path: root/proto.ha

use comparray;
use endian;
use mcproto;
use nbt;
use fmt;
use strings;
use trace;

fn decode_position(ctx: *mcproto::Context) (BlockPos | trace::failed) = {
	const v = mcproto::decode_long(ctx)?: i64;
	return BlockPos {
		x = (v >> 38): i32,
		y = (v << 52 >> 52): i16,
		z = (v << 26 >> 38): i32,
	};
};

fn decode_nbt(ctx: *mcproto::Context) ((str, nbt::Object) | trace::failed) = {
	let in = ctx.dec.input[ctx.dec.pos..];
	match (nbt::load(&in)) {
	case let res: (str, nbt::Object) =>
		ctx.dec.pos += len(ctx.dec.input) - ctx.dec.pos - len(in);
		return res;
	case nbt::Invalid =>
		return mcproto::error(ctx, "Invalid NBT");
	};
};

type Handler = fn(ctx: *mcproto::Context)
	(void | trace::failed);

fn game_handle_packet(ctx: *mcproto::Context, packet_id: i32)
		(void | trace::failed) = {
	const handler = if (packet_id: size < len(PROTO_HANDLERS))
		PROTO_HANDLERS[packet_id: size] else null;
	match (handler) {
	case let handler: *Handler =>
		const ctx_ = mcproto::context(ctx, "0x{:02x}", packet_id);
		return handler(&ctx_);
	case null =>
		// TODO: implement all the packets ._.
		// erroring here would spam too much for now...
		void;
	};
};

const PROTO_HANDLERS: [_]nullable *Handler = [
	null, // 0x00
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	&handle_block_update,
	null,
	null,
	null,
	null,
	null,
	null,
	null, // 0x10
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	&handle_unload_chunk,
	null,
	null,
	null,
	null, // handle_keep_alive; handled in client_handle_packet.
	&handle_chunk_data_and_update_light,
	null,
	null,
	null,
	null, // handle_login; handled in client_handle_packet.
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null, // 0x30
	null,
	null,
	null,
	&handle_combat_death,
	null,
	null,
	null,
	&handle_synchronize_player_position,
	null,
	null,
	null,
	null,
	&handle_respawn,
	null,
	&handle_update_section_blocks,
	null, // 0x40
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	&handle_set_center_chunk,
	null,
	&handle_set_default_spawn_position,
	null,
	null,
	null,
	null, // 0x50
	null,
	null,
	&handle_set_health,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null, // 0x60
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
	null,
];

