Redo API for vanilla CanPlace and CanDestroy NBT

Now properly serializes and deserializes, is factored into hashcodes and
equality checks, etc

Deprecates the old Material based system and replaces it with a new one
based around NamespacedKeys and NamespacedTags. This allows the API to
extend beyond vanilla and Material enum based properties to datapack
based tags and elements.

Fixes GH-1635

Spigot-API-Patches/0097-Expand-World.spawnParticle-API-and-add-Builder.patch

@@ -1,4 +1,4 @@
-From 43beb0d7397bc0067f08e4ec41ddfb4d46145f7d Mon Sep 17 00:00:00 2001
+From 9688d6dab34b7bac4f43b9c390fb582772b04b06 Mon Sep 17 00:00:00 2001
 From: Aikar <aikar@aikar.co>
 Date: Tue, 29 Aug 2017 23:58:48 -0400
 Subject: [PATCH] Expand World.spawnParticle API and add Builder

Spigot-API-Patches/0151-Add-an-API-for-CanPlaceOn-and-CanDestroy-NBT-values.patch

@@ -1,14 +1,226 @@
-From 7ac07ac07ac07ac07ac07ac07ac07ac07ac07ac0 Mon Sep 17 00:00:00 2001
+From 89e9f2e1093c104637f4bfd282c774b88b1bccc8 Mon Sep 17 00:00:00 2001
 From: Mark Vainomaa <mikroskeem@mikroskeem.eu>
 Date: Wed, 12 Sep 2018 18:53:35 +0300
 Subject: [PATCH] Add an API for CanPlaceOn and CanDestroy NBT values
 
