From a35b5a09b01e09dd77982c060b8394f5c9bcdaff Mon Sep 17 00:00:00 2001
From: Pete Vilter <pete.vilter@gmail.com>
Date: Sun, 24 Nov 2024 19:02:33 -0500
Subject: [PATCH] Market tweaks (#499)

* split into own folder

* round the amounts

* sort the order book

* add test

* don't let one sell go to multiple buys
---
 apps/actors/systems/kvSync/ddTests.ts         |    2 +-
 .../kvSync/examples/commodityMarket.tsx       |  328 -----
 .../kvSync/examples/commodityMarket/choose.ts |   32 +
 .../commodityMarket.dd.txt                    | 1107 +++++++----------
 .../kvSync/examples/commodityMarket/index.ts  |   17 +
 .../examples/commodityMarket/mutations.ts     |   86 ++
 .../kvSync/examples/commodityMarket/types.ts  |   48 +
 .../kvSync/examples/commodityMarket/ui.tsx    |  170 +++
 8 files changed, 833 insertions(+), 957 deletions(-)
 delete mode 100644 apps/actors/systems/kvSync/examples/commodityMarket.tsx
 create mode 100644 apps/actors/systems/kvSync/examples/commodityMarket/choose.ts
 rename apps/actors/systems/kvSync/examples/{ => commodityMarket}/commodityMarket.dd.txt (67%)
 create mode 100644 apps/actors/systems/kvSync/examples/commodityMarket/index.ts
 create mode 100644 apps/actors/systems/kvSync/examples/commodityMarket/mutations.ts
 create mode 100644 apps/actors/systems/kvSync/examples/commodityMarket/types.ts
 create mode 100644 apps/actors/systems/kvSync/examples/commodityMarket/ui.tsx

diff --git a/apps/actors/systems/kvSync/ddTests.ts b/apps/actors/systems/kvSync/ddTests.ts
index ab9a1fcf..922ed3ec 100644
--- a/apps/actors/systems/kvSync/ddTests.ts
+++ b/apps/actors/systems/kvSync/ddTests.ts
@@ -51,7 +51,7 @@ export function kvSyncTests(writeResults: boolean): Suite {
       name: "commodityMarket",
       test() {
         runDDTestAtPath(
-          "apps/actors/systems/kvSync/examples/commodityMarket.dd.txt",
+          "apps/actors/systems/kvSync/examples/commodityMarket/commodityMarket.dd.txt",
           (inputs) => kvSyncTest(commodityMarket, inputs),
           writeResults
         );
diff --git a/apps/actors/systems/kvSync/examples/commodityMarket.tsx b/apps/actors/systems/kvSync/examples/commodityMarket.tsx
deleted file mode 100644
index 55f018fc..00000000
--- a/apps/actors/systems/kvSync/examples/commodityMarket.tsx
+++ /dev/null
@@ -1,328 +0,0 @@
-import React, { useState } from "react";
-import { KVApp } from "./types";
-import {
-  MutationCtx,
-  MutationInvocation,
-  TSMutationDefns,
-  UserInput,
-  WriteOp,
-} from "../types";
-import { Client, makeClient, useLiveQuery } from "../hooks";
-import { ChooseFn, UIProps } from "../../../types";
-import { ClientState, QueryStatus, TransactionState } from "../client";
-import { LoginWrapper } from "../uiCommon/loginWrapper";
-import { Inspector } from "../uiCommon/inspector";
-import { Table } from "../../../../../uiCommon/generic/table";
-import { LoggedInHeader } from "../uiCommon/loggedInHeader";
-import { Json } from "../../../../../util/json";
-import { randomFromList, randStep2 } from "../../../../../util/util";
-
-function MarketUI(props: UIProps<ClientState, UserInput>) {
-  const client = makeClient(props);
-
-  return (
-    <LoginWrapper
-      client={client}
-      loggedIn={(user) => <MarketInner client={client} user={user} />}
-    />
-  );
-}
-
-function MarketInner(props: { client: Client; user: string }) {
-  const [orders, orderQueryStatus] = useOrders(props.client);