fn handle_login(ctx: *mcproto::Context) (void | trace::failed) = {
	const ctx_ = mcproto::context(ctx, "player id");
	const player_id = mcproto::decode_int(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "is hardcore");
	const is_hardcore = mcproto::decode_bool(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "gamemode");
	const gamemode = mcproto::decode_byte(&ctx_)?: Gamemode;
	if (gamemode >= Gamemode::COUNT) {
		return mcproto::error(&ctx_, "Invalid gamemode 0x{:02x}",
			gamemode: u8);
	};
	const ctx_ = mcproto::context(ctx, "previous gamemode");
	const prev_gamemode = mcproto::decode_byte(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "dimension count");
	const dim_count = mcproto::decode_varint(&ctx_)?;
	for (let i = 0i32; i < dim_count; i += 1) {
		const ctx_ = mcproto::context(ctx, "dimension name {}", i);
		const dim_name = mcproto::decode_string(&ctx_, 0x7fff)?;
	};
	const ctx_ = mcproto::context(ctx, "registry");
	const registry = decode_nbt(&ctx_)?;
	free(registry.0);
	const registry = registry.1;
	defer nbt::finish(registry);
	const ctx_ = mcproto::context(ctx, "dimension type");
	const dim_type = mcproto::decode_string(&ctx_, 0x7fff)?;
	const ctx_ = mcproto::context(ctx, "dimension name");
	const dim_name = mcproto::decode_string(&ctx_, 0x7fff)?;
	const ctx_ = mcproto::context(ctx, "hashed seed");
	const hashed_seed = mcproto::decode_long(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "max players");
	const max_players = mcproto::decode_varint(&ctx_)?;
	if (max_players < 0) {
		return mcproto::error(&ctx_, "Max players must not be negative");
	};
	const ctx_ = mcproto::context(ctx, "view distance");
	const view_distance = mcproto::decode_varint(&ctx_)?;
	if (view_distance <= 0) {
		return mcproto::error(&ctx_, "View distance must be positive");
	};
	const ctx_ = mcproto::context(ctx, "simulation distance");
	const sim_distance = mcproto::decode_varint(&ctx_)?;
	if (sim_distance <= 0) {
		return mcproto::error(&ctx_,
			"Simulation distance must be positive");
	};
	const ctx_ = mcproto::context(ctx, "reduced debug info");
	const reduced_debug_info = mcproto::decode_bool(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "enable respawn screen");
	const enable_respawn_screen = mcproto::decode_bool(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "is debug");
	const is_debug = mcproto::decode_bool(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "is flat");
	const is_flat = mcproto::decode_bool(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "has death location");
	if (mcproto::decode_bool(&ctx_)?) {
		const ctx_ = mcproto::context(ctx, "death dimension");
		const death_dim = mcproto::decode_string(&ctx_, 0x7fff)?;
		const ctx_ = mcproto::context(ctx, "death position");
		const death_pos = decode_position(&ctx_)?;
	};
	mcproto::expect_end(ctx)?;

	GAMEMODE = gamemode;
	trace::info(&trace::root, "gamemode {}", strgamemode(GAMEMODE));

	assert(len(DIM_TYPES) == 0);
	match (nbt_get(&registry, "minecraft:dimension_type")) {
	case let reg: nbt::Object =>
		match (nbt_get(&reg, "value")) {
		case let reg: []nbt::Value =>
			for (let i = 0z; i < len(reg); i += 1) {
				const entry = match (reg[i]) {
				case let entry: nbt::Object =>
					yield entry;
				case =>
					return mcproto::error(ctx, "Invalid registry");
				};
				const name = match (nbt_get(&entry, "name")) {
				case let name: str =>
					yield strings::dup(name);
				case =>
					return mcproto::error(ctx, "Invalid registry");
				};
				const elem = match (nbt_get(&entry, "element")) {
				case let elem: nbt::Object =>
					yield elem;
				case =>
					return mcproto::error(ctx, "Invalid registry");
				};
				const min_y = match (nbt_get(&elem, "min_y")) {
				case let min_y: i32 =>
					if (min_y & 0xf != 0)
						return mcproto::error(ctx, "Invalid registry");
					min_y >>= 4;
					if (min_y: i8 != min_y)
						return mcproto::error(ctx, "Invalid registry");
					yield min_y: i8;
				case =>
					return mcproto::error(ctx, "Invalid registry");
				};
				const height = match (nbt_get(&elem, "height")) {
				case let height: i32 =>
					if (height & 0xf != 0)
						return mcproto::error(ctx, "Invalid registry");
					height >>= 4;
					if (height: u8 != height: u32)
						return mcproto::error(ctx, "Invalid registry");
					yield height: u8;
				case =>
					return mcproto::error(ctx, "Invalid registry");
				};
				if (min_y + height: i8 < min_y) {
					return mcproto::error(ctx, "Invalid registry");
				};
				append(DIM_TYPES, DimType {
					name = name,
					min_y = min_y,
					height = height,
				});
			};
		case =>
			return mcproto::error(ctx, "Invalid registry");
		};
	case =>
		return mcproto::error(ctx, "Invalid registry");
	};

	let found = false;
	for (let i = 0z; i < len(DIM_TYPES); i += 1) {
		if (DIM_TYPES[i].name == dim_type) {
			found = true;
			DIM_TYPE = i;
		};
	};
	if (!found) {
		return mcproto::error(ctx, "Unknown dimension type {}", dim_type);
	};
	trace::info(&trace::root, "dimension type {}", DIM_TYPES[DIM_TYPE].name);