 
+diff --git a/src/main/java/com/destroystokyo/paper/Namespaced.java b/src/main/java/com/destroystokyo/paper/Namespaced.java
+new file mode 100644
+index 00000000..2baf58b7
+--- /dev/null
++++ b/src/main/java/com/destroystokyo/paper/Namespaced.java
+@@ -0,0 +1,36 @@
++package com.destroystokyo.paper;
++
++/**
++ * Represents a namespaced resource, see {@link org.bukkit.NamespacedKey} for single elements
++ * or {@link com.destroystokyo.paper.NamespacedTag} for a collection of elements
++ *
++ * Namespaces may only contain lowercase alphanumeric characters, periods,
++ * underscores, and hyphens.
++ * <p>
++ * Keys may only contain lowercase alphanumeric characters, periods,
++ * underscores, hyphens, and forward slashes.
++ * <p>
++ * You should not be implementing this interface yourself, use {@link org.bukkit.NamespacedKey}
++ * or {@link com.destroystokyo.paper.NamespacedTag} as needed instead.
++ */
++public interface Namespaced {
++    /**
++     * Gets the namespace this resource is a part of
++     * <p>
++     * This is contractually obligated to only contain lowercase alphanumeric characters,
++     * periods, underscores, and hyphens.
++     *
++     * @return resource namespace
++     */
++    String getNamespace();
++
++    /**
++     * Gets the key corresponding to this resource
++     * <p>
++     * This is contractually obligated to only contain lowercase alphanumeric characters,
++     * periods, underscores, hyphens, and forward slashes.
++     *
++     * @return resource key
++     */
++    String getKey();
++}
+diff --git a/src/main/java/com/destroystokyo/paper/NamespacedTag.java b/src/main/java/com/destroystokyo/paper/NamespacedTag.java
+new file mode 100644
+index 00000000..89949827
+--- /dev/null
++++ b/src/main/java/com/destroystokyo/paper/NamespacedTag.java
+@@ -0,0 +1,138 @@
++package com.destroystokyo.paper;
++
++import com.google.common.base.Preconditions;
++import java.util.Locale;
++import java.util.UUID;
++import java.util.regex.Pattern;
++import org.bukkit.plugin.Plugin;
++
++/**
++ * Represents a String based key pertaining to a tagged entry. Consists of two components - a namespace
++ * and a key.
++ * <p>
++ * Namespaces may only contain lowercase alphanumeric characters, periods,
++ * underscores, and hyphens.
++ * <p>
++ * Keys may only contain lowercase alphanumeric characters, periods,
++ * underscores, hyphens, and forward slashes.
++ *
++ */
++// Paper - entire class, based on org.bukkit.NamespacedKey
++public final class NamespacedTag implements com.destroystokyo.paper.Namespaced {
++
++    /**
++     * The namespace representing all inbuilt keys.
++     */
++    public static final String MINECRAFT = "minecraft";
++    /**
++     * The namespace representing all keys generated by Bukkit for backwards
++     * compatibility measures.
++     */
++    public static final String BUKKIT = "bukkit";
++    //
++    private static final Pattern VALID_NAMESPACE = Pattern.compile("[a-z0-9._-]+");
++    private static final Pattern VALID_KEY = Pattern.compile("[a-z0-9/._-]+");
++    //
++    private final String namespace;
++    private final String key;
++
++    /**
++     * Create a key in a specific namespace.
++     *
++     * @param namespace String representing a grouping of keys
++     * @param key Name for this specific key
++     * @deprecated should never be used by plugins, for internal use only!!
++     */
++    @Deprecated
++    public NamespacedTag(String namespace, String key) {
++        Preconditions.checkArgument(namespace != null && VALID_NAMESPACE.matcher(namespace).matches(), "Invalid namespace. Must be [a-z0-9._-]: %s", namespace);
++        Preconditions.checkArgument(key != null && VALID_KEY.matcher(key).matches(), "Invalid key. Must be [a-z0-9/._-]: %s", key);
++
++        this.namespace = namespace;
++        this.key = key;
++
++        String string = toString();
++        Preconditions.checkArgument(string.length() < 256, "NamespacedTag must be less than 256 characters", string);
++    }
++
++    /**
++     * Create a key in the plugin's namespace.
++     * <p>
++     * Namespaces may only contain lowercase alphanumeric characters, periods,
++     * underscores, and hyphens.
++     * <p>
++     * Keys may only contain lowercase alphanumeric characters, periods,
++     * underscores, hyphens, and forward slashes.
++     *
++     * @param plugin the plugin to use for the namespace
++     * @param key the key to create
++     */
++    public NamespacedTag(Plugin plugin, String key) {
++        Preconditions.checkArgument(plugin != null, "Plugin cannot be null");
++        Preconditions.checkArgument(key != null, "Key cannot be null");
++
++        this.namespace = plugin.getName().toLowerCase(Locale.ROOT);
++        this.key = key.toLowerCase().toLowerCase(Locale.ROOT);
++
++        // Check validity after normalization
++        Preconditions.checkArgument(VALID_NAMESPACE.matcher(this.namespace).matches(), "Invalid namespace. Must be [a-z0-9._-]: %s", this.namespace);
++        Preconditions.checkArgument(VALID_KEY.matcher(this.key).matches(), "Invalid key. Must be [a-z0-9/._-]: %s", this.key);
++
++        String string = toString();
++        Preconditions.checkArgument(string.length() < 256, "NamespacedTag must be less than 256 characters (%s)", string);
++    }
++
++    public String getNamespace() {
++        return namespace;
++    }
++
++    public String getKey() {
++        return key;
++    }
++
++    @Override
++    public int hashCode() {
++        int hash = 7;
++        hash = 47 * hash + this.namespace.hashCode();
++        hash = 47 * hash + this.key.hashCode();
++        return hash;
++    }
++
++    @Override
++    public boolean equals(Object obj) {
++        if (obj == null) {
++            return false;
++        }
++        if (getClass() != obj.getClass()) {
++            return false;
++        }
++        final NamespacedTag other = (NamespacedTag) obj;
++        return this.namespace.equals(other.namespace) && this.key.equals(other.key);
++    }
++
++    @Override
++    public String toString() {
++        return "#" + this.namespace + ":" + this.key;
++    }
++
++    /**
++     * Return a new random key in the {@link #BUKKIT} namespace.
++     *
++     * @return new key
++     * @deprecated should never be used by plugins, for internal use only!!
++     */
++    @Deprecated
++    public static NamespacedTag randomKey() {
++        return new NamespacedTag(BUKKIT, UUID.randomUUID().toString());
++    }
++
++    /**
++     * Get a key in the Minecraft namespace.
++     *
++     * @param key the key to use
++     * @return new key in the Minecraft namespace
++     */
++    public static NamespacedTag minecraft(String key) {
++        return new NamespacedTag(MINECRAFT, key);
++    }
++}
+diff --git a/src/main/java/org/bukkit/NamespacedKey.java b/src/main/java/org/bukkit/NamespacedKey.java
+index fe8d3468..074769c1 100644
+--- a/src/main/java/org/bukkit/NamespacedKey.java
++++ b/src/main/java/org/bukkit/NamespacedKey.java
+@@ -17,7 +17,7 @@ import org.bukkit.plugin.Plugin;
+  * underscores, hyphens, and forward slashes.
+  *
+  */
+-public final class NamespacedKey {
++public final class NamespacedKey implements com.destroystokyo.paper.Namespaced { // Paper - implement namespaced
+ 
+     /**
+      * The namespace representing all inbuilt keys.
+@@ -81,10 +81,12 @@ public final class NamespacedKey {
+         Preconditions.checkArgument(string.length() < 256, "NamespacedKey must be less than 256 characters (%s)", string);
+     }
+ 
++    @Override // Paper
+     public String getNamespace() {
+         return namespace;
+     }
+ 
++    @Override // Paper
+     public String getKey() {
+         return key;
+     }
 diff --git a/src/main/java/org/bukkit/inventory/meta/ItemMeta.java b/src/main/java/org/bukkit/inventory/meta/ItemMeta.java
-index 7ac07ac07ac0..7ac07ac07ac0 100644
+index 2278d470..13a153c8 100644
 --- a/src/main/java/org/bukkit/inventory/meta/ItemMeta.java
 +++ b/src/main/java/org/bukkit/inventory/meta/ItemMeta.java
-@@ -348,4 +348,33 @@ public interface ItemMeta extends Cloneable, ConfigurationSerializable {
+@@ -348,4 +348,83 @@ public interface ItemMeta extends Cloneable, ConfigurationSerializable {
  
