Implement direct P2P session scaffolding

src/netcode/session.rs

@@ -1,49 +1,234 @@
-//! Bringing up the GGRS session and reporting what it does.
+//! Bringing up GGRS sessions and reporting their connection lifecycle.
+
+use std::net::SocketAddr;
 
 use bevy::prelude::*;
 use bevy_ggrs::{ggrs::UdpNonBlockingSocket, prelude::*};
+use thiserror::Error;
 
-use crate::args::Args;
+use crate::args::{parse_socket_addr, Args};
 use crate::netcode::GGRSCfg;
 
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum PlayerConnection {
+    Local,
+    Remote(SocketAddr),
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Resource)]
+pub struct SessionConfig {
+    pub local_port: u16,
+    pub players: Vec<PlayerConnection>,
+}
+
+#[derive(Debug, Error, PartialEq, Eq)]
+pub enum SessionConfigError {
+    #[error("a session must have at least one player")]
+    NoPlayers,
+    #[error("local UDP port must be nonzero")]
+    LocalPortZero,
+    #[error("invalid network player declaration `{0}`; expected HANDLE=local or HANDLE=ADDRESS")]
+    InvalidPlayerDeclaration(String),
+    #[error("network player handle {0} is outside the session player range")]
+    PlayerHandleOutOfRange(usize),
+    #[error("network player handle {0} was declared more than once")]
+    DuplicatePlayerHandle(usize),
+    #[error("network player {0} has an invalid address: {1}")]
+    InvalidRemoteAddress(usize, String),
+    #[error("at least one player must be local")]
+    NoLocalPlayers,
+    #[error("network player declarations are not supported in sync-test or replay mode")]
+    UnsupportedOfflineNetworkConfig,
+}
+
+impl SessionConfig {
+    pub fn from_args(args: &Args, player_count: usize) -> Result<Self, SessionConfigError> {
+        if player_count == 0 {
+            return Err(SessionConfigError::NoPlayers);
+        }
+        if args.local_port == 0 {
+            return Err(SessionConfigError::LocalPortZero);
+        }
+        if (args.synctest || args.play_replay.is_some()) && !args.net_players.is_empty() {
+            return Err(SessionConfigError::UnsupportedOfflineNetworkConfig);
+        }
+
+        let mut players = vec![PlayerConnection::Local; player_count];
+        for declaration in &args.net_players {
+            let Some((handle, address)) = declaration.split_once('=') else {
+                return Err(SessionConfigError::InvalidPlayerDeclaration(
+                    declaration.clone(),
+                ));
+            };
+            let handle = handle
+                .parse::<usize>()
+                .map_err(|_| SessionConfigError::InvalidPlayerDeclaration(declaration.clone()))?;
+            if handle >= player_count {
+                return Err(SessionConfigError::PlayerHandleOutOfRange(handle));
+            }
+            if !matches!(players[handle], PlayerConnection::Local)
+                || args.net_players[..]
+                    .iter()
+                    .take_while(|item| *item != declaration)
+                    .any(|item| {
+                        item.split_once('=')
+                            .and_then(|(handle, _)| handle.parse::<usize>().ok())
+                            == Some(handle)
+                    })
+            {
+                return Err(SessionConfigError::DuplicatePlayerHandle(handle));
+            }
+            players[handle] = if address == "local" {
+                PlayerConnection::Local
+            } else {
+                PlayerConnection::Remote(
+                    parse_socket_addr(address)
+                        .map_err(|error| SessionConfigError::InvalidRemoteAddress(handle, error))?,
+                )
+            };
+        }
+
+        if !players
+            .iter()
+            .any(|player| matches!(player, PlayerConnection::Local))
+        {
+            return Err(SessionConfigError::NoLocalPlayers);
+        }
+        Ok(Self {
+            local_port: args.local_port,
+            players,
+        })
+    }
+}
+
 pub fn create_session(args: &Args, player_count: usize) -> Result<Session<GGRSCfg>> {
+    let config = SessionConfig::from_args(args, player_count)
+        .map_err(|error| bevy::ecs::error::BevyError::from(error.to_string()))?;
     let mut sess_build = SessionBuilder::<GGRSCfg>::new()
         .with_num_players(player_count)?
         .with_check_distance(args.check_distance)
-        .with_input_delay(args.input_delay); // (optional) set input delay for the local player
+        .with_input_delay(args.input_delay);
 