	VIEW_DISTANCE = view_distance;
	trace::info(&trace::root, "view distance {}", VIEW_DISTANCE);

	game_init();
};

fn handle_respawn(ctx: *mcproto::Context) (void | trace::failed) = {
	const ctx_ = mcproto::context(ctx, "dimension type");
	const dim_type = mcproto::decode_string(&ctx_, 0x7fff)?;
	const ctx_ = mcproto::context(ctx, "dimension name");
	const dim_name = mcproto::decode_string(&ctx_, 0x7fff)?;
	const ctx_ = mcproto::context(ctx, "hashed seed");
	const hashed_seed = mcproto::decode_long(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "gamemode");
	const gamemode = mcproto::decode_byte(&ctx_)?: Gamemode;
	if (gamemode >= Gamemode::COUNT) {
		return mcproto::error(&ctx_, "Invalid gamemode 0x{:02x}",
			gamemode: u8);
	};
	const ctx_ = mcproto::context(ctx, "previous gamemode");
	const prev_gamemode = mcproto::decode_byte(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "is debug");
	const is_debug = mcproto::decode_bool(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "is flat");
	const is_flat = mcproto::decode_bool(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "copy metadata");
	const copy_metadata = mcproto::decode_bool(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "has death location");
	if (mcproto::decode_bool(&ctx_)?) {
		const ctx_ = mcproto::context(ctx, "death dimension");
		const death_dim = mcproto::decode_string(&ctx_, 0x7fff)?;
		const ctx_ = mcproto::context(ctx, "death position");
		const death_pos = decode_position(&ctx_)?;
	};
	mcproto::expect_end(ctx)?;

	game_despawn();

	GAMEMODE = gamemode;
	trace::info(&trace::root, "gamemode {}", strgamemode(GAMEMODE));

	let found = false;
	for (let i = 0z; i < len(DIM_TYPES); i += 1) {
		if (DIM_TYPES[i].name == dim_type) {
			found = true;
			DIM_TYPE = i;
		};
	};
	if (!found) {
		return mcproto::error(ctx, "Unknown dimension type {}",
			dim_type);
	};
	trace::info(&trace::root, "dimension type {}",
		DIM_TYPES[DIM_TYPE].name);

	game_respawn();
};

fn handle_keep_alive(ctx: *mcproto::Context) (void | trace::failed) = {
	const ctx_ = mcproto::context(ctx, "id");
	const id = mcproto::decode_long(&ctx_)?;
	mcproto::expect_end(ctx)?;

	let out: []u8 = [];
	defer free(out);
	mcproto::encode_long(&out, id);
	network_send(0x11, out);
};

fn handle_set_center_chunk(ctx: *mcproto::Context)
		(void | trace::failed) = {
	const ctx_ = mcproto::context(ctx, "x");
	const x = mcproto::decode_varint(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "z");
	const z = mcproto::decode_varint(&ctx_)?;
	mcproto::expect_end(ctx)?;

	setview(ChunkPos { x = x, z = z });
};

type SyncPositionFlags = enum u8 {
	X = 0x1,
	Y = 0x2,
	Z = 0x4,
	// TODO: confirm that these are the correct way around;
	// update wiki to clarify.
	YAW = 0x8,
	PITCH = 0xa,
};

fn handle_synchronize_player_position(ctx: *mcproto::Context)
		(void | trace::failed) = {
	const ctx_ = mcproto::context(ctx, "x");
	let x = mcproto::decode_double(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "y");
	let y = mcproto::decode_double(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "z");
	let z = mcproto::decode_double(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "yaw");
	let yaw = mcproto::decode_float(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "pitch");
	let pitch = mcproto::decode_float(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "flags");
	const flags = mcproto::decode_byte(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "teleport id");
	const id = mcproto::decode_varint(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "dismount");
	const dismount = mcproto::decode_bool(&ctx_)?;
	mcproto::expect_end(ctx)?;

	if (flags & SyncPositionFlags::X != 0) x += PLAYER_POS[0];
	if (flags & SyncPositionFlags::Y != 0) y += PLAYER_POS[1];
	if (flags & SyncPositionFlags::Z != 0) z += PLAYER_POS[2];
	if (flags & SyncPositionFlags::YAW != 0) yaw += PLAYER_YAW;
	if (flags & SyncPositionFlags::PITCH != 0) pitch += PLAYER_PITCH;

