playing.rs

struct Playing {
  state: GameState,
  event_queue: VecDeque<Vec<Event>>,
  event_time: f32,
}

impl Playing {
  fn handle_input(&mut self, input: InputEvent) {
    match input_event {
      KeyboardInput(Key::Right) => self.event_queue.extend(self.state.handle(Dir::Right)),
      // ...,
    }
  }
  
  fn advance(&mut self, delta_t: f32) {
    if events.is_empty() { return; }
    
    self.event_time += delta_t * how_fast_i_want_things_to_animate * self.event_queue.size();
    if self.event_time > 1.0 {
      let events = self.event_queue.pop_front().unwrap();
      for event in events {
        self.state.apply(&event);
      }
      
      if let Some(front) = self.event_queue.front() {
        for event in events {
          event.play_sound_effect();
        }
      }
      
      self.event_time = 0.0;
    }
  }
  
  fn draw_stuff(&self) {
    let player_movement = self.events.iter().find(|e| matches!(e, Event::PlayerMove(_)));
      
    let player_offset = match player_movement {
      None => v3(0.0, 0.0, 0.0),
      Some(Dir::Right) => v3(1.0, 0.0, 0.0),
      // ...,
    };
      
    let player_location = self.state.player_location.to_v3() + player_offset * self.animation_time;
    
    render_the_player_model(player_location);
    
    // ...
  }
}

struct GameState {
  player_location: Vec2<i32>,
  enemies: Vec<Enemy>,
  // ...
}

impl GameState {
  fn handle(&self, player_move_dir: Dir) -> Vec<Vec<Event>> {
    let mut result = vec![];
    
    result.push_back(vec![Event::PlayerMove(player_move_dir)]);
    
    let mut enemy_reactions = vec![];
    
    for (i, enemy) in self.enemies.iter().enumerate() {
      enemy_reactions.push_back(Event::EnemyMove(i, Dir::random()))
    }
    
    // All the enemies move simultaneously
    result.push_back(enemy_reactions);
    
    result
  }
  
  impl apply(&mut self, event: &Event) {
    match event {
      Event::PlayerMove(dir) => self.player_location += dir,
      Event::EnemyMove(i, dir) => self.enemies.location += dir,
      // ...
    }
  }
}