-  const [trades, tradeQueryStatus] = useTrades(props.client);
-
-  return (
-    <>
-      <LoggedInHeader user={props.user} client={props.client}>
-        <h2>Market</h2>
-      </LoggedInHeader>
-
-      <h3>Orders</h3>
-
-      {orderQueryStatus === "Loading" ? (
-        <em>Loading...</em>
-      ) : (
-        <Table<Order>
-          data={orders}
-          getKey={(order) => order.id.toString()}
-          columns={[
-            { name: "id", render: (order) => order.id },
-            { name: "price", render: (order) => `$${order.price}` },
-            { name: "amount", render: (order) => order.amount },
-            { name: "side", render: (order) => order.side },
-            { name: "user", render: (order) => order.user },
-            { name: "status", render: (order) => order.status },
-          ]}
-        />
-      )}
-
-      <h3>Create Order</h3>
-
-      <OrderForm client={props.client} />
-
-      <h3>Trades</h3>
-
-      {tradeQueryStatus === "Loading" ? (
-        <em>Loading...</em>
-      ) : (
-        <Table<Trade>
-          data={trades}
-          getKey={(trade) => trade.id.toString()}
-          columns={[
-            { name: "id", render: (trade) => trade.id },
-            { name: "price", render: (trade) => `$${trade.price}` },
-            { name: "amount", render: (trade) => trade.amount },
-            { name: "buy order", render: (trade) => trade.buyOrder },
-            { name: "sell order", render: (trade) => trade.sellOrder },
-          ]}
-        />
-      )}
-
-      <Inspector client={props.client} />
-    </>
-  );
-}
-
-function OrderForm(props: { client: Client }) {
-  const [price, setPrice] = useState(10);
-  const [amount, setAmount] = useState(100);
-  const [side, setSide] = useState<OrderSide>("buy");
-
-  return (
-    <form
-      onSubmit={(evt) => {
-        evt.preventDefault();
-
-        props.client.runMutation("Order", [price, amount, side]);
-      }}
-    >
-      Amount:{" "}
-      <input
-        type="number"
-        placeholder="Amount"
-        value={amount}
-        onChange={(evt) => setAmount(parseInt(evt.target.value))}
-      />{" "}
-      Price:{" "}
-      <input
-        type="number"
-        placeholder="Price"
-        value={price}
-        onChange={(evt) => setPrice(parseInt(evt.target.value))}
-      />
-      <div>
-        <label>
-          <input
-            type="radio"
-            value="buy"
-            checked={side === "buy"}
-            onChange={(evt) => setSide("buy")}
-          />
-          Buy
-        </label>
-        <label>
-          <input
-            type="radio"
-            value="sell"
-            checked={side === "sell"}
-            onChange={(evt) => setSide("sell")}
-          />
-          Sell
-        </label>
-      </div>
-      <button type="submit">Create Order</button>
-    </form>
-  );
-}
-
-type OfferStatus = "open" | "sold";
-
-type OrderSide = "sell" | "buy";
-
-type Order = {
-  id: number;
-  price: number;
-  amount: number;
-  side: OrderSide;
-  user: string;
-  status: OfferStatus;
-};
-
-type Trade = {
-  id: number;
-  price: number;
-  amount: number;
-  buyOrder: number;
-  sellOrder: number;
-};
-
-type OrderWithState = Order & { state: TransactionState };
-
-function useOrders(client: Client): [OrderWithState[], QueryStatus] {
-  const [rawOrders, queryStatus] = useLiveQuery(client, "list-orders", {
-    prefix: "/orders/",
-  });
-