-    for i in 0..player_count {
-        sess_build = sess_build.add_player(PlayerType::Local, i)?;
+    for (handle, player) in config.players.iter().enumerate() {
+        let player_type = match player {
+            PlayerConnection::Local => PlayerType::Local,
+            PlayerConnection::Remote(address) => PlayerType::Remote(*address),
+        };
+        sess_build = sess_build.add_player(player_type, handle)?;
     }
 
     if args.synctest {
-        println!("Start synctest!");
-        let sess = sess_build.start_synctest_session()?;
-        Ok(Session::SyncTest(sess))
+        info!("starting GGRS sync test");
+        Ok(Session::SyncTest(sess_build.start_synctest_session()?))
     } else {
-        println!("Start p2p!");
-        let socket = UdpNonBlockingSocket::bind_to_port(6969)?;
-        let sess = sess_build.start_p2p_session(socket)?;
-        Ok(Session::P2P(sess))
+        info!(
+            "starting direct UDP P2P session on port {}",
+            config.local_port
+        );
+        let socket = UdpNonBlockingSocket::bind_to_port(config.local_port)?;
+        Ok(Session::P2P(sess_build.start_p2p_session(socket)?))
     }
 }
 
-pub fn print_events_system(session: Option<ResMut<Session<GGRSCfg>>>) {
-    let Some(mut session) = session else {
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default, Resource)]
+pub enum ConnectionStatus {
+    #[default]
+    Connecting,
+    Running,
+    Interrupted,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Resource)]
+pub struct MatchDisconnected {
+    pub address: SocketAddr,
+}
+
+pub fn print_events_system(
+    mut commands: Commands,
+    mut next_state: ResMut<NextState<crate::AppState>>,
+    mut status: Option<ResMut<ConnectionStatus>>,
+    session: Option<ResMut<Session<GGRSCfg>>>,
+) {
+    let (Some(mut session), Some(status)) = (session, status.as_deref_mut()) else {
         return;
     };
-    match session.as_mut() {
-        Session::P2P(s) => {
-            for event in s.events() {
-                match event {
-                    GgrsEvent::Disconnected { .. } | GgrsEvent::NetworkInterrupted { .. } => {
-                        warn!("GGRS event: {event:?}")
-                    }
-                    GgrsEvent::DesyncDetected { .. } => error!("GGRS event: {event:?}"),
-                    _ => info!("GGRS event: {event:?}"),
-                }
+    let Session::P2P(session) = session.as_mut() else {
+        return;
+    };
+    for event in session.events() {
+        match event {
+            GgrsEvent::NetworkInterrupted { addr, .. } => {
+                warn!("GGRS network interrupted: {addr}");
+                *status = ConnectionStatus::Interrupted;
             }
+            GgrsEvent::NetworkResumed { addr } => {
+                info!("GGRS network resumed: {addr}");
+                *status = ConnectionStatus::Running;
+            }
+            GgrsEvent::Disconnected { addr } => {
+                error!("GGRS peer disconnected: {addr}");
+                commands.insert_resource(MatchDisconnected { address: addr });
+                next_state.set(crate::AppState::MatchDisconnected);
+            }
+            GgrsEvent::Synchronized { .. } => {
+                info!("GGRS session synchronized");
+                *status = ConnectionStatus::Running;
+            }
+            GgrsEvent::DesyncDetected { .. } => error!("GGRS desync detected: {event:?}"),
+            _ => info!("GGRS event: {event:?}"),
         }
-        _ => {}
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use clap::Parser;
+
+    fn args(values: &[&str]) -> Args {
+        Args::try_parse_from(values).unwrap()
+    }
+
+    #[test]
+    fn defaults_to_local_players() {
+        let config = SessionConfig::from_args(&args(&["game", "--players", "2"]), 2).unwrap();
+        assert_eq!(
+            config.players,
+            [PlayerConnection::Local, PlayerConnection::Local]
+        );
+    }
+
+    #[test]
+    fn configures_remote_players_by_handle() {
+        let config = SessionConfig::from_args(
+            &args(&["game", "--players", "2", "--net-player", "1=127.0.0.1:7001"]),
+            2,
+        )
+        .unwrap();
+        assert!(matches!(config.players[0], PlayerConnection::Local));
+        assert!(matches!(config.players[1], PlayerConnection::Remote(_)));
+    }
+
+    #[test]
+    fn validates_handles_and_local_ownership() {
+        let duplicate = args(&[
+            "game",
+            "--players",
+            "2",
+            "--net-player",
+            "1=127.0.0.1:7001",
+            "--net-player",
+            "1=127.0.0.1:7002",
+        ]);
+        assert!(matches!(
+            SessionConfig::from_args(&duplicate, 2),
+            Err(SessionConfigError::DuplicatePlayerHandle(1))
+        ));
+
+        let no_local = args(&["game", "--players", "1", "--net-player", "0=127.0.0.1:7001"]);
+        assert!(matches!(
+            SessionConfig::from_args(&no_local, 1),
+            Err(SessionConfigError::NoLocalPlayers)
+        ));
     }
 }