Add allowedCalldata terms builder in @metamask/delegation-core

Author: jeffsmale90

packages/delegation-core/src/caveats/allowedCalldata.ts

@@ -0,0 +1,74 @@
+import { bytesToHex, remove0x, type BytesLike } from '@metamask/utils';
+
+import {
+  defaultOptions,
+  prepareResult,
+  type EncodingOptions,
+  type ResultValue,
+} from '../returns';
+import type { Hex } from '../types';
+import { toHexString } from '../utils';
+
+/**
+ * Terms for configuring an AllowedCalldata caveat.
+ */
+export type AllowedCalldataTerms = {
+  startIndex: number;
+  value: BytesLike;
+};
+
+/**
+ * Creates terms for an AllowedCalldata caveat that ensures the provided execution calldata
+ * matches the expected calldata at the specified index.
+ *
+ * @param terms - The terms for the AllowedCalldata caveat.
+ * @param encodingOptions - The encoding options for the result.
+ * @returns The terms as the calldata itself.
+ * @throws Error if the `calldata` is invalid.
+ */
+export function createAllowedCalldataTerms(
+  terms: AllowedCalldataTerms,
+  encodingOptions?: EncodingOptions<'hex'>,
+): Hex;
+export function createAllowedCalldataTerms(
+  terms: AllowedCalldataTerms,
+  encodingOptions: EncodingOptions<'bytes'>,
+): Uint8Array;
+/**
+ * Creates terms for an AllowedCalldata caveat that ensures the provided execution calldata
+ * matches the expected calldata at the specified index.
+ * @param terms - The terms for the AllowedCalldata caveat.
+ * @param encodingOptions - The encoding options for the result.
+ * @returns The terms as the calldata itself.
+ * @throws Error if the `calldata` is invalid.
+ */
+export function createAllowedCalldataTerms(
+  terms: AllowedCalldataTerms,
+  encodingOptions: EncodingOptions<ResultValue> = defaultOptions,
+): Hex | Uint8Array {
+  const { startIndex, value } = terms;
+
+  if (startIndex < 0) {
+    throw new Error('Invalid startIndex: must be zero or positive');
+  }
+
+  if (!Number.isInteger(startIndex)) {
+    throw new Error('Invalid startIndex: must be a whole number');
+  }
+
+  let unprefixedValue: string;
+
+  if (typeof value === 'string') {
+    if (!value.startsWith('0x')) {
+      throw new Error('Invalid value: must be a hex string starting with 0x');
+    }
+    unprefixedValue = remove0x(value);
+  } else {
+    unprefixedValue = bytesToHex(value);
+  }
+
+  const indexHex = toHexString({ value: startIndex, size: 32 });
+
+  // The terms are the index encoded as 32 bytes followed by the expected value.
+  return prepareResult(`0x${indexHex}${unprefixedValue}`, encodingOptions);
+}

packages/delegation-core/src/caveats/index.ts

@@ -6,3 +6,4 @@ export { createNativeTokenStreamingTerms } from './nativeTokenStreaming';
 export { createERC20StreamingTerms } from './erc20Streaming';
 export { createERC20TokenPeriodTransferTerms } from './erc20TokenPeriodTransfer';
 export { createNonceTerms } from './nonce';
+export { createAllowedCalldataTerms } from './allowedCalldata';

packages/delegation-core/src/index.ts

@@ -13,6 +13,7 @@ export {
   createERC20StreamingTerms,
   createERC20TokenPeriodTransferTerms,
   createNonceTerms,
+  createAllowedCalldataTerms,
 } from './caveats';
 
 export {