Add '/paper mobcaps' and '/paper playermobcaps'

Add commands to get the mobcaps for a world, as well as the mobcaps for
each player when per-player mob spawning is enabled.

Also has a hover text on each mob category listing what entity types are
in said category

paper-server/patches/sources/net/minecraft/world/level/NaturalSpawner.java.patch

@@ -62,7 +62,24 @@
                  list.add(enumcreaturetype);
              }
          }
-@@ -164,9 +192,9 @@
+@@ -144,6 +172,16 @@
+         gameprofilerfiller.pop();
+     }
+ 
++    // Paper start - Add mobcaps commands
++    public static int globalLimitForCategory(final ServerLevel level, final MobCategory category, final int spawnableChunkCount) {
++        final int categoryLimit = level.getWorld().getSpawnLimitUnsafe(CraftSpawnCategory.toBukkit(category));
++        if (categoryLimit < 1) {
++            return categoryLimit;
++        }
++        return categoryLimit * spawnableChunkCount / NaturalSpawner.MAGIC_NUMBER;
++    }
++    // Paper end - Add mobcaps commands
++
+     public static void spawnCategoryForChunk(MobCategory group, ServerLevel world, LevelChunk chunk, NaturalSpawner.SpawnPredicate checker, NaturalSpawner.AfterSpawnCallback runner) {
+         BlockPos blockposition = NaturalSpawner.getRandomPosWithin(world, chunk);
+ 
+@@ -164,9 +202,9 @@
          StructureManager structuremanager = world.structureManager();
          ChunkGenerator chunkgenerator = world.getChunkSource().getGenerator();
          int i = pos.getY();
@@ -74,7 +91,7 @@
              BlockPos.MutableBlockPos blockposition_mutableblockposition = new BlockPos.MutableBlockPos();
              int j = 0;
              int k = 0;
-@@ -195,7 +223,7 @@
+@@ -195,7 +233,7 @@
                              if (entityhuman != null) {
                                  double d2 = entityhuman.distanceToSqr(d0, (double) i, d1);
  
@@ -83,7 +100,7 @@
                                      if (biomesettingsmobs_c == null) {
                                          Optional<MobSpawnSettings.SpawnerData> optional = NaturalSpawner.getRandomSpawnMobAt(world, structuremanager, chunkgenerator, group, world.random, blockposition_mutableblockposition);
  
-@@ -207,7 +235,13 @@
+@@ -207,7 +245,13 @@
                                          j1 = biomesettingsmobs_c.minCount + world.random.nextInt(1 + biomesettingsmobs_c.maxCount - biomesettingsmobs_c.minCount);
                                      }
  
@@ -98,7 +115,7 @@
                                          Mob entityinsentient = NaturalSpawner.getMobForSpawn(world, biomesettingsmobs_c.type);
  
                                          if (entityinsentient == null) {
-@@ -217,10 +251,15 @@
+@@ -217,10 +261,15 @@
                                          entityinsentient.moveTo(d0, (double) i, d1, world.random.nextFloat() * 360.0F, 0.0F);
                                          if (NaturalSpawner.isValidPositionForMob(world, entityinsentient, d2)) {
                                              groupdataentity = entityinsentient.finalizeSpawn(world, world.getCurrentDifficultyAt(entityinsentient.blockPosition()), EntitySpawnReason.NATURAL, groupdataentity);
@@ -118,7 +135,7 @@
                                              if (j >= entityinsentient.getMaxSpawnClusterSize()) {
                                                  return;
                                              }
-@@ -250,10 +289,31 @@
+@@ -250,10 +299,31 @@
          return squaredDistance <= 576.0D ? false : (world.getSharedSpawnPos().closerToCenterThan(new Vec3((double) pos.getX() + 0.5D, (double) pos.getY(), (double) pos.getZ() + 0.5D), 24.0D) ? false : Objects.equals(new ChunkPos(pos), chunk.getPos()) || world.isNaturalSpawningAllowed((BlockPos) pos));
      }
  
@@ -152,7 +169,7 @@
      }
  
      @Nullable
-@@ -268,6 +328,7 @@
+@@ -268,6 +338,7 @@
              NaturalSpawner.LOGGER.warn("Can't spawn entity of type: {}", BuiltInRegistries.ENTITY_TYPE.getKey(type));
          } catch (Exception exception) {
              NaturalSpawner.LOGGER.warn("Failed to create mob", exception);
@@ -160,7 +177,7 @@
          }
  
          return null;
-@@ -356,6 +417,7 @@
+@@ -356,6 +427,7 @@
                                      entity = biomesettingsmobs_c.type.create(world.getLevel(), EntitySpawnReason.NATURAL);
                                  } catch (Exception exception) {
                                      NaturalSpawner.LOGGER.warn("Failed to create mob", exception);
@@ -168,7 +185,7 @@
                                      continue;
                                  }
  
