Implement mocka backend

nomos-services/data-availability/Cargo.toml

@@ -8,6 +8,8 @@ edition = "2021"
 [dependencies]
 async-trait = "0.1"
 futures = "0.3"
+moka = { version = "0.11", features = ["future"] }
+nomos-core = { path = "../../nomos-core" }
 nomos-network = { path = "../network" }
 overwatch-rs = { git = "https://github.com/logos-co/Overwatch", branch = "main" }
 tracing = "0.1"

nomos-services/data-availability/src/backend/memory_cache.rs

@@ -0,0 +1,41 @@
+use moka::future::{Cache, CacheBuilder};
+use nomos_core::blob::Blob;
+use std::time::Duration;
+
+pub struct BlobCacheSettings {
+    max_capacity: usize,
+    evicting_period: Duration,
+}
+
+pub struct BlobCache<H, B>(Cache<H, B>);
+
+impl<B> BlobCache<B::Hash, B>
+where
+    B: Clone + Blob + Send + Sync + 'static,
+    B::Hash: Send + Sync + 'static,
+{
+    pub fn new(settings: BlobCacheSettings) -> Self {
+        let BlobCacheSettings {
+            max_capacity,
+            evicting_period,
+        } = settings;
+        let cache = CacheBuilder::new(max_capacity as u64)
+            .time_to_live(evicting_period)
+            // can we leverage this to evict really old blobs?
+            .time_to_idle(evicting_period)
+            .build();
+        Self(cache)
+    }
+
+    pub async fn add(&self, blob: B) {
+        self.0.insert(blob.hash(), blob).await
+    }
+
+    pub async fn remove(&self, hash: &B::Hash) {
+        self.0.remove(hash).await;
+    }
+
+    pub async fn pending_blobs(&self) -> Box<dyn Iterator<Item = B> + Send + '_> {
+        Box::new(self.0.iter().map(|t| t.1))
+    }
+}