      Spigot spigot();
      // Spigot end
@@ -17,29 +229,79 @@ index 7ac07ac07ac0..7ac07ac07ac0 100644
 +     * Gets set of materials what given item can destroy in {@link org.bukkit.GameMode#ADVENTURE}
 +     *
 +     * @return Set of materials
++     * @deprecated Minecraft does not limit this to the material enum, Use {@link #getDestroyableKeys()} as a replacement
 +     */
++    @Deprecated
 +    Set<org.bukkit.Material> getCanDestroy();
 +
 +    /**
 +     * Sets set of materials what given item can destroy in {@link org.bukkit.GameMode#ADVENTURE}
 +     *
 +     * @param canDestroy Set of materials
++     * @deprecated Minecraft does not limit this to the material enum, Use {@link #setDestroyableKeys(Collection)} as a replacement
 +     */
++    @Deprecated
 +    void setCanDestroy(Set<org.bukkit.Material> canDestroy);
 +
 +    /**
 +     * Gets set of materials where given item can be placed on in {@link org.bukkit.GameMode#ADVENTURE}
 +     *
 +     * @return Set of materials
++     * @deprecated Minecraft does not limit this to the material enum, Use {@link #getPlaceableKeys()} as a replacement
 +     */
++    @Deprecated
 +    Set<org.bukkit.Material> getCanPlaceOn();
 +
 +    /**
 +     * Sets set of materials where given item can be placed on in {@link org.bukkit.GameMode#ADVENTURE}
 +     *
 +     * @param canPlaceOn Set of materials
++     * @deprecated Minecraft does not limit this to the material enum, Use {@link #setPlaceableKeys(Collection)} as a replacement
 +     */
++    @Deprecated
 +    void setCanPlaceOn(Set<org.bukkit.Material> canPlaceOn);
++
++    /**
++     * Gets the collection of namespaced keys that the item can destroy in {@link org.bukkit.GameMode#ADVENTURE}
++     *
++     * @return Set of {@link com.destroystokyo.paper.Namespaced}
++     */
++    Set<com.destroystokyo.paper.Namespaced> getDestroyableKeys();
++
++    /**
++     * Sets the collection of namespaced keys that the item can destroy in {@link org.bukkit.GameMode#ADVENTURE}
++     *
++     * @param canDestroy Set of {@link com.destroystokyo.paper.Namespaced}
++     */
++    void setDestroyableKeys(Collection<com.destroystokyo.paper.Namespaced> canDestroy);
++
++    /**
++     * Gets the collection of namespaced keys that the item can be placed on in {@link org.bukkit.GameMode#ADVENTURE}
++     *
++     * @return Set of {@link com.destroystokyo.paper.Namespaced}
++     */
++    Set<com.destroystokyo.paper.Namespaced> getPlaceableKeys();
++
++    /**
++     * Sets the set of namespaced keys that the item can be placed on in {@link org.bukkit.GameMode#ADVENTURE}
++     *
++     * @param canPlaceOn Set of {@link Collection<com.destroystokyo.paper.Namespaced>}
++     */
++    void setPlaceableKeys(Collection<com.destroystokyo.paper.Namespaced> canPlaceOn);
++
++    /**
++     * Checks for the existence of any keys that the item can be placed on
++     *
++     * @return true if this item has placeable keys
++     */
++    boolean hasPlaceableKeys();
++
++    /**
++     * Checks for the existence of any keys that the item can destroy
++     *
++     * @return true if this item has destroyable keys
++     */
++    boolean hasDestroyableKeys();
 +    // Paper end
  }
 -- 

Spigot-Server-Patches/0231-Add-ArmorStand-Item-Meta.patch

@@ -1,4 +1,4 @@
-From 0ef5b7e0531f5bf10aa78276ce5bc886c820f81c Mon Sep 17 00:00:00 2001
+From 94d320edecd9da9e43c9720be5cd42d71a89bdad Mon Sep 17 00:00:00 2001
 From: Zach Brown <zach.brown@destroystokyo.com>
 Date: Sat, 27 Jan 2018 17:04:14 -0500
 Subject: [PATCH] Add ArmorStand Item Meta
@@ -354,7 +354,7 @@ index 000000000..0e8acf12e
 +    }
 +}
 diff --git a/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaItem.java b/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaItem.java
-index 081904dad..6a95f5fa3 100644
+index 081904dad..dacca4bc4 100644
 --- a/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaItem.java
 +++ b/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaItem.java
 @@ -152,6 +152,7 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
@@ -370,8 +370,8 @@ index 081904dad..6a95f5fa3 100644
                          CraftMetaBlockState.BLOCK_ENTITY_TAG.NBT,
                          CraftMetaKnowledgeBook.BOOK_RECIPES.NBT,
 -                        CraftMetaTropicalFishBucket.VARIANT.NBT
-+                        // Paper start
 +                        CraftMetaTropicalFishBucket.VARIANT.NBT,
++                        // Paper start
 +                        CraftMetaArmorStand.ENTITY_TAG.NBT,
 +                        CraftMetaArmorStand.INVISIBLE.NBT,
 +                        CraftMetaArmorStand.NO_BASE_PLATE.NBT,