-@@ -369,7 +431,7 @@
+@@ -369,7 +441,7 @@
  
                                      if (entityinsentient.checkSpawnRules(world, EntitySpawnReason.CHUNK_GENERATION) && entityinsentient.checkSpawnObstruction(world)) {
                                          groupdataentity = entityinsentient.finalizeSpawn(world, world.getCurrentDifficultyAt(entityinsentient.blockPosition()), EntitySpawnReason.CHUNK_GENERATION, groupdataentity);
@@ -177,7 +194,7 @@
                                          flag = true;
                                      }
                                  }
-@@ -482,10 +544,12 @@
+@@ -482,10 +554,12 @@
              return this.unmodifiableMobCategoryCounts;
          }
  

paper-server/src/main/java/io/papermc/paper/command/PaperCommand.java

@@ -40,6 +40,7 @@ public final class PaperCommand extends Command {
         commands.put(Set.of("dumpplugins"), new DumpPluginsCommand());
         commands.put(Set.of("syncloadinfo"), new SyncLoadInfoCommand());
         commands.put(Set.of("dumpitem"), new DumpItemCommand());
+        commands.put(Set.of("mobcaps", "playermobcaps"), new MobcapsCommand());
 
         return commands.entrySet().stream()
             .flatMap(entry -> entry.getKey().stream().map(s -> Map.entry(s, entry.getValue())))

paper-server/src/main/java/io/papermc/paper/command/subcommands/MobcapsCommand.java

