docs: update gameAssetContract.js -> offer-up.contract.js

snippets/zoe/contracts/test-bundle-source.js

@@ -17,7 +17,7 @@ import { makeZoeKitForTest } from '@agoric/zoe/tools/setup-zoe.js';
 
 // #region contractPath
 const myRequire = createRequire(import.meta.url);
-const contractPath = myRequire.resolve(`../src/gameAssetContract.js`);
+const contractPath = myRequire.resolve(`../src/offer-up.contract.js`);
 // #endregion contractPath
 
 test('bundleSource() bundles the contract for use with zoe', async t => {

snippets/zoe/src/offer-up.contract.js

@@ -0,0 +1,97 @@
+// #region file
+/** @file Contract to mint and sell a few Item NFTs at a time. */
+// @ts-check
+
+import { Far } from '@endo/far';
+import { M, getCopyBagEntries } from '@endo/patterns';
+import { AssetKind } from '@agoric/ertp/src/amountMath.js';
+import { atomicRearrange } from '@agoric/zoe/src/contractSupport/atomicTransfer.js';
+import '@agoric/zoe/exported.js';
+
+const { Fail, quote: q } = assert;
+
+// #region bagUtils
+/** @type { (xs: bigint[]) => bigint } */
+const sum = xs => xs.reduce((acc, x) => acc + x, 0n);
+
+/**
+ * @param {import('@endo/patterns').CopyBag} bag
+ * @returns {bigint[]}
+ */
+const bagCounts = bag => {
+  const entries = getCopyBagEntries(bag);
+  return entries.map(([_k, ct]) => ct);
+};
+// #endregion bagUtils
+
+/**
+ * In addition to the standard `issuers` and `brands` terms,
+ * this contract is parameterized by terms for price and,
+ * optionally, a maximum number of items sold for that price (default: 3).
+ *
+ * @typedef {{
+ *   tradePrice: Amount;
+ *   maxItems?: bigint;
+ * }} OfferUpTerms
+ */
+
+// #region start
+/** @param {ZCF<OfferUpTerms>} zcf */
+export const start = async zcf => {
+  const { tradePrice, maxItems = 3n } = zcf.getTerms();
+
+  const itemMint = await zcf.makeZCFMint('Item', AssetKind.COPY_BAG);
+  // #endregion start
+  const { brand: itemBrand } = itemMint.getIssuerRecord();
+
+  /** a seat for allocating proceeds of sales */
+  const proceeds = zcf.makeEmptySeatKit().zcfSeat;
+  // #region handler
+  /** @type {OfferHandler} */
+  const tradeHandler = buyerSeat => {
+    // give and want are guaranteed by Zoe to match proposalShape
+    const { want } = buyerSeat.getProposal();
+
+    sum(bagCounts(want.Items.value)) <= maxItems ||
+      Fail`max ${q(maxItems)} items allowed: ${q(want.Items)}`;
+
+    const newItems = itemMint.mintGains(want);
+    atomicRearrange(
+      zcf,
+      harden([
+        // price from buyer to proceeds
+        [buyerSeat, proceeds, { Price: tradePrice }],
+        // new items to buyer
+        [newItems, buyerSeat, want],
+      ]),
+    );
+
+    buyerSeat.exit(true);
+    newItems.exit();
+    return 'trade complete';
+  };
+  // #endregion handler
+
+  // #region makeInvitation
+  const proposalShape = harden({
+    give: { Price: M.gte(tradePrice) },
+    want: { Items: { brand: itemBrand, value: M.bag() } },
+    exit: M.any(),
+  });
+
+  const makeTradeInvitation = () =>
+    zcf.makeInvitation(tradeHandler, 'buy items', undefined, proposalShape);
+
+  // Mark the publicFacet Far, i.e. reachable from outside the contract
+  const publicFacet = Far('Items Public Facet', {
+    makeTradeInvitation,
+  });
+  // #endregion makeInvitation
+
+  // #region started
+  return harden({ publicFacet });
+  // #endregion started
+};
+
+harden(start);
+// #endregion file