feat: add staging area

crates/mempool/Cargo.toml

@@ -10,6 +10,7 @@ workspace = true
 
 [dependencies]
 async-trait.workspace = true
+derive_more.workspace =  true
 starknet_mempool_infra = { path = "../mempool_infra", version = "0.0" }
 starknet_api.workspace = true
 starknet_mempool_types = { path = "../mempool_types", version = "0.0" }

crates/mempool/src/lib.rs

@@ -1,3 +1,4 @@
 pub mod mempool;
 pub(crate) mod priority_queue;
+pub mod staging_area;
 pub mod transaction_store;

crates/mempool/src/mempool.rs

@@ -13,7 +13,8 @@ use starknet_mempool_types::mempool_types::{
 };
 use tokio::sync::mpsc::Receiver;
 
-use crate::priority_queue::TransactionPriorityQueue;
+use crate::priority_queue::{PrioritizedTransaction, TransactionPriorityQueue};
+use crate::staging_area::StagingArea;
 use crate::transaction_store::TransactionStore;
 
 #[cfg(test)]
@@ -25,6 +26,7 @@ pub struct Mempool {
     txs_queue: TransactionPriorityQueue,
     // All transactions currently held in the mempool.
     tx_store: TransactionStore,
+    staging: StagingArea,
     state: HashMap<ContractAddress, AccountState>,
 }
 
@@ -34,6 +36,7 @@ impl Mempool {
             txs_queue: TransactionPriorityQueue::default(),
             tx_store: TransactionStore::default(),
             state: HashMap::default(),
+            staging: StagingArea::default(),
         };
 
         for MempoolInput { tx, account: Account { sender_address, state } } in inputs.into_iter() {
@@ -74,13 +77,25 @@ impl Mempool {
         let mut txs: Vec<ThinTransaction> = Vec::default();
         for pq_tx in &pq_txs {
             let tx = self.tx_store.remove(&pq_tx.tx_hash)?;
+            // TODO(Mohammad): remove from store and staging area in `commit_block`.
             self.state.remove(&tx.sender_address);
+            self.staging.insert(tx.tx_hash)?;
             txs.push(tx);
         }
 
         Ok(txs)
     }
 
+    // TODO(Ayelet): implement a method that returns the next eligible transaction for the given
+    // sender address to be added to priority queue.
+    #[allow(dead_code)]
+    fn get_next_eligible_tx(
+        &self,
+        _sender_address: ContractAddress,
+    ) -> Option<PrioritizedTransaction> {
+        todo!()
+    }
+
     /// Adds a new transaction to the mempool.
     /// TODO: support fee escalation and transactions with future nonces.
     /// TODO: change input type to `MempoolInput`.

crates/mempool/src/staging_area.rs

@@ -0,0 +1,21 @@
+use starknet_api::transaction::TransactionHash;
+use starknet_mempool_types::errors::MempoolError;
+
+#[derive(Clone, Debug, Default, derive_more::Deref, derive_more::DerefMut)]
+pub struct StagingArea(Vec<TransactionHash>);
+impl StagingArea {
+    pub fn insert(&mut self, tx_hash: TransactionHash) -> Result<(), MempoolError> {
+        if self.0.contains(&tx_hash) {
+            return Err(MempoolError::DuplicateTransaction { tx_hash });
+        }
+        self.0.push(tx_hash);
+
+        Ok(())
+    }
+
+    pub fn remove(&mut self, n: usize) {
+        (0..n).for_each(|_| {
+            self.0.remove(0);
+        });
+    }
+}