feat(querydb): get_chain_tip endpoint

src/querydb/prelude.rs

@@ -1,5 +1,5 @@
 use pallas;
-use redb::{MultimapTableDefinition, TableDefinition};
+use redb::{MultimapTableDefinition, StorageError, TableDefinition, TableError, TransactionError};
 
 // Given a block, table "block" maps its hash to its CBOR representation
 pub type BlockKeyType<'a> = &'a [u8; 32];
@@ -56,3 +56,10 @@ pub enum ReDBError {
     TableError(redb::TableError),
     TransactionError(redb::TransactionError),
 }
+
+pub enum ReadError {
+    ChainTipNotFound,
+    TransactionError(TransactionError),
+    TableError(TableError),
+    StorageError(StorageError),
+}

src/querydb/store.rs

@@ -3,7 +3,9 @@ use pallas::{
     crypto::hash::Hash,
     ledger::traverse::{MultiEraBlock, MultiEraOutput, MultiEraPolicyAssets, MultiEraTx},
 };
-use redb::{Database, MultimapTable, ReadableTable, Table, WriteTransaction};
+use redb::{
+    Database, MultimapTable, ReadOnlyTable, ReadTransaction, ReadableTable, Table, WriteTransaction,
+};
 use std::{ops::Deref, path::Path};
 
 pub struct Store {
@@ -106,8 +108,20 @@ impl Store {
         Ok(())
     }
 
-    pub fn get_chain_tip(&self) -> &[u8] {
-        unimplemented!()
+    pub fn get_chain_tip(&self) -> Result<Vec<u8>, ReadError> {
+        let read_tx: ReadTransaction = self
+            .inner_store
+            .begin_read()
+            .map_err(ReadError::TransactionError)?;
+        let chain_tip_table: ReadOnlyTable<ChainTipKeyType, ChainTipValueType> = read_tx
+            .open_table(CHAIN_TIP_TABLE)
+            .map_err(ReadError::TableError)?;
+        let res = chain_tip_table
+            .last()
+            .map_err(ReadError::StorageError)?
+            .ok_or(ReadError::ChainTipNotFound)
+            .map(|entry| Vec::from(entry.1.value()));
+        res
     }
 
     pub fn get_chain_parameters(&self) {