use crate::prelude::Scene;

pub mod session; use session::Session;
pub mod scene;

pub struct App {
    pub session:Session,

    pub document:web_sys::Document,
    pub menu:web_sys::Element,
    pub container:web_sys::Element,

    unload:Option<fn()>,
}
impl App {
    pub fn init() -> Result<Self,()>
    {
        match web_sys::window() {
            Some(window) => match window.document() {
                Some(document) => {
                    let menu = document.create_element("nav");
                    let container = document.create_element("main");

                    if menu.is_ok() && container.is_ok() {
                        Ok(Self {
                            session:Session::new(),

                            document:document,
                            menu:menu.unwrap(),
                            container:container.unwrap(),

                            unload:None,
                        })
                    } else {
                        Err(())
                    }
                }
                None => Err(())
            }
            None => Err(())
        }
    }

    pub fn load<S:Scene>(&mut self)
    {
        match self.unload {
            Some(proc) => { proc(); }
            None => { }
        }

        self.document_clear();
        S::load();
        self.unload = Some(S::unload);
    }

    pub fn document_clear(&self)
    {
        match self.document.body() {
            Some(body) => {
                while let Some(child) = body.last_child() {
                    body.remove_child(&child).ok();
                }
            }
            None => { }
        }
    }
}