1use anyhow::{anyhow, Result};
 2use std::{borrow::Cow, cell::RefCell, collections::HashMap};
 3
 4pub trait AssetSource: 'static {
 5    fn load(&self, path: &str) -> Result<Cow<[u8]>>;
 6}
 7
 8impl AssetSource for () {
 9    fn load(&self, path: &str) -> Result<Cow<[u8]>> {
10        Err(anyhow!(
11            "get called on empty asset provider with \"{}\"",
12            path
13        ))
14    }
15}
16
17pub struct AssetCache {
18    source: Box<dyn AssetSource>,
19    svgs: RefCell<HashMap<String, usvg::Tree>>,
20}
21
22impl AssetCache {
23    pub fn new(source: impl AssetSource) -> Self {
24        Self {
25            source: Box::new(source),
26            svgs: RefCell::new(HashMap::new()),
27        }
28    }
29
30    pub fn svg(&self, path: &str) -> Result<usvg::Tree> {
31        let mut svgs = self.svgs.borrow_mut();
32        if let Some(svg) = svgs.get(path) {
33            Ok(svg.clone())
34        } else {
35            let bytes = self.source.load(path)?;
36            let svg = usvg::Tree::from_data(&bytes, &usvg::Options::default())?;
37            svgs.insert(path.to_string(), svg.clone());
38            Ok(svg)
39        }
40    }
41}