veloren/server/src/lib.rs

#![deny(unsafe_code)]
#![allow(clippy::option_map_unit_fn)]
#![feature(bool_to_option, drain_filter, option_zip)]

pub mod alias_validator;
pub mod chunk_generator;
pub mod client;
pub mod cmd;
pub mod error;
pub mod events;
pub mod input;
pub mod login_provider;
pub mod metrics;
pub mod persistence;
pub mod settings;
pub mod state_ext;
pub mod sys;
#[cfg(not(feature = "worldgen"))] mod test_world;

// Reexports
pub use crate::{error::Error, events::Event, input::Input, settings::ServerSettings};

use crate::{
    alias_validator::AliasValidator,
    chunk_generator::ChunkGenerator,
    client::{Client, RegionSubscription},
    cmd::ChatCommandExt,
    login_provider::LoginProvider,
    state_ext::StateExt,
    sys::sentinel::{DeletedEntities, TrackedComps},
};
use common::{
    cmd::ChatCommand,
    comp::{self, ChatType},
    event::{EventBus, ServerEvent},
    msg::{ClientState, ServerInfo, ServerMsg},
    outcome::Outcome,
    recipe::default_recipe_book,
    state::{State, TimeOfDay},
    sync::WorldSyncExt,
    terrain::TerrainChunkSize,
    vol::{ReadVol, RectVolSize},
};
use futures_executor::block_on;
use futures_timer::Delay;
use futures_util::{select, FutureExt};
use metrics::{ServerMetrics, TickMetrics};
use network::{Network, Pid, ProtocolAddr};
use persistence::character::{CharacterLoader, CharacterLoaderResponseType, CharacterUpdater};
use specs::{join::Join, Builder, Entity as EcsEntity, RunNow, SystemData, WorldExt};
use std::{
    i32,
    ops::{Deref, DerefMut},
    sync::Arc,
    time::{Duration, Instant},
};
#[cfg(not(feature = "worldgen"))]
use test_world::{World, WORLD_SIZE};
use tracing::{debug, error, info, warn};
use uvth::{ThreadPool, ThreadPoolBuilder};
use vek::*;
#[cfg(feature = "worldgen")]
use world::{
    civ::SiteKind,
    sim::{FileOpts, WorldOpts, DEFAULT_WORLD_MAP, WORLD_SIZE},
    World,
};

#[macro_use] extern crate diesel;
#[macro_use] extern crate diesel_migrations;

const CLIENT_TIMEOUT: f64 = 20.0; // Seconds

#[derive(Copy, Clone)]
struct SpawnPoint(Vec3<f32>);

// Tick count used for throttling network updates
// Note this doesn't account for dt (so update rate changes with tick rate)
#[derive(Copy, Clone, Default)]
pub struct Tick(u64);

pub struct Server {
    state: State,
    world: Arc<World>,
    map: Vec<u32>,

    network: Network,

    thread_pool: ThreadPool,

    metrics: ServerMetrics,
    tick_metrics: TickMetrics,
}

impl Server {
    /// Create a new `Server`
    #[allow(clippy::expect_fun_call)] // TODO: Pending review in #587
    #[allow(clippy::needless_update)] // TODO: Pending review in #587
    pub fn new(settings: ServerSettings) -> Result<Self, Error> {
        let mut state = State::default();
        state.ecs_mut().insert(settings.clone());
        state.ecs_mut().insert(EventBus::<ServerEvent>::default());
        state
            .ecs_mut()
            .insert(LoginProvider::new(settings.auth_server_address.clone()));
        state.ecs_mut().insert(Tick(0));
        state.ecs_mut().insert(ChunkGenerator::new());
        state
            .ecs_mut()
            .insert(CharacterUpdater::new(settings.persistence_db_dir.clone()));
        state
            .ecs_mut()
            .insert(CharacterLoader::new(settings.persistence_db_dir.clone()));
        state
            .ecs_mut()
            .insert(persistence::character::CharacterUpdater::new(
                settings.persistence_db_dir.clone(),
            ));
        state
            .ecs_mut()
            .insert(comp::AdminList(settings.admins.clone()));
        state.ecs_mut().insert(Vec::<Outcome>::new());