-  const orders = Object.entries(rawOrders).map(
-    ([id, rawOrder]): OrderWithState => {
-      const order = rawOrder.value as any;
-      const mapped = readOrder(order);
-      return {
-        ...mapped,
-        state: client.state.transactions[rawOrder.transactionID]?.state,
-      };
-    }
-  );
-
-  return [orders, queryStatus];
-}
-
-function readOrder(rawOrder: Json): Order {
-  const order = rawOrder as any;
-  return {
-    id: order.id as number,
-    price: order.price as number,
-    amount: order.amount as number,
-    status: order.status as OfferStatus,
-    side: order.side as OrderSide,
-    user: order.user as string,
-  };
-}
-
-function useTrades(client: Client): [Trade[], QueryStatus] {
-  const [rawTrades, queryStatus] = useLiveQuery(client, "list-trades", {
-    prefix: "/trades/",
-  });
-
-  const trades = Object.entries(rawTrades).map(([id, rawTrade]): Trade => {
-    const trade = rawTrade.value as any;
-    return readTrade(trade);
-  });
-
-  return [trades, queryStatus];
-}
-
-function readTrade(rawTrade: Json): Trade {
-  const trade = rawTrade as any;
-  return {
-    id: trade.id as number,
-    price: trade.price as number,
-    amount: trade.amount as number,
-    buyOrder: trade.buyOrder as number,
-    sellOrder: trade.sellOrder as number,
-  };
-}
-
-const mutations: TSMutationDefns = {
-  Order: (ctx, [price, amount, side]) => {
-    const id = ctx.rand();
-    ctx.write(`/orders/${id}`, {
-      id,
-      price,
-      amount,
-      side,
-      status: "open",
-      user: ctx.curUser,
-    });
-  },
-};
-
-function matchOrders(ctx: MutationCtx, evt: WriteOp) {
-  // Prevent us from going on forever
-  if (evt.desc.type !== "Insert") {
-    return;
-  }
-
-  const orders = ctx.scan("/orders/").map(readOrder);
-
-  const buys = orders
-    .filter((order) => order.side === "buy" && order.status === "open")
-    .sort((a, b) => b.price - a.price);
-  const sells = orders
-    .filter((order) => order.side === "sell" && order.status === "open")
-    .sort((a, b) => a.price - b.price);
-
-  for (const buy of buys) {
-    // TODO: keep buying while there's more to buy
-    for (const sell of sells) {
-      if (buy.price >= sell.price) {
-        const amount = Math.min(buy.amount, sell.amount);
-        const price = (buy.price + sell.price) / 2;
-
-        // Execute the trade
-        const newBuyAmount = buy.amount - amount;
-        const newBuy: Order = {
-          ...buy,
-          amount: newBuyAmount,
-          status: newBuyAmount === 0 ? "sold" : "open",
-        };
-        ctx.write(`/orders/${buy.id}`, newBuy);
-
-        const newSellAmount = sell.amount - amount;
-        const newSell: Order = {
-          ...sell,
-          amount: newSellAmount,
-          status: newSellAmount === 0 ? "sold" : "open",
-        };
-        ctx.write(`/orders/${sell.id}`, newSell);
-
-        // console.log("matchOrders", { newBuy, newSell });
-
-        const tradeID = ctx.rand();
-        ctx.write(`/trades/${tradeID}`, {
-          id: tradeID,
-          buyOrder: buy.id,
-          sellOrder: sell.id,
-          amount,
-          price,
-        });
-
-        if (newBuyAmount === 0) {
-          break;
-        }
-      }
-    }
-  }
-}
-
-function choose(
-  clients: {
-    [id: string]: ClientState;
-  },
-  randomSeed: number
-): [{ clientID: string; invocation: MutationInvocation } | null, number] {
-  const [clientID, randomSeed1] = randomFromList(
