AutistMask/src/shared/chainSwitch.js

// The popup's network switch.
//
// A network switch reaches the popup's `state` in one of two ways:
//
// - onChainSwitch() below makes the switch the user picks in Settings, with
//   applyChainSwitchFields() (chainSwitchFields.js).
// - followStoredSettings() in src/popup/index.js takes a switch the background
//   or another popup page saved, from the stored record, with
//   takeStoredNetwork() (state.js), which copies it with
//   copyChainSwitchFields() (chainSwitchFields.js).
//
// Both change `state` inside a save, holding the lock, and both reset the
// popup's own caches through clearPopupCaches(), so a reset added there
// reaches both. A field applyChainSwitchFields() sets has to be copied by
// copyChainSwitchFields() too.
//
// Adding a new chain (e.g. ETC) requires only a new entry in
// networks.js — no per-caller wiring is needed.
//
// The background does NOT come through here: this function mutates the
// module-level `state` singleton, which the MV3 service worker never
// populates, and a background switch performed on it wrote DEFAULT_STATE over
// the user's whole profile
// (https://git.eeqj.de/sneak/AutistMask/issues/316). The field mutations
// themselves live in chainSwitchFields.js, which takes the record to mutate as
// an argument; src/background/state.js applies them inside a read-modify-write
// against storage, and the singleton is not reachable from the background
// bundle at all (enforced by the ESLint rule in eslint.config.js).

const { applyChainSwitchFields } = require("./chainSwitchFields");
const { clearPrices } = require("./prices");

// The popup's own caches a network switch resets. Prices are chain-specific
// (testnet tokens are worthless, ETC has different pricing, etc.). In-memory
// and per bundle, so this is the popup's own cache — the only context that
// ever fills it.
function clearPopupCaches() {
    clearPrices();
}

// Switch the active chain and reset all chain-specific cached state.
// Returns the network configuration object for the new chain, or null when
// `state` already has that network once the save holds the lock, and nothing
// is switched.
//
// `state` is switched inside the save that stores the switch, holding the
// lock, so it is never switched while a follow of a switch saved elsewhere
// waits for the lock (followStoredSettings() in src/popup/index.js): that
// follow runs first, and this switch is made after it.
//
// The save writes only the fields that differ from what this page last saved.
// When this page last saved a balance of "0", clearing that balance is no
// change. So the switch also resets these fields in the stored record:
//
// - every address's balance and token balances;
// - the time of the last balance refresh;
// - the fraud contracts.
//
// A balance or a fraud contract that the background or another page stored
// since this page's last save is then not kept under the new network
// (https://git.eeqj.de/sneak/AutistMask/issues/653,
// https://git.eeqj.de/sneak/AutistMask/issues/692).
//
// Before the switch, `state` takes the tracked tokens that another page stored
// since this page's last save (takeStoredTrackedTokens() in state.js). The
// switch then puts them away under the previous network, the network they were
// added on. When the stored record is on another network, a switch saved
// elsewhere has not reached this page yet. The stored record's tokens are then
// that network's, and none are taken.
async function onChainSwitch(newNetworkId) {
    const { state, saveState, takeStoredTrackedTokens } = require("./state");
    let net = null;
    await saveState((stored) => {
        if (state.networkId === newNetworkId) return false;
        if (stored.networkId === state.networkId) {
            takeStoredTrackedTokens(stored);
        }
        net = applyChainSwitchFields(state, newNetworkId);
        stored.lastBalanceRefresh = 0;
        stored.fraudContracts = [];
        for (const wallet of stored.wallets) {
            for (const addr of wallet.addresses) {
                addr.balance = "0";
                addr.tokenBalances = [];
            }
        }
        clearPopupCaches();
    });
    return net;
}

module.exports = { onChainSwitch, clearPopupCaches };