chore: add remote feature flag for multichain accounts (#33112)

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## **Description**

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also include relevant motivation and context. Have in mind the following
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1. What is the reason for the change?
2. What is the improvement/solution?
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Add remote feature flag for multichain accounts. The feature flag
structure is,

```ts
{
  enabled: boolean;
  featureVersion: string;
  minimumVersion: string;
};
```

## **Related issues**

Fixes: None

## **Manual testing steps**

Not applicable

## **Screenshots/Recordings**

applicable

## **Pre-merge author checklist**

- [ ] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask
Extension Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [ ] I've completed the PR template to the best of my ability
- [ ] I’ve included tests if applicable
- [ ] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [ ] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-extension/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

Author: gantunesr

ui/selectors/index.js

@@ -10,3 +10,4 @@ export * from './accounts';
 export * from './remote-feature-flags';
 export * from './origin-throttling';
 export * from './multichain/networks';
+export * from './multichain-accounts';

ui/selectors/multichain-accounts/feature-flags.test.ts

@@ -0,0 +1,93 @@
+import { type RemoteFeatureFlagsState } from '../remote-feature-flags';
+import {
+  type MultichainAccountsFeatureFlag,
+  getIsMultichainAccountsState1Enabled,
+  getIsMultichainAccountsState2Enabled,
+} from './feature-flags';
+
+jest.mock('../../../package.json', () => ({
+  version: '12.0.0',
+}));
+
+type TestState = RemoteFeatureFlagsState & {
+  metamask: {
+    remoteFeatureFlags: {
+      enableMultichainAccounts: MultichainAccountsFeatureFlag;
+    };
+  };
+};
+
+const disabledStateMock: MultichainAccountsFeatureFlag = {
+  enabled: false,
+  featureVersion: null,
+  minimumVersion: null,
+};
+
+const state1Mock: MultichainAccountsFeatureFlag = {
+  enabled: true,
+  featureVersion: '1',
+  minimumVersion: '13.0.0',
+};
+
+const state2Mock: MultichainAccountsFeatureFlag = {
+  enabled: true,
+  featureVersion: '2',
+  minimumVersion: '14.0.0',
+};
+
+const getMockState = (
+  multichainAccountsFeatureFlagMock: MultichainAccountsFeatureFlag,
+): TestState =>
+  Object.freeze({
+    metamask: {
+      remoteFeatureFlags: {
+        enableMultichainAccounts: multichainAccountsFeatureFlagMock,
+      },
+    },
+  });
+
+describe('Multichain Accounts Feature Flags', () => {
+  beforeEach(() => {
+    jest.clearAllMocks(); // Clears all mocks before each test
+  });
+
+  describe('getIsMultichainAccountsState1Enabled', () => {
+    it('returns false for disabled state', () => {
+      expect(
+        getIsMultichainAccountsState1Enabled(getMockState(disabledStateMock)),
+      ).toBe(false);
+    });
+
+    it('returns true for state 1', () => {
+      expect(
+        getIsMultichainAccountsState1Enabled(getMockState(state1Mock)),
+      ).toBe(true);
+    });
+
+    it('returns true for state 2', () => {
+      expect(
+        getIsMultichainAccountsState1Enabled(getMockState(state2Mock)),
+      ).toBe(true);
+    });
+  });
+
+  describe('getIsMultichainAccountsState2Enabled', () => {
+    it('returns false for disabled state', () => {
+      expect(
+        getIsMultichainAccountsState2Enabled(getMockState(disabledStateMock)),
+      ).toBe(false);
+    });
+
+    it('returns false for state 1', () => {
+      expect(
+        getIsMultichainAccountsState2Enabled(getMockState(state1Mock)),
+      ).toBe(false);
+    });
+
+    it('returns true for state 2', () => {
+      expect(
+        getIsMultichainAccountsState2Enabled(getMockState(state2Mock)),
+      ).toBe(true);
+    });
+  });
+});

