baritone/src/main/java/baritone/behavior/ElytraBehavior.java

/*
 * This file is part of Baritone.
 *
 * Baritone is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Baritone is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Baritone.  If not, see <https://www.gnu.org/licenses/>.
 */

package baritone.behavior;

import baritone.Baritone;
import baritone.api.event.events.ChunkEvent;
import baritone.api.event.events.TickEvent;
import baritone.api.event.events.type.EventState;
import baritone.api.utils.BetterBlockPos;
import baritone.api.utils.Helper;
import baritone.api.utils.Rotation;
import baritone.api.utils.RotationUtils;
import baritone.behavior.elytra.NetherPathfinderContext;
import baritone.behavior.elytra.UnpackedSegment;
import baritone.utils.BlockStateInterface;
import com.mojang.realmsclient.util.Pair;
import net.minecraft.block.material.Material;
import net.minecraft.block.state.IBlockState;
import net.minecraft.entity.item.EntityFireworkRocket;
import net.minecraft.init.Blocks;
import net.minecraft.util.EnumFacing;
import net.minecraft.util.EnumHand;
import net.minecraft.util.math.BlockPos;
import net.minecraft.util.math.MathHelper;
import net.minecraft.util.math.RayTraceResult;
import net.minecraft.util.math.Vec3d;
import net.minecraft.world.chunk.Chunk;

import java.util.*;
import java.util.concurrent.CompletableFuture;
import java.util.function.UnaryOperator;

public final class ElytraBehavior extends Behavior implements Helper {

    /**
     * 2b2t seed
     */
    private static final long NETHER_SEED = 146008555100680L;

    // Used exclusively for PathRenderer
    public List<Pair<Vec3d, Vec3d>> lines;
    public BlockPos aimPos;
    public List<BetterBlockPos> visiblePath;

    // :sunglasses:
    private final NetherPathfinderContext context;
    private final PathManager pathManager;
    private int sinceFirework;

    public ElytraBehavior(Baritone baritone) {
        super(baritone);
        this.context = new NetherPathfinderContext(NETHER_SEED);
        this.lines = new ArrayList<>();
        this.visiblePath = Collections.emptyList();
        this.pathManager = new PathManager();
    }

    private final class PathManager {

        private BlockPos destination;
        private List<BetterBlockPos> path;
        private boolean completePath;

        private int playerNear;
        private int goingTo;

        private boolean recalculating;

        public PathManager() {
            // lol imagine initializing fields normally
            this.clear();
        }

        public void tick() {
            // Recalculate closest path node
            this.playerNear = this.calculateNear(this.playerNear);

            // Obstacles are more important than an incomplete path, handle those first.
            this.pathfindAroundObstacles();
            this.attemptNextSegment();
        }

        public void pathToDestination(BlockPos destination) {
            this.destination = destination;
            this.path0(ctx.playerFeet(), destination, UnaryOperator.identity())
                    .thenRun(() -> {
                        final int distance = (int) this.pathAt(0).distanceTo(this.pathAt(this.path.size() - 1));
                        if (this.completePath) {
                            logDirect(String.format("Computed path (%d blocks)", distance));
                        } else {
                            logDirect(String.format("Computed segment (Next %d blocks)", distance));
                        }
                    });
        }

        public void pathRecalcSegment(final int upToIncl) {
            if (this.recalculating) {
                return;
            }

            this.recalculating = true;
            final List<BetterBlockPos> after = this.path.subList(upToIncl, this.path.size());
            final boolean complete = this.completePath;

            this.path0(ctx.playerFeet(), this.path.get(upToIncl), segment -> segment.append(after.stream(), complete))
                    .thenRun(() -> {
                        this.recalculating = false;
                        final int recompute = this.path.size() - after.size() - 1;
                        final int distance = (int) this.pathAt(0).distanceTo(this.pathAt(recompute));
                        logDirect(String.format("Recomputed segment (Next %d blocks)", distance));
                    });
        }

        public void pathNextSegment(final int afterIncl) {
            if (this.recalculating) {
                return;
            }

            this.recalculating = true;
            final List<BetterBlockPos> before = this.path.subList(0, afterIncl + 1);

            this.path0(this.path.get(afterIncl), this.destination, segment -> segment.prepend(before.stream()))
                    .thenRun(() -> {
                        this.recalculating = false;
                        final int recompute = this.path.size() - before.size() - 1;
                        final int distance = (int) this.pathAt(0).distanceTo(this.pathAt(recompute));