Spigot-Server-Patches/0359-Implement-an-API-for-CanPlaceOn-and-CanDestroy-NBT-v.patch

@@ -1,98 +1,246 @@
-From 7ac07ac07ac07ac07ac07ac07ac07ac07ac07ac0 Mon Sep 17 00:00:00 2001
+From 18054d7c3c094b5f2977a5affe5d96376dad120b Mon Sep 17 00:00:00 2001
 From: Mark Vainomaa <mikroskeem@mikroskeem.eu>
 Date: Wed, 12 Sep 2018 18:53:55 +0300
 Subject: [PATCH] Implement an API for CanPlaceOn and CanDestroy NBT values
 
 
+diff --git a/src/main/java/net/minecraft/server/ArgumentBlock.java b/src/main/java/net/minecraft/server/ArgumentBlock.java
+index 35c436d19..fcfb17e4e 100644
+--- a/src/main/java/net/minecraft/server/ArgumentBlock.java
++++ b/src/main/java/net/minecraft/server/ArgumentBlock.java
+@@ -42,7 +42,7 @@ public class ArgumentBlock {
+     private final boolean j;
+     private final Map<IBlockState<?>, Comparable<?>> k = Maps.newHashMap();
+     private final Map<String, String> l = Maps.newHashMap();
+-    private MinecraftKey m = new MinecraftKey("");
++    private MinecraftKey m = new MinecraftKey(""); public MinecraftKey getBlockKey() { return this.m; } // Paper - OBFHELPER
+     private BlockStateList<Block, IBlockData> n;
+     private IBlockData o;
+     @Nullable
+@@ -71,11 +71,13 @@ public class ArgumentBlock {
+         return this.p;
+     }
+ 
++    public @Nullable MinecraftKey getTagKey() { return d(); } // Paper - OBFHELPER
+     @Nullable
+     public MinecraftKey d() {
+         return this.q;
+     }
+ 
++    public ArgumentBlock parse(boolean parseTile) throws CommandSyntaxException { return this.a(parseTile); } // Paper - OBFHELPER
+     public ArgumentBlock a(boolean flag) throws CommandSyntaxException {
+         this.s = this::l;
+         if (this.i.canRead() && this.i.peek() == '#') {
+@@ -135,7 +137,7 @@ public class ArgumentBlock {
+         if (this.q != null && !this.q.getKey().isEmpty()) {
+             Tag tag = TagsBlock.a().a(this.q);
+             if (tag != null) {
+-                for(Block block : tag.a()) {
++                for(Block block : (java.util.Collection<Block>) tag.a()) { // Paper - decompiler fix
+                     for(IBlockState iblockstate : block.getStates().d()) {
+                         if (!this.l.containsKey(iblockstate.a()) && iblockstate.a().startsWith(sx)) {
+                             suggestionsbuilder.suggest(iblockstate.a() + '=');
+@@ -163,7 +165,7 @@ public class ArgumentBlock {
+             if (this.q != null) {
+                 Tag tag = TagsBlock.a().a(this.q);
+                 if (tag != null) {
+-                    for(Block block : tag.a()) {
++                    for(Block block : (java.util.Collection<Block>) tag.a()) { // Paper - decompiler fix
+                         if (block.isTileEntity()) {
+                             return true;
+                         }
+@@ -198,9 +200,9 @@ public class ArgumentBlock {
+     private static <T extends Comparable<T>> SuggestionsBuilder a(SuggestionsBuilder suggestionsbuilder, IBlockState<T> iblockstate) {
+         for(Comparable comparable : iblockstate.d()) {
+             if (comparable instanceof Integer) {
+-                suggestionsbuilder.suggest(comparable);
++                suggestionsbuilder.suggest((Integer) comparable); // Paper - decompiler fix
+             } else {
+-                suggestionsbuilder.suggest(iblockstate.a(comparable));
++                suggestionsbuilder.suggest(iblockstate.a((T) comparable)); // Paper - decompiler fix
+             }
+         }
+ 
+@@ -213,7 +215,7 @@ public class ArgumentBlock {
+             Tag tag = TagsBlock.a().a(this.q);
+             if (tag != null) {
+                 label40:
+-                for(Block block : tag.a()) {
++                for(Block block : (java.util.Collection<Block>) tag.a()) { // Paper - decompiler fix
+                     IBlockState iblockstate = block.getStates().a(sx);
+                     if (iblockstate != null) {
+                         a(suggestionsbuilder, iblockstate);
+@@ -254,7 +256,7 @@ public class ArgumentBlock {
+                 boolean flag = false;
+                 boolean flag1 = false;
+ 
+-                for(Block block : tag.a()) {
++                for(Block block : (java.util.Collection<Block>) tag.a()) { // Paper - decompiler fix
+                     flag |= !block.getStates().d().isEmpty();
+                     flag1 |= block.isTileEntity();
+                     if (flag && flag1) {
+@@ -453,8 +455,8 @@ public class ArgumentBlock {
+     private <T extends Comparable<T>> void a(IBlockState<T> iblockstate, String sx, int ix) throws CommandSyntaxException {
+         Optional optional = iblockstate.b(sx);
+         if (optional.isPresent()) {
+-            this.o = (IBlockData)this.o.set(iblockstate, (Comparable)optional.get());
+-            this.k.put(iblockstate, optional.get());
++            this.o = (IBlockData)this.o.set(iblockstate, (T)optional.get()); // Paper - decompiler fix
++            this.k.put(iblockstate, (Comparable<?>) optional.get()); // Paper - decompiler fix
+         } else {
+             this.i.setCursor(ix);
+             throw e.createWithContext(this.i, this.m.toString(), iblockstate.a(), sx);
+@@ -489,7 +491,7 @@ public class ArgumentBlock {
+     private static <T extends Comparable<T>> void a(StringBuilder stringbuilder, IBlockState<T> iblockstate, Comparable<?> comparable) {
+         stringbuilder.append(iblockstate.a());
+         stringbuilder.append('=');
+-        stringbuilder.append(iblockstate.a(comparable));
++        stringbuilder.append(iblockstate.a((T) comparable)); // Paper - decompile fix
+     }
+ 
+     public CompletableFuture<Suggestions> a(SuggestionsBuilder suggestionsbuilder) {
 diff --git a/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaItem.java b/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaItem.java
-index 7ac07ac07ac0..7ac07ac07ac0 100644
+index dacca4bc4..0b040527f 100644
 --- a/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaItem.java
 +++ b/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaItem.java
-@@ -252,6 +252,12 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
+@@ -78,6 +78,12 @@ import javax.annotation.Nullable;
+ import static org.spigotmc.ValidateUtils.*;
+ // Spigot end
+ 
++// Paper start
++import com.destroystokyo.paper.Namespaced;
++import com.destroystokyo.paper.NamespacedTag;
++import java.util.Collections;
++// Paper end
++
+ /**
+  * Children must include the following:
+  *
+@@ -252,6 +258,10 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
      static final ItemMetaKey UNBREAKABLE = new ItemMetaKey("Unbreakable");
      @Specific(Specific.To.NBT)
      static final ItemMetaKey DAMAGE = new ItemMetaKey("Damage");
 +    // Paper start - Implement an API for CanPlaceOn and CanDestroy NBT values
-+    @Specific(Specific.To.NBT)
 +    static final ItemMetaKey CAN_DESTROY = new ItemMetaKey("CanDestroy");
-+    @Specific(Specific.To.NBT)
 +    static final ItemMetaKey CAN_PLACE_ON = new ItemMetaKey("CanPlaceOn");
 +    // Paper end
  
