implement server ticks, block updates, and classic fluid mechanics

src/level.rs

@@ -1,3 +1,9 @@
+use std::collections::BTreeSet;
+
+use crate::{packet::server::ServerPacket, util::neighbors};
+
+use self::block::BLOCK_INFO;
+
 pub mod block;
 pub mod generation;
 
@@ -13,6 +19,10 @@ pub struct Level {
 
 	/// the blocks which make up the level
 	pub blocks: Vec<u8>,
+	/// index of blocks which need to be updated in the next tick
+	pub awaiting_update: BTreeSet<usize>,
+	/// list of updates to apply to the world on the next tick
+	pub updates: Vec<BlockUpdate>,
 }
 
 impl Level {
@@ -23,6 +33,8 @@ impl Level {
 			y_size,
 			z_size,
 			blocks: vec![0; x_size * y_size * z_size],
+			awaiting_update: Default::default(),
+			updates: Default::default(),
 		}
 	}
 
@@ -31,6 +43,14 @@ impl Level {
 		x + z * self.x_size + y * self.x_size * self.z_size
 	}
 
+	/// gets the coordinates for the given index
+	pub fn coordinates(&self, index: usize) -> (usize, usize, usize) {
+		let y = index / (self.x_size * self.z_size);
+		let z = (index / self.x_size) % self.z_size;
+		let x = index % self.z_size;
+		(x, y, z)
+	}
+
 	/// gets the block at the given position
 	pub fn get_block(&self, x: usize, y: usize, z: usize) -> u8 {
 		self.blocks[self.index(x, y, z)]
@@ -41,4 +61,40 @@ impl Level {
 		let index = self.index(x, y, z);
 		self.blocks[index] = block;
 	}
+
+	/// applies the level's queued updates
+	pub fn apply_updates(&mut self) -> Vec<ServerPacket> {
+		self.updates.dedup_by(|a, b| a.index == b.index);
+		let mut packets = Vec::with_capacity(self.updates.len());
+
+		for update in std::mem::take(&mut self.updates) {
+			let (x, y, z) = self.coordinates(update.index);
+			self.blocks[update.index] = update.block;
+			packets.push(ServerPacket::SetBlock {
+				x: x as i16,
+				y: y as i16,
+				z: z as i16,
+				block_type: update.block,
+			});
+			for (nx, ny, nz) in neighbors(self, x, y, z) {
+				let info = BLOCK_INFO
+					.get(&self.get_block(nx, ny, nz))
+					.expect("missing block");
+				if info.block_type.needs_update_when_neighbor_changed() {
+					self.awaiting_update.insert(self.index(nx, ny, nz));
+				}
+			}
+		}
+
+		packets
+	}
+}
+
+/// struct describing a block update for the level to handle
+#[derive(Debug, Clone)]
+pub struct BlockUpdate {
+	/// the index of the block to be updated
+	pub index: usize,
+	/// the block type to set the block to
+	pub block: u8,
 }

src/level/block.rs

@@ -24,7 +24,10 @@ pub static BLOCK_INFO: LazyLock<BTreeMap<u8, BlockInfo>> = LazyLock::new(|| {
 		(
 			0x08,
 			BlockInfo::new("water_flowing")
-				.block_type(BlockType::FluidFlowing { stationary: 0x09 })
+				.block_type(BlockType::FluidFlowing {
+					stationary: 0x09,
+					ticks_to_spread: 1,
+				})
 				.perm(PlayerType::Operator, PlayerType::Normal),
 		),
 		(
@@ -36,7 +39,10 @@ pub static BLOCK_INFO: LazyLock<BTreeMap<u8, BlockInfo>> = LazyLock::new(|| {
 		(
 			0x0a,
 			BlockInfo::new("lava_flowing")
-				.block_type(BlockType::FluidFlowing { stationary: 0x0b })
+				.block_type(BlockType::FluidFlowing {
+					stationary: 0x0b,
+					ticks_to_spread: 5,
+				})
 				.perm(PlayerType::Operator, PlayerType::Normal),
 		),
 		(
@@ -152,7 +158,30 @@ pub enum BlockType {
 	/// a slab
 	Slab,
 	/// fluid which is actively flowing
-	FluidFlowing { stationary: u8 },
+	FluidFlowing {
+		stationary: u8,
+		ticks_to_spread: usize,
+	},
 	/// fluid which is stationary
 	FluidStationary { moving: u8 },
 }
+
+impl BlockType {
+	/// gets whether this block type needs an update after being placed
+	#[allow(clippy::match_like_matches_macro)]
+	pub fn needs_update_on_place(&self) -> bool {
+		match self {
+			BlockType::FluidFlowing { .. } => true,
+			_ => false,
+		}
+	}
+
+	/// gets whether this block type needs an update when one of it's direct neighbors changes
+	#[allow(clippy::match_like_matches_macro)]
+	pub fn needs_update_when_neighbor_changed(&self) -> bool {
+		match self {
+			BlockType::FluidStationary { .. } => true,
+			_ => false,
+		}
+	}
+}

src/main.rs

@@ -11,6 +11,7 @@ mod level;
 mod packet;
 mod player;
 mod server;
+mod util;
 
 const CONFIG_FILE: &str = "./server-config.json";
 

src/server.rs

@@ -5,10 +5,19 @@ use std::sync::Arc;
 
 use tokio::{net::TcpListener, sync::RwLock};
 