                        if (this.completePath) {
                            logDirect(String.format("Computed path (%d blocks)", distance));
                        } else {
                            logDirect(String.format("Computed next segment (Next %d blocks)", distance));
                        }
                    });
        }

        private Vec3d pathAt(int i) {
            return new Vec3d(
                    this.path.get(i).x + 0.5,
                    this.path.get(i).y + 0.5,
                    this.path.get(i).z + 0.5
            );
        }

        public void clear() {
            this.path = Collections.emptyList();
            this.playerNear = 0;
            this.goingTo = 0;
            this.completePath = true;
        }

        private void setPath(final UnpackedSegment segment) {
            this.path = segment.collect();
            this.removeBacktracks();
            this.playerNear = 0;
            this.goingTo = 0;
            this.completePath = segment.isFinished();
        }

        public List<BetterBlockPos> getPath() {
            return this.path;
        }

        public int getNear() {
            return this.playerNear;
        }

        public void setGoingTo(int index) {
            this.goingTo = index;
        }

        public BetterBlockPos goingTo() {
            return this.path.get(this.goingTo);
        }

        // mickey resigned
        private CompletableFuture<Void> path0(BlockPos src, BlockPos dst, UnaryOperator<UnpackedSegment> operator) {
            return ElytraBehavior.this.context.pathFindAsync(src, dst)
                    .thenApply(UnpackedSegment::from)
                    .thenApply(operator)
                    .thenAcceptAsync(this::setPath, ctx.minecraft()::addScheduledTask);
        }

        private void pathfindAroundObstacles() {
            if (this.recalculating) {
                return;
            }

            outer:
            while (true) {
                int rangeStartIncl = playerNear;
                int rangeEndExcl = playerNear;
                while (rangeEndExcl < path.size() && ctx.world().isBlockLoaded(path.get(rangeEndExcl), false)) {
                    rangeEndExcl++;
                }
                if (rangeStartIncl >= rangeEndExcl) {
                    // not loaded yet?
                    return;
                }
                if (!passable(ctx.world().getBlockState(path.get(rangeStartIncl)))) {
                    // we're in a wall
                    return; // previous iterations of this function SHOULD have fixed this by now :rage_cat:
                }
                for (int i = rangeStartIncl; i < rangeEndExcl - 1; i++) {
                    if (!clearView(pathAt(i), pathAt(i + 1))) {
                        // obstacle. where do we return to pathing?
                        // find the next valid segment
                        this.pathRecalcSegment(rangeEndExcl - 1);
                        break outer;
                    }
                }
                break;
            }
        }

        private void attemptNextSegment() {
            if (this.recalculating) {
                return;
            }

            final int last = this.path.size() - 1;
            if (!this.completePath && ctx.world().isBlockLoaded(this.path.get(last), false)) {
                this.pathNextSegment(last);
            }
        }

        private int calculateNear(int index) {
            final BetterBlockPos pos = ctx.playerFeet();
            for (int i = index; i >= Math.max(index - 1000, 0); i -= 10) {
                if (path.get(i).distanceSq(pos) < path.get(index).distanceSq(pos)) {
                    index = i; // intentional: this changes the bound of the loop
                }
            }
            for (int i = index; i < Math.min(index + 1000, path.size()); i += 10) {
                if (path.get(i).distanceSq(pos) < path.get(index).distanceSq(pos)) {
                    index = i; // intentional: this changes the bound of the loop
                }
            }
            for (int i = index; i >= Math.max(index - 50, 0); i--) {
                if (path.get(i).distanceSq(pos) < path.get(index).distanceSq(pos)) {
                    index = i; // intentional: this changes the bound of the loop
                }
            }
            for (int i = index; i < Math.min(index + 50, path.size()); i++) {
                if (path.get(i).distanceSq(pos) < path.get(index).distanceSq(pos)) {
                    index = i; // intentional: this changes the bound of the loop
                }
            }
            return index;
        }

        private void removeBacktracks() {
            Map<BetterBlockPos, Integer> positionFirstSeen = new HashMap<>();
            for (int i = 0; i < this.path.size(); i++) {
                BetterBlockPos pos = this.path.get(i);
                if (positionFirstSeen.containsKey(pos)) {
                    int j = positionFirstSeen.get(pos);
                    while (i > j) {
                        this.path.remove(i);
                        i--;
                    }
                } else {
                    positionFirstSeen.put(pos, i);
                }
            }
        }
    }