        // System timers for performance monitoring
        state.ecs_mut().insert(sys::EntitySyncTimer::default());
        state.ecs_mut().insert(sys::MessageTimer::default());
        state.ecs_mut().insert(sys::SentinelTimer::default());
        state.ecs_mut().insert(sys::SubscriptionTimer::default());
        state.ecs_mut().insert(sys::TerrainSyncTimer::default());
        state.ecs_mut().insert(sys::TerrainTimer::default());
        state.ecs_mut().insert(sys::WaypointTimer::default());
        state.ecs_mut().insert(sys::InviteTimeoutTimer::default());
        state.ecs_mut().insert(sys::PersistenceTimer::default());

        // System schedulers to control execution of systems
        state
            .ecs_mut()
            .insert(sys::PersistenceScheduler::every(Duration::from_secs(10)));

        // Server-only components
        state.ecs_mut().register::<RegionSubscription>();
        state.ecs_mut().register::<Client>();

        //Alias validator
        let banned_words_paths = &settings.banned_words_files;
        let mut banned_words = Vec::new();
        for path in banned_words_paths {
            let mut list = match std::fs::File::open(&path) {
                Ok(file) => match ron::de::from_reader(&file) {
                    Ok(vec) => vec,
                    Err(error) => {
                        tracing::warn!(?error, ?file, "Couldn't deserialize banned words file");
                        return Err(Error::Other(format!(
                            "Couldn't read banned words file \"{}\"",
                            path.to_string_lossy()
                        )));
                    },
                },
                Err(error) => {
                    tracing::warn!(?error, ?path, "Couldn't open banned words file");
                    return Err(Error::Other(format!(
                        "Couldn't open banned words file \"{}\". Error: {}",
                        path.to_string_lossy(),
                        error
                    )));
                },
            };
            banned_words.append(&mut list);
        }
        let banned_words_count = banned_words.len();
        tracing::debug!(?banned_words_count);
        tracing::trace!(?banned_words);
        state.ecs_mut().insert(AliasValidator::new(banned_words));

        #[cfg(feature = "worldgen")]
        let world = World::generate(settings.world_seed, WorldOpts {
            seed_elements: true,
            world_file: if let Some(ref opts) = settings.map_file {
                opts.clone()
            } else {
                // Load default map from assets.
                FileOpts::LoadAsset(DEFAULT_WORLD_MAP.into())
            },
            ..WorldOpts::default()
        });
        #[cfg(feature = "worldgen")]
        let map = world.get_map_data();

        #[cfg(not(feature = "worldgen"))]
        let world = World::generate(settings.world_seed);
        #[cfg(not(feature = "worldgen"))]
        let map = vec![0];

        #[cfg(feature = "worldgen")]
        let spawn_point = {
            // NOTE: all of these `.map(|e| e as [type])` calls should compile into no-ops,
            // but are needed to be explicit about casting (and to make the compiler stop
            // complaining)

            // spawn in the chunk, that is in the middle of the world
            let center_chunk: Vec2<i32> = WORLD_SIZE.map(|e| e as i32) / 2;

            // Find a town to spawn in that's close to the centre of the world
            let spawn_chunk = world
                .civs()
                .sites()
                .filter(|site| matches!(site.kind, SiteKind::Settlement))
                .map(|site| site.center)
                .min_by_key(|site_pos| site_pos.distance_squared(center_chunk))
                .unwrap_or(center_chunk);

            // calculate the absolute position of the chunk in the world
            // (we could add TerrainChunkSize::RECT_SIZE / 2 here, to spawn in the midde of
            // the chunk)
            let spawn_location = spawn_chunk.map2(TerrainChunkSize::RECT_SIZE, |e, sz| {
                e as i32 * sz as i32 + sz as i32 / 2
            });

            // get a z cache for the collumn in which we want to spawn
            let mut block_sampler = world.sample_blocks();
            let z_cache = block_sampler
                .get_z_cache(spawn_location, world.index())
                .expect(&format!("no z_cache found for chunk: {}", spawn_chunk));

            // get the minimum and maximum z values at which there could be soild blocks
            let (min_z, _, max_z) = z_cache.get_z_limits(&mut block_sampler, world.index());
            // round range outwards, so no potential air block is missed
            let min_z = min_z.floor() as i32;
            let max_z = max_z.ceil() as i32;

