refactor: tagging related cleanup

I started working on improving unconstrained tagging as proposed in [this forum post](https://forum.aztec.network/t/on-note-discovery-and-index-coordination/7165) and the initial step in implementing that is the following:

1. store the tagging indexes requested during execution in a cache (just like we do with notes),
2. when the execution is finished take the cache and along with a tx hash dump it into db.

Given that the cache will reside in `PrivateExecutionOracle` I now need to orchestrate the sync there.

When trying to do that (to be done in a [PR up the stack](#17445)) I realized that the current tagging-related API was cumbersome and this made me do the following in this PR:
1. Have the API accept directionalAppTaggingSecret on the input instead of appTaggingSecret and recipient as now I can just compute it in the `PrivateExecutionOracle` and request info based on that,
2. I moved the tagging functionality from stdlib to PXE as there was no reason to have it in stdlib,
3. I simplified a bunch of random things.

This PR is a bit random so if something is not clear LMK.

Author: benesjan

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

@@ -5,10 +5,12 @@ import type { AztecAddress } from '@aztec/stdlib/aztec-address';
 import type { L2Block } from '@aztec/stdlib/block';
 import type { CompleteAddress, ContractInstance } from '@aztec/stdlib/contract';
 import type { KeyValidationRequest } from '@aztec/stdlib/kernel';
+import type { DirectionalAppTaggingSecret } from '@aztec/stdlib/logs';
 import type { NoteStatus } from '@aztec/stdlib/note';
 import { type MerkleTreeId, type NullifierMembershipWitness, PublicDataWitness } from '@aztec/stdlib/trees';
 import type { BlockHeader, NodeStats } from '@aztec/stdlib/tx';
 
+import type { Tag } from '../tagging/tag.js';
 import type { NoteData } from './oracle/interfaces.js';
 import type { MessageLoadOracleInputs } from './oracle/message_load_oracle_inputs.js';
 
@@ -214,13 +216,36 @@ export interface ExecutionDataProvider {
   assertCompatibleOracleVersion(version: number): void;
 
   /**
-   * Returns the next app tag for a given sender and recipient pair.
+   * Calculates the directional app tagging secret for a given contract, sender and recipient.
    * @param contractAddress - The contract address to silo the secret for
    * @param sender - The address sending the note
    * @param recipient - The address receiving the note
+   * @returns The directional app tagging secret
+   */
+  calculateDirectionalAppTaggingSecret(
+    contractAddress: AztecAddress,
+    sender: AztecAddress,
+    recipient: AztecAddress,
+  ): Promise<DirectionalAppTaggingSecret>;
+
+  /**
+   * Updates the local index of the shared tagging secret of a (sender, recipient, contract) tuple if a log with
+   * a larger index is found from the node.
+   * @param secret - The secret that's unique for (sender, recipient, contract) tuple while the direction
+   * of sender -> recipient matters.
+   * @param contractAddress - The address of the contract that the logs are tagged for. Needs to be provided to store
+   * because the function performs second round of siloing which is necessary because kernels do it as well (they silo
+   * first field of the private log which corresponds to the tag).
+   */
+  syncTaggedLogsAsSender(secret: DirectionalAppTaggingSecret, contractAddress: AztecAddress): Promise<void>;
+
+  /**
+   * Returns the next app tag for a given directional app tagging secret.
+   * @param secret - The secret that's unique for (sender, recipient, contract) tuple while
+   * direction of sender -> recipient matters.
    * @returns The computed tag.
    */
-  getNextAppTagAsSender(contractAddress: AztecAddress, sender: AztecAddress, recipient: AztecAddress): Promise<Fr>;
+  getNextAppTagAsSender(secret: DirectionalAppTaggingSecret): Promise<Tag>;
 
   /**
    * Synchronizes the private logs tagged with scoped addresses and all the senders in the address book. Stores the found

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

@@ -9,6 +9,7 @@ import type { Note, NoteStatus } from '@aztec/stdlib/note';
 import { type MerkleTreeId, type NullifierMembershipWitness, PublicDataWitness } from '@aztec/stdlib/trees';
 import type { BlockHeader } from '@aztec/stdlib/tx';
 
+import type { Tag } from '../../tagging/tag.js';
 import type { UtilityContext } from '../noir-structs/utility_context.js';
 import type { MessageLoadOracleInputs } from './message_load_oracle_inputs.js';
 
@@ -154,6 +155,6 @@ export interface IPrivateExecutionOracle {
   privateNotifySetMinRevertibleSideEffectCounter(minRevertibleSideEffectCounter: number): Promise<void>;
   privateGetSenderForTags(): Promise<AztecAddress | undefined>;
   privateSetSenderForTags(senderForTags: AztecAddress): Promise<void>;
-  privateGetNextAppTagAsSender(sender: AztecAddress, recipient: AztecAddress): Promise<Fr>;
+  privateGetNextAppTagAsSender(sender: AztecAddress, recipient: AztecAddress): Promise<Tag>;
   utilityEmitOffchainEffect(data: Fr[]): Promise<void>;
 }