    @Override
    public void onChunkEvent(ChunkEvent event) {
        if (event.getState() == EventState.POST && event.getType().isPopulate()) {
            final Chunk chunk = ctx.world().getChunk(event.getX(), event.getZ());
            this.context.queueForPacking(chunk);
        }
    }

    public void path(BlockPos destination) {
        this.pathManager.pathToDestination(destination);
    }

    public void cancel() {
        this.visiblePath = Collections.emptyList();
        this.pathManager.clear();
        this.aimPos = null;
        this.sinceFirework = 0;
    }

    @Override
    public void onTick(TickEvent event) {
        if (event.getType() == TickEvent.Type.OUT) {
            return;
        }
        this.lines.clear();

        final List<BetterBlockPos> path = this.pathManager.getPath();
        if (path.isEmpty()) {
            return;
        }

        this.pathManager.tick();

        final int playerNear = this.pathManager.getNear();
        this.visiblePath = path.subList(
                Math.max(playerNear - 30, 0),
                Math.min(playerNear + 30, path.size())
        );

        if (!ctx.player().isElytraFlying()) {
            return;
        }

        baritone.getInputOverrideHandler().clearAllKeys();

        if (ctx.player().collidedHorizontally) {
            logDirect("hbonk");
        }
        if (ctx.player().collidedVertically) {
            logDirect("vbonk");
        }

        Vec3d start = ctx.playerFeetAsVec();
        boolean firework = isFireworkActive();
        sinceFirework++;
        final long t = System.currentTimeMillis();
        outermost:
        for (int relaxation = 0; relaxation < 3; relaxation++) { // try for a strict solution first, then relax more and more (if we're in a corner or near some blocks, it will have to relax its constraints a bit)
            int[] heights = firework ? new int[]{20, 10, 5, 0} : new int[]{0}; // attempt to gain height, if we can, so as not to waste the boost
            boolean requireClear = relaxation == 0;
            int steps = relaxation < 2 ? firework ? 5 : Baritone.settings().elytraSimulationTicks.value : 3;
            int lookahead = relaxation == 0 ? 2 : 3; // ideally this would be expressed as a distance in blocks, rather than a number of voxel steps
            //int minStep = Math.max(0, playerNear - relaxation);
            int minStep = playerNear;
            for (int i = Math.min(playerNear + 20, path.size() - 1); i >= minStep; i--) {
                for (int dy : heights) {
                    Vec3d dest = this.pathManager.pathAt(i).add(0, dy, 0);
                    if (dy != 0) {
                        if (i + lookahead >= path.size()) {
                            continue;
                        }
                        if (start.distanceTo(dest) < 40) {
                            if (!clearView(dest, this.pathManager.pathAt(i + lookahead).add(0, dy, 0)) || !clearView(dest, this.pathManager.pathAt(i + lookahead))) {
                                // aka: don't go upwards if doing so would prevent us from being able to see the next position **OR** the modified next position
                                continue;
                            }
                        } else {
                            // but if it's far away, allow gaining altitude if we could lose it again by the time we get there
                            if (!clearView(dest, this.pathManager.pathAt(i))) {
                                continue;
                            }
                        }
                    }
                    if (requireClear ? isClear(start, dest) : clearView(start, dest)) {
                        Rotation rot = RotationUtils.calcRotationFromVec3d(start, dest, ctx.playerRotations());
                        long a = System.currentTimeMillis();
                        Float pitch = solvePitch(dest.subtract(start), steps, relaxation == 2);
                        if (pitch == null) {
                            baritone.getLookBehavior().updateTarget(new Rotation(rot.getYaw(), ctx.playerRotations().getPitch()), false);
                            continue;
                        }
                        long b = System.currentTimeMillis();
                        System.out.println("Solved pitch in " + (b - a) + " total time " + (b - t));
                        this.pathManager.setGoingTo(i);
                        this.aimPos = path.get(i).add(0, dy, 0);
                        baritone.getLookBehavior().updateTarget(new Rotation(rot.getYaw(), pitch), false);
                        break outermost;
                    }
                }
            }
            if (relaxation == 2) {
                logDirect("no pitch solution, probably gonna crash in a few ticks LOL!!!");
                return;
            }
        }