-    randomSeed,
-    Object.keys(clients)
-  );
-
-  const [amount1, randomSeed2] = randStep2(randomSeed1);
-  const [price, randomSeed3] = randStep2(randomSeed2);
-  const side = randomFromList(randomSeed3, ["buy", "sell"])[0] as OrderSide;
-
-  return [
-    {
-      clientID,
-      invocation: {
-        type: "Invocation",
-        name: "Order",
-        args: [price * 100, amount1 * 100, side],
-      },
-    },
-    randomSeed3,
-  ];
-}
-
-export const commodityMarket: KVApp = {
-  name: "Commodity Market",
-  mutations,
-  ui: MarketUI,
-  triggers: [
-    {
-      prefix: "/orders/",
-      fn: matchOrders,
-    },
-  ],
-  choose,
-};
diff --git a/apps/actors/systems/kvSync/examples/commodityMarket/choose.ts b/apps/actors/systems/kvSync/examples/commodityMarket/choose.ts
new file mode 100644
index 00000000..c19d56c3
--- /dev/null
+++ b/apps/actors/systems/kvSync/examples/commodityMarket/choose.ts
@@ -0,0 +1,32 @@
+import { randomFromList, randStep2 } from "../../../../../../util/util";
+import { ClientState } from "../../client";
+import { MutationInvocation } from "../../types";
+import { OrderSide } from "./types";
+
+export function choose(
+  clients: {
+    [id: string]: ClientState;
+  },
+  randomSeed: number
+): [{ clientID: string; invocation: MutationInvocation } | null, number] {
+  const [clientID, randomSeed1] = randomFromList(
+    randomSeed,
+    Object.keys(clients)
+  );
+
+  const [amount1, randomSeed2] = randStep2(randomSeed1);
+  const [price, randomSeed3] = randStep2(randomSeed2);
+  const side = randomFromList(randomSeed3, ["buy", "sell"])[0] as OrderSide;
+
+  return [
+    {
+      clientID,
+      invocation: {
+        type: "Invocation",
+        name: "Order",
+        args: [Math.round(price * 100), Math.round(amount1 * 100), side],
+      },
+    },
+    randomSeed3,
+  ];
+}
diff --git a/apps/actors/systems/kvSync/examples/commodityMarket.dd.txt b/apps/actors/systems/kvSync/examples/commodityMarket/commodityMarket.dd.txt
similarity index 67%
rename from apps/actors/systems/kvSync/examples/commodityMarket.dd.txt
rename to apps/actors/systems/kvSync/examples/commodityMarket/commodityMarket.dd.txt
index 30bcb41d..0f421730 100644
--- a/apps/actors/systems/kvSync/examples/commodityMarket.dd.txt
+++ b/apps/actors/systems/kvSync/examples/commodityMarket/commodityMarket.dd.txt
@@ -108,7 +108,10 @@ addClient{id: "0"}.
 signUp{clientID: "0", username: "alice", password: ""}.
 addClient{id: "1"}.
 signUp{clientID: "1", username: "bob", password: ""}.
-explore{seed: 123548762349586, steps: 100}.
+runMutation{from: "0", name: "Order", args: [10, 100, "buy"]}.
+runMutation{from: "0", name: "Order", args: [10, 100, "buy"]}.
+runMutation{from: "0", name: "Order", args: [10, 100, "buy"]}.
+runMutation{from: "0", name: "Order", args: [10, 100, "sell"]}.
 .jsonState
 ----
 application/json
@@ -119,21 +122,21 @@ application/json
         "transactionID": "0.00037566525896607457",
         "value": {
           "id": 0.31381383055244927,
-          "price": 37.316768604625736,
-          "amount": 20.142637957020327,
-          "side": "sell",
+          "price": 10,
+          "amount": 100,
+          "side": "buy",
           "status": "open",
           "user": "alice"
         }
       },
       {
-        "transactionID": "0.5728273955852048",
+        "transactionID": "0.2581415779498793",
         "value": {
           "id": 0.31381383055244927,
