use std::error::Error;
use async_trait::async_trait;
use web_sys::{CanvasRenderingContext2d, HtmlCanvasElement};
use crate::rendering::Renderer;
use wasm_bindgen::JsCast;

pub struct WebRenderer {
    canvas: HtmlCanvasElement,
    context: CanvasRenderingContext2d
}

#[async_trait]
impl Renderer for WebRenderer {
    async fn get(canvas_element_id: &str) -> Result<Self, Box<dyn Error>> {
        let window = web_sys::window().ok_or("window needs to exist")?;
        let document = window.document().ok_or("window.document needs to exist")?;
        let canvas_element = document.get_element_by_id(canvas_element_id).ok_or("canvas element does not exist")?;
        let typed_canvas_element: HtmlCanvasElement = canvas_element.dyn_into::<web_sys::HtmlCanvasElement>().map_err(|_| ()).unwrap();
        let context = typed_canvas_element.get_context("2d").unwrap().unwrap().dyn_into::<CanvasRenderingContext2d>().unwrap();
        Ok(Self {
            canvas: typed_canvas_element,
            context
        })
    }
}