            {TileType.WALL, TileType.WALL, TileType.WALL, TileType.WALL, TileType.WALL,},
-            {TileType.WALL, TileType.EMPTY, TileType.EMPTY, TileType.EMPTY, TileType.WALL,},
-            {TileType.WALL, TileType.EMPTY, TileType.WALL, TileType.EMPTY, TileType.WALL,},
-            {TileType.WALL, TileType.EMPTY, TileType.WALL, TileType.EMPTY, TileType.WALL,},
-            {TileType.WALL, TileType.EMPTY, TileType.EMPTY, TileType.EMPTY, TileType.WALL,},
-            {TileType.WALL, TileType.EMPTY, TileType.WALL, TileType.EMPTY, TileType.WALL,},
-            {TileType.WALL, TileType.EMPTY, TileType.EMPTY, TileType.EMPTY, TileType.WALL,},
-            {TileType.WALL, TileType.WALL, TileType.WALL, TileType.WALL, TileType.WALL,},
-        };
-        Board board = new Board(8, 5, tileBoard);
-        Pacman pacman = new Pacman(new Position(1, 1), 3.0, Direction.NONE, 1);
-        Map<Position, Entity> entities = new HashMap<>();
-        Map<Position, Items> items = new HashMap<>();
-
-        return new GameState(board, pacman, entities, items);
-    }
-    
-}