        final BetterBlockPos goingTo = this.pathManager.goingTo();

        if (!firework
                && sinceFirework > 10
                && (Baritone.settings().wasteFireworks.value || ctx.player().posY < goingTo.y + 5) // don't firework if trying to descend
                && (ctx.player().posY < goingTo.y - 5 || start.distanceTo(new Vec3d(goingTo.x + 0.5, ctx.player().posY, goingTo.z + 0.5)) > 5) // UGH!!!!!!!
                && new Vec3d(ctx.player().motionX, ctx.player().posY < goingTo.y ? Math.max(0, ctx.player().motionY) : ctx.player().motionY, ctx.player().motionZ).length() < Baritone.settings().elytraFireworkSpeed.value // ignore y component if we are BOTH below where we want to be AND descending
        ) {
            logDirect("firework");
            ctx.playerController().processRightClick(ctx.player(), ctx.world(), EnumHand.MAIN_HAND);
            sinceFirework = 0;
        }
    }

    private boolean isFireworkActive() {
        // TODO: Validate that the EntityFireworkRocket is attached to ctx.player()
        return ctx.world().loadedEntityList.stream()
                .anyMatch(x -> (x instanceof EntityFireworkRocket) && ((EntityFireworkRocket) x).isAttachedToEntity());
    }

    private boolean isClear(Vec3d start, Vec3d dest) {
        Vec3d perpendicular = dest.subtract(start).crossProduct(new Vec3d(0, 1, 0)).normalize();
        return clearView(start, dest)
                && clearView(start.add(0, 2, 0), dest.add(0, 2, 0))
                && clearView(start.add(0, -2, 0), dest.add(0, -2, 0))
                && clearView(start.add(perpendicular), dest.add(perpendicular))
                && clearView(start.subtract(perpendicular), dest.subtract(perpendicular));
    }

    private boolean clearView(Vec3d start, Vec3d dest) {
        lines.add(Pair.of(start, dest));
        RayTraceResult result = rayTraceBlocks(start, dest);
        return result == null || result.typeOfHit == RayTraceResult.Type.MISS;
    }

    private Float solvePitch(Vec3d goalDirection, int steps, boolean desperate) {
        // we are at a certain velocity, but we have a target velocity
        // what pitch would get us closest to our target velocity?
        // yaw is easy so we only care about pitch

        goalDirection = goalDirection.normalize();
        Rotation good = RotationUtils.calcRotationFromVec3d(new Vec3d(0, 0, 0), goalDirection, ctx.playerRotations()); // lazy lol

        boolean firework = isFireworkActive();
        Float bestPitch = null;
        double bestDot = Double.NEGATIVE_INFINITY;
        Vec3d motion = new Vec3d(ctx.player().motionX, ctx.player().motionY, ctx.player().motionZ);
        BlockStateInterface bsi = new BlockStateInterface(ctx);
        float minPitch = desperate ? -90 : Math.max(good.getPitch() - Baritone.settings().elytraPitchRange.value, -89);
        float maxPitch = desperate ? 90 : Math.min(good.getPitch() + Baritone.settings().elytraPitchRange.value, 89);
        outer:
        for (float pitch = minPitch; pitch <= maxPitch; pitch++) {
            Vec3d stepped = motion;
            Vec3d totalMotion = new Vec3d(0, 0, 0);
            for (int i = 0; i < steps; i++) {
                stepped = step(stepped, pitch, good.getYaw(), firework);
                Vec3d actualPositionPrevTick = ctx.playerFeetAsVec().add(totalMotion);
                totalMotion = totalMotion.add(stepped);
                Vec3d actualPosition = ctx.playerFeetAsVec().add(totalMotion);
                for (int x = MathHelper.floor(Math.min(actualPosition.x, actualPositionPrevTick.x) - 0.31); x <= Math.max(actualPosition.x, actualPositionPrevTick.x) + 0.31; x++) {
                    for (int y = MathHelper.floor(Math.min(actualPosition.y, actualPositionPrevTick.y) - 0.2); y <= Math.max(actualPosition.y, actualPositionPrevTick.y) + 0.8; y++) {
                        for (int z = MathHelper.floor(Math.min(actualPosition.z, actualPositionPrevTick.z) - 0.31); z <= Math.max(actualPosition.z, actualPositionPrevTick.z) + 0.31; z++) {
                            if (!passable(bsi.get0(x, y, z))) {
                                continue outer;
                            }
                        }
                    }
                }
            }
            double directionalGoodness = goalDirection.dotProduct(totalMotion.normalize());
            // tried to incorporate a "speedGoodness" but it kept making it do stupid stuff (aka always losing altitude)
            double goodness = directionalGoodness;
            if (goodness > bestDot) {
                bestDot = goodness;
                bestPitch = pitch;
            }
        }
        return bestPitch;
    }

