GH-132 Move level-related calculations to LevelUtil. (#132)

* Move level-related calculations to LevelUtil.

* Move to level package.

* Fix checkstyle.

src/main/java/com/eternalcode/discordapp/leveling/LevelController.java

@@ -23,24 +23,6 @@ public LevelController(LevelConfig levelConfig, LevelService levelService, JDA j
         this.jda = jda;
     }
 
-    /**
-     * This method is called when an ExperienceChangeEvent occurs. It updates the user's level based on their experience points
-     * and sends a message to a designated TextChannel when the user levels up.
-     * <p>
-     * It calculates the next level using the formula: N = P * L^2 + P * L + P
-     * where:
-     * <p> - N represents the points needed to reach the next level,
-     * <p> - P is the points needed for one level (provided by LevelConfig),
-     * <p> - L is the current level.
-     * <p>
-     * Example level calculations:
-     * <p> Level 1: N = 100 * 1^2 + 100 * 1 + 100 = 300
-     * <p> Level 2: N = 100 * 2^2 + 100 * 2 + 100 = 700
-     * <p> Level 3: N = 100 * 3^2 + 100 * 3 + 100 = 1200
-     * <p> Level 4: N = 100 * 4^2 + 100 * 4 + 100 = 1700
-     * <p> Level 5: N = 100 * 5^2 + 100 * 5 + 100 = 2300
-     */
-
     @Override
     public void update(ExperienceChangeEvent event) {
         Experience experience = event.experience();
@@ -53,9 +35,7 @@ public void update(ExperienceChangeEvent event) {
         this.levelService.find(userId).thenApply(userLevel -> {
             int currentLevel = userLevel.getCurrentLevel();
 
-            int pointsNeededForNextLevel = (int) (pointsNeededForOneLevel * Math.pow(currentLevel + 1, 2)
-                + pointsNeededForOneLevel * (currentLevel + 1)
-                + pointsNeededForOneLevel);
+            int pointsNeededForNextLevel = LevelUtil.calculatePointsForNextLevel(currentLevel, pointsNeededForOneLevel);
 
             if (experiencePoints <= pointsNeededForNextLevel) {
                 return null;

src/main/java/com/eternalcode/discordapp/leveling/LevelUtil.java

@@ -0,0 +1,37 @@
+package com.eternalcode.discordapp.leveling;
+
+public final class LevelUtil {
+
+    public LevelUtil() {
+        throw new UnsupportedOperationException("This class cannot be instantiated");
+    }
+
+    /**
+     * Calculates the points needed to achieve the next level.
+     * <p>
+     * This method is called when an ExperienceChangeEvent occurs. It updates the user's level based on their experience points
+     * and sends a message to a designated TextChannel when the user levels up.
+     * <p>
+     * It calculates the next level using the formula: N = P * L^2 + P * L + P
+     * where:
+     * <p> - N represents the points needed to reach the next level,
+     * <p> - P is the points needed for one level (provided by LevelConfig),
+     * <p> - L is the current level.
+     * <p>
+     * Example level calculations:
+     * <p> Level 1: N = 100 * 1^2 + 100 * 1 + 100 = 300
+     * <p> Level 2: N = 100 * 2^2 + 100 * 2 + 100 = 700
+     * <p> Level 3: N = 100 * 3^2 + 100 * 3 + 100 = 1200
+     * <p> Level 4: N = 100 * 4^2 + 100 * 4 + 100 = 1700
+     * <p> Level 5: N = 100 * 5^2 + 100 * 5 + 100 = 2300
+     *
+     * @param currentLevel Current level.
+     * @param pointsNeededForOneLevel Points needed for one level.
+     * @return The calculated points needed for the next level.
+     */
+    public static int calculatePointsForNextLevel(int currentLevel, double pointsNeededForOneLevel) {
+        return (int) (pointsNeededForOneLevel * Math.pow(currentLevel + 1, 2)
+            + pointsNeededForOneLevel * (currentLevel + 1)
+            + pointsNeededForOneLevel);
+    }
+}