feat: combine-invitation-makers exo

- Takes two or more InvitationMaker exos and combines them into a new one.
- Useful for combining exos that are already instantiated

packages/orchestration/src/exos/combine-invitation-makers.js

@@ -0,0 +1,53 @@
+import { M } from '@endo/patterns';
+import {
+  prepareGuardedAttenuator,
+  makeSyncMethodCallback,
+} from '@agoric/internal/src/callback.js';
+import { getMethodNames } from '@agoric/internal';
+
+/**
+ * @import {InvitationMakers} from '@agoric/smart-wallet/src/types.js';
+ * @import {Zone} from '@agoric/zone';
+ */
+
+// TODO use a helper from Endo https://github.com/endojs/endo/issues/2448
+/**
+ * Takes two or more InvitationMaker exos and combines them into a new one.
+ *
+ * @param {Zone} zone
+ * @param {import('@endo/patterns').InterfaceGuard[]} interfaceGuards
+ */
+export const prepareCombineInvitationMakers = (zone, ...interfaceGuards) => {
+  const methodGuards = interfaceGuards.map(ig => ig.payload.methodGuards);
+  const CombinedInterfaceGuard = M.interface(
+    'CombinedInvitationMakers interface',
+    Object.assign({}, ...methodGuards),
+  );
+
+  const mixin = prepareGuardedAttenuator(zone, CombinedInterfaceGuard, {
+    tag: 'CombinedInvitationMakers',
+  });
+
+  /**
+   * @template {InvitationMakers[]} IM
+   * @param {IM} invitationMakers
+   * @returns {IM[number]}
+   */
+  const combineInvitationMakers = (...invitationMakers) => {
+    const overrides = {};
+    for (const invMakers of invitationMakers) {
+      // remove '__getInterfaceGuard__', '__getMethodNames__'
+      const names = getMethodNames(invMakers).filter(n => !n.startsWith('__'));
+      for (const key of names) {
+        overrides[key] = makeSyncMethodCallback(invMakers, key);
+      }
+    }
+    return mixin({
+      overrides,
+    });
+  };
+
+  return combineInvitationMakers;
+};
+
+/** @typedef {ReturnType<typeof prepareCombineInvitationMakers>} MakeCombineInvitationMakers */