Code/net/minecraft/world/entity/monster/PatrollingMonster.java

package net.minecraft.world.entity.monster;

import java.util.EnumSet;
import java.util.List;
import javax.annotation.Nullable;
import net.minecraft.core.BlockPos;
import net.minecraft.core.registries.Registries;
import net.minecraft.nbt.CompoundTag;
import net.minecraft.util.RandomSource;
import net.minecraft.world.DifficultyInstance;
import net.minecraft.world.entity.EntitySpawnReason;
import net.minecraft.world.entity.EntityType;
import net.minecraft.world.entity.EquipmentSlot;
import net.minecraft.world.entity.SpawnGroupData;
import net.minecraft.world.entity.ai.goal.Goal;
import net.minecraft.world.entity.ai.navigation.PathNavigation;
import net.minecraft.world.entity.raid.Raid;
import net.minecraft.world.level.Level;
import net.minecraft.world.level.LevelAccessor;
import net.minecraft.world.level.LightLayer;
import net.minecraft.world.level.ServerLevelAccessor;
import net.minecraft.world.level.levelgen.Heightmap;
import net.minecraft.world.phys.Vec3;

public abstract class PatrollingMonster extends Monster {
    private static final boolean DEFAULT_PATROL_LEADER = false;
    private static final boolean DEFAULT_PATROLLING = false;
    @Nullable
    private BlockPos patrolTarget;
    private boolean patrolLeader = false;
    private boolean patrolling = false;

    protected PatrollingMonster(EntityType<? extends PatrollingMonster> p_33046_, Level p_33047_) {
        super(p_33046_, p_33047_);
    }

    @Override
    protected void registerGoals() {
        super.registerGoals();
        this.goalSelector.addGoal(4, new PatrollingMonster.LongDistancePatrolGoal<>(this, 0.7, 0.595));
    }

    @Override
    public void addAdditionalSaveData(CompoundTag p_33063_) {
        super.addAdditionalSaveData(p_33063_);
        p_33063_.storeNullable("patrol_target", BlockPos.CODEC, this.patrolTarget);
        p_33063_.putBoolean("PatrolLeader", this.patrolLeader);
        p_33063_.putBoolean("Patrolling", this.patrolling);
    }

    @Override
    public void readAdditionalSaveData(CompoundTag p_33055_) {
        super.readAdditionalSaveData(p_33055_);
        this.patrolTarget = p_33055_.read("patrol_target", BlockPos.CODEC).orElse(null);
        this.patrolLeader = p_33055_.getBooleanOr("PatrolLeader", false);
        this.patrolling = p_33055_.getBooleanOr("Patrolling", false);
    }

    public boolean canBeLeader() {
        return true;
    }

    @Nullable
    @Override
    public SpawnGroupData finalizeSpawn(ServerLevelAccessor p_33049_, DifficultyInstance p_33050_, EntitySpawnReason p_370139_, @Nullable SpawnGroupData p_33052_) {
        if (p_370139_ != EntitySpawnReason.PATROL
            && p_370139_ != EntitySpawnReason.EVENT
            && p_370139_ != EntitySpawnReason.STRUCTURE
            && p_33049_.getRandom().nextFloat() < 0.06F
            && this.canBeLeader()) {
            this.patrolLeader = true;
        }

        if (this.isPatrolLeader()) {
            this.setItemSlot(EquipmentSlot.HEAD, Raid.getOminousBannerInstance(this.registryAccess().lookupOrThrow(Registries.BANNER_PATTERN)));
            this.setDropChance(EquipmentSlot.HEAD, 2.0F);
        }

        if (p_370139_ == EntitySpawnReason.PATROL) {
            this.patrolling = true;
        }

        return super.finalizeSpawn(p_33049_, p_33050_, p_370139_, p_33052_);
    }

    public static boolean checkPatrollingMonsterSpawnRules(
        EntityType<? extends PatrollingMonster> p_219026_, LevelAccessor p_219027_, EntitySpawnReason p_363098_, BlockPos p_219029_, RandomSource p_219030_
    ) {
        return p_219027_.getBrightness(LightLayer.BLOCK, p_219029_) > 8 ? false : checkAnyLightMonsterSpawnRules(p_219026_, p_219027_, p_363098_, p_219029_, p_219030_);
    }

