metamask-extension/docs/confirmation-refactoring/confirmation-backend-architecture/README.md

Confirmation Background Architecture and Code Cleanup

Current Implementation:

Current confirmation implementation in the background consists of following pieces:

1. TransactionController and utility, helper classes used by it: TransactionController is very important piece in transaction processing. It is described here. It consists of 4 important parts:
   • txStateManager: responsible for the state of a transaction and storing the transaction
   • pendingTxTracker: watching blocks for transactions to be include and emitting confirmed events
   • txGasUtil: gas calculations and safety buffering
   • nonceTracker: calculating nonces
2. MessageManagers: There are 3 different message managers responsible for processing signature requests. These are detailed here.
3. MetamaskController : MetamaskController is responsible for gluing together the different pieces in transaction processing. It is responsible to inject dependencies in TransactionController, MessageManagers, handling different events, responses to DAPP requests, etc.

Areas of Code Cleanup:

1. Migrating to @metamask/transaction-controller. TransactionController in extension repo should eventually get replaced by core repo TransactionController. This controller is maintained by core team and also used in Metamask Mobile App.
2. Migrating to @metamask/message-manager. Message Managers in extension repo should be deprecated in favour of core repo MessageManagers.
3. Cleanup Code in MetamaskController. Metamaskcontroller is where TransactionController and different MessageManagers are initialized. It is responsible for injecting required dependencies. Also, it is responsible for handling incoming DAPP requests and invoking appropriate methods in these background classes. Over the period of time lot of code that should have been part of TransactionController and MessageManagers has ended up in MetamaskController. We need to cleanup this code and move to the appropriate classes.
   • Code here to check if eth_sign is enabled in preferences and perform other validation on the incoming request should be part of MessageManager
   • Method to sign messages signMessage, signPersonalMessage, signTypedMessage can be simplified by injecting KeyringController into MessageManagers.
   • There are about 11 different methods to add, approve, reject different types of signature requests. These can probably be moved to a helper class, thus reducing lines of code from MetamaskController .
   • This code can better be placed in TransactionController.
   • A lot of other methods in MetamaskController which are related to TransactionController and the state of TransactionController can be moved into TransactionController itself like method1, method2, method3, etc.

Using ApprovalController for Confirmations

ApprovalController is written as a helper to PermissionController. Its role is to manage requests that require user approval. It can also be used in confirmation code to launch UI. Thus the use of showUserConfirmation function in MetamaskController can be removed. But ApprovalController will need some changes to be able to use it for confirmations, for example, it does not support multiple parallel requests from the same origin.