CavePopulator.java

package net.glowstone.generator.populators;

import org.bukkit.Chunk;
import org.bukkit.Location;
import org.bukkit.Material;
import org.bukkit.World;
import org.bukkit.block.Block;
import org.bukkit.generator.BlockPopulator;

import java.util.HashSet;
import java.util.Random;
import java.util.Set;

/**
 * BlockPopulator for snake-based caves.
 */
public class CavePopulator extends BlockPopulator {

    private static class FinishSnakeTask implements Runnable {

        private final Location[] snake;

        public FinishSnakeTask(Set<Location> snake) {
            this.snake = snake.toArray(new Location[snake.size()]);
        }

        @Override
        public void run() {
            for (Location loc : snake) {
                Block block = loc.getBlock();
                if (!block.isEmpty() && !block.isLiquid() && block.getType() != Material.BEDROCK) {
                    block.setType(Material.AIR);
                }
            }

            for (Location loc : snake) {
                loc.getWorld().unloadChunkRequest(loc.getBlockX() / 16, loc.getBlockZ() / 16);
            }
        }
    }

    @Override
    public void populate(final World world, final Random random, Chunk source) {
        if (random.nextInt(100) < 10) {
            final int x = 4 + random.nextInt(8) + source.getX() * 16;
            final int z = 4 + random.nextInt(8) + source.getZ() * 16;
            int maxY = world.getHighestBlockYAt(x, z);
            if (maxY < 16) {
                maxY = 32;
            }

            final int y = random.nextInt(maxY);
            new Thread(new Runnable() {
                @Override
                public void run() {
                    Set<Location> snake = startSnake(world, random, x, y, z);
                    // Bukkit.getServer().getScheduler().scheduleSyncDelayedTask(GenPlugin.instance, new FinishSnake(world, snake));

                    if (random.nextInt(16) > 5) {
                        if (y > 36) {
                            snake = startSnake(world, random, x, y / 2, z);
                            // Bukkit.getServer().getScheduler().scheduleSyncDelayedTask(GenPlugin.instance, new FinishSnake(world, snake));
                        } else if (y < 24) {
                            snake = startSnake(world, random, x, y * 2, z);
                            // Bukkit.getServer().getScheduler().scheduleSyncDelayedTask(GenPlugin.instance, new FinishSnake(world, snake));
                        }
                    }
                }
            }).start();
        }
    }

    private static Set<Location> startSnake(World world, Random random, int blockX, int blockY, int blockZ) {
        Set<Location> snakeBlocks = new HashSet<>();

        int airHits = 0;
        while (true) {
            if (airHits > 2000) {
                break;
            }

            if (random.nextInt(20) == 0) {
                blockY++;
            } else if (world.getBlockTypeIdAt(blockX, blockY + 2, blockZ) == 0) {
                blockY += 2;
            } else if (world.getBlockTypeIdAt(blockX + 2, blockY, blockZ) == 0) {
                blockX++;
            } else if (world.getBlockTypeIdAt(blockX - 2, blockY, blockZ) == 0) {
                blockX--;
            } else if (world.getBlockTypeIdAt(blockX, blockY, blockZ + 2) == 0) {
                blockZ++;
            } else if (world.getBlockTypeIdAt(blockX, blockY, blockZ - 2) == 0) {
                blockZ--;
            } else if (world.getBlockTypeIdAt(blockX + 1, blockY, blockZ) == 0) {
                blockX++;
            } else if (world.getBlockTypeIdAt(blockX - 1, blockY, blockZ) == 0) {
                blockX--;
            } else if (world.getBlockTypeIdAt(blockX, blockY, blockZ + 1) == 0) {
                blockZ++;
            } else if (world.getBlockTypeIdAt(blockX, blockY, blockZ - 1) == 0) {
                blockZ--;
            } else if (random.nextBoolean()) {
                if (random.nextBoolean()) {
                    blockX++;
                } else {
                    blockZ++;
                }
            } else {
                if (random.nextBoolean()) {
                    blockX--;
                } else {
                    blockZ--;
                }
            }

            if (world.getBlockTypeIdAt(blockX, blockY, blockZ) != 0) {
                int radius = 1 + random.nextInt(3);
                int radius2 = radius * radius + 1;
                for (int x = -radius; x <= radius; x++) {
                    for (int y = -radius; y <= radius; y++) {
                        for (int z = -radius; z <= radius; z++) {
                            if (x * x + y * y + z * z <= radius2 && y >= 0 && y < 128) {
                                if (world.getBlockTypeIdAt(blockX + x, blockY + y, blockZ + z) == 0) {
                                    airHits++;
                                } else {
                                    snakeBlocks.add(new Location(world, blockX + x, blockY + y, blockZ + z));
                                }
                            }
                        }
                    }
                }
            } else {
                airHits++;
            }
        }

        return snakeBlocks;
    }
}