@@ -0,0 +1,229 @@
+package io.papermc.paper.command.subcommands;
+
+import com.google.common.collect.ImmutableMap;
+import io.papermc.paper.command.CommandUtil;
+import io.papermc.paper.command.PaperSubcommand;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.function.ToIntFunction;
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.ComponentLike;
+import net.kyori.adventure.text.JoinConfiguration;
+import net.kyori.adventure.text.TextComponent;
+import net.kyori.adventure.text.format.NamedTextColor;
+import net.kyori.adventure.text.format.TextColor;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.entity.MobCategory;
+import net.minecraft.world.level.NaturalSpawner;
+import org.bukkit.Bukkit;
+import org.bukkit.World;
+import org.bukkit.command.CommandSender;
+import org.bukkit.craftbukkit.CraftWorld;
+import org.bukkit.craftbukkit.entity.CraftPlayer;
+import org.bukkit.entity.Player;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public final class MobcapsCommand implements PaperSubcommand {
+    static final Map<MobCategory, TextColor> MOB_CATEGORY_COLORS = ImmutableMap.<MobCategory, TextColor>builder()
+        .put(MobCategory.MONSTER, NamedTextColor.RED)
+        .put(MobCategory.CREATURE, NamedTextColor.GREEN)
+        .put(MobCategory.AMBIENT, NamedTextColor.GRAY)
+        .put(MobCategory.AXOLOTLS, TextColor.color(0x7324FF))
+        .put(MobCategory.UNDERGROUND_WATER_CREATURE, TextColor.color(0x3541E6))
+        .put(MobCategory.WATER_CREATURE, TextColor.color(0x006EFF))
+        .put(MobCategory.WATER_AMBIENT, TextColor.color(0x00B3FF))
+        .put(MobCategory.MISC, TextColor.color(0x636363))
+        .build();
+
+    @Override
+    public boolean execute(final CommandSender sender, final String subCommand, final String[] args) {
+        switch (subCommand) {
+            case "mobcaps" -> this.printMobcaps(sender, args);
+            case "playermobcaps" -> this.printPlayerMobcaps(sender, args);
+        }
+        return true;
+    }
+
+    @Override
+    public List<String> tabComplete(final CommandSender sender, final String subCommand, final String[] args) {
+        return switch (subCommand) {
+            case "mobcaps" -> CommandUtil.getListMatchingLast(sender, args, this.suggestMobcaps(args));
+            case "playermobcaps" -> CommandUtil.getListMatchingLast(sender, args, this.suggestPlayerMobcaps(sender, args));
+            default -> throw new IllegalArgumentException();
+        };
+    }
+
+    private List<String> suggestMobcaps(final String[] args) {
+        if (args.length == 1) {
+            final List<String> worlds = new ArrayList<>(Bukkit.getWorlds().stream().map(World::getName).toList());
+            worlds.add("*");
+            return worlds;
+        }
+
+        return Collections.emptyList();
+    }
+
+    private List<String> suggestPlayerMobcaps(final CommandSender sender, final String[] args) {
+        if (args.length == 1) {
+            final List<String> list = new ArrayList<>();
+            for (final Player player : Bukkit.getOnlinePlayers()) {
+                if (!(sender instanceof Player senderPlayer) || senderPlayer.canSee(player)) {
+                    list.add(player.getName());
+                }
+            }
+            return list;
+        }
+
+        return Collections.emptyList();
+    }
+
+    private void printMobcaps(final CommandSender sender, final String[] args) {
+        final List<World> worlds;
+        if (args.length == 0) {
+            if (sender instanceof Player player) {
+                worlds = List.of(player.getWorld());
+            } else {
+                sender.sendMessage(Component.text("Must specify a world! ex: '/paper mobcaps world'", NamedTextColor.RED));
+                return;
+            }
+        } else if (args.length == 1) {
+            final String input = args[0];
+            if (input.equals("*")) {
+                worlds = Bukkit.getWorlds();
+            } else {
+                final @Nullable World world = Bukkit.getWorld(input);
+                if (world == null) {
+                    sender.sendMessage(Component.text("'" + input + "' is not a valid world!", NamedTextColor.RED));
+                    return;
+                } else {
+                    worlds = List.of(world);
+                }
+            }
+        } else {
+            sender.sendMessage(Component.text("Too many arguments!", NamedTextColor.RED));
+            return;
+        }
+
+        for (final World world : worlds) {
+            final ServerLevel level = ((CraftWorld) world).getHandle();
+            final NaturalSpawner.@Nullable SpawnState state = level.getChunkSource().getLastSpawnState();
+
+            final int chunks;
+            if (state == null) {
+                chunks = 0;
+            } else {
+                chunks = state.getSpawnableChunkCount();
+            }
+            sender.sendMessage(Component.join(JoinConfiguration.noSeparators(),
+                Component.text("Mobcaps for world: "),
+                Component.text(world.getName(), NamedTextColor.AQUA),
+                Component.text(" (" + chunks + " spawnable chunks)")
+            ));
+
+            sender.sendMessage(createMobcapsComponent(
+                category -> {
+                    if (state == null) {
+                        return 0;
+                    } else {
+                        return state.getMobCategoryCounts().getOrDefault(category, 0);
+                    }
+                },
+                category -> NaturalSpawner.globalLimitForCategory(level, category, chunks)
+            ));
+        }
+    }
+
+    private void printPlayerMobcaps(final CommandSender sender, final String[] args) {
+        final @Nullable Player player;
+        if (args.length == 0) {
+            if (sender instanceof Player pl) {
+                player = pl;
+            } else {
+                sender.sendMessage(Component.text("Must specify a player! ex: '/paper playermobcount playerName'", NamedTextColor.RED));
+                return;
+            }
+        } else if (args.length == 1) {
+            final String input = args[0];
+            player = Bukkit.getPlayerExact(input);
+            if (player == null) {
+                sender.sendMessage(Component.text("Could not find player named '" + input + "'", NamedTextColor.RED));
+                return;
+            }
+        } else {
+            sender.sendMessage(Component.text("Too many arguments!", NamedTextColor.RED));
+            return;
+        }
+
+        final ServerPlayer serverPlayer = ((CraftPlayer) player).getHandle();
+        final ServerLevel level = serverPlayer.serverLevel();
+
+        if (!level.paperConfig().entities.spawning.perPlayerMobSpawns) {
+            sender.sendMessage(Component.text("Use '/paper mobcaps' for worlds where per-player mob spawning is disabled.", NamedTextColor.RED));
+            return;
+        }
+
+        sender.sendMessage(Component.join(JoinConfiguration.noSeparators(), Component.text("Mobcaps for player: "), Component.text(player.getName(), NamedTextColor.GREEN)));
+        sender.sendMessage(createMobcapsComponent(
+            category -> level.chunkSource.chunkMap.getMobCountNear(serverPlayer, category),
+            category -> level.getWorld().getSpawnLimitUnsafe(org.bukkit.craftbukkit.util.CraftSpawnCategory.toBukkit(category))
+        ));
+    }
+
+    private static Component createMobcapsComponent(final ToIntFunction<MobCategory> countGetter, final ToIntFunction<MobCategory> limitGetter) {
+        return MOB_CATEGORY_COLORS.entrySet().stream()
+            .map(entry -> {
+                final MobCategory category = entry.getKey();
+                final TextColor color = entry.getValue();
+
+                final Component categoryHover = Component.join(JoinConfiguration.noSeparators(),
+                    Component.text("Entity types in category ", TextColor.color(0xE0E0E0)),
+                    Component.text(category.getName(), color),
+                    Component.text(':', NamedTextColor.GRAY),
+                    Component.newline(),
+                    Component.newline(),
+                    BuiltInRegistries.ENTITY_TYPE.entrySet().stream()
+                        .filter(it -> it.getValue().getCategory() == category)
+                        .map(it -> Component.translatable(it.getValue().getDescriptionId()))
+                        .collect(Component.toComponent(Component.text(", ", NamedTextColor.GRAY)))
+                );
+
+                final Component categoryComponent = Component.text()
+                    .content("  " + category.getName())
+                    .color(color)
+                    .hoverEvent(categoryHover)
+                    .build();
+
+                final TextComponent.Builder builder = Component.text()
+                    .append(
+                        categoryComponent,
+                        Component.text(": ", NamedTextColor.GRAY)
+                    );
+                final int limit = limitGetter.applyAsInt(category);
+                if (limit != -1) {
+                    builder.append(
+                        Component.text(countGetter.applyAsInt(category)),
+                        Component.text("/", NamedTextColor.GRAY),
+                        Component.text(limit)
+                    );
+                } else {
+                    builder.append(Component.text()
+                        .append(
+                            Component.text('n'),
+                            Component.text("/", NamedTextColor.GRAY),
+                            Component.text('a')
+                        )
+                        .hoverEvent(Component.text("This category does not naturally spawn.")));
+                }
+                return builder;
+            })
+            .map(ComponentLike::asComponent)
+            .collect(Component.toComponent(Component.newline()));
+    }
+}