-          "price": 37.316768604625736,
+          "price": 10,
           "amount": 0,
           "status": "sold",
-          "side": "sell",
+          "side": "buy",
           "user": "alice"
         }
       }
@@ -143,21 +146,166 @@ application/json
         "transactionID": "0.26905546502122235",
         "value": {
           "id": 0.015206331866985496,
-          "price": 16.929892745735025,
-          "amount": 85.09055332754791,
+          "price": 10,
+          "amount": 100,
+          "side": "buy",
+          "status": "open",
+          "user": "alice"
+        }
+      }
+    ],
+    "/orders/0.5100409435201818": [
+      {
+        "transactionID": "0.5728273955852048",
+        "value": {
+          "id": 0.5100409435201818,
+          "price": 10,
+          "amount": 100,
           "side": "buy",
           "status": "open",
           "user": "alice"
         }
+      }
+    ],
+    "/orders/0.5855064094862961": [
+      {
+        "transactionID": "0.2581415779498793",
+        "value": {
+          "id": 0.5855064094862961,
+          "price": 10,
+          "amount": 100,
+          "side": "sell",
+          "status": "open",
+          "user": "alice"
+        }
       },
       {
         "transactionID": "0.2581415779498793",
+        "value": {
+          "id": 0.5855064094862961,
+          "price": 10,
+          "amount": 0,
+          "status": "sold",
+          "side": "sell",
+          "user": "alice"
+        }
+      }
+    ],
+    "/trades/0.6062274799740198": [
+      {
+        "transactionID": "0.2581415779498793",
+        "value": {
+          "id": 0.6062274799740198,
+          "buyOrder": 0.31381383055244927,
+          "sellOrder": 0.5855064094862961,
+          "amount": 100,
+          "price": 10
+        }
+      }
+    ]
+  },
+  "user0": {},
+  "client0": {
+    "/orders/0.31381383055244927": [
+      {
+        "transactionID": "0.00037566525896607457",
+        "value": {
+          "id": 0.31381383055244927,
+          "price": 10,
+          "amount": 100,
+          "side": "buy",
+          "status": "open",
+          "user": "alice"
+        }
+      }
+    ],
+    "/orders/0.015206331866985496": [
+      {
+        "transactionID": "0.26905546502122235",
         "value": {
           "id": 0.015206331866985496,
-          "price": 16.929892745735025,
-          "amount": 74.38574868662819,
+          "price": 10,
+          "amount": 100,
+          "side": "buy",
+          "status": "open",
+          "user": "alice"
+        }
+      }
+    ],
+    "/orders/0.5100409435201818": [
+      {
+        "transactionID": "0.5728273955852048",
+        "value": {
+          "id": 0.5100409435201818,
+          "price": 10,
+          "amount": 100,
+          "side": "buy",
+          "status": "open",
+          "user": "alice"
+        }
+      }
+    ],
+    "/orders/0.5855064094862961": [
+      {
+        "transactionID": "0.2581415779498793",
+        "value": {
+          "id": 0.5855064094862961,
+          "price": 10,
+          "amount": 100,
+          "side": "sell",
+          "status": "open",
+          "user": "alice"
+        }
+      }
+    ]
+  },
+  "user1": {},
+  "client1": {}
+}
+
+addClient{id: "0"}.
+signUp{clientID: "0", username: "alice", password: ""}.
+addClient{id: "1"}.
+signUp{clientID: "1", username: "bob", password: ""}.
+explore{seed: 123548762349586, steps: 100}.
