feat: add EthKeyring type

jest.config.js

@@ -22,7 +22,11 @@ module.exports = {
   collectCoverage: true,
 
   // An array of glob patterns indicating a set of files for which coverage information should be collected
-  collectCoverageFrom: ['./src/**/*.ts', '!./src/**/*.test-d.ts'],
+  collectCoverageFrom: [
+    './src/**/*.ts',
+    '!./src/**/index.ts',
+    '!./src/**/*.test-d.ts',
+  ],
 
   // The directory where Jest should output its coverage files
   coverageDirectory: 'coverage',

src/internal/eth/EthKeyring.ts

@@ -0,0 +1,44 @@
+import type { Json, Keyring } from '@metamask/utils';
+
+import type {
+  EthBaseTransaction,
+  EthBaseUserOperation,
+  EthUserOperation,
+  EthUserOperationPatch,
+} from '../../eth';
+
+export type EthKeyring<State extends Json> = Keyring<State> & {
+  /**
+   * Convert a base transaction to a base UserOperation.
+   *
+   * @param address - Address of the sender.
+   * @param transactions - Base transactions to include in the UserOperation.
+   * @returns A pseudo-UserOperation that can be used to construct a real.
+   */
+  prepareUserOperation(
+    address: string,
+    transactions: EthBaseTransaction[],
+  ): Promise<EthBaseUserOperation>;
+
+  /**
+   * Patches properties of a UserOperation. Currently, only the
+   * `paymasterAndData` can be patched.
+   *
+   * @param address - Address of the sender.
+   * @param userOp - UserOperation to patch.
+   * @returns A patch to apply to the UserOperation.
+   */
+  patchUserOperation(
+    address: string,
+    userOp: EthUserOperation,
+  ): Promise<EthUserOperationPatch>;
+
+  /**
+   * Signs an UserOperation.
+   *
+   * @param address - Address of the sender.
+   * @param userOp - UserOperation to sign.
+   * @returns The signature of the UserOperation.
+   */
+  signUserOperation(address: string, userOp: EthUserOperation): Promise<string>;
+};

src/internal/eth/index.ts

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