feat: ExecutionTaggingIndexCache

Author: benesjan

yarn-project/pxe/src/contract_function_simulator/execution_tagging_index_cache.ts

@@ -0,0 +1,16 @@
+import type { AztecAddress } from '@aztec/stdlib/aztec-address';
+
+/**
+ * A map that stores the tagging index for a given sender and recipient pair.
+ */
+export class ExecutionTaggingIndexCache {
+  private taggingIndexMap: Map<string, number> = new Map();
+
+  public getTaggingIndex(sender: AztecAddress, recipient: AztecAddress): number | undefined {
+    return this.taggingIndexMap.get(`${sender}-${recipient}`);
+  }
+
+  public setTaggingIndex(sender: AztecAddress, recipient: AztecAddress, index: number) {
+    this.taggingIndexMap.set(`${sender}-${recipient}`, index);
+  }
+}

yarn-project/pxe/src/contract_function_simulator/oracle/private_execution_oracle.ts

@@ -28,6 +28,7 @@ import {
 
 import type { ExecutionDataProvider } from '../execution_data_provider.js';
 import type { ExecutionNoteCache } from '../execution_note_cache.js';
+import { ExecutionTaggingIndexCache } from '../execution_tagging_index_cache.js';
 import type { HashedValuesCache } from '../hashed_values_cache.js';
 import { pickNotes } from '../pick_notes.js';
 import type { IPrivateExecutionOracle, NoteData } from './interfaces.js';
@@ -75,6 +76,7 @@ export class PrivateExecutionOracle extends UtilityExecutionOracle implements IP
     capsules: Capsule[],
     private readonly executionCache: HashedValuesCache,
     private readonly noteCache: ExecutionNoteCache,
+    private readonly taggingIndexCache: ExecutionTaggingIndexCache,
     executionDataProvider: ExecutionDataProvider,
     private totalPublicCalldataCount: number = 0,
     protected sideEffectCounter: number = 0,
@@ -192,6 +194,11 @@ export class PrivateExecutionOracle extends UtilityExecutionOracle implements IP
    * @returns An app tag to be used in a log.
    */
   public async privateGetNextAppTagAsSender(sender: AztecAddress, recipient: AztecAddress): Promise<Fr> {
+    // here we would check if we have the index in cache and if so, return it from there.
+    // --> If not, we would call the executionDataProvider.getNextAppTagAsSender.
+
+    // What do I need to store in cache? Just { contractAddress-sender-recipient: index }
+
     return await this.executionDataProvider.getNextAppTagAsSender(this.contractAddress, sender, recipient);
   }