chore: change sell items to add make invitation method to public facet (

#2779)

packages/zoe/src/contracts/sellItems.js

@@ -49,14 +49,10 @@ const start = zcf => {
     return defaultAcceptanceMsg;
   };
 
-  /** @type {SellItemsPublicFacet} */
-  const publicFacet = Far('SellItemsPublicFacet', {
-    getAvailableItems: () => {
-      assert(sellerSeat && !sellerSeat.hasExited(), X`no items are for sale`);
-      return sellerSeat.getAmountAllocated('Items');
-    },
-    getItemsIssuer: () => issuers.Items,
-  });
+  const getAvailableItems = () => {
+    assert(sellerSeat && !sellerSeat.hasExited(), X`no items are for sale`);
+    return sellerSeat.getAmountAllocated('Items');
+  };
 
   const buy = buyerSeat => {
     assertProposalShape(buyerSeat, {
@@ -101,22 +97,31 @@ const start = zcf => {
     // The buyer's offer has been processed.
     buyerSeat.exit();
 
-    if (amountMath.isEmpty(publicFacet.getAvailableItems())) {
+    if (amountMath.isEmpty(getAvailableItems())) {
       zcf.shutdown('All items sold.');
     }
     return defaultAcceptanceMsg;
   };
 
+  const makeBuyerInvitation = () => {
+    const itemsAmount = sellerSeat.getAmountAllocated('Items');
+    assert(
+      sellerSeat && !amountMath.isEmpty(itemsAmount),
+      X`no items are for sale`,
+    );
+    return zcf.makeInvitation(buy, 'buyer');
+  };
+
+  /** @type {SellItemsPublicFacet} */
+  const publicFacet = Far('SellItemsPublicFacet', {
+    getAvailableItems,
+    getItemsIssuer: () => issuers.Items,
+    makeBuyerInvitation,
+  });
+
   /** @type {SellItemsCreatorFacet} */
   const creatorFacet = Far('SellItemsCreatorFacet', {
-    makeBuyerInvitation: () => {
-      const itemsAmount = sellerSeat.getAmountAllocated('Items');
-      assert(
-        sellerSeat && !amountMath.isEmpty(itemsAmount),
-        X`no items are for sale`,
-      );
-      return zcf.makeInvitation(buy, 'buyer');
-    },
+    makeBuyerInvitation,
     getAvailableItems: publicFacet.getAvailableItems,
     getItemsIssuer: publicFacet.getItemsIssuer,
   });