feat(cardano-services): blockfrost chain history provider now caches transactions locally

Author: AngelCastilloB

packages/cardano-services-client/src/ChainHistoryProvider/BlockfrostChainHistoryProvider.ts

@@ -34,6 +34,7 @@ type BlockfrostTx = Pick<Responses['address_transactions_content'][0], 'block_he
 const compareTx = (a: BlockfrostTx, b: BlockfrostTx) => a.block_height - b.block_height || a.tx_index - b.tx_index;
 
 export class BlockfrostChainHistoryProvider extends BlockfrostProvider implements ChainHistoryProvider {
+  private readonly cache: Map<string, Cardano.HydratedTx> = new Map();
   private networkInfoProvider: NetworkInfoProvider;
 
   constructor(client: BlockfrostClient, networkInfoProvider: NetworkInfoProvider, logger: Logger) {
@@ -475,11 +476,31 @@ export class BlockfrostChainHistoryProvider extends BlockfrostProvider implement
   }
 
   public async transactionsByHashes({ ids }: TransactionsByIdsArgs): Promise<Cardano.HydratedTx[]> {
-    try {
-      return Promise.all(ids.map((id) => this.fetchTransaction(id)));
-    } catch (error) {
-      throw this.toProviderError(error);
+    const cachedTransactions: Cardano.HydratedTx[] = [];
+    const idsToFetch: Cardano.TransactionId[] = [];
+
+    for (const id of ids) {
+      if (this.cache.has(id)) {
+        cachedTransactions.push(this.cache.get(id)!);
+      } else {
+        idsToFetch.push(id);
+      }
+    }
+
+    let fetchedTransactions: Cardano.HydratedTx[] = [];
+    if (idsToFetch.length > 0) {
+      try {
+        fetchedTransactions = await Promise.all(idsToFetch.map((id) => this.fetchTransaction(id)));
+
+        for (const tx of fetchedTransactions) {
+          this.cache.set(tx.id, tx);
+        }
+      } catch (error) {
+        throw this.toProviderError(error);
+      }
     }
+
+    return [...cachedTransactions, ...fetchedTransactions];
   }
 
   // eslint-disable-next-line sonarjs/cognitive-complexity

packages/cardano-services-client/test/ChainHistoryProvider/BlockfrostChainHistoryProvider.test.ts

@@ -590,5 +590,25 @@ describe('blockfrostChainHistoryProvider', () => {
         expect(response[0]).toEqual(expectedHydratedTxCBOR);
       });
     });
+
+    test('caches transactions and returns them from the cache on subsequent calls', async () => {
+      const firstResponse = await provider.transactionsByHashes({
+        ids: ['1e043f100dce12d107f679685acd2fc0610e10f72a92d412794c9773d11d8477' as Cardano.TransactionId]
+      });
+
+      expect(firstResponse).toHaveLength(1);
+      expect(firstResponse[0]).toEqual(expectedHydratedTxCBOR);
+      expect(request).toHaveBeenCalled();
+
+      request.mockClear();
+
+      const secondResponse = await provider.transactionsByHashes({
+        ids: ['1e043f100dce12d107f679685acd2fc0610e10f72a92d412794c9773d11d8477' as Cardano.TransactionId]
+      });
+
+      expect(secondResponse).toHaveLength(1);
+      expect(secondResponse[0]).toEqual(expectedHydratedTxCBOR);
+      expect(request).not.toHaveBeenCalled();
+    });
   });
 });