Add basic item matching support

worldedit-core/src/main/java/com/sk89q/worldedit/blocks/BaseItem.java

@@ -22,7 +22,9 @@
 import com.sk89q.jnbt.CompoundTag;
 import com.sk89q.worldedit.WorldEdit;
 import com.sk89q.worldedit.util.concurrency.LazyReference;
+import com.sk89q.worldedit.util.nbt.BinaryTag;
 import com.sk89q.worldedit.util.nbt.CompoundBinaryTag;
+import com.sk89q.worldedit.util.nbt.NbtUtils;
 import com.sk89q.worldedit.util.nbt.TagStringIO;
 import com.sk89q.worldedit.world.NbtValued;
 import com.sk89q.worldedit.world.item.ItemType;
@@ -106,6 +108,26 @@ public void setNbtReference(@Nullable LazyReference<CompoundBinaryTag> nbtData)
         this.nbtData = nbtData;
     }
 
+    /**
+     * Gets whether the current item matches the given mask.
+     *
+     * <p>
+     * See {@link NbtUtils#matches(BinaryTag, BinaryTag)} for specifics of NBT behavior.
+     * </p>
+     *
+     * @param mask The mask to test against
+     * @return if it matches the mask
+     */
+    public boolean matches(BaseItem mask) {
+        checkNotNull(mask);
+
+        if (!mask.getType().equals(getType())) {
+            return false;
+        }
+
+        return NbtUtils.matches(mask.getNbt(), getNbt());
+    }
+
     @Override
     public String toString() {
         String nbtString = "";

worldedit-core/src/main/java/com/sk89q/worldedit/util/nbt/NbtUtils.java

@@ -47,4 +47,96 @@ public static <T extends BinaryTag> T getChildTag(CompoundBinaryTag tag, String
         return childTagCast;
     }
 
+    /**
+     * Tests a {@link BinaryTag} against a "mask" {@link BinaryTag}.
+     *
+     * <p>
+     * This method true if "test" contains all values from "mask". It does not
+     * matter if it contains more, as long as the mask values are present.
+     *
+     * For list tags, compound lists are treated as unordered sets, whereas
+     * non-compound lists are treated as ordered. This matches the way Minecraft
+     * treats NBT in items.
+     * </p>
+     *
+     * @param mask The mask tag
+     * @param test The tested tag
+     * @return If the test tag contains the values from the mask
+     */
+    public static boolean matches(BinaryTag mask, BinaryTag test) {
+        if (mask == null) {
+            // If our mask is null, all match
+            return true;
+        }
+        if (test == null) {
+            // If our mask is not null but our test is, never match
+            return false;
+        }
+
+        if (mask.type() != test.type()) {
+            // If the types differ, they do not match
+            return false;
+        }
+
+        if (mask.type() == BinaryTagTypes.COMPOUND) {
+            // For compounds, we ensure that all the keys are available and values match
+            CompoundBinaryTag maskCompound = (CompoundBinaryTag) mask;
+            CompoundBinaryTag testCompound = (CompoundBinaryTag) test;
+
+            for (String binaryKey : maskCompound.keySet()) {
+                if (!matches(maskCompound.get(binaryKey), testCompound.get(binaryKey))) {
+                    return false;
+                }
+            }
+
+            return true;
+        } else if (mask.type() == BinaryTagTypes.LIST) {
+            // For lists, we ensure that all the values match
+            ListBinaryTag maskList = (ListBinaryTag) mask;
+            ListBinaryTag testList = (ListBinaryTag) test;
+
+            if (!maskList.elementType().equals(testList.elementType())) {
+                // These lists are of different types
+                return false;
+            }
+
+            if (maskList.elementType() == BinaryTagTypes.COMPOUND) {
+                // Treat compound lists like a set, due to how MC handle them
+                for (BinaryTag binaryTag : maskList) {
+                    boolean found = false;
+                    for (BinaryTag testTag : testList) {
+                        if (matches(binaryTag, testTag)) {
+                            found = true;
+                            break;
+                        }
+                    }
+                    if (!found) {
+                        return false;
+                    }
+                }
+            } else {
+                int startIndex = 0;
+                for (BinaryTag binaryTag : maskList) {
+                    boolean found = false;
+                    for (int i = startIndex; i < testList.size(); i++) {
+                        BinaryTag testTag = testList.get(i);
+                        if (matches(binaryTag, testTag)) {
+                            found = true;
+                            startIndex = i + 1;
+                            break;
+                        }
+                    }
+                    if (!found) {
+                        return false;
+                    }
+                }
+            }
+
+            return true;
+        } else {
+            // For types that are just a value, we can do direct equality.
+            return mask.equals(test);
+        }
+    }
+
 }