-use crate::{level::Level, player::Player};
+use crate::{
+	level::{
+		block::{BlockType, BLOCK_INFO},
+		BlockUpdate, Level,
+	},
+	player::Player,
+	util::neighbors_minus_up,
+};
 
 use self::config::ServerConfig;
 
+const TICK_DURATION: std::time::Duration = std::time::Duration::from_millis(50);
+
 /// the server
 #[derive(Debug)]
 pub struct Server {
@@ -64,6 +73,10 @@ impl Server {
 
 	/// starts the server
 	pub async fn run(&mut self) -> std::io::Result<()> {
+		let data = self.data.clone();
+		tokio::spawn(async move {
+			handle_ticks(data).await;
+		});
 		loop {
 			let (stream, addr) = self.listener.accept().await?;
 			println!("connection from {addr}");
@@ -76,3 +89,85 @@ impl Server {
 		}
 	}
 }
+
+/// function to tick the server
+async fn handle_ticks(data: Arc<RwLock<ServerData>>) {
+	let mut current_tick = 0;
+	loop {
+		tick(&mut *data.write().await, current_tick);
+		current_tick = current_tick.wrapping_add(1);
+		tokio::time::sleep(TICK_DURATION).await;
+	}
+}
+
+/// function which ticks the server once
+fn tick(data: &mut ServerData, tick: usize) {
+	let level = &mut data.level;
+
+	let mut packets = level.apply_updates();
+
+	let awaiting_update = std::mem::take(&mut level.awaiting_update);
+	if !awaiting_update.is_empty() {
+		println!("hm");
+	}
+	for index in awaiting_update {
+		let (x, y, z) = level.coordinates(index);
+		let block_id = level.get_block(x, y, z);
+		let block = BLOCK_INFO.get(&block_id).expect("should never fail");
+		println!("{block:#?}");
+		match &block.block_type {
+			BlockType::FluidFlowing {
+				stationary,
+				ticks_to_spread,
+			} => {
+				if tick % ticks_to_spread == 0 {
+					let update = BlockUpdate {
+						index,
+						block: *stationary,
+					};
+					level.updates.push(update);
+					for (nx, ny, nz) in neighbors_minus_up(level, x, y, z) {
+						let block_at = level.get_block(nx, ny, nz);
+						let update = if block_at == 0 {
+							level.awaiting_update.insert(level.index(nx, ny, nz));
+							BlockUpdate {
+								index: level.index(nx, ny, nz),
+								block: block_id,
+							}
+						} else {
+							continue;
+						};
+						level.updates.push(update);
+					}
+				} else {
+					level.awaiting_update.insert(index);
+				}
+			}
+			BlockType::FluidStationary { moving } => {
+				let mut needs_update = false;
+				for (nx, ny, nz) in neighbors_minus_up(level, x, y, z) {
+					if level.get_block(nx, ny, nz) == 0 {
+						needs_update = true;
+						break;
+					}
+				}
+				if needs_update {
+					let index = level.index(x, y, z);
+					level.updates.push(BlockUpdate {
+						index,
+						block: *moving,
+					});
+					level.awaiting_update.insert(index);
+				}
+			}
+			_ => {}
+		}
+	}
+
+	packets.extend(level.apply_updates());
+	for packet in packets {
+		for player in &mut data.players {
+			player.packets_to_send.push(packet.clone());
+		}
+	}
+}

src/server/network.rs

@@ -10,7 +10,7 @@ use tokio::{
 };
 
 use crate::{
-	level::{block::BLOCK_INFO, Level},
+	level::{block::BLOCK_INFO, BlockUpdate, Level},
 	packet::{client::ClientPacket, server::ServerPacket, PacketWriter, ARRAY_LENGTH},
 	player::{Player, PlayerType},
 	server::config::ServerProtectionMode,
@@ -233,7 +233,18 @@ async fn handle_stream_inner(
 									}
 
 									let new_block_info = BLOCK_INFO.get(&block_type);
-									let mut cancel = new_block_info.is_none();
+									if new_block_info.is_none() {
+										reply_queue.push_back(ServerPacket::Message {
+											player_id: -1,
+											message: format!(
+												"Unknown block ID: 0x{:0x}",
+												block_type
+											),
+										});
+										continue;
+									}
+									let new_block_info = new_block_info.expect("will never fail");
+									let mut cancel = false;
 									let block =
 										data.level.get_block(x as usize, y as usize, z as usize);
 									let block_info = BLOCK_INFO
@@ -241,29 +252,23 @@ async fn handle_stream_inner(
 										.expect("missing block information for block!");
 