	PLAYER_POS = [x: f32, y: f32, z: f32];
	PLAYER_YAW = yaw;
	PLAYER_PITCH = pitch;

	let out: []u8 = [];
	defer free(out);
	mcproto::encode_varint(&out, id);
	network_send(0x00, out);

	// TODO: is this necessary? (probably for anticheat reasons, at
	// least...)
	let out: []u8 = [];
	defer free(out);
	mcproto::encode_double(&out, PLAYER_POS[0]);
	mcproto::encode_double(&out, PLAYER_POS[1]);
	mcproto::encode_double(&out, PLAYER_POS[2]);
	mcproto::encode_float(&out, PLAYER_YAW);
	mcproto::encode_float(&out, PLAYER_PITCH);
	mcproto::encode_bool(&out, true);
	network_send(0x14, out);
};

fn handle_set_health(ctx: *mcproto::Context) (void | trace::failed) = {
	const ctx_ = mcproto::context(ctx, "health");
	const health = mcproto::decode_float(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "food");
	const food = mcproto::decode_varint(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "saturation");
	const saturation = mcproto::decode_float(&ctx_)?;
	mcproto::expect_end(ctx)?;

	PLAYER_HEALTH = health;
	PLAYER_FOOD = food;
	PLAYER_SATURATION = saturation;
};

fn handle_combat_death(ctx: *mcproto::Context) (void | trace::failed) = {
	const ctx_ = mcproto::context(ctx, "player id");
	const player_id = mcproto::decode_varint(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "entity id");
	const entity_id = mcproto::decode_int(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "message");
	const message = mcproto::decode_string(&ctx_, 0x7fff)?;
	mcproto::expect_end(ctx)?;

	trace::info(&trace::root, "death: {}", message);

	death_show(message);
};

fn handle_set_default_spawn_position(ctx: *mcproto::Context)
		(void | trace::failed) = {
	const ctx_ = mcproto::context(ctx, "position");
	const pos = decode_position(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "yaw");
	const yaw = mcproto::decode_float(&ctx_)?;

	LOADING_RECEIVED_SPAWN_POSITION = true;
};

fn handle_block_update(ctx: *mcproto::Context) (void | trace::failed) = {
	const ctx_ = mcproto::context(ctx, "position");
	const pos = decode_position(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "blockstate");
	const bstate = mcproto::decode_varint(&ctx_)?;
	if (bstate & ~0xffff != 0) {
		return mcproto::error(&ctx_, "Blockstate id too large");
	};
	const bstate = bstate: u16;
	mcproto::expect_end(&ctx_)?;

	if (getsection(block_section(pos)) is null) {
		mcproto::log(ctx, trace::level::WARN,
			"Block update references nonexistent chunk: ( {} {} {} )",
			pos.x, pos.y, pos.z);
		return;
	};

	setblock(pos, bstate);
};

