Add xp-points-paywall= Functions

Add Functions used by the new CommandTag: `xp-points-paywall=`

src/me/rockyhawk/commandpanels/Utils.java

@@ -151,4 +151,61 @@ public class Utils implements Listener {
         }
         return false;
     }
+    // START - PATCH
+    // @author thelonelywolf@https://github.com/TheLonelyWolf1
+    // @date 06 August 2021
+    
+    // Calculate amount of EXP needed to level up
+    public static int getExpToLevelUp(int level){
+        if(level <= 15){
+            return 2*level+7;
+        } else if(level <= 30){
+            return 5*level-38;
+        } else {
+            return 9*level-158;
+        }
+    }
+ 
+    // Calculate total experience up to a level
+    public static int getExpAtLevel(int level){
+        if(level <= 16){
+            return (int) (Math.pow(level,2) + 6*level);
+        } else if(level <= 31){
+            return (int) (2.5*Math.pow(level,2) - 40.5*level + 360.0);
+        } else {
+            return (int) (4.5*Math.pow(level,2) - 162.5*level + 2220.0);
+        }
+    }
+ 
+    // Calculate player's current EXP amount
+    public static int getPlayerExp(Player player){
+        int exp = 0;
+        int level = player.getLevel();
+     
+        // Get the amount of XP in past levels
+        exp += getExpAtLevel(level);
+     
+        // Get amount of XP towards next level
+        exp += Math.round(getExpToLevelUp(level) * player.getExp());
+     
+        return exp;
+    }
+    
+    // Give or take EXP
+    public static int changePlayerExp(Player player, int exp){
+     // Get player's current exp
+     int currentExp = getPlayerExp(player);
+     
+     // Reset player's current exp to 0
+     player.setExp(0);
+     player.setLevel(0);
+     
+     // Give the player their exp back, with the difference
+     int newExp = currentExp - exp;
+     player.giveExp(newExp);
+     
+     // Return the player's new exp amount
+     return newExp;
+    }
+     // END - PATCH
 }