paper-server/src/main/java/org/bukkit/craftbukkit/CraftServer.java

@@ -2334,6 +2334,11 @@ public final class CraftServer implements Server {
 
     @Override
     public int getSpawnLimit(SpawnCategory spawnCategory) {
+        // Paper start - Add mobcaps commands
+        return this.getSpawnLimitUnsafe(spawnCategory);
+    }
+    public int getSpawnLimitUnsafe(final SpawnCategory spawnCategory) {
+        // Paper end - Add mobcaps commands
         return this.spawnCategoryLimit.getOrDefault(spawnCategory, -1);
     }
 

paper-server/src/main/java/org/bukkit/craftbukkit/CraftWorld.java

@@ -1713,9 +1713,14 @@ public class CraftWorld extends CraftRegionAccessor implements World {
         Preconditions.checkArgument(spawnCategory != null, "SpawnCategory cannot be null");
         Preconditions.checkArgument(CraftSpawnCategory.isValidForLimits(spawnCategory), "SpawnCategory.%s are not supported", spawnCategory);
 
+        // Paper start - Add mobcaps commands
+        return this.getSpawnLimitUnsafe(spawnCategory);
+    }
+    public final int getSpawnLimitUnsafe(final SpawnCategory spawnCategory) {
         int limit = this.spawnCategoryLimit.getOrDefault(spawnCategory, -1);
         if (limit < 0) {
-            limit = this.server.getSpawnLimit(spawnCategory);
+            limit = this.server.getSpawnLimitUnsafe(spawnCategory);
+            // Paper end - Add mobcaps commands
         }
         return limit;
     }

paper-server/src/test/java/io/papermc/paper/command/subcommands/MobcapsCommandTest.java

@@ -0,0 +1,22 @@
+package io.papermc.paper.command.subcommands;
+
+import java.util.HashSet;
+import java.util.Set;
+import net.minecraft.world.entity.MobCategory;
+import org.bukkit.support.environment.Normal;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+@Normal
+public class MobcapsCommandTest {
+    @Test
+    public void testMobCategoryColors() {
+        final Set<String> missing = new HashSet<>();
+        for (final MobCategory value : MobCategory.values()) {
+            if (!MobcapsCommand.MOB_CATEGORY_COLORS.containsKey(value)) {
+                missing.add(value.getName());
+            }
+        }
+        Assertions.assertTrue(missing.isEmpty(), "MobcapsCommand.MOB_CATEGORY_COLORS map missing TextColors for [" + String.join(", ", missing + "]"));
+    }
+}