// file: crates/engines/engine-v1-common/unit_tests/game_loop.rs
// version: 1

#[derive(Default)]
struct CountingGame {
    updates: u64,
    last_frame: std::option::Option<crate::EngineFrame>,
}

impl crate::EngineGame for CountingGame {
    fn update(&mut self, frame: crate::EngineFrame, _input: crate::InputState) {
        self.updates = self.updates.saturating_add(1);
        self.last_frame = std::option::Option::Some(frame);
        return;
    }
}

#[test]
fn fixed_step_runner_advances_index_and_elapsed_time() {
    game_logging_lib::with_test_tracing("fixed_step_runner_advances_index_and_elapsed_time", || {
        let mut game = CountingGame::default();
        let mut runner = crate::FixedStepRunner::new(std::time::Duration::from_millis(16));
        runner.tick(&mut game, crate::InputState::none());
        runner.tick(&mut game, crate::InputState::none());
        assert_eq!(game.updates, 2);
        assert_eq!(runner.next_frame_index(), 2);
        assert_eq!(runner.elapsed(), std::time::Duration::from_millis(32));
        assert_eq!(game.last_frame.map(crate::EngineFrame::index), std::option::Option::Some(1));
    });
}