Improve match finishing behaviour

src/match_runtime.rs

@@ -2,7 +2,7 @@
 
 use bevy::input::InputSystems;
 use bevy::prelude::*;
-use bevy_ggrs::{RunGgrsSystems, prelude::*};
+use bevy_ggrs::{ConfirmedFrameCount, RollbackFrameCount, RunGgrsSystems, prelude::*};
 
 use crate::{
     AppState,
@@ -15,6 +15,8 @@ pub struct MatchState {
     pub elapsed_frames: u32,
     /// Indexed by the player's session handle.
     pub players: Vec<PlayerMatchState>,
+    /// The rollback frame on which the match first finished.
+    pub finished_at_frame: Option<i32>,
 }
 
 #[derive(Clone, Debug, Hash, PartialEq, Eq)]
@@ -47,6 +49,7 @@ impl MatchState {
                     deaths: 0,
                 })
                 .collect(),
+            finished_at_frame: None,
         }
     }
 
@@ -65,7 +68,8 @@ impl MatchState {
             }
         }
 
-        if let MatchRules::Stock {
+        if config.players.len() > 1
+            && let MatchRules::Stock {
                 starting_stocks: _,
                 time_limit_frames: _,
             } = config.rules
@@ -88,6 +92,19 @@ impl MatchState {
 
         false
     }
+
+    fn advance_frame(&mut self, config: &MatchConfig, frame: i32) {
+        self.elapsed_frames = self.elapsed_frames.saturating_add(1);
+
+        if self.finished_at_frame.is_none() && self.is_match_finished(config) {
+            self.finished_at_frame = Some(frame);
+        }
+    }
+
+    fn finish_is_confirmed(&self, confirmed_frame: i32) -> bool {
+        self.finished_at_frame
+            .is_some_and(|finished_at| confirmed_frame >= finished_at)
+    }
 }
 
 pub struct MatchRuntimePlugin;
@@ -100,13 +117,20 @@ impl Plugin for MatchRuntimePlugin {
             .configure_sets(PreUpdate, RunGgrsSystems.run_if(ggrs_should_run))
             .add_systems(OnEnter(AppState::InMatch), reset_pause)
             .add_systems(OnExit(AppState::InMatch), reset_pause)
+            .add_systems(
+                GgrsSchedule,
+                update_match_rules.in_set(crate::schedule::GameplaySet::MatchRules),
+            )
             .add_systems(
                 PreUpdate,
-                (toggle_pause, check_match_finished)
-                    .chain()
+                toggle_pause
                     .after(InputSystems)
                     .before(RunGgrsSystems)
                     .run_if(in_state(AppState::InMatch)),
+            )
+            .add_systems(
+                Update,
+                transition_after_confirmed_finish.run_if(in_state(AppState::InMatch)),
             );
     }
 }
@@ -143,12 +167,20 @@ fn reset_pause(mut pause: ResMut<PauseState>, mut virtual_time: ResMut<Time<Virt
     virtual_time.unpause();
 }
 
-pub fn check_match_finished(
-    match_state: Res<MatchState>,
+fn update_match_rules(
+    mut match_state: ResMut<MatchState>,
     match_config: Res<MatchConfig>,
+    frame: Res<RollbackFrameCount>,
+) {
+    match_state.advance_frame(&match_config, frame.0);
+}
+
+fn transition_after_confirmed_finish(
+    match_state: Res<MatchState>,
+    confirmed_frame: Res<ConfirmedFrameCount>,
     mut next_state: ResMut<NextState<AppState>>,
 ) {
-    if match_state.is_match_finished(&match_config) {
+    if match_state.finish_is_confirmed(confirmed_frame.0) {
         next_state.set(AppState::MatchResults);
     }
 }
@@ -185,6 +217,7 @@ mod tests {
         }));
 
         assert_eq!(state.elapsed_frames, 0);
+        assert_eq!(state.finished_at_frame, None);
         assert_eq!(state.players.len(), 2);
         assert!(state.players.iter().all(|player| {
             player.stocks_remaining == Some(4) && player.score == 0 && player.deaths == 0
@@ -204,4 +237,73 @@ mod tests {
                 .all(|player| player.stocks_remaining.is_none())
         );
     }
+
+    #[test]
+    fn timed_match_finishes_on_its_rollback_frame() {
+        let config = config(MatchRules::Timed {
+            time_limit_frames: 2,
+        });
+        let mut state = MatchState::from_config(&config);
+
+        state.advance_frame(&config, 10);
+        assert_eq!(state.elapsed_frames, 1);
+        assert_eq!(state.finished_at_frame, None);
+
+        state.advance_frame(&config, 11);
+        assert_eq!(state.elapsed_frames, 2);
+        assert_eq!(state.finished_at_frame, Some(11));
+        assert!(!state.finish_is_confirmed(10));
+        assert!(state.finish_is_confirmed(11));
+
+        state.advance_frame(&config, 12);
+        assert_eq!(state.finished_at_frame, Some(11));
+    }
+
+    #[test]
+    fn corrected_rollback_state_does_not_keep_speculative_finish() {
+        let config = config(MatchRules::Stock {
+            starting_stocks: 1,
+            time_limit_frames: None,
+        });
+        let state_before_prediction = MatchState::from_config(&config);
+        let mut predicted_state = state_before_prediction.clone();
+        predicted_state.players[1].stocks_remaining = Some(0);
+        predicted_state.advance_frame(&config, 20);
+        assert_eq!(predicted_state.finished_at_frame, Some(20));
+
+        let mut corrected_state = state_before_prediction;
+        corrected_state.advance_frame(&config, 20);
+        assert_eq!(corrected_state.finished_at_frame, None);
+        assert!(!corrected_state.finish_is_confirmed(20));
+    }
+
+    #[test]
+    fn single_player_stock_match_does_not_finish_by_elimination() {
+        let mut config = config(MatchRules::Stock {
+            starting_stocks: 1,
+            time_limit_frames: None,
+        });
+        config.players.truncate(1);
+        let mut state = MatchState::from_config(&config);
+
+        state.advance_frame(&config, 1);
+        assert_eq!(state.finished_at_frame, None);
+
+        state.players[0].stocks_remaining = Some(0);
+        state.advance_frame(&config, 2);
+        assert_eq!(state.finished_at_frame, None);
+    }
+
+    #[test]
+    fn single_player_stock_match_can_finish_by_time_limit() {
+        let mut config = config(MatchRules::Stock {
+            starting_stocks: 1,
+            time_limit_frames: Some(1),
+        });
+        config.players.truncate(1);
+        let mut state = MatchState::from_config(&config);
+
+        state.advance_frame(&config, 7);
+        assert_eq!(state.finished_at_frame, Some(7));
+    }
 }

src/schedule.rs

@@ -25,6 +25,8 @@ pub enum GameplaySet {
     Animation,
     /// Resolve attacks
     Attacks,
+    /// Advance match rules and detect the end of the match.
+    MatchRules,
 }
 
 /// Declares the order of [`GameplaySet`] inside [`GgrsSchedule`]. Added by
@@ -43,6 +45,7 @@ impl Plugin for GameplaySchedulePlugin {
                 GameplaySet::Animation,
                 GameplaySet::Collision,
                 GameplaySet::Attacks,
+                GameplaySet::MatchRules,
             )
                 .chain(),
         );