            // loop over all blocks from min_z to max_z + 1
            // until the first air block is found
            // (up to max_z + 1, because max_z could still be a soild block)
            // if no air block is found default to max_z + 1
            let z = (min_z..(max_z + 1) + 1)
                .find(|z| {
                    block_sampler
                        .get_with_z_cache(
                            Vec3::new(spawn_location.x, spawn_location.y, *z),
                            Some(&z_cache),
                            false,
                            world.index(),
                        )
                        .map(|b| b.is_air())
                        .unwrap_or(false)
                })
                .unwrap_or(max_z + 1);

            // build the actual spawn point and
            // add 0.5, so that the player spawns in the middle of the block
            Vec3::new(spawn_location.x, spawn_location.y, z).map(|e| (e as f32)) + 0.5
        };

        #[cfg(not(feature = "worldgen"))]
        let spawn_point = Vec3::new(0.0, 0.0, 256.0);

        // set the spawn point we calculated above
        state.ecs_mut().insert(SpawnPoint(spawn_point));

        // Set starting time for the server.
        state.ecs_mut().write_resource::<TimeOfDay>().0 = settings.start_time;

        // Register trackers
        sys::sentinel::register_trackers(&mut state.ecs_mut());

        state.ecs_mut().insert(DeletedEntities::default());

        let mut metrics = ServerMetrics::new();
        // register all metrics submodules here
        let tick_metrics = TickMetrics::new(metrics.registry(), metrics.tick_clone())
            .expect("Failed to initialize server tick metrics submodule.");
        metrics
            .run(settings.metrics_address)
            .expect("Failed to initialize server metrics submodule.");

        let thread_pool = ThreadPoolBuilder::new()
            .name("veloren-worker".to_string())
            .build();
        let (network, f) = Network::new(Pid::new());
        thread_pool.execute(f);
        block_on(network.listen(ProtocolAddr::Tcp(settings.gameserver_address)))?;

        let this = Self {
            state,
            world: Arc::new(world),
            map,

            network,

            thread_pool,

            metrics,
            tick_metrics,
        };

        // Run pending DB migrations (if any)
        debug!("Running DB migrations...");

        if let Some(e) = persistence::run_migrations(&settings.persistence_db_dir).err() {
            info!(?e, "Migration error");
        }

        debug!(?settings, "created veloren server with");

        let git_hash = *common::util::GIT_HASH;
        let git_date = *common::util::GIT_DATE;
        info!(?git_hash, ?git_date, "Server version",);

        Ok(this)
    }

    pub fn get_server_info(&self) -> ServerInfo {
        let settings = self.state.ecs().fetch::<ServerSettings>();
        ServerInfo {
            name: settings.server_name.clone(),
            description: settings.server_description.clone(),
            git_hash: common::util::GIT_HASH.to_string(),
            git_date: common::util::GIT_DATE.to_string(),
            auth_provider: settings.auth_server_address.clone(),
        }
    }

    pub fn with_thread_pool(mut self, thread_pool: ThreadPool) -> Self {
        self.thread_pool = thread_pool;
        self
    }

    /// Get a reference to the server's settings
    pub fn settings(&self) -> impl Deref<Target = ServerSettings> + '_ {
        self.state.ecs().fetch::<ServerSettings>()
    }

    /// Get a mutable reference to the server's settings
    pub fn settings_mut(&mut self) -> impl DerefMut<Target = ServerSettings> + '_ {
        self.state.ecs_mut().fetch_mut::<ServerSettings>()
    }

    /// Get a reference to the server's game state.
    pub fn state(&self) -> &State { &self.state }

    /// Get a mutable reference to the server's game state.
    pub fn state_mut(&mut self) -> &mut State { &mut self.state }

    /// Get a reference to the server's world.
    pub fn world(&self) -> &World { &self.world }

    /// Execute a single server tick, handle input and update the game state by
    /// the given duration.
    pub fn tick(&mut self, _input: Input, dt: Duration) -> Result<Vec<Event>, Error> {
        self.state.ecs().write_resource::<Tick>().0 += 1;
        // This tick function is the centre of the Veloren universe. Most server-side
        // things are managed from here, and as such it's important that it
        // stays organised. Please consult the core developers before making
        // significant changes to this code. Here is the approximate order of
        // things. Please update it as this code changes.
        //
        // 1) Collect input from the frontend, apply input effects to the
        //    state of the game
        // 2) Go through any events (timer-driven or otherwise) that need handling
        //    and apply them to the state of the game
        // 3) Go through all incoming client network communications, apply them to
        //    the game state
        // 4) Perform a single LocalState tick (i.e: update the world and entities
        //    in the world)
        // 5) Go through the terrain update queue and apply all changes to
        //    the terrain
        // 6) Send relevant state updates to all clients
        // 7) Check for persistence updates related to character data, and message the
        //    relevant entities
        // 8) Update Metrics with current data
        // 9) Finish the tick, passing control of the main thread back
        //    to the frontend

