Code/net/minecraft/world/entity/ai/village/VillageSiege.java

package net.minecraft.world.entity.ai.village;

import com.mojang.logging.LogUtils;
import javax.annotation.Nullable;
import net.minecraft.core.BlockPos;
import net.minecraft.server.level.ServerLevel;
import net.minecraft.tags.BiomeTags;
import net.minecraft.util.Mth;
import net.minecraft.world.entity.EntitySpawnReason;
import net.minecraft.world.entity.EntityType;
import net.minecraft.world.entity.monster.Monster;
import net.minecraft.world.entity.monster.Zombie;
import net.minecraft.world.entity.player.Player;
import net.minecraft.world.level.CustomSpawner;
import net.minecraft.world.level.levelgen.Heightmap;
import net.minecraft.world.phys.Vec3;
import org.slf4j.Logger;

public class VillageSiege implements CustomSpawner {
    private static final Logger LOGGER = LogUtils.getLogger();
    private boolean hasSetupSiege;
    private VillageSiege.State siegeState = VillageSiege.State.SIEGE_DONE;
    private int zombiesToSpawn;
    private int nextSpawnTime;
    private int spawnX;
    private int spawnY;
    private int spawnZ;

    @Override
    public void tick(ServerLevel p_27013_, boolean p_27014_, boolean p_27015_) {
        if (!p_27013_.isBrightOutside() && p_27014_) {
            float f = p_27013_.getTimeOfDay(0.0F);
            if (f == 0.5) {
                this.siegeState = p_27013_.random.nextInt(10) == 0 ? VillageSiege.State.SIEGE_TONIGHT : VillageSiege.State.SIEGE_DONE;
            }

            if (this.siegeState != VillageSiege.State.SIEGE_DONE) {
                if (!this.hasSetupSiege) {
                    if (!this.tryToSetupSiege(p_27013_)) {
                        return;
                    }

                    this.hasSetupSiege = true;
                }

                if (this.nextSpawnTime > 0) {
                    this.nextSpawnTime--;
                } else {
                    this.nextSpawnTime = 2;
                    if (this.zombiesToSpawn > 0) {
                        this.trySpawn(p_27013_);
                        this.zombiesToSpawn--;
                    } else {
                        this.siegeState = VillageSiege.State.SIEGE_DONE;
                    }
                }
            }
        } else {
            this.siegeState = VillageSiege.State.SIEGE_DONE;
            this.hasSetupSiege = false;
        }
    }

    private boolean tryToSetupSiege(ServerLevel p_27008_) {
        for (Player player : p_27008_.players()) {
            if (!player.isSpectator()) {
                BlockPos blockpos = player.blockPosition();
                if (p_27008_.isVillage(blockpos) && !p_27008_.getBiome(blockpos).is(BiomeTags.WITHOUT_ZOMBIE_SIEGES)) {
                    for (int i = 0; i < 10; i++) {
                        float f = p_27008_.random.nextFloat() * (float) (Math.PI * 2);
                        this.spawnX = blockpos.getX() + Mth.floor(Mth.cos(f) * 32.0F);
                        this.spawnY = blockpos.getY();
                        this.spawnZ = blockpos.getZ() + Mth.floor(Mth.sin(f) * 32.0F);
                        if (this.findRandomSpawnPos(p_27008_, new BlockPos(this.spawnX, this.spawnY, this.spawnZ)) != null) {
                            this.nextSpawnTime = 0;
                            this.zombiesToSpawn = 20;
                            break;
                        }
                    }

                    return true;
                }
            }
        }

        return false;
    }

    private void trySpawn(ServerLevel p_27017_) {
        Vec3 vec3 = this.findRandomSpawnPos(p_27017_, new BlockPos(this.spawnX, this.spawnY, this.spawnZ));
        if (vec3 != null) {
            Zombie zombie;
            try {
                zombie = new Zombie(p_27017_);
                zombie.finalizeSpawn(p_27017_, p_27017_.getCurrentDifficultyAt(zombie.blockPosition()), EntitySpawnReason.EVENT, null);
            } catch (Exception exception) {
                LOGGER.warn("Failed to create zombie for village siege at {}", vec3, exception);
                return;
            }

            zombie.snapTo(vec3.x, vec3.y, vec3.z, p_27017_.random.nextFloat() * 360.0F, 0.0F);
            p_27017_.addFreshEntityWithPassengers(zombie);
        }
    }

    @Nullable
    private Vec3 findRandomSpawnPos(ServerLevel p_27010_, BlockPos p_27011_) {
        for (int i = 0; i < 10; i++) {
            int j = p_27011_.getX() + p_27010_.random.nextInt(16) - 8;
            int k = p_27011_.getZ() + p_27010_.random.nextInt(16) - 8;
            int l = p_27010_.getHeight(Heightmap.Types.WORLD_SURFACE, j, k);
            BlockPos blockpos = new BlockPos(j, l, k);
            if (p_27010_.isVillage(blockpos) && Monster.checkMonsterSpawnRules(EntityType.ZOMBIE, p_27010_, EntitySpawnReason.EVENT, blockpos, p_27010_.random)) {
                return Vec3.atBottomCenterOf(blockpos);
            }
        }

        return null;
    }

    static enum State {
        SIEGE_CAN_ACTIVATE,
        SIEGE_TONIGHT,
        SIEGE_DONE;
    }
}