    @Override
    public boolean removeWhenFarAway(double p_33073_) {
        return !this.patrolling || p_33073_ > 16384.0;
    }

    public void setPatrolTarget(BlockPos p_33071_) {
        this.patrolTarget = p_33071_;
        this.patrolling = true;
    }

    public BlockPos getPatrolTarget() {
        return this.patrolTarget;
    }

    public boolean hasPatrolTarget() {
        return this.patrolTarget != null;
    }

    public void setPatrolLeader(boolean p_33076_) {
        this.patrolLeader = p_33076_;
        this.patrolling = true;
    }

    public boolean isPatrolLeader() {
        return this.patrolLeader;
    }

    public boolean canJoinPatrol() {
        return true;
    }

    public void findPatrolTarget() {
        this.patrolTarget = this.blockPosition().offset(-500 + this.random.nextInt(1000), 0, -500 + this.random.nextInt(1000));
        this.patrolling = true;
    }

    protected boolean isPatrolling() {
        return this.patrolling;
    }

    protected void setPatrolling(boolean p_33078_) {
        this.patrolling = p_33078_;
    }

    public static class LongDistancePatrolGoal<T extends PatrollingMonster> extends Goal {
        private static final int NAVIGATION_FAILED_COOLDOWN = 200;
        private final T mob;
        private final double speedModifier;
        private final double leaderSpeedModifier;
        private long cooldownUntil;

        public LongDistancePatrolGoal(T p_33084_, double p_33085_, double p_33086_) {
            this.mob = p_33084_;
            this.speedModifier = p_33085_;
            this.leaderSpeedModifier = p_33086_;
            this.cooldownUntil = -1L;
            this.setFlags(EnumSet.of(Goal.Flag.MOVE));
        }

        @Override
        public boolean canUse() {
            boolean flag = this.mob.level().getGameTime() < this.cooldownUntil;
            return this.mob.isPatrolling() && this.mob.getTarget() == null && !this.mob.hasControllingPassenger() && this.mob.hasPatrolTarget() && !flag;
        }

        @Override
        public void start() {
        }

        @Override
        public void stop() {
        }

        @Override
        public void tick() {
            boolean flag = this.mob.isPatrolLeader();
            PathNavigation pathnavigation = this.mob.getNavigation();
            if (pathnavigation.isDone()) {
                List<PatrollingMonster> list = this.findPatrolCompanions();
                if (this.mob.isPatrolling() && list.isEmpty()) {
                    this.mob.setPatrolling(false);
                } else if (flag && this.mob.getPatrolTarget().closerToCenterThan(this.mob.position(), 10.0)) {
                    this.mob.findPatrolTarget();
                } else {
                    Vec3 vec3 = Vec3.atBottomCenterOf(this.mob.getPatrolTarget());
                    Vec3 vec31 = this.mob.position();
                    Vec3 vec32 = vec31.subtract(vec3);
                    vec3 = vec32.yRot(90.0F).scale(0.4).add(vec3);
                    Vec3 vec33 = vec3.subtract(vec31).normalize().scale(10.0).add(vec31);
                    BlockPos blockpos = BlockPos.containing(vec33);
                    blockpos = this.mob.level().getHeightmapPos(Heightmap.Types.MOTION_BLOCKING_NO_LEAVES, blockpos);
                    if (!pathnavigation.moveTo(blockpos.getX(), blockpos.getY(), blockpos.getZ(), flag ? this.leaderSpeedModifier : this.speedModifier)) {
                        this.moveRandomly();
                        this.cooldownUntil = this.mob.level().getGameTime() + 200L;
                    } else if (flag) {
                        for (PatrollingMonster patrollingmonster : list) {
                            patrollingmonster.setPatrolTarget(blockpos);
                        }
                    }
                }
            }
        }

        private List<PatrollingMonster> findPatrolCompanions() {
            return this.mob
                .level()
                .getEntitiesOfClass(
                    PatrollingMonster.class, this.mob.getBoundingBox().inflate(16.0), p_359244_ -> p_359244_.canJoinPatrol() && !p_359244_.is(this.mob)
                );
        }

        private boolean moveRandomly() {
            RandomSource randomsource = this.mob.getRandom();
            BlockPos blockpos = this.mob
                .level()
                .getHeightmapPos(
                    Heightmap.Types.MOTION_BLOCKING_NO_LEAVES,
                    this.mob.blockPosition().offset(-8 + randomsource.nextInt(16), 0, -8 + randomsource.nextInt(16))
                );
            return this.mob.getNavigation().moveTo(blockpos.getX(), blockpos.getY(), blockpos.getZ(), this.speedModifier);
        }
    }
}