        // 1) Build up a list of events for this frame, to be passed to the frontend.
        let mut frontend_events = Vec::new();

        // 2)

        let before_new_connections = Instant::now();

        // 3) Handle inputs from clients
        block_on(self.handle_new_connections(&mut frontend_events))?;

        let before_message_system = Instant::now();

        // Run message recieving sys before the systems in common for decreased latency
        // (e.g. run before controller system)
        sys::message::Sys.run_now(&self.state.ecs());

        let before_state_tick = Instant::now();

        // 4) Tick the server's LocalState.
        // 5) Fetch any generated `TerrainChunk`s and insert them into the terrain.
        // in sys/terrain.rs
        self.state.tick(dt, sys::add_server_systems, false);

        let before_handle_events = Instant::now();

        // Handle game events
        frontend_events.append(&mut self.handle_events());

        let before_update_terrain_and_regions = Instant::now();

        // Apply terrain changes and update the region map after processing server
        // events so that changes made by server events will be immediately
        // visble to client synchronization systems, minimizing the latency of
        // `ServerEvent` mediated effects
        self.state.update_region_map();
        self.state.apply_terrain_changes();

        let before_sync = Instant::now();

        // 6) Synchronise clients with the new state of the world.
        sys::run_sync_systems(self.state.ecs_mut());

        let before_world_tick = Instant::now();

        // Tick the world
        self.world.tick(dt);

        let before_entity_cleanup = Instant::now();

        // Remove NPCs that are outside the view distances of all players
        // This is done by removing NPCs in unloaded chunks
        let to_delete = {
            let terrain = self.state.terrain();
            (
                &self.state.ecs().entities(),
                &self.state.ecs().read_storage::<comp::Pos>(),
                !&self.state.ecs().read_storage::<comp::Player>(),
            )
                .join()
                .filter(|(_, pos, _)| terrain.get(pos.0.map(|e| e.floor() as i32)).is_err())
                .map(|(entity, _, _)| entity)
                .collect::<Vec<_>>()
        };

        for entity in to_delete {
            if let Err(e) = self.state.delete_entity_recorded(entity) {
                error!(?e, "Failed to delete agent outside the terrain");
            }
        }

        // 7 Persistence updates
        let before_persistence_updates = Instant::now();

        // Get character-related database responses and notify the requesting client
        self.state
            .ecs()
            .read_resource::<persistence::character::CharacterLoader>()
            .messages()
            .for_each(|query_result| match query_result.result {
                CharacterLoaderResponseType::CharacterList(result) => match result {
                    Ok(character_list_data) => self.notify_client(
                        query_result.entity,
                        ServerMsg::CharacterListUpdate(character_list_data),
                    ),
                    Err(error) => self.notify_client(
                        query_result.entity,
                        ServerMsg::CharacterActionError(error.to_string()),
                    ),
                },
                CharacterLoaderResponseType::CharacterData(result) => {
                    let message = match *result {
                        Ok(character_data) => ServerEvent::UpdateCharacterData {
                            entity: query_result.entity,
                            components: character_data,
                        },
                        Err(error) => {
                            // We failed to load data for the character from the DB. Notify the
                            // client to push the state back to character selection, with the error
                            // to display
                            self.notify_client(
                                query_result.entity,
                                ServerMsg::CharacterDataLoadError(error.to_string()),
                            );

                            // Clean up the entity data on the server
                            ServerEvent::ExitIngame {
                                entity: query_result.entity,
                            }
                        },
                    };

                    self.state
                        .ecs()
                        .read_resource::<EventBus<ServerEvent>>()
                        .emit_now(message);
                },
            });

        let end_of_server_tick = Instant::now();

