use wasm_bindgen::prelude::JsValue;
use wasm_bindgen::JsCast;
use web_sys::CanvasRenderingContext2d;

pub struct Canvas {
    context: CanvasRenderingContext2d,
    width: u32,
    height: u32,
    scaled_width: u32,
    scaled_height: u32,
}

impl Canvas {
    pub fn new(attr_id: &str, width: u32, height: u32) -> Canvas {
        let document = web_sys::window().unwrap().document().unwrap();
        let canvas = document.get_element_by_id(attr_id).unwrap();
        let canvas: web_sys::HtmlCanvasElement = canvas
            .dyn_into::<web_sys::HtmlCanvasElement>()
            .unwrap();

        let context = canvas
            .get_context("2d")
            .unwrap()
            .unwrap()
            .dyn_into::<web_sys::CanvasRenderingContext2d>()
            .unwrap();

        let scaled_width = canvas.width() / width;
        let scaled_height = canvas.height() / height;

        Canvas {
            context,
            width,
            height,
            scaled_width,
            scaled_height,
        }
    }

    pub fn clear(&self) {
        self.context.set_fill_style(&JsValue::from_str("white"));

        self.context.fill_rect(
            f64::from(0),
            f64::from(0),
            f64::from(self.width * self.scaled_width),
            f64::from(self.height * self.scaled_height)
        );
    }

    pub fn draw(&self, x: u32, y: u32, color: &str) {
        assert!(x < self.width);
        assert!(y < self.height);

        self.context.set_fill_style(&JsValue::from_str(color));

        self.context.fill_rect(
            f64::from(x * self.scaled_width),
            f64::from(y * self.scaled_height),
            f64::from(self.scaled_width),
            f64::from(self.scaled_height)
        );
    }
}