      private IChatBaseComponent displayName;
      private IChatBaseComponent locName;
-@@ -262,6 +268,10 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
+@@ -262,6 +272,10 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
      private int hideFlag;
      private boolean unbreakable;
      private int damage;
 +    // Paper start - Implement an API for CanPlaceOn and CanDestroy NBT values
-+    private Set<Material> canPlaceOn = Sets.newHashSet();
++    private Set<Namespaced> placeableKeys;
-+    private Set<Material> canDestroy = Sets.newHashSet();
++    private Set<Namespaced> destroyableKeys;
 +    // Paper end
  
      private static final Set<String> HANDLED_TAGS = Sets.newHashSet();
  
-@@ -292,6 +302,10 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
+@@ -292,6 +306,15 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
          this.hideFlag = meta.hideFlag;
          this.unbreakable = meta.unbreakable;
          this.damage = meta.damage;
 +        // Paper start - Implement an API for CanPlaceOn and CanDestroy NBT values
-+        this.canDestroy = new java.util.HashSet<>(meta.canDestroy);
++        if (meta.hasPlaceableKeys()) {
-+        this.canPlaceOn = new java.util.HashSet<>(meta.canPlaceOn);
++            this.placeableKeys = new java.util.HashSet<>(meta.placeableKeys);
++        }
++
++        if (meta.hasDestroyableKeys()) {
++            this.destroyableKeys = new java.util.HashSet<>(meta.destroyableKeys);
++        }
 +        // Paper end
          this.unhandledTags.putAll(meta.unhandledTags);
  