        // 8) Update Metrics
        // Get system timing info
        let entity_sync_nanos = self
            .state
            .ecs()
            .read_resource::<sys::EntitySyncTimer>()
            .nanos as i64;
        let message_nanos = self.state.ecs().read_resource::<sys::MessageTimer>().nanos as i64;
        let sentinel_nanos = self.state.ecs().read_resource::<sys::SentinelTimer>().nanos as i64;
        let subscription_nanos = self
            .state
            .ecs()
            .read_resource::<sys::SubscriptionTimer>()
            .nanos as i64;
        let terrain_sync_nanos = self
            .state
            .ecs()
            .read_resource::<sys::TerrainSyncTimer>()
            .nanos as i64;
        let terrain_nanos = self.state.ecs().read_resource::<sys::TerrainTimer>().nanos as i64;
        let waypoint_nanos = self.state.ecs().read_resource::<sys::WaypointTimer>().nanos as i64;
        let invite_timeout_nanos = self
            .state
            .ecs()
            .read_resource::<sys::InviteTimeoutTimer>()
            .nanos as i64;
        let stats_persistence_nanos = self
            .state
            .ecs()
            .read_resource::<sys::PersistenceTimer>()
            .nanos as i64;
        let total_sys_ran_in_dispatcher_nanos =
            terrain_nanos + waypoint_nanos + invite_timeout_nanos;

        // Report timing info
        self.tick_metrics
            .tick_time
            .with_label_values(&["new connections"])
            .set((before_message_system - before_new_connections).as_nanos() as i64);
        self.tick_metrics
            .tick_time
            .with_label_values(&["state tick"])
            .set(
                (before_handle_events - before_state_tick).as_nanos() as i64
                    - total_sys_ran_in_dispatcher_nanos,
            );
        self.tick_metrics
            .tick_time
            .with_label_values(&["handle server events"])
            .set((before_update_terrain_and_regions - before_handle_events).as_nanos() as i64);
        self.tick_metrics
            .tick_time
            .with_label_values(&["update terrain and region map"])
            .set((before_sync - before_update_terrain_and_regions).as_nanos() as i64);
        self.tick_metrics
            .tick_time
            .with_label_values(&["world tick"])
            .set((before_entity_cleanup - before_world_tick).as_nanos() as i64);
        self.tick_metrics
            .tick_time
            .with_label_values(&["entity cleanup"])
            .set((before_persistence_updates - before_entity_cleanup).as_nanos() as i64);
        self.tick_metrics
            .tick_time
            .with_label_values(&["persistence_updates"])
            .set((end_of_server_tick - before_persistence_updates).as_nanos() as i64);
        self.tick_metrics
            .tick_time
            .with_label_values(&["entity sync"])
            .set(entity_sync_nanos);
        self.tick_metrics
            .tick_time
            .with_label_values(&["message"])
            .set(message_nanos);
        self.tick_metrics
            .tick_time
            .with_label_values(&["sentinel"])
            .set(sentinel_nanos);
        self.tick_metrics
            .tick_time
            .with_label_values(&["subscription"])
            .set(subscription_nanos);
        self.tick_metrics
            .tick_time
            .with_label_values(&["terrain sync"])
            .set(terrain_sync_nanos);
        self.tick_metrics
            .tick_time
            .with_label_values(&["terrain"])
            .set(terrain_nanos);
        self.tick_metrics
            .tick_time
            .with_label_values(&["waypoint"])
            .set(waypoint_nanos);
        self.tick_metrics
            .tick_time
            .with_label_values(&["invite timeout"])
            .set(invite_timeout_nanos);
        self.tick_metrics
            .tick_time
            .with_label_values(&["persistence:stats"])
            .set(stats_persistence_nanos);

        // Report other info
        self.tick_metrics
            .player_online
            .set(self.state.ecs().read_storage::<Client>().join().count() as i64);
        self.tick_metrics
            .time_of_day
            .set(self.state.ecs().read_resource::<TimeOfDay>().0);
        if self.tick_metrics.is_100th_tick() {
            let mut chonk_cnt = 0;
            let chunk_cnt = self.state.terrain().iter().fold(0, |a, (_, c)| {
                chonk_cnt += 1;
                a + c.sub_chunks_len()
            });
            self.tick_metrics.chonks_count.set(chonk_cnt as i64);
            self.tick_metrics.chunks_count.set(chunk_cnt as i64);

            let entity_count = self.state.ecs().entities().join().count();
            self.tick_metrics.entity_count.set(entity_count as i64);
        }
        //self.metrics.entity_count.set(self.state.);
        self.tick_metrics
            .tick_time
            .with_label_values(&["metrics"])
            .set(end_of_server_tick.elapsed().as_nanos() as i64);
        self.metrics.tick();

        // 9) Finish the tick, pass control back to the frontend.