fn handle_update_section_blocks(ctx: *mcproto::Context)
		(void | trace::failed) = {
	const ctx_ = mcproto::context(ctx, "section position");
	const section_pos = mcproto::decode_long(&ctx_)?: i64;
	const section_pos = SectionPos {
		x = (section_pos >> 42): i32,
		y = (section_pos << 44 >> 44): i8,
		z = (section_pos << 22 >> 42): i32,
	};
	if (getsection(section_pos) is null) {
		mcproto::log(ctx, trace::level::WARN,
			"Section update references nonexistent chunk: [ {} {} {} ]",
			section_pos.x, section_pos.y, section_pos.z);
		return;
	};
	const ctx_ = mcproto::context(ctx, "suppress light updates");
	const suppress_light_updates = mcproto::decode_bool(&ctx_)?;
	const ctx_ = mcproto::context(ctx, "block count");
	const nblocks = mcproto::decode_varint(&ctx_)?;
	for (let i = 0i32; i < nblocks; i += 1) {
		const ctx_ = mcproto::context(ctx, "entry {}", i);
		// TODO: should be varlong
		const entry = mcproto::decode_varint(&ctx_)?;
		const pos = BlockPos {
			x = (section_pos.x << 4) + (entry >> 8 & 0xf),
			y = (section_pos.y: i16 << 4) + (entry & 0xf): i16,
			z = (section_pos.z << 4) + (entry >> 4 & 0xf),
		};
		const bstate = entry >> 12;
		if (bstate & ~0xffff != 0) {
			return mcproto::error(&ctx_, "Blockstate id too large");
		};
		const bstate = bstate: u16;

		setblock(pos, bstate);
	};
	mcproto::expect_end(ctx)?;
};

fn handle_chunk_data_and_update_light(ctx: *mcproto::Context)
		(void | trace::failed) = {
	const ctx_ = mcproto::context(ctx, "x");
	const x = mcproto::decode_int(&ctx_)?: i32;
	const ctx_ = mcproto::context(ctx, "z");
	const z = mcproto::decode_int(&ctx_)?: i32;
	const chunk_pos = ChunkPos { x = x, z = z };
	if (getchunk(chunk_pos) is null) {
		return mcproto::error(ctx,
			"Chunk out of range: [ {} {} ]",
			chunk_pos.x, chunk_pos.z);
	};
	const ctx_ = mcproto::context(ctx, "heightmaps");
	const heightmaps = decode_nbt(&ctx_)?;
	free(heightmaps.0);
	const heightmaps = heightmaps.1;
	defer nbt::finish(heightmaps);
	const ctx_ = mcproto::context(ctx, "data length");
	const datalen = mcproto::decode_varint(&ctx_)?;
	if (datalen < 0) {
		return mcproto::error(&ctx_, "Data length must not be negative");
	};
	const datalen = datalen: u32;
	const ctx_ = mcproto::context(ctx, "chunk data");
	mcproto::decode_nbytes(&ctx_, datalen)?;
	let cdec = *ctx.dec;
	cdec.input = cdec.input[..cdec.pos];
	cdec.pos -= datalen;
	const cctx = mcproto::root(&cdec);

	const chunk = chunk_init(chunk_pos);

	for (let i = 0z; i < CHUNKS_HEIGHT; i += 1) {
		const cctx_ = mcproto::context(&cctx, "block count");
		const block_count = mcproto::decode_short(&cctx_)?;
		const cctx_ = mcproto::context(&cctx, "bits per entry");
		const bpe = mcproto::decode_byte(&cctx_)?;

		const bstates = if (bpe == 0) { // constant
			const cctx_ = mcproto::context(&cctx, "constant value");
			const value = mcproto::decode_varint(&cctx_)?;
			if (value > 0xffff) {
				return mcproto::error(&cctx_, "Blockstate id too large");
			};
			const cctx_ = mcproto::context(&cctx, "array length");
			const arraylen = mcproto::decode_varint(&cctx_)?;
			if (arraylen != 0) {
				return mcproto::error(&cctx_,
					"Chunk data array must be empty when bpe = 0");
			};
			let array = comparray::new(1, 4096);
			comparray::clear(&array, value: u16);
			yield array;
		} else {
			let array = if (bpe >= 9) { // direct
				yield comparray::new(0, 4096);
			} else { // indirect
				const cctx_ = mcproto::context(&cctx,
					"palette length");
				const palettelen =
					mcproto::decode_varint(&cctx_)?: u32;
				if (palettelen >= 256 || palettelen < 2) {
					// = 256 is actually possible, but it's
					// going to be a huge pain. oh well.
					return mcproto::error(&cctx_, "Uh oh.");
				};
				let array =
					comparray::new(palettelen: u8, 4096);
				let palette = comparray::get_palette(&array);
				for (let i = 0z; i < palettelen; i += 1) {
					const cctx_ = mcproto::context(&cctx,
						"palette entry {}", i);
					const value =
						mcproto::decode_varint(&cctx_)?;
					if (value > 0xffff) {
						return mcproto::error(&cctx_,
							"Blockstate id too large");
					};
					palette[i] = value: u16;
				};
				yield array;
			};