    public static boolean passable(IBlockState state) {
        return state.getMaterial() == Material.AIR;
    }

    private static Vec3d step(Vec3d motion, float rotationPitch, float rotationYaw, boolean firework) {
        double motionX = motion.x;
        double motionY = motion.y;
        double motionZ = motion.z;
        float flatZ = MathHelper.cos(-rotationYaw * 0.017453292F - (float) Math.PI); // 0.174... is Math.PI / 180
        float flatX = MathHelper.sin(-rotationYaw * 0.017453292F - (float) Math.PI);
        float pitchBase = -MathHelper.cos(-rotationPitch * 0.017453292F);
        float pitchHeight = MathHelper.sin(-rotationPitch * 0.017453292F);
        Vec3d lookDirection = new Vec3d(flatX * pitchBase, pitchHeight, flatZ * pitchBase);

        if (firework) {
            // See EntityFireworkRocket
            motionX += lookDirection.x * 0.1 + (lookDirection.x * 1.5 - motionX) * 0.5;
            motionY += lookDirection.y * 0.1 + (lookDirection.y * 1.5 - motionY) * 0.5;
            motionZ += lookDirection.z * 0.1 + (lookDirection.z * 1.5 - motionZ) * 0.5;
        }

        float pitchRadians = rotationPitch * 0.017453292F;
        double pitchBase2 = Math.sqrt(lookDirection.x * lookDirection.x + lookDirection.z * lookDirection.z);
        double flatMotion = Math.sqrt(motionX * motionX + motionZ * motionZ);
        double thisIsAlwaysOne = lookDirection.length();
        float pitchBase3 = MathHelper.cos(pitchRadians);
        //System.out.println("always the same lol " + -pitchBase + " " + pitchBase3);
        //System.out.println("always the same lol " + Math.abs(pitchBase3) + " " + pitchBase2);
        //System.out.println("always 1 lol " + thisIsAlwaysOne);
        pitchBase3 = (float) ((double) pitchBase3 * (double) pitchBase3 * Math.min(1, thisIsAlwaysOne / 0.4));
        motionY += -0.08 + (double) pitchBase3 * 0.06;
        if (motionY < 0 && pitchBase2 > 0) {
            double speedModifier = motionY * -0.1 * (double) pitchBase3;
            motionY += speedModifier;
            motionX += lookDirection.x * speedModifier / pitchBase2;
            motionZ += lookDirection.z * speedModifier / pitchBase2;
        }
        if (pitchRadians < 0) { // if you are looking down (below level)
            double anotherSpeedModifier = flatMotion * (double) (-MathHelper.sin(pitchRadians)) * 0.04;
            motionY += anotherSpeedModifier * 3.2;
            motionX -= lookDirection.x * anotherSpeedModifier / pitchBase2;
            motionZ -= lookDirection.z * anotherSpeedModifier / pitchBase2;
        }
        if (pitchBase2 > 0) { // this is always true unless you are looking literally straight up (let's just say the bot will never do that)
            motionX += (lookDirection.x / pitchBase2 * flatMotion - motionX) * 0.1;
            motionZ += (lookDirection.z / pitchBase2 * flatMotion - motionZ) * 0.1;
        }
        motionX *= 0.99;
        motionY *= 0.98;
        motionZ *= 0.99;
        //System.out.println(motionX + " " + motionY + " " + motionZ);

