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use std::collections::HashMap;
use std::fmt::Debug;
use std::hash::Hash;
use std::sync::Arc;
use std::time::{Duration, SystemTime, UNIX_EPOCH};
use tokio::sync::Mutex;
use tokio::time::sleep;
struct InnerCacheLayer<K, V> {
pub map: HashMap<K, Arc<Mutex<Option<V>>>>,
pub expiration_map: HashMap<u64, Vec<K>>,
}
pub struct AsyncCacheStore<K, V> {
inner: Mutex<InnerCacheLayer<K, V>>,
}
impl<K: 'static + Eq + Hash + Debug + Sync + Send + Clone, V: 'static + Sync + Send>
AsyncCacheStore<K, V>
{
pub fn new(expire: u64) -> Arc<Self> {
if expire < 3 {
panic!("'expire' shouldn't be lower than 3.")
}
let a = Arc::new(AsyncCacheStore {
inner: Mutex::new(InnerCacheLayer {
map: HashMap::new(),
expiration_map: HashMap::new(),
}),
});
let cloned = a.clone();
let first_refresh = SystemTime::now()
.duration_since(UNIX_EPOCH)
.unwrap()
.as_secs()
- 1;
tokio::spawn(async move {
let mut n = first_refresh;
loop {
let now = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_millis() as u64;
if (n + expire) * 1000 < now {
sleep(Duration::from_secs(1)).await;
continue;
}
sleep(Duration::from_millis((n + expire) * 1000 - now)).await;
let mut lock = cloned.inner.lock().await;
match lock.expiration_map.remove(&n) {
Some(expired) => {
for item in expired {
lock.map.remove(&item);
}
}
None => {}
}
n += 1;
}
});
a
}
pub async fn get(&self, key: K) -> Arc<Mutex<Option<V>>> {
let mut lock = self.inner.lock().await;
let val = match lock.map.get(&key) {
Some(v) => v.clone(),
None => {
let v = Arc::new(Mutex::new(None));
lock.map.insert(key.clone(), v.clone());
let current_time = SystemTime::now()
.duration_since(UNIX_EPOCH)
.unwrap()
.as_secs();
match lock.expiration_map.get_mut(¤t_time) {
Some(arr) => {
arr.push(key);
}
None => {
lock.expiration_map.insert(current_time, vec![key]);
}
}
v
}
};
val
}
}