+.jsonState
+----
+application/json
+{
+  "server": {
+    "/orders/0.31381383055244927": [
+      {
+        "transactionID": "0.00037566525896607457",
+        "value": {
+          "id": 0.31381383055244927,
+          "price": 37,
+          "amount": 20,
+          "side": "sell",
           "status": "open",
+          "user": "alice"
+        }
+      },
+      {
+        "transactionID": "0.5728273955852048",
+        "value": {
+          "id": 0.31381383055244927,
+          "price": 37,
+          "amount": 0,
+          "status": "sold",
+          "side": "sell",
+          "user": "alice"
+        }
+      }
+    ],
+    "/orders/0.015206331866985496": [
+      {
+        "transactionID": "0.26905546502122235",
+        "value": {
+          "id": 0.015206331866985496,
+          "price": 17,
+          "amount": 85,
           "side": "buy",
+          "status": "open",
           "user": "alice"
         }
       },
@@ -165,8 +313,8 @@ application/json
         "transactionID": "0.619620117004607",
         "value": {
           "id": 0.015206331866985496,
-          "price": 16.929892745735025,
-          "amount": 67.19771946519401,
+          "price": 17,
+          "amount": 78,
           "status": "open",
           "side": "buy",
           "user": "alice"
@@ -176,8 +324,8 @@ application/json
         "transactionID": "0.787366886890835",
         "value": {
           "id": 0.015206331866985496,
-          "price": 16.929892745735025,
-          "amount": 32.872100763835114,
+          "price": 17,
+          "amount": 44,
           "status": "open",
           "side": "buy",
           "user": "alice"
@@ -187,7 +335,7 @@ application/json
         "transactionID": "0.8598554999193694",
         "value": {
           "id": 0.015206331866985496,
-          "price": 16.929892745735025,
+          "price": 17,
           "amount": 0,
           "status": "sold",
           "side": "buy",
@@ -200,8 +348,8 @@ application/json
         "transactionID": "0.5728273955852048",
         "value": {
           "id": 0.5100409435201818,
-          "price": 60.20900012013409,
-          "amount": 88.19302724506056,
+          "price": 60,
+          "amount": 88,
           "side": "buy",
           "status": "open",
           "user": "alice"
@@ -211,8 +359,8 @@ application/json
         "transactionID": "0.5728273955852048",
         "value": {
           "id": 0.5100409435201818,
-          "price": 60.20900012013409,
-          "amount": 68.05038928804024,
+          "price": 60,
+          "amount": 68,
           "status": "open",
           "side": "buy",
           "user": "alice"
@@ -222,8 +370,8 @@ application/json
         "transactionID": "0.2581415779498793",
         "value": {
           "id": 0.5100409435201818,
-          "price": 60.20900012013409,
-          "amount": 57.34558464712052,
+          "price": 60,
+          "amount": 57,
           "status": "open",
           "side": "buy",
           "user": "alice"
@@ -233,7 +381,7 @@ application/json
         "transactionID": "0.0003834916282291446",
         "value": {
           "id": 0.5100409435201818,
-          "price": 60.20900012013409,
+          "price": 60,
           "amount": 0,
           "status": "sold",
           "side": "buy",
@@ -248,8 +396,8 @@ application/json
           "id": 0.2581415779498793,
           "buyOrder": 0.5100409435201818,
           "sellOrder": 0.31381383055244927,
-          "amount": 20.142637957020327,
-          "price": 48.762884362379914
+          "amount": 20,
+          "price": 48.5
         }
       }
     ],
@@ -258,8 +406,8 @@ application/json
         "transactionID": "0.2581415779498793",
         "value": {
           "id": 0.5855064094862961,
-          "price": 15.652298755619952,
-          "amount": 10.70480464091972,
+          "price": 16,
+          "amount": 11,
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-          "price": 16.929892745735025,
-          "amount": 85.09055332754791,
+          "price": 17,
+          "amount": 85,
           "side": "buy",
           "status": "open",
           "user": "alice"
@@ -1657,8 +1508,8 @@ application/json
         "transactionID": "0.5728273955852048",
         "value": {
           "id": 0.5100409435201818,
-          "price": 60.20900012013409,
-          "amount": 88.19302724506056,
+          "price": 60,
+          "amount": 88,
           "side": "buy",
           "status": "open",
           "user": "alice"
@@ -1670,8 +1521,8 @@ application/json
         "transactionID": "0.2581415779498793",
         "value": {
           "id": 0.5855064094862961,
-          "price": 15.652298755619952,
-          "amount": 10.70480464091972,
+          "price": 16,
+          "amount": 11,
           "side": "sell",