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

@@ -438,7 +438,7 @@ export class Oracle {
       AztecAddress.fromString(sender),
       AztecAddress.fromString(recipient),
     );
-    return [toACVMField(tag)];
+    return [toACVMField(tag.value)];
   }
 
   async utilityFetchTaggedLogs([pendingTaggedLogArrayBaseSlot]: ACVMField[]): Promise<ACVMField[]> {

yarn-project/pxe/src/contract_function_simulator/oracle/private_execution.test.ts

@@ -47,6 +47,7 @@ import {
 } from '@aztec/stdlib/hash';
 import { KeyValidationRequest } from '@aztec/stdlib/kernel';
 import { computeAppNullifierSecretKey, deriveKeys } from '@aztec/stdlib/keys';
+import { DirectionalAppTaggingSecret } from '@aztec/stdlib/logs';
 import { L1Actor, L1ToL2Message, L2Actor } from '@aztec/stdlib/messaging';
 import { Note } from '@aztec/stdlib/note';
 import { makeHeader } from '@aztec/stdlib/testing';
@@ -64,6 +65,7 @@ import { jest } from '@jest/globals';
 import { Matcher, type MatcherCreator, type MockProxy, mock } from 'jest-mock-extended';
 import { toFunctionSelector } from 'viem';
 
+import { Tag } from '../../tagging/tag.js';
 import { ContractFunctionSimulator } from '../contract_function_simulator.js';
 import type { ExecutionDataProvider } from '../execution_data_provider.js';
 import { MessageLoadOracleInputs } from './message_load_oracle_inputs.js';
@@ -301,11 +303,9 @@ describe('Private Execution test suite', () => {
       throw new Error(`Unknown address: ${address}. Recipient: ${recipient}, Owner: ${owner}`);
     });
 
-    executionDataProvider.getNextAppTagAsSender.mockImplementation(
-      (_contractAddress: AztecAddress, _sender: AztecAddress, _recipient: AztecAddress) => {
-        return Promise.resolve(Fr.random());
-      },
-    );
+    executionDataProvider.getNextAppTagAsSender.mockImplementation((_secret: DirectionalAppTaggingSecret) => {
+      return Promise.resolve(Tag.compute({ secret: _secret, index: 0 }));
+    });
     executionDataProvider.getFunctionArtifact.mockImplementation(async (address, selector) => {
       const contract = contracts[address.toString()];
       if (!contract) {
@@ -331,6 +331,9 @@ describe('Private Execution test suite', () => {
     });
 
     executionDataProvider.syncTaggedLogs.mockImplementation((_, __) => Promise.resolve());
+    executionDataProvider.calculateDirectionalAppTaggingSecret.mockResolvedValue(
+      DirectionalAppTaggingSecret.fromString('0x1'),
+    );
     executionDataProvider.loadCapsule.mockImplementation((_, __) => Promise.resolve(null));
 
     executionDataProvider.getPublicStorageAt.mockImplementation(

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

@@ -26,6 +26,7 @@ import {
   type TxContext,
 } from '@aztec/stdlib/tx';
 
+import type { Tag } from '../../tagging/tag.js';
 import type { ExecutionDataProvider } from '../execution_data_provider.js';
 import type { ExecutionNoteCache } from '../execution_note_cache.js';
 import type { HashedValuesCache } from '../hashed_values_cache.js';
@@ -191,8 +192,22 @@ export class PrivateExecutionOracle extends UtilityExecutionOracle implements IP
    * @param recipient - The address receiving the log
    * @returns An app tag to be used in a log.
    */
-  public async privateGetNextAppTagAsSender(sender: AztecAddress, recipient: AztecAddress): Promise<Fr> {
-    return await this.executionDataProvider.getNextAppTagAsSender(this.contractAddress, sender, recipient);
+  public async privateGetNextAppTagAsSender(sender: AztecAddress, recipient: AztecAddress): Promise<Tag> {
+    const directionalAppTaggingSecret = await this.executionDataProvider.calculateDirectionalAppTaggingSecret(
+      this.contractAddress,
+      sender,
+      recipient,
+    );
+
+    // TODO(benesjan): In a follow-up PR we will load here the index from the ExecutionTaggingIndexCache if present
+    // and if not we will obtain it from the execution data provider.
+
+    this.log.debug(`Syncing tagged logs as sender ${sender} for contract ${this.contractAddress}`, {
+      directionalAppTaggingSecret,
+      recipient,
+    });
+    await this.executionDataProvider.syncTaggedLogsAsSender(directionalAppTaggingSecret, this.contractAddress);
+    return this.executionDataProvider.getNextAppTagAsSender(directionalAppTaggingSecret);
   }
 
   /**