          this.internalTag = meta.internalTag;
-@@ -347,6 +361,31 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
+@@ -347,6 +370,33 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
          if (tag.hasKey(DAMAGE.NBT)) {
              damage = tag.getInt(DAMAGE.NBT);
          }
 +        // Paper start - Implement an API for CanPlaceOn and CanDestroy NBT values
 +        if (tag.hasKey(CAN_DESTROY.NBT)) {
++            this.destroyableKeys = Sets.newHashSet();
 +            NBTTagList list = tag.getList(CAN_DESTROY.NBT, CraftMagicNumbers.NBT.TAG_STRING);
 +            for (int i = 0; i < list.size(); i++) {
-+                Material material = Material.matchMaterial(list.getString(i), false);
++                Namespaced namespaced = this.deserializeNamespaced(list.getString(i));
-+                if (material == null) {
++                if (namespaced == null) {
 +                    continue;
 +                }
 +
-+                this.canDestroy.add(material);
++                this.destroyableKeys.add(namespaced);
 +            }
 +        }
 +
 +        if (tag.hasKey(CAN_PLACE_ON.NBT)) {
++            this.placeableKeys = Sets.newHashSet();
 +            NBTTagList list = tag.getList(CAN_PLACE_ON.NBT, CraftMagicNumbers.NBT.TAG_STRING);
 +            for (int i = 0; i < list.size(); i++) {
-+                Material material = Material.matchMaterial(list.getString(i), false);
++                Namespaced namespaced = this.deserializeNamespaced(list.getString(i));
-+                if (material == null) {
++                if (namespaced == null) {
 +                    continue;
 +                }
 +
-+                this.canPlaceOn.add(material);
++                this.placeableKeys.add(namespaced);
 +            }
 +        }
 +        // Paper end
  
          Set<String> keys = tag.getKeys();
          for (String key : keys) {
-@@ -579,6 +618,25 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
+@@ -468,6 +518,36 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
+             setDamage(damage);
+         }
+ 
++        // Paper start - Implement an API for CanPlaceOn and CanDestroy NBT values
++        Iterable<?> canPlaceOnSerialized = SerializableMeta.getObject(Iterable.class, map, CAN_PLACE_ON.BUKKIT, true);
++        if (canPlaceOnSerialized != null) {
++            this.placeableKeys = Sets.newHashSet();
++            for (Object canPlaceOnElement : canPlaceOnSerialized) {
++                String canPlaceOnRaw = (String) canPlaceOnElement;
++                Namespaced value = this.deserializeNamespaced(canPlaceOnRaw);
++                if (value == null) {
++                    continue;
++                }
++
++                this.placeableKeys.add(value);
++            }
++        }
++
++        Iterable<?> canDestroySerialized = SerializableMeta.getObject(Iterable.class, map, CAN_DESTROY.BUKKIT, true);
++        if (canDestroySerialized != null) {
++            this.destroyableKeys = Sets.newHashSet();
++            for (Object canDestroyElement : canDestroySerialized) {
++                String canDestroyRaw = (String) canDestroyElement;
++                Namespaced value = this.deserializeNamespaced(canDestroyRaw);
++                if (value == null) {
++                    continue;
++                }
++
++                this.destroyableKeys.add(value);
++            }
++        }
++        // Paper end
++
+         String internal = SerializableMeta.getString(map, "internal", true);
+         if (internal != null) {
+             ByteArrayInputStream buf = new ByteArrayInputStream(Base64.decodeBase64(internal));
+@@ -579,6 +659,23 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
          if (hasDamage()) {
              itemTag.setInt(DAMAGE.NBT, damage);
          }
 +        // Paper start - Implement an API for CanPlaceOn and CanDestroy NBT values
-+        if (!this.canPlaceOn.isEmpty()) {
++        if (hasPlaceableKeys()) {
-+            List<String> items = this.canPlaceOn.stream()
++            List<String> items = this.placeableKeys.stream()
-+                .map(Material::getKey)
++                .map(this::serializeNamespaced)
-+                .map(org.bukkit.NamespacedKey::toString)
 +                .collect(java.util.stream.Collectors.toList());
 +
 +            itemTag.set(CAN_PLACE_ON.NBT, createStringList(items));
 +        }
 +
-+        if (!this.canDestroy.isEmpty()) {
++        if (hasDestroyableKeys()) {
-+            List<String> items = this.canDestroy.stream()
++            List<String> items = this.destroyableKeys.stream()
-+                .map(Material::getKey)
++                .map(this::serializeNamespaced)
-+                .map(org.bukkit.NamespacedKey::toString)
 +                .collect(java.util.stream.Collectors.toList());
 +
 +            itemTag.set(CAN_DESTROY.NBT, createStringList(items));
@@ -101,7 +249,82 @@ index 7ac07ac07ac0..7ac07ac07ac0 100644
  
