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use std::borrow::Borrow;
use std::collections::HashMap;
use std::hash::Hash;
use std::rc::Rc;
pub trait ResourceLoader<'l, TResult> {
type Args: ?Sized;
fn load(&'l self, data: &Self::Args) -> Result<TResult, String>;
}
pub struct ResourceManager<'l, TKey, TResult, TLoader>
where
TKey: Hash + Eq,
TLoader: 'l + ResourceLoader<'l, TResult>,
{
loader: &'l TLoader,
cache: HashMap<TKey, Rc<TResult>>,
}
impl<'l, TKey, TResult, TLoader> ResourceManager<'l, TKey, TResult, TLoader>
where
TKey: Hash + Eq,
TLoader: ResourceLoader<'l, TResult>,
{
pub fn new(loader: &'l TLoader) -> Self {
ResourceManager {
cache: HashMap::new(),
loader: loader,
}
}
pub fn load<D>(&mut self, details: &D) -> Result<Rc<TResult>, String>
where
TLoader: ResourceLoader<'l, TResult, Args = D>,
D: Eq + Hash + ?Sized,
TKey: Borrow<D> + for<'a> From<&'a D>,
{
self.cache.get(details).cloned().map_or_else(
|| {
let resource = Rc::new(self.loader.load(details)?);
self.cache.insert(details.into(), resource.clone());
Ok(resource)
},
Ok,
)
}
}