			const bpe = if (bpe <= 4) 4u8
				else if (bpe <= 8) bpe: u8
				else 15u8;

			const cctx_ = mcproto::context(&cctx, "array length");
			const arraylen = mcproto::decode_varint(&cctx_)?;
			const epl = 64 / bpe;
			const arraylen_ = (4096z + epl - 1) / epl;
			if (arraylen: size != arraylen_) {
				return mcproto::error(&cctx_,
					"Chunk data array with bpe = {} must have length {}, not {}",
					bpe, arraylen_, arraylen);
			};
			const cctx_ = mcproto::context(&cctx, "array data");
			let arraydata =
				mcproto::decode_nbytes(&cctx_,
					arraylen: size * 8)?;

			let pos = 0z;
			let long = 0u64;
			let shift = 64u8;
			const mask = (1u64 << bpe) - 1;
			for (let i = 0z; i < 4096; i += 1) {
				if (shift + bpe > 64) {
					long = endian::begetu64(
						arraydata[pos..pos + 8]);
					pos += 8;
					shift = 0;
				};
				const value = long >> shift & mask;
				shift += bpe;
				if (array.palette_size != 0
						&& value > array.palette_size) {
					return mcproto::error(&cctx_,
						"Palette index out of range (entry {})",
						i);
				};
				if (array.palette_size == 0 && value > 0xffff) {
					return mcproto::error(&cctx_,
						"Blockstate id too large (entry {})",
						i);
				};
				comparray::set(&array, i, value: u16);
			};

			yield array;
		};

		const cctx_ = mcproto::context(&cctx, "bits per entry");
		const bpe = mcproto::decode_byte(&cctx_)?;
		if (bpe == 0) { // constant
			const cctx_ = mcproto::context(&cctx, "constant value");
			mcproto::decode_varint(&cctx_)?;
		} else if (bpe < 4) { // indirect
			const cctx_ = mcproto::context(&cctx, "palette length");
			const palettelen = mcproto::decode_varint(&cctx)?: u32;
			for (let i = 0z; i < palettelen; i += 1) {
				const cctx_ = mcproto::context(&cctx,
					"palette entry {}", i);
				mcproto::decode_varint(&cctx_)?;
			};
		};
		const cctx_ = mcproto::context(&cctx, "array length");
		const arraylen = mcproto::decode_varint(&cctx_)?: u32;
		const cctx_ = mcproto::context(&cctx, "array data");
		mcproto::decode_nbytes(&cctx_, arraylen: size * 8)?;

		const section = &(chunk.sections as *[*]Section)[i];
		section.bstates = bstates;
		section.dirty = true;
	};

	// other stuff we don't care about for now.
};

fn handle_unload_chunk(ctx: *mcproto::Context)
		(void | trace::failed) = {
	const ctx_ = mcproto::context(ctx, "x");
	const x = mcproto::decode_int(&ctx_)?: i32;
	const ctx_ = mcproto::context(ctx, "z");
	const z = mcproto::decode_int(&ctx_)?: i32;
	chunk_destroy(ChunkPos { x = x, z = z });
};

// this is really awkward, but i hear a "match overhaul" is coming that should
// improve things...
fn nbt_get(obj: *nbt::Object, key: str)
		(...nbt::Value | void) = {
	match (nbt::get(obj, key)) {
	case let value: *nbt::Value =>
		return *value;
	case null =>
		return void;
	};
};