efibs / mc-lasertag-mod

public class NbtUtil {

    /**

     * Converts a NbtCompound deserialized from a .litematic file and converts it into a NbtCompound with the format of a .nbt file

     * @param litematic

     * @param mainRegionName

     * @return

     */

    public static NbtCompound convertLitematicToNbt(NbtCompound litematic, String mainRegionName) {

        // Create new nbt compound

        var nbt = new NbtCompound();

        // Get the regions element

        var regionsElement = litematic.get("Regions");

        // If the regions element is not a nbt compound

        if (!(regionsElement instanceof NbtCompound)) {

            return null;

        }

        // Cast

        var regionsCompound = (NbtCompound)regionsElement;

        // Get the main region element

        var mainRegionElement = regionsCompound.get(mainRegionName);

        // If the main region element is not a nbt compound

        if (!(mainRegionElement instanceof NbtCompound)) {

            return null;

        }

        // Cast

        var mainRegionCompound = (NbtCompound)mainRegionElement;

        // Add size nbt list

        if (!addSize(nbt, mainRegionCompound)) {

            return null;

        }

        // Add entities list

        if (!addEntities(nbt, mainRegionCompound)) {

            return null;

        }

        // Get size element

        var sizeElement = mainRegionCompound.get("Size");

        // Check

        if (!(sizeElement instanceof NbtCompound)) {

            return null;

        }

        // Cast

        var sizeCompound = (NbtCompound)sizeElement;

        // Get the palette

        var paletteElement = mainRegionCompound.get("BlockStatePalette");

        // Check

        if (!(paletteElement instanceof NbtList)) {

            return null;

        }

        // Cast

        var paletteList = (NbtList)paletteElement;

        // Add blocks list

        if (!addBlockList(nbt, mainRegionCompound, sizeCompound, paletteList)) {

            return null;

        }

        // Add palette list

        nbt.put("palette", paletteElement);

        // Add data version int

        nbt.put("DataVersion", litematic.get("MinecraftDataVersion"));

        return nbt;

    }

    //region convertLitematicToNbt helper

    private static boolean addSize(NbtCompound nbt, NbtCompound litematicMainRegion) {

        // Get size element

        var sizeElement = litematicMainRegion.get("Size");

        // If is not nbt compound

        if (!(sizeElement instanceof NbtCompound)) {

            return false;

        }

        // Cast

        var sizeCompound = (NbtCompound)sizeElement;

        // Convert to list

        var sizeList = xyzCompoundToList(sizeCompound);

        // Put

        nbt.put("size", sizeList);

        return true;

    }

    private static boolean addEntities(NbtCompound nbt, NbtCompound litematicMainRegion) {

        // Get the entities element

        var entitiesElement = litematicMainRegion.get("Entities");

        // If is not nbt list

        if (!(entitiesElement instanceof NbtList)) {

            return false;

        }

        // Cast

        var entitiesList = (NbtList)entitiesElement;

        // Create new list

        var list = new NbtList();

        // For every entity

        for (var entity : entitiesList) {

            // If is not nbtCompound

            if (!(entity instanceof NbtCompound)) {

                return false;

            }

            // Cast

            var entityCompound = (NbtCompound)entity;

            // Add to list

            if (!addEntityToList(list, entityCompound)) {

                return false;

            }

        }

        // Put

        nbt.put("entities", list);

        return true;

    }

    private static boolean addEntityToList(NbtList list, NbtCompound litematicEntity) {

        // Get pos of entity

        var posElement = litematicEntity.get("Pos");

        // If pos is not nbt list

        if (!(posElement instanceof NbtList)) {

            return false;

        }

        // Cast

        var posList = (NbtList)posElement;

        // Create new entity

        var entity = new NbtCompound();

        // Add pos to entity

        entity.put("pos", posList);

        // Remove pos from litematica entity

        litematicEntity.remove("Pos");

        // Add nbt to entity

        entity.put("nbt", litematicEntity);

        // Add entity to list

        list.add(entity);

        return true;

    }

    private static boolean addBlockList(NbtCompound nbt, NbtCompound litematicMainRegion, NbtCompound size, NbtList palette) {

        // Create block list

        var list = new NbtList();

        // Get size

        var sizeX = ((NbtInt)size.get("x")).intValue();

        var sizeY = ((NbtInt)size.get("y")).intValue();

        var sizeZ = ((NbtInt)size.get("z")).intValue();

        // Get block state array element

        var blockStateArrayElement = litematicMainRegion.get("BlockStates");

        // If is not long array

        if (!(blockStateArrayElement instanceof NbtLongArray)) {

            return false;

        }

        // Cast

        var blockStateArray = (NbtLongArray)blockStateArrayElement;

        // Calculate number of bits

        var bits = Math.max(2, Integer.SIZE - Integer.numberOfLeadingZeros(palette.size() - 1));

        // Calculate max entry value

        var maxEntryValue = (1L << bits) - 1L;

        // Iterate over every possible block

        for (long x = 0; x < sizeX; x++) {

            for (long y = 0; y < sizeY; y++) {

                for (long z = 0; z < sizeZ; z++) {

                    // Get index in array

                    var index = (y * sizeX * sizeZ) + (z * sizeX) + x;

                    // Get the block state index in the palette

                    var paletteIndex = getBlockAt(blockStateArray, index, bits, maxEntryValue);

                    // Create block nbt compound

                    var block = new NbtCompound();

                    // Create pos list

                    var pos = new NbtList();

                    pos.add(NbtInt.of((int) x));

                    pos.add(NbtInt.of((int) y));

                    pos.add(NbtInt.of((int) z));

                    // Add pos to block

                    block.put("pos", pos);

                    // Add state to block

                    block.put("state", NbtInt.of(paletteIndex));

                    // Add block to list

                    list.add(block);

                }

            }

        }

        // Add block list to nbt

        nbt.put("blocks", list);

        return true;

    }

    private static int getBlockAt(NbtLongArray array, long index, int bitsPerEntry, long maxEntryValue) {

        var startOffset = index * (long) bitsPerEntry;

        var startArrIndex = (int) (startOffset >> 6); // startOffset / 64

        var endArrIndex = (int) (((index + 1L) * (long) bitsPerEntry - 1L) >> 6);

        var startBitOffset = (int) (startOffset & 0x3F); // startOffset % 64

        var valAtStartIndex = array.get(startArrIndex).longValue();

        if (startArrIndex == endArrIndex)

        {

            return (int) (valAtStartIndex >>> startBitOffset & maxEntryValue);

        }

        else

        {

            var valAtEndIndex = array.get(endArrIndex).longValue();

            var endOffset = 64 - startBitOffset;

            return (int) ((valAtStartIndex >>> startBitOffset | valAtEndIndex << endOffset) & maxEntryValue);

        }

    }

    //endregion

    public static NbtList xyzCompoundToList(NbtCompound compound) {

        // Create list

        var list = new NbtList();

        // Add to list

        list.add(0, compound.get("x"));

        list.add(1, compound.get("y"));

        list.add(2, compound.get("z"));

        return list;