First creation of an NMS Handler. Not sure if relocation works yet.

Signed-off-by: Gabriel Harris-Rouquette <gabizou@me.com>

bukkit/1_13/src/main/java/com/gmail/nossr50/bukkit/v1_13/NmsHandler.java

@@ -0,0 +1,101 @@
+package com.gmail.nossr50.bukkit.v1_13;
+
+import com.gmail.nossr50.VersionedHandler;
+import com.gmail.nossr50.mcMMO;
+import com.google.common.base.Joiner;
+import com.google.common.collect.ImmutableMap;
+import net.minecraft.server.v1_13_R2.EntityTypes;
+import net.minecraft.server.v1_13_R2.IBlockData;
+import net.minecraft.server.v1_13_R2.IBlockState;
+import net.minecraft.server.v1_13_R2.IRegistry;
+import net.minecraft.server.v1_13_R2.MinecraftKey;
+import net.minecraft.server.v1_13_R2.RegistryMaterials;
+import net.minecraft.server.v1_13_R2.WorldServer;
+import org.bukkit.block.Block;
+import org.bukkit.block.BlockState;
+import org.bukkit.craftbukkit.v1_13_R2.block.CraftBlock;
+import org.bukkit.craftbukkit.v1_13_R2.block.CraftBlockState;
+import org.bukkit.craftbukkit.v1_13_R2.entity.CraftEntity;
+import org.bukkit.entity.Entity;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+public class NmsHandler extends VersionedHandler {
+
+    private static final IRegistry<net.minecraft.server.v1_13_R2.Block> BLOCK_REGISTRY = IRegistry.BLOCK;
+    private static final IRegistry<EntityTypes<?>> ENTITY_REGISTRY = IRegistry.ENTITY_TYPE;
+    /**
+     * We use {@link RegistryMaterials} because we don't want to default to another block state,
+     * if a {@link IBlockData} is not registered, we need to generate an ID and register that key to
+     * that {@link IBlockData}. By default, this should be populated during plugin startup by
+     * calling some init method, but that will be determined later.
+     */
+    private static final IRegistry<IBlockData> BLOCK_STATE_REGISTRY = new RegistryMaterials<>();
+
+    NmsHandler(mcMMO plugin) {
+        super(plugin);
+    }
+
+    @Override
+    public String getIdFor(Block block) {
+        // We have to get the underlying nms block by the block, which might as well just be the type id.
+        final WorldServer world = ((CraftBlock) block).getCraftWorld().getHandle();
+        // The registry.c(T) will return MinecraftKey, and the toString() returns the "$mod:$name", so "minecraft:stone"
+        final IBlockData blockState = world.getType(((CraftBlock) block).getPosition());
+        // Sadly, Mojang doesn't store the string id onto blocks, states, or any of their types, they just call the registry.
+        final MinecraftKey key = BLOCK_REGISTRY.getKey(blockState.getBlock());
+        // Sometimes, there's a rare case with mods where the key is going to be null, but should never happen in bukkit/spigot.
+        return key == null ? "minecraft:air" : key.toString();
+    }
+
+    @Override
+    public String getIdFor(Entity entity) {
+        // Every entity knows it's "type". Here, we just use the right method getter to get the EntityTypes instance for that entity
+        final EntityTypes<?> entityType = ((CraftEntity) entity).getHandle().P();
+        // And then... well. we get the string id from the registry!
+        final MinecraftKey key = ENTITY_REGISTRY.getKey(entityType);
+        // If the key is null, well, we've got bigger problems...
+        return key == null ? "minecraft:slime" : key.toString();
+    }
+
+    @SuppressWarnings("Duplicates")
+    @Override
+    public String getIdFor(BlockState block) {
+        // Much like #getIdFor(Block) except here we have the "state" by numerical id. So.. we have to grab it from
+        // the world.
+        final CraftBlockState craftState = (CraftBlockState) block;
+        final IBlockData nmsState = craftState.getHandle();
+        final net.minecraft.server.v1_13_R2.Block nmsBlock = nmsState.getBlock();
+        final MinecraftKey blockKey = BLOCK_REGISTRY.getKey(nmsBlock);
+        // Now we can check if our blockstate registry actually has the block state.
+        final MinecraftKey stateKey = BLOCK_STATE_REGISTRY.getKey(nmsState);
+        if (stateKey != null) { // If the state has been registered by the handler, then by all means.
+            return stateKey.toString();
+        }
+        // If not, well, it needs to have a key generated and registered.
+        final String nameSpace = blockKey.getKey();
+        StringBuilder builder = new StringBuilder();
+        builder.append(nameSpace); // We only want to get the block id, not the domain id, since that's going to be appended later
+
+        // Get the full Property -> Value mapping for the block state
+        final ImmutableMap<IBlockState<?>, Comparable<?>> properties = nmsState.getStateMap();
+        if (!properties.isEmpty()) {
+            builder.append('[');
+            Joiner joiner = Joiner.on(',');
+            List<String> propertyValues = new ArrayList<>();
+            // Yadadadada, go through all property entries and add each as a string for the "propertyName=value" (like "variant=oak")
+            for (Map.Entry<IBlockState<?>, Comparable<?>> entry : properties.entrySet()) {
+                // a() gets the inputted "name" for the state, the value, well, that gets the value, which is always toStringable.
+                propertyValues.add(entry.getKey().a() + "=" + entry.getValue());
+            }
+            builder.append(joiner.join(propertyValues));
+            builder.append(']');
+        }
+        // Now we can make the MinecraftKey...
+        final MinecraftKey newKey = new MinecraftKey(builder.toString());
+        BLOCK_STATE_REGISTRY.a(newKey, nmsState);
+        return newKey.toString();
+    }
+}