 									// check if player has ability to place/break these blocks
-									if let Some(new_block_info) = new_block_info {
-										let player_type = data
-											.players
-											.iter()
-											.find_map(|p| {
-												(p.id == *own_id).then_some(p.player_type)
-											})
-											.unwrap_or_default();
-										if player_type < new_block_info.place_permissions {
-											cancel = true;
-											reply_queue.push_back(ServerPacket::Message {
-												player_id: -1,
-												message: "Not allowed to place this block."
-													.to_string(),
-											});
-										} else if player_type < block_info.break_permissions {
-											cancel = true;
-											reply_queue.push_back(ServerPacket::Message {
-												player_id: -1,
-												message: "Not allowed to break this block."
-													.to_string(),
-											});
-										}
+									let player_type = data
+										.players
+										.iter()
+										.find_map(|p| (p.id == *own_id).then_some(p.player_type))
+										.unwrap_or_default();
+									if player_type < new_block_info.place_permissions {
+										cancel = true;
+										reply_queue.push_back(ServerPacket::Message {
+											player_id: -1,
+											message: "Not allowed to place this block.".to_string(),
+										});
+									} else if player_type < block_info.break_permissions {
+										cancel = true;
+										reply_queue.push_back(ServerPacket::Message {
+											player_id: -1,
+											message: "Not allowed to break this block.".to_string(),
+										});
 									}
 
 									if cancel {
@@ -275,16 +280,14 @@ async fn handle_stream_inner(
 										});
 										continue;
 									}
-									let packet = ServerPacket::SetBlock {
-										x,
-										y,
-										z,
-										block_type,
-									};
-									data.level
-										.set_block(x as usize, y as usize, z as usize, block_type);
-									for player in &mut data.players {
-										player.packets_to_send.push(packet.clone());
+									let (x, y, z) = (x as usize, y as usize, z as usize);
+									let index = data.level.index(x, y, z);
+									data.level.updates.push(BlockUpdate {
+										index,
+										block: block_type,
+									});
+									if new_block_info.block_type.needs_update_on_place() {
+										data.level.awaiting_update.insert(index);
 									}
 								}
 								ClientPacket::PositionOrientation {

src/util.rs

@@ -0,0 +1,62 @@
+use crate::level::Level;
+
+const NEIGHBORS: &[(isize, isize, isize)] = &[
+	(0, 1, 0),
+	(0, -1, 0),
+	(-1, 0, 0),
+	(1, 0, 0),
+	(0, 0, -1),
+	(0, 0, 1),
+];
+
+/// gets a block's direct neighbors which are in the bounds of the level
+pub fn neighbors(level: &Level, x: usize, y: usize, z: usize) -> Vec<(usize, usize, usize)> {
+	get_many_relative_coords(level, x, y, z, NEIGHBORS.iter().copied())
+}
+
+/// gets a blocks direct neighbors (excluding above the block) which are in the bounds of the level
+pub fn neighbors_minus_up(
+	level: &Level,
+	x: usize,
+	y: usize,
+	z: usize,
+) -> Vec<(usize, usize, usize)> {
+	get_many_relative_coords(level, x, y, z, NEIGHBORS.iter().skip(1).copied())
+}
+
+/// adds relative coordinates to the given ones, returning `None` if the coordinates would be out of bounds for hte level
+pub fn get_relative_coords(
+	level: &Level,
+	x: usize,
+	y: usize,
+	z: usize,
+	rx: isize,
+	ry: isize,
+	rz: isize,
+) -> Option<(usize, usize, usize)> {
+	Some((
+		x.checked_add_signed(rx)
+			.and_then(|x| (x < level.x_size).then_some(x))?,
+		y.checked_add_signed(ry)
+			.and_then(|y| (y < level.y_size).then_some(y))?,
+		z.checked_add_signed(rz)
+			.and_then(|z| (z < level.z_size).then_some(z))?,
+	))
+}
+
+/// takes an iterator of relative changes to apply to the given coordinates and returns a `Vec` of the ones in bounds of the level
+pub fn get_many_relative_coords<T>(
+	level: &Level,
+	x: usize,
+	y: usize,
+	z: usize,
+	coords: T,
+) -> Vec<(usize, usize, usize)>
+where
+	T: IntoIterator<Item = (isize, isize, isize)>,
+{
+	coords
+		.into_iter()
+		.filter_map(|(rx, ry, rz)| get_relative_coords(level, x, y, z, rx, ry, rz))
+		.collect()
+}