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

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

bukkit/1_12/src/main/java/com/gmail/nossr50/bukkit/v1_12/NmsHandler.java

@@ -0,0 +1,106 @@
+package com.gmail.nossr50.bukkit.v1_12;
+
+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_12_R1.Chunk;
+import net.minecraft.server.v1_12_R1.EntityTypes;
+import net.minecraft.server.v1_12_R1.IBlockData;
+import net.minecraft.server.v1_12_R1.IBlockState;
+import net.minecraft.server.v1_12_R1.MinecraftKey;
+import net.minecraft.server.v1_12_R1.RegistryBlocks;
+import net.minecraft.server.v1_12_R1.RegistryMaterials;
+import org.bukkit.block.Block;
+import org.bukkit.block.BlockState;
+import org.bukkit.craftbukkit.v1_12_R1.CraftChunk;
+import org.bukkit.craftbukkit.v1_12_R1.block.CraftBlockState;
+import org.bukkit.craftbukkit.v1_12_R1.entity.CraftEntity;
+import org.bukkit.entity.Entity;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+public class NmsHandler extends VersionedHandler {
+    /**
+     * Static reference to the block registry. Don't really care about the fact that
+     * it is being stored as a reference here, but for imports reasons, it's smaller
+     * line length makes it optimal to read for method usages.
+     */
+    private static final RegistryBlocks<MinecraftKey, net.minecraft.server.v1_12_R1.Block> BLOCK_REGISTRY = net.minecraft.server.v1_12_R1.Block.REGISTRY;
+    /**
+     * We can keep track of block state id's by generating them on demand, i.e., when
+     * they're being requested from Blocks, or BlockDatas.
+     */
+    private static final RegistryMaterials<MinecraftKey, 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 Chunk chunk = ((CraftChunk) block.getChunk()).getHandle();
+        // Get the block state from the underlying chunk (stored by reference in CraftBlock)
+        final IBlockData blockState = chunk.a(block.getX(), block.getY(), block.getZ());
+        // 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.b(blockState.getBlock());
+        return 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 net.minecraft.server.v1_12_R1.Entity nmsEntity = ((CraftEntity) entity).getHandle();
+        // And then... well. we get the string id from the registry, based on the entity class to id mapping in EntityTypes.
+        final MinecraftKey key = EntityTypes.a(nmsEntity);
+        // 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) {
+        // Since we don't really want to trust what "BlockState" gives us, and the API doesn't give us anything but
+        // what the API wants to give us, we have to dig into internals to get the true BlockState representation
+        final CraftBlockState craftState = (CraftBlockState) block;
+        // Because CraftBlock also stores the chunk reference, we can short cut in to use the chunk, instead of pinging
+        // the chunk map on WorldServer
+        final CraftChunk craftChunk = (CraftChunk) craftState.getChunk();
+        // Then query for the block state from the chunk.
+        final IBlockData nmsState = craftChunk.getHandle().a(block.getX(), block.getY(), block.getZ());
+        // And then we're gucci
+        final net.minecraft.server.v1_12_R1.Block nmsBlock = nmsState.getBlock();
+        final MinecraftKey blockKey = BLOCK_REGISTRY.b(nmsBlock);
+        // Now we can check if our blockstate registry actually has the block state.
+        final MinecraftKey stateKey = BLOCK_STATE_REGISTRY.b(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.t();
+        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();
+    }
+}