ui/selectors/multichain-accounts/feature-flags.ts

@@ -0,0 +1,115 @@
+import {
+  Infer,
+  object,
+  boolean,
+  nullable,
+  string,
+  assert,
+} from '@metamask/superstruct';
+import semver from 'semver';
+import packageJson from '../../../package.json';
+import {
+  getRemoteFeatureFlags,
+  type RemoteFeatureFlagsState,
+} from '../remote-feature-flags';
+
+/**
+ * Feature flag structure for multichain accounts features
+ */
+const MultichainAccountsFeatureFlag = object({
+  enabled: boolean(),
+  featureVersion: nullable(string()),
+  minimumVersion: nullable(string()),
+});
+
+/**
+ * Feature flag type for multichain accounts features
+ */
+export type MultichainAccountsFeatureFlag = Infer<
+  typeof MultichainAccountsFeatureFlag
+>;
+
+const APP_VERSION = packageJson.version;
+const FEATURE_VERSION_1 = '1';
+const FEATURE_VERSION_2 = '2';
+
+/**
+ * Checks if the multichain accounts feature is enabled for a given state and feature version.
+ *
+ * @param enableMultichainAccounts - The MetaMask state object
+ * @param featureVersion - The specific feature version to check
+ * @returns boolean - True if the feature is enabled for the given state and version, false otherwise.
+ */
+export const isMultichainAccountsFeatureEnabled = (
+  enableMultichainAccounts: MultichainAccountsFeatureFlag,
+  featureVersion: string,
+) => {
+  const {
+    enabled,
+    featureVersion: currentFeatureVersion,
+    minimumVersion,
+  } = enableMultichainAccounts;
+
+  return (
+    enabled &&
+    currentFeatureVersion &&
+    minimumVersion &&
+    currentFeatureVersion === featureVersion &&
+    semver.gte(minimumVersion, APP_VERSION)
+  );
+};
+
+/**
+ * Selector to get the multichain accounts remote feature flags.
+ *
+ * @param state - The MetaMask state object
+ * @returns MultichainAccountsFeatureFlag - The feature flags for multichain accounts.
+ */
+export const getMultichainAccountsRemoteFeatureFlags = (
+  state: RemoteFeatureFlagsState,
+) => {
+  const multichainAccountsFeatureFlags =
+    getRemoteFeatureFlags(state).enableMultichainAccounts;
+
+  try {
+    assert(multichainAccountsFeatureFlags, MultichainAccountsFeatureFlag);
+  } catch (error) {
+    console.warn('Invalid multichain accounts feature flags:', error);
+    return {
+      enabled: false,
+      featureVersion: null,
+      minimumVersion: null,
+    };
+  }
+
+  return multichainAccountsFeatureFlags;
+};
+
+/**
+ * Selector to check if the multichain accounts feature is enabled for state 1.
+ *
+ * @param state - The MetaMask state object
+ * @returns boolean - True if the feature is enabled for state 1, false otherwise.
+ */
+export const getIsMultichainAccountsState1Enabled = (
+  state: RemoteFeatureFlagsState,
+) => {
+  const flags = getMultichainAccountsRemoteFeatureFlags(state);
+  return (
+    isMultichainAccountsFeatureEnabled(flags, FEATURE_VERSION_2) ||
+    isMultichainAccountsFeatureEnabled(flags, FEATURE_VERSION_1)
+  );
+};
+
+/**
+ * Selector to check if the multichain accounts feature is enabled for state 2.
+ *
+ * @param state - The MetaMask state object
+ * @returns boolean - True if the feature is enabled for state 2, false otherwise.
+ */
+export const getIsMultichainAccountsState2Enabled = (
+  state: RemoteFeatureFlagsState,
+) => {
+  const flags = getMultichainAccountsRemoteFeatureFlags(state);
+  return isMultichainAccountsFeatureEnabled(flags, FEATURE_VERSION_2);
+};

ui/selectors/multichain-accounts/index.ts

@@ -0,0 +1 @@
+export * from './feature-flags';