refactor:moved key watch wake logic to specific module

src/database/abstraction/watchers.rs

@@ -0,0 +1,54 @@
+use parking_lot::RwLock;
+use std::{
+    collections::{hash_map, HashMap},
+    future::Future,
+    pin::Pin,
+};
+use tokio::sync::watch;
+
+#[derive(Default)]
+pub(super) struct Watchers {
+    watchers: RwLock<HashMap<Vec<u8>, (watch::Sender<()>, watch::Receiver<()>)>>,
+}
+
+impl Watchers {
+    pub(super) fn watch<'a>(
+        &'a self,
+        prefix: &[u8],
+    ) -> Pin<Box<dyn Future<Output = ()> + Send + 'a>> {
+        let mut rx = match self.watchers.write().entry(prefix.to_vec()) {
+            hash_map::Entry::Occupied(o) => o.get().1.clone(),
+            hash_map::Entry::Vacant(v) => {
+                let (tx, rx) = tokio::sync::watch::channel(());
+                v.insert((tx, rx.clone()));
+                rx
+            }
+        };
+
+        Box::pin(async move {
+            // Tx is never destroyed
+            rx.changed().await.unwrap();
+        })
+    }
+    pub(super) fn wake(&self, key: &[u8]) {
+        let watchers = self.watchers.read();
+        let mut triggered = Vec::new();
+
+        for length in 0..=key.len() {
+            if watchers.contains_key(&key[..length]) {
+                triggered.push(&key[..length]);
+            }
+        }
+
+        drop(watchers);
+
+        if !triggered.is_empty() {
+            let mut watchers = self.watchers.write();
+            for prefix in triggered {
+                if let Some(tx) = watchers.remove(prefix) {
+                    let _ = tx.0.send(());
+                }
+            }
+        };
+    }
+}