        return new Vec3d(motionX, motionY, motionZ);
    }

    // TODO: Use the optimized version from builder-2
    private RayTraceResult rayTraceBlocks(Vec3d start, Vec3d end) {
        int x1 = MathHelper.floor(end.x);
        int y1 = MathHelper.floor(end.y);
        int z1 = MathHelper.floor(end.z);
        int x2 = MathHelper.floor(start.x);
        int y2 = MathHelper.floor(start.y);
        int z2 = MathHelper.floor(start.z);
        BlockPos blockpos = new BlockPos(x2, y2, z2);
        IBlockState iblockstate = ctx.world().getBlockState(blockpos);
        if (!passable(iblockstate)) {
            return Blocks.SPONGE.getDefaultState().collisionRayTrace(ctx.world(), blockpos, start, end);
        }
        int steps = 200;
        while (steps-- >= 0) {
            if (Double.isNaN(start.x) || Double.isNaN(start.y) || Double.isNaN(start.z)) {
                return null;
            }
            if (x2 == x1 && y2 == y1 && z2 == z1) {
                return null;
            }
            boolean hitX = true;
            boolean hitY = true;
            boolean hitZ = true;
            double nextX = 999.0D;
            double nextY = 999.0D;
            double nextZ = 999.0D;
            if (x1 > x2) {
                nextX = (double) x2 + 1.0D;
            } else if (x1 < x2) {
                nextX = (double) x2 + 0.0D;
            } else {
                hitX = false;
            }
            if (y1 > y2) {
                nextY = (double) y2 + 1.0D;
            } else if (y1 < y2) {
                nextY = (double) y2 + 0.0D;
            } else {
                hitY = false;
            }
            if (z1 > z2) {
                nextZ = (double) z2 + 1.0D;
            } else if (z1 < z2) {
                nextZ = (double) z2 + 0.0D;
            } else {
                hitZ = false;
            }
            double stepX = 999.0D;
            double stepY = 999.0D;
            double stepZ = 999.0D;
            double dirX = end.x - start.x;
            double dirY = end.y - start.y;
            double dirZ = end.z - start.z;
            if (hitX) {
                stepX = (nextX - start.x) / dirX;
            }
            if (hitY) {
                stepY = (nextY - start.y) / dirY;
            }
            if (hitZ) {
                stepZ = (nextZ - start.z) / dirZ;
            }
            if (stepX == -0.0D) {
                stepX = -1.0E-4D;
            }
            if (stepY == -0.0D) {
                stepY = -1.0E-4D;
            }
            if (stepZ == -0.0D) {
                stepZ = -1.0E-4D;
            }
            EnumFacing dir;
            if (stepX < stepY && stepX < stepZ) {
                dir = x1 > x2 ? EnumFacing.WEST : EnumFacing.EAST;
                start = new Vec3d(nextX, start.y + dirY * stepX, start.z + dirZ * stepX);
            } else if (stepY < stepZ) {
                dir = y1 > y2 ? EnumFacing.DOWN : EnumFacing.UP;
                start = new Vec3d(start.x + dirX * stepY, nextY, start.z + dirZ * stepY);
            } else {
                dir = z1 > z2 ? EnumFacing.NORTH : EnumFacing.SOUTH;
                start = new Vec3d(start.x + dirX * stepZ, start.y + dirY * stepZ, nextZ);
            }
            x2 = MathHelper.floor(start.x) - (dir == EnumFacing.EAST ? 1 : 0);
            y2 = MathHelper.floor(start.y) - (dir == EnumFacing.UP ? 1 : 0);
            z2 = MathHelper.floor(start.z) - (dir == EnumFacing.SOUTH ? 1 : 0);
            blockpos = new BlockPos(x2, y2, z2);
            IBlockState iblockstate1 = ctx.world().getBlockState(blockpos);
            if (!passable(iblockstate1)) {
                return Blocks.NETHERRACK.getDefaultState().collisionRayTrace(ctx.world(), blockpos, start, end);
            }
        }
        return null;
    }
}