package net.minecraft.util;

import java.util.Optional;
import net.minecraft.core.BlockPos;
import net.minecraft.core.Direction;
import net.minecraft.server.level.ServerLevel;
import net.minecraft.tags.BlockTags;
import net.minecraft.world.entity.EntitySpawnReason;
import net.minecraft.world.entity.EntityType;
import net.minecraft.world.entity.Mob;
import net.minecraft.world.level.block.Block;
import net.minecraft.world.level.block.Blocks;
import net.minecraft.world.level.block.LeavesBlock;
import net.minecraft.world.level.block.StainedGlassBlock;
import net.minecraft.world.level.block.StainedGlassPaneBlock;
import net.minecraft.world.level.block.state.BlockState;

public class SpawnUtil {
	public static <T extends Mob> Optional<T> trySpawnMob(
		final EntityType<T> entityType,
		final EntitySpawnReason spawnReason,
		final ServerLevel level,
		final BlockPos start,
		final int spawnAttempts,
		final int spawnRangeXZ,
		final int spawnRangeY,
		final SpawnUtil.Strategy strategy,
		final boolean checkCollisions
	) {
		BlockPos.MutableBlockPos searchPos = start.mutable();
		RandomSource random = level.getRandom();

		for (int i = 0; i < spawnAttempts; i++) {
			int dx = Mth.randomBetweenInclusive(random, -spawnRangeXZ, spawnRangeXZ);
			int dz = Mth.randomBetweenInclusive(random, -spawnRangeXZ, spawnRangeXZ);
			searchPos.setWithOffset(start, dx, spawnRangeY, dz);
			if (level.getWorldBorder().isWithinBounds(searchPos)
				&& moveToPossibleSpawnPosition(level, spawnRangeY, searchPos, strategy)
				&& (!checkCollisions || level.noCollision(entityType.getSpawnAABB(searchPos.getX() + 0.5, searchPos.getY(), searchPos.getZ() + 0.5)))) {
				T mob = (T)entityType.create(level, null, searchPos, spawnReason, false, false);
				if (mob != null) {
					if (mob.checkSpawnRules(level, spawnReason) && mob.checkSpawnObstruction(level)) {
						level.addFreshEntityWithPassengers(mob);
						mob.playAmbientSound();
						return Optional.of(mob);
					}

					mob.discard();
				}
			}
		}

		return Optional.empty();
	}

	private static boolean moveToPossibleSpawnPosition(
		final ServerLevel level, final int spawnRangeY, final BlockPos.MutableBlockPos searchPos, final SpawnUtil.Strategy strategy
	) {
		BlockPos.MutableBlockPos abovePos = new BlockPos.MutableBlockPos().set(searchPos);
		BlockState aboveState = level.getBlockState(abovePos);

		for (int y = spawnRangeY; y >= -spawnRangeY; y--) {
			searchPos.move(Direction.DOWN);
			abovePos.setWithOffset(searchPos, Direction.UP);
			BlockState currentState = level.getBlockState(searchPos);
			if (strategy.canSpawnOn(level, searchPos, currentState, abovePos, aboveState)) {
				searchPos.move(Direction.UP);
				return true;
			}

			aboveState = currentState;
		}

		return false;
	}

	public interface Strategy {
		@Deprecated
		SpawnUtil.Strategy LEGACY_IRON_GOLEM = (level, pos, blockState, abovePos, aboveState) -> !blockState.is(Blocks.COBWEB)
				&& !blockState.is(Blocks.CACTUS)
				&& !blockState.is(Blocks.GLASS_PANE)
				&& !(blockState.getBlock() instanceof StainedGlassPaneBlock)
				&& !(blockState.getBlock() instanceof StainedGlassBlock)
				&& !(blockState.getBlock() instanceof LeavesBlock)
				&& !blockState.is(Blocks.CONDUIT)
				&& !blockState.is(Blocks.ICE)
				&& !blockState.is(Blocks.TNT)
				&& !blockState.is(Blocks.GLOWSTONE)
				&& !blockState.is(Blocks.BEACON)
				&& !blockState.is(Blocks.SEA_LANTERN)
				&& !blockState.is(Blocks.FROSTED_ICE)
				&& !blockState.is(Blocks.TINTED_GLASS)
				&& !blockState.is(Blocks.GLASS)
			? (aboveState.isAir() || aboveState.liquid()) && (blockState.isSolid() || blockState.is(Blocks.POWDER_SNOW))
			: false;
		SpawnUtil.Strategy ON_TOP_OF_COLLIDER = (level, pos, blockState, abovePos, aboveState) -> aboveState.getCollisionShape(level, abovePos).isEmpty()
			&& Block.isFaceFull(blockState.getCollisionShape(level, pos), Direction.UP);
		SpawnUtil.Strategy ON_TOP_OF_COLLIDER_NO_LEAVES = (level, pos, blockState, abovePos, aboveState) -> aboveState.getCollisionShape(level, abovePos).isEmpty()
			&& !blockState.is(BlockTags.LEAVES)
			&& Block.isFaceFull(blockState.getCollisionShape(level, pos), Direction.UP);

		boolean canSpawnOn(ServerLevel level, BlockPos pos, BlockState blockState, BlockPos abovePos, BlockState aboveState);
	}
}