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//! Environment interactions.
use std::any::Any;
use std::cell::RefCell;
use std::collections::{hash_map::Entry, HashMap};
use std::fmt::{self, Debug, Formatter};
use std::fs;
use std::path::{Path, PathBuf};
use std::rc::Rc;
use crate::font::FontLoader;
/// A reference-counted shared environment.
pub type SharedEnv = Rc<RefCell<Env>>;
/// Encapsulates all environment dependencies (fonts, resources).
#[derive(Debug)]
pub struct Env {
/// Loads fonts from a dynamic font source.
pub fonts: FontLoader,
/// Loads resource from the file system.
pub resources: ResourceLoader,
}
/// Loads resource from the file system.
pub struct ResourceLoader {
paths: HashMap<PathBuf, ResourceId>,
entries: Vec<Box<dyn Any>>,
}
/// A unique identifier for a resource.
#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
pub struct ResourceId(usize);
impl ResourceLoader {
/// Create a new resource loader.
pub fn new() -> Self {
Self { paths: HashMap::new(), entries: vec![] }
}
/// Load a resource from a path.
pub fn load<R: 'static>(
&mut self,
path: impl AsRef<Path>,
parse: impl FnOnce(Vec<u8>) -> Option<R>,
) -> Option<(ResourceId, &R)> {
let path = path.as_ref();
let id = match self.paths.entry(path.to_owned()) {
Entry::Occupied(entry) => *entry.get(),
Entry::Vacant(entry) => {
let id = *entry.insert(ResourceId(self.entries.len()));
let data = fs::read(path).ok()?;
let resource = parse(data)?;
self.entries.push(Box::new(resource));
id
}
};
Some((id, self.get_loaded(id)))
}
/// Retrieve a previously loaded resource by its id.
///
/// # Panics
/// This panics if no resource with this id was loaded.
pub fn get_loaded<R: 'static>(&self, id: ResourceId) -> &R {
self.entries[id.0].downcast_ref().expect("bad resource type")
}
}
impl Debug for ResourceLoader {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
f.debug_set().entries(self.paths.keys()).finish()
}
}
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