          for (Map.Entry<String, NBTBase> e : unhandledTags.entrySet()) {
              itemTag.set(e.getKey(), e.getValue());
-@@ -1247,7 +1305,9 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
+@@ -667,7 +764,8 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
+ 
+     @Overridden
+     boolean isEmpty() {
+-        return !(hasDisplayName() || hasLocalizedName() || hasEnchants() || hasLore() || hasRepairCost() || !unhandledTags.isEmpty() || hideFlag != 0 || isUnbreakable() || hasDamage() || hasAttributeModifiers());
++        return !(hasDisplayName() || hasLocalizedName() || hasEnchants() || hasLore() || hasRepairCost() || !unhandledTags.isEmpty() || hideFlag != 0 || isUnbreakable() || hasDamage() || hasAttributeModifiers()
++            || hasPlaceableKeys() || hasDestroyableKeys()); // Paper - Implement an API for CanPlaceOn and CanDestroy NBT values
+     }
+ 
+     public String getDisplayName() {
+@@ -1003,7 +1101,11 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
+                 && (this.unhandledTags.equals(that.unhandledTags))
+                 && (this.hideFlag == that.hideFlag)
+                 && (this.isUnbreakable() == that.isUnbreakable())
+-                && (this.hasDamage() ? that.hasDamage() && this.damage == that.damage : !that.hasDamage());
++                && (this.hasDamage() ? that.hasDamage() && this.damage == that.damage : !that.hasDamage())
++                // Paper start - Implement an API for CanPlaceOn and CanDestroy NBT values
++                && (this.hasPlaceableKeys() ? that.hasPlaceableKeys() && this.placeableKeys.equals(that.placeableKeys) : !that.hasPlaceableKeys())
++                && (this.hasDestroyableKeys() ? that.hasDestroyableKeys() && this.destroyableKeys.equals(that.destroyableKeys) : !that.hasDestroyableKeys());
++                // Paper end
+     }
+ 
+     /**
+@@ -1034,6 +1136,10 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
+         hash = 61 * hash + (isUnbreakable() ? 1231 : 1237);
+         hash = 61 * hash + (hasDamage() ? this.damage : 0);
+         hash = 61 * hash + (hasAttributeModifiers() ? this.attributeModifiers.hashCode() : 0);
++        // Paper start - Implement an API for CanPlaceOn and CanDestroy NBT values
++        hash = 61 * hash + (hasPlaceableKeys() ? this.placeableKeys.hashCode() : 0);
++        hash = 61 * hash + (hasDestroyableKeys() ? this.destroyableKeys.hashCode() : 0);
++        // Paper end
+         return hash;
+     }
+ 
+@@ -1054,6 +1160,15 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
+             clone.hideFlag = this.hideFlag;
+             clone.unbreakable = this.unbreakable;
+             clone.damage = this.damage;
++            // Paper start - Implement an API for CanPlaceOn and CanDestroy NBT values
++            if (this.placeableKeys != null) {
++                clone.placeableKeys = Sets.newHashSet(this.placeableKeys);
++            }
++
++            if (this.destroyableKeys != null) {
++                clone.destroyableKeys = Sets.newHashSet(this.destroyableKeys);
++            }
++            // Paper end
+             return clone;
+         } catch (CloneNotSupportedException e) {
+             throw new Error(e);
+@@ -1103,6 +1218,24 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
+             builder.put(DAMAGE.BUKKIT, damage);
+         }
+ 
++        // Paper start - Implement an API for CanPlaceOn and CanDestroy NBT values
++        if (hasPlaceableKeys()) {
++            List<String> cerealPlaceable = this.placeableKeys.stream()
++                .map(this::serializeNamespaced)
++                .collect(java.util.stream.Collectors.toList());
++
++            builder.put(CAN_PLACE_ON.BUKKIT, cerealPlaceable);
++        }
++
++        if (hasDestroyableKeys()) {
++            List<String> cerealDestroyable = this.destroyableKeys.stream()
++                .map(this::serializeNamespaced)
++                .collect(java.util.stream.Collectors.toList());
++
++            builder.put(CAN_DESTROY.BUKKIT, cerealDestroyable);
++        }
++        // Paper end
++
+         final Map<String, NBTBase> internalTags = new HashMap<String, NBTBase>(unhandledTags);
+         serializeInternal(internalTags);
+         if (!internalTags.isEmpty()) {
+@@ -1247,7 +1380,9 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
                          CraftMetaArmorStand.NO_BASE_PLATE.NBT,
                          CraftMetaArmorStand.SHOW_ARMS.NBT,
                          CraftMetaArmorStand.SMALL.NBT,
@@ -112,39 +335,151 @@ index 7ac07ac07ac0..7ac07ac07ac0 100644
                          // Paper end
                  ));
              }
-@@ -1294,4 +1354,35 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
+@@ -1294,4 +1429,147 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable {
          return spigot;
      }
      // Spigot end
 +    // Paper start - Implement an API for CanPlaceOn and CanDestroy NBT values
 +    @Override
++    @SuppressWarnings("deprecation")
 +    public Set<Material> getCanDestroy() {
-+        return new java.util.HashSet<>(canDestroy);
++        return this.destroyableKeys == null ? Collections.emptySet() : legacyGetMatsFromKeys(this.destroyableKeys);
 +    }
 +
 +    @Override
 +    @SuppressWarnings("deprecation")
 +    public void setCanDestroy(Set<Material> canDestroy) {
-+        if (canDestroy.stream().anyMatch(Material::isLegacy)) {
++        Validate.notNull(canDestroy, "Cannot replace with null set!");
