Implement max player limit (#194)

* Implement max player limit

* Removed unnecessary `return`.

* Moved server full check to start of `handle_login_start`

Also removed unnecessary debug log.

* Use  instead of  for max players; add disable logic

* Fix semicolon missing

pumpkin-config/src/lib.rs

@@ -64,7 +64,7 @@ pub struct BasicConfiguration {
     /// The seed for world generation.
     #[serde(default = "String::new")]
     pub seed: String,
-    /// The maximum number of players allowed on the server.
+    /// The maximum number of players allowed on the server. Specifying `0` disables the limit.
     #[serde_inline_default(10000)]
     pub max_players: u32,
     /// The maximum view distance for players.

pumpkin/src/client/client_packet.rs

@@ -1,4 +1,4 @@
-use num_traits::FromPrimitive;
+use num_traits::{FromPrimitive, ToPrimitive};
 use pumpkin_config::{ADVANCED_CONFIG, BASIC_CONFIG};
 use pumpkin_core::text::TextComponent;
 use pumpkin_protocol::{
@@ -78,6 +78,18 @@ impl Client {
     pub async fn handle_login_start(&self, server: &Server, login_start: SLoginStart) {
         log::debug!("login start");
 
+        // Don't allow new logons when server is full.
+        // If max players is set to zero, then there is no max player count enforced.
+        // TODO: If client is an operator or otherwise suitable elevated permissions, allow client to bypass this requirement.
+        let max_players = BASIC_CONFIG
+            .max_players
+            .to_usize()
+            .expect("Unable to convert to usize");
+        if max_players > 0 && server.get_player_count().await >= max_players {
+            self.kick("The server is currently full, please try again later")
+                .await;
+        }
+
         if !Self::is_valid_player_name(&login_start.name) {
             self.kick("Invalid characters in username").await;
             return;
@@ -166,14 +178,14 @@ impl Client {
 
         // Don't allow duplicate UUIDs
         if let Some(online_player) = &server.get_player_by_uuid(profile.id).await {
-            log::debug!("Player (IP '{}', username '{}') tried to log in with the same UUID ('{}') as an online player (IP '{}', username '{}')", &self.address.lock().await.to_string(), &profile.name, &profile.id.to_string(), &online_player.client.address.lock().await.to_string(), &online_player.gameprofile.name);
+            log::debug!("Player (IP '{}', username '{}') tried to log in with the same UUID ('{}') as an online player (IP '{}', username '{}')", &self.address.lock().await, &profile.name, &profile.id, &online_player.client.address.lock().await, &online_player.gameprofile.name);
             self.kick("You are already connected to this server").await;
             return;
         }
 
         // Don't allow a duplicate username
         if let Some(online_player) = &server.get_player_by_name(&profile.name).await {
-            log::debug!("A player (IP '{}', attempted username '{}') tried to log in with the same username as an online player (UUID '{}', IP '{}', username '{}')", &self.address.lock().await.to_string(), &profile.name, &profile.id.to_string(), &online_player.client.address.lock().await.to_string(), &online_player.gameprofile.name);
+            log::debug!("A player (IP '{}', attempted username '{}') tried to log in with the same username as an online player (UUID '{}', IP '{}', username '{}')", &self.address.lock().await, &profile.name, &profile.id, &online_player.client.address.lock().await, &online_player.gameprofile.name);
             self.kick("A player with this username is already connected")
                 .await;
             return;

pumpkin/src/server/mod.rs

@@ -164,6 +164,15 @@ impl Server {
         None
     }
 
+    /// Get the player count sum in all worlds
+    pub async fn get_player_count(&self) -> usize {
+        let mut count = 0;
+        for world in &self.worlds {
+            count += world.current_players.lock().await.len();
+        }
+        count
+    }
+
     /// Generates a new entity id
     /// This should be global
     pub fn new_entity_id(&self) -> EntityId {