use super::*;

pub struct StateManager {
    stack: Vec<Box<dyn State>>,
}

impl StateManager {
    pub fn new() -> Self {
        Self { stack: Vec::new() }
    }
    pub fn switch(&mut self, state: Box<dyn State>) {
        *self.stack.last_mut().unwrap() = state;
    }
    pub fn push(&mut self, state: Box<dyn State>) {
        self.stack.push(state);
    }
    pub fn pop(&mut self) {
        self.stack.pop();
    }
    pub fn current_state(&mut self) -> Option<&mut dyn State> {
        self.stack.last_mut().map(|state| state.deref_mut())
    }
}

impl State for StateManager {
    fn update(&mut self, delta_time: f64) {
        if let Some(state) = self.current_state() {
            state.update(delta_time);
            if let Some(transition) = state.transition() {
                match transition {
                    Transition::Pop => self.pop(),
                    Transition::Push(state) => self.push(state),
                    Transition::Switch(state) => self.switch(state),
                }
            }
        }
    }
    fn handle_event(&mut self, event: Event) {
        if let Some(state) = self.current_state() {
            state.handle_event(event);
        }
    }
    fn draw(&mut self, framebuffer: &mut ugli::Framebuffer) {
        if let Some(state) = self.current_state() {
            state.draw(framebuffer);
        }
    }
    fn transition(&mut self) -> Option<Transition> {
        if self.stack.is_empty() {
            Some(Transition::Pop)
        } else {
            None
        }
    }
}