-+            throw new IllegalArgumentException("canDestroy set must not contain any legacy materials!");
++        legacyClearAndReplaceKeys(this.destroyableKeys, canDestroy);
-+        }
-+        this.canDestroy.clear();
-+        this.canDestroy.addAll(canDestroy);
 +    }
 +
 +    @Override
++    @SuppressWarnings("deprecation")
 +    public Set<Material> getCanPlaceOn() {
-+        return new java.util.HashSet<>(canPlaceOn);
++        return this.placeableKeys == null ? Collections.emptySet() : legacyGetMatsFromKeys(this.placeableKeys);
 +    }
 +
 +    @Override
 +    @SuppressWarnings("deprecation")
 +    public void setCanPlaceOn(Set<Material> canPlaceOn) {
-+        if (canPlaceOn.stream().anyMatch(Material::isLegacy)) {
++        Validate.notNull(canPlaceOn, "Cannot replace with null set!");
-+            throw new IllegalArgumentException("canPlaceOn set must not contain any legacy materials!");
++        legacyClearAndReplaceKeys(this.placeableKeys, canPlaceOn);
++    }
++
++    @Override
++    public Set<Namespaced> getDestroyableKeys() {
++        return this.destroyableKeys == null ? Collections.emptySet() : Sets.newHashSet(this.destroyableKeys);
++    }
++
++    @Override
++    public void setDestroyableKeys(Collection<Namespaced> canDestroy) {
++        Validate.notNull(canDestroy, "Cannot replace with null collection!");
++        Validate.isTrue(ofAcceptableType(canDestroy), "Can only use NamespacedKey or NamespacedTag objects!");
++        this.destroyableKeys.clear();
++        this.destroyableKeys.addAll(canDestroy);
++    }
++
++    @Override
++    public Set<Namespaced> getPlaceableKeys() {
++        return this.placeableKeys == null ? Collections.emptySet() : Sets.newHashSet(this.placeableKeys);
++    }
++
++    @Override
++    public void setPlaceableKeys(Collection<Namespaced> canPlaceOn) {
++        Validate.notNull(canPlaceOn, "Cannot replace with null collection!");
++        Validate.isTrue(ofAcceptableType(canPlaceOn), "Can only use NamespacedKey or NamespacedTag objects!");
++        this.placeableKeys.clear();
++        this.placeableKeys.addAll(canPlaceOn);
++    }
++
++    @Override
++    public boolean hasPlaceableKeys() {
++        return this.placeableKeys != null && !this.placeableKeys.isEmpty();
++    }
++
++    @Override
++    public boolean hasDestroyableKeys() {
++        return this.destroyableKeys != null && !this.destroyableKeys.isEmpty();
++    }
++
++    @Deprecated
++    private void legacyClearAndReplaceKeys(Collection<Namespaced> toUpdate, Collection<Material> beingSet) {
++        if (beingSet.stream().anyMatch(Material::isLegacy)) {
++            throw new IllegalArgumentException("Set must not contain any legacy materials!");
 +        }
-+        this.canPlaceOn.clear();
++
-+        this.canPlaceOn.addAll(canPlaceOn);
++        toUpdate.clear();
++        toUpdate.addAll(beingSet.stream().map(Material::getKey).collect(java.util.stream.Collectors.toSet()));
++    }
++
++    @Deprecated
++    private Set<Material> legacyGetMatsFromKeys(Collection<Namespaced> names) {
++        Set<Material> mats = Sets.newHashSet();
++        for (Namespaced key : names) {
++            if (!(key instanceof org.bukkit.NamespacedKey)) {
++                continue;
++            }
++
++            Material material = Material.matchMaterial(key.toString(), false);
++            if (material != null) {
++                mats.add(material);
++            }
++        }
++
++        return mats;
++    }
++
++    private @Nullable Namespaced deserializeNamespaced(String raw) {
++        boolean isTag = raw.codePointAt(0) == '#';
++        net.minecraft.server.ArgumentBlock blockParser = new net.minecraft.server.ArgumentBlock(new com.mojang.brigadier.StringReader(raw), true);
++        try {
++            blockParser = blockParser.parse(false);
++        } catch (com.mojang.brigadier.exceptions.CommandSyntaxException e) {
++            e.printStackTrace();
++            return null;
++        }
++
++        net.minecraft.server.MinecraftKey key;
++        if (isTag) {
++            key = blockParser.getTagKey();
++        } else {
++            key = blockParser.getBlockKey();
++        }
++
++        if (key == null) {
++            return null;
++        }
++
++        // don't DC the player if something slips through somehow
++        Namespaced resource = null;
++        try {
++            if (isTag) {
++                resource = new NamespacedTag(key.b(), key.getKey());
++            } else {
++                resource = CraftNamespacedKey.fromMinecraft(key);
++            }
++        } catch (IllegalArgumentException ex) {
++            org.bukkit.Bukkit.getLogger().warning("Namespaced resource does not validate: " + key.toString());
++            ex.printStackTrace();
++        }
++
++        return resource;
++    }
++
++    private @Nonnull String serializeNamespaced(Namespaced resource) {
++        return resource.toString();
++    }
++
++    // not a fan of this
++    private boolean ofAcceptableType(Collection<Namespaced> namespacedResources) {
++        boolean valid = true;
++        for (Namespaced resource : namespacedResources) {
++            if (valid && !(resource instanceof org.bukkit.NamespacedKey || resource instanceof com.destroystokyo.paper.NamespacedTag)) {
++                valid = false;
++            }
++        }
++
++        return valid;
 +    }
 +    // Paper end
  }