From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Lukas Planz <lukas.planz@web.de>
Date: Tue, 5 Sep 2023 20:34:20 +0200
Subject: [PATCH] Add experience points API


diff --git a/src/main/java/net/minecraft/world/entity/player/Player.java b/src/main/java/net/minecraft/world/entity/player/Player.java
index 7f3466340891b4409d1399ebeb2ca865d77841cd..3e597833b57377b855505b8a0f2744801c791f90 100644
--- a/src/main/java/net/minecraft/world/entity/player/Player.java
+++ b/src/main/java/net/minecraft/world/entity/player/Player.java
@@ -1833,7 +1833,7 @@ public abstract class Player extends LivingEntity {
     }
 
     public int getXpNeededForNextLevel() {
-        return this.experienceLevel >= 30 ? 112 + (this.experienceLevel - 30) * 9 : (this.experienceLevel >= 15 ? 37 + (this.experienceLevel - 15) * 5 : 7 + this.experienceLevel * 2);
+        return this.experienceLevel >= 30 ? 112 + (this.experienceLevel - 30) * 9 : (this.experienceLevel >= 15 ? 37 + (this.experienceLevel - 15) * 5 : 7 + this.experienceLevel * 2); // Paper - diff on change
     }
     // Paper start - send SoundEffect to everyone who can see fromEntity
     private static void sendSoundEffect(Player fromEntity, double x, double y, double z, SoundEvent soundEffect, SoundSource soundCategory, float volume, float pitch) {
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
index 39bf2b92cd8907afa13b9bf7f02553cd2539023b..da63b4050be25dcb91d04df8c2fcc643cbb0751d 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
@@ -1821,6 +1821,49 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
         Preconditions.checkArgument(exp >= 0, "Total experience points must not be negative (%s)", exp);
         this.getHandle().totalExperience = exp;
     }
+    // Paper start
+    @Override
+    public int calculateTotalExperiencePoints() {
+        return calculateTotalExperiencePoints(this.getLevel()) + Math.round(this.getExperiencePointsNeededForNextLevel() * getExp());
+    }
+
+    @Override
+    public void setExperienceLevelAndProgress(final int totalExperience) {
+        Preconditions.checkArgument(totalExperience >= 0, "Total experience points must not be negative (%s)", totalExperience);
+        int level = calculateLevelsForExperiencePoints(totalExperience);
+        int remainingPoints = totalExperience - calculateTotalExperiencePoints(level);
+
+        this.getHandle().experienceLevel = level;
+        this.getHandle().experienceProgress = (float) remainingPoints / this.getExperiencePointsNeededForNextLevel();
+        this.getHandle().lastSentExp = -1;
+    }
+
+    @Override
+    public int getExperiencePointsNeededForNextLevel() {
+        return this.getHandle().getXpNeededForNextLevel();
+    }
+
+    // See https://minecraft.wiki/w/Experience#Leveling_up for reference
+    private int calculateTotalExperiencePoints(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);
+        }
+    }
+
+    private int calculateLevelsForExperiencePoints(int points) {
+        if (points <= 352) { // Level 0-16
+            return (int) Math.floor(Math.sqrt(points + 9) - 3);
+        } else if (points <= 1507) { // Level 17-31
+            return (int) Math.floor(8.1 + Math.sqrt(0.4 * (points - (7839.0 / 40.0))));
+        } else { // 32+
+            return (int) Math.floor((325.0 / 18.0) + Math.sqrt((2.0 / 9.0) * (points - (54215.0 / 72.0))));
+        }
+    }
+    // Paper end
 
     @Override
     public void sendExperienceChange(float progress) {