Add experience points API

paper-server/patches/sources/net/minecraft/world/entity/player/Player.java.patch

@@ -35,7 +35,7 @@
      public final InventoryMenu inventoryMenu;
      public AbstractContainerMenu containerMenu;
      protected FoodData foodData = new FoodData();
-@@ -181,14 +191,26 @@
+@@ -181,13 +191,25 @@
      private Optional<GlobalPos> lastDeathLocation;
      @Nullable
      public FishingHook fishing;
@@ -49,7 +49,7 @@
      private int currentImpulseContextResetGraceTime;
 +    public boolean affectsSpawning = true; // Paper - Affects Spawning API
 +    public net.kyori.adventure.util.TriState flyingFallDamage = net.kyori.adventure.util.TriState.NOT_SET; // Paper - flying fall damage
- 
++
 +    // CraftBukkit start
 +    public boolean fauxSleeping;
 +    public int oldLevel = -1;
@@ -59,10 +59,9 @@
 +        return (CraftHumanEntity) super.getBukkitEntity();
 +    }
 +    // CraftBukkit end
-+
+ 
      public Player(Level world, BlockPos pos, float yaw, GameProfile gameProfile) {
          super(EntityType.PLAYER, world);
-         this.lastItemInMainHand = ItemStack.EMPTY;
 @@ -244,6 +266,13 @@
  
          if (this.isSleeping()) {
@@ -95,10 +94,12 @@
      }
  
      private boolean isEquipped(Item item) {
-@@ -513,6 +542,18 @@
+@@ -511,7 +540,19 @@
- 
+             super.handleEntityEvent(status);
          }
  
++    }
++
 +    // Paper start - Inventory close reason; unused code, but to keep signatures aligned
 +    public void closeContainer(org.bukkit.event.inventory.InventoryCloseEvent.Reason reason) {
 +        closeContainer();
@@ -108,12 +109,11 @@
 +    // Paper start - special close for unloaded inventory
 +    public void closeUnloadedInventory(org.bukkit.event.inventory.InventoryCloseEvent.Reason reason) {
 +        this.containerMenu = this.inventoryMenu;
-+    }
+     }
 +    // Paper end - special close for unloaded inventory
-+
+ 
      public void closeContainer() {
          this.containerMenu = this.inventoryMenu;
-     }
 @@ -523,8 +564,14 @@
      public void rideTick() {
          if (!this.level().isClientSide && this.wantsToStopRiding() && this.isPassenger()) {
@@ -541,9 +541,12 @@
      }
  
      @Override
-@@ -1664,11 +1828,30 @@
+@@ -1662,13 +1826,32 @@
+     }
+ 
      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);
++        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; calculateTotalExperiencePoints
      }
 +    // Paper start - send while respecting visibility
 +    private static void sendSoundEffect(Player fromEntity, double x, double y, double z, SoundEvent soundEffect, SoundSource soundCategory, float volume, float pitch) {

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java

@@ -1933,6 +1933,49 @@ 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) {