        Ok(frontend_events)
    }

    /// Clean up the server after a tick.
    pub fn cleanup(&mut self) {
        // Cleanup the local state
        self.state.cleanup();
    }

    /// Handle new client connections.
    async fn handle_new_connections(
        &mut self,
        frontend_events: &mut Vec<Event>,
    ) -> Result<(), Error> {
        //TIMEOUT 0.1 ms for msg handling
        const TIMEOUT: Duration = Duration::from_micros(100);
        loop {
            let participant = match select!(
                _ = Delay::new(TIMEOUT).fuse() => None,
                pr = self.network.connected().fuse() => Some(pr),
            ) {
                None => return Ok(()),
                Some(pr) => pr?,
            };
            debug!("New Participant connected to the server");

            let singleton_stream = match select!(
                _ = Delay::new(TIMEOUT*100).fuse() => None,
                sr = participant.opened().fuse() => Some(sr),
            ) {
                None => {
                    warn!("Either Slowloris attack or very slow client, dropping");
                    return Ok(()); //return rather then continue to give removes a tick more to send data.
                },
                Some(Ok(s)) => s,
                Some(Err(e)) => {
                    warn!(?e, "Failed to open a Stream from remote client. dropping");
                    continue;
                },
            };

            let mut client = Client {
                client_state: ClientState::Connected,
                participant: std::sync::Mutex::new(Some(participant)),
                singleton_stream,
                network_error: std::sync::atomic::AtomicBool::new(false),
                last_ping: self.state.get_time(),
                login_msg_sent: false,
            };

            if self.settings().max_players
                <= self.state.ecs().read_storage::<Client>().join().count()
            {
                // Note: in this case the client is dropped
                client.notify(ServerMsg::TooManyPlayers);
            } else {
                let entity = self
                    .state
                    .ecs_mut()
                    .create_entity_synced()
                    .with(client)
                    .build();
                // Send client all the tracked components currently attached to its entity as
                // well as synced resources (currently only `TimeOfDay`)
                debug!("Starting initial sync with client.");
                self.state
                    .ecs()
                    .write_storage::<Client>()
                    .get_mut(entity)
                    .unwrap()
                    .notify(ServerMsg::InitialSync {
                        // Send client their entity
                        entity_package: TrackedComps::fetch(&self.state.ecs())
                            .create_entity_package(entity, None, None, None),
                        server_info: self.get_server_info(),
                        time_of_day: *self.state.ecs().read_resource(),
                        max_group_size: self.settings().max_player_group_size,
                        world_map: (WORLD_SIZE.map(|e| e as u32), self.map.clone()),
                        recipe_book: (&*default_recipe_book()).clone(),
                    });

                frontend_events.push(Event::ClientConnected { entity });
                debug!("Done initial sync with client.");
            }
        }
    }

    pub fn notify_client<S>(&self, entity: EcsEntity, msg: S)
    where
        S: Into<ServerMsg>,
    {
        if let Some(client) = self.state.ecs().write_storage::<Client>().get_mut(entity) {
            client.notify(msg.into())
        }
    }

    pub fn generate_chunk(&mut self, entity: EcsEntity, key: Vec2<i32>) {
        self.state
            .ecs()
            .write_resource::<ChunkGenerator>()
            .generate_chunk(entity, key, &mut self.thread_pool, self.world.clone());
    }

    fn process_chat_cmd(&mut self, entity: EcsEntity, cmd: String) {
        // Separate string into keyword and arguments.
        let sep = cmd.find(' ');
        let (kwd, args) = match sep {
            Some(i) => (cmd[..i].to_string(), cmd[(i + 1)..].to_string()),
            None => (cmd, "".to_string()),
        };

        // Find the command object and run its handler.
        if let Ok(command) = kwd.parse::<ChatCommand>() {
            command.execute(self, entity, args);
        } else {
            self.notify_client(
                entity,
                ChatType::CommandError.server_msg(format!(
                    "Unknown command '/{}'.\nType '/help' for available commands",
                    kwd
                )),
            );
        }
    }

    fn entity_is_admin(&self, entity: EcsEntity) -> bool {
        self.state
            .read_storage::<comp::Admin>()
            .get(entity)
            .is_some()
    }

    pub fn number_of_players(&self) -> i64 { self.tick_metrics.player_online.get() }
}

impl Drop for Server {
    fn drop(&mut self) { self.state.notify_registered_clients(ServerMsg::Shutdown); }
}