metamask-extension/docs/confirmation-refactoring/confirmation-state-management/README.md

Confirmation Pages - Frontend State Management

State Management is very important piece to keep frontend confirmation code simplified. Currently state management is fragmented over places and is complicated. Following guidelines will be useful for designing State Magagement:

1. Use state obtained from backend (redux store state.metamask) as single source of truth
2. For state derived from the backend state hooks can be written, these will internally use backend state
3. For temporary UI state shared across multiple components React Context can be used, minimise the scope of the context to just the components that need them (this is useful to avoid un-necessary re-rendering cycles in the app)
4. Confirmation React components fall into 2 categories:
   • Smart components: state access should go here
   • Dumb components: they are used for layout mainly and should ideally have required state data passed to them via props
5. Redux state is a good candidate for implementing state machine on frontend, if require anywhere in confirmation pages. Though currently transient state is mostly confined to single component state machine may not be needed.

Refactorings:

• There are confirmations related ducks here:

  • confirm-transaction: this is redundant and we should be able to get rid of it.
  • gas: this is not used anywhere and can be removed.
  • send: this duck is important state machine for send flow and we should continue to maintain.

• gasFeeContext is huge context written on top of gasFeeInput hook. The context / hook provides about 20 different values used in different places in confirmation pages. We need to break this down:

  • Context is required only to provide temporary UI state for confirmation pages which includes:

    • transaction - active transaction on confirmation pages
    • editGasMode - cancel, speedup, swap or default, this is also temporary UI state

    The context can be included in /pages/confirm-transaction-base and around TokenAllowance in /pages/confirm-approve.

  • Hooks can be created for values derived from values derived from above context and metamask state. This include:

    • maxFeePerGas
    • maxPriorityFeePerGas
    • supportEIP1559
    • balanceError
    • minimumCostInHexWei
    • maximumCostInHexWei
    • hasSimulationError
    • estimateUsed

  • Values which can be obtained from metamask state using selectors should be removed from this context. This includes:

    • gasFeeEstimates
    • isNetworkBusy

  • minimumGasLimitDec is a constant value 21000 should be removed from the context, this can be moved to constants file.

  • Create separate hook for transaction functions here, this hook can consume GasFeeContext.

  • Setters and manual update functions are only used by legacy gas component edit-gas-fee-popover. This component uses useGasFeeInputs hook. We need to create a smaller hook just for this component using the above context and hooks.

• confirm-transaction-base.container.js and confirm-transaction-base.component.js has a lot of code to derive values from state and selected transactions. This can be simplified by using hooks that will he created.
• We will have a lot of hooks for transaction related fields, these can be grouped into same file / folder.

As we work on the components we will be able to identify more areas of improvement.