           "status": "open",
           "user": "alice"
@@ -1683,8 +1534,8 @@ application/json
         "transactionID": "0.6062274799740198",
         "value": {
           "id": 0.8652590050969823,
-          "price": 40.85953444322528,
-          "amount": 5.2026452545101245,
+          "price": 41,
+          "amount": 5,
           "side": "buy",
           "status": "open",
           "user": "alice"
@@ -1696,8 +1547,8 @@ application/json
         "transactionID": "0.40809971923762905",
         "value": {
           "id": 0.9319858592301475,
-          "price": 61.90427058553721,
-          "amount": 30.009038122379255,
+          "price": 62,
+          "amount": 30,
           "side": "buy",
           "status": "open",
           "user": "alice"
@@ -1709,8 +1560,8 @@ application/json
         "transactionID": "0.8863366133406168",
         "value": {
           "id": 0.6594613051595737,
-          "price": 50.936840475478064,
-          "amount": 22.160465058088736,
+          "price": 51,
+          "amount": 22,
           "side": "sell",
           "status": "open",
           "user": "alice"
@@ -1722,8 +1573,8 @@ application/json
         "transactionID": "0.5661584819351868",
         "value": {
           "id": 0.42560927982033164,
-          "price": 30.447008628814487,
-          "amount": 11.175727156154558,
+          "price": 30,
+          "amount": 11,
           "side": "buy",
           "status": "open",
           "user": "alice"
@@ -1735,8 +1586,8 @@ application/json
         "transactionID": "0.21517043534216512",
         "value": {
           "id": 0.3695129378414833,
-          "price": 54.946238738434616,
-          "amount": 38.136190025262714,
+          "price": 55,
+          "amount": 38,
           "side": "sell",
           "status": "open",
           "user": "alice"
@@ -1748,8 +1599,8 @@ application/json
         "transactionID": "0.4039512359573983",
         "value": {
           "id": 0.20842740052233208,
-          "price": 18.209919676380157,
-          "amount": 53.90124409822863,
+          "price": 18,
+          "amount": 54,
           "side": "sell",
           "status": "open",
           "user": "alice"
@@ -1761,8 +1612,8 @@ application/json
         "transactionID": "0.03932677352738266",
         "value": {
           "id": 0.9650901932875534,
-          "price": 44.04468768652965,
-          "amount": 65.18974501191614,
+          "price": 44,
+          "amount": 65,
           "side": "sell",
           "status": "open",
           "user": "alice"
@@ -1774,8 +1625,8 @@ application/json
         "transactionID": "0.27087885678827656",
         "value": {
           "id": 0.6609517467775864,
-          "price": 53.02912770121277,
-          "amount": 25.849528681346705,
+          "price": 53,
+          "amount": 26,
           "side": "sell",
           "status": "open",
           "user": "alice"
@@ -1787,8 +1638,8 @@ application/json
         "transactionID": "0.6160107442326944",
         "value": {
           "id": 0.29258132380673785,
-          "price": 21.071714974075288,
-          "amount": 71.29892732137715,
+          "price": 21,
+          "amount": 71,
           "side": "sell",
           "status": "open",
           "user": "alice"
@@ -1800,8 +1651,8 @@ application/json
         "transactionID": "0.4143147560901146",
         "value": {
           "id": 0.3881101900600923,
-          "price": 63.037587481585874,
-          "amount": 57.545251220041195,
+          "price": 63,
+          "amount": 58,
           "side": "sell",
           "status": "open",
           "user": "alice"
@@ -1813,8 +1664,8 @@ application/json
         "transactionID": "0.9679691288321923",
         "value": {
           "id": 0.6571485331814256,
-          "price": 59.59723588041703,
-          "amount": 38.92185379650616,
+          "price": 60,
+          "amount": 39,
           "side": "sell",
           "status": "open",
           "user": "alice"
@@ -1826,8 +1677,8 @@ application/json
         "transactionID": "0.6953998633617534",
         "value": {
           "id": 0.5855059047094602,
-          "price": 50.51039704169183,
-          "amount": 8.898108507411656,
+          "price": 51,
+          "amount": 9,
           "side": "buy",
           "status": "open",
           "user": "alice"
@@ -1842,8 +1693,8 @@ application/json
         "transactionID": "0.0003834916282291446",
         "value": {
           "id": 0.4453516187568676,
-          "price": 45.81208093633138,
-          "amount": 91.73236223099042,
+          "price": 46,
+          "amount": 92,
           "side": "sell",
           "status": "open",
           "user": "bob"
@@ -1855,8 +1706,8 @@ application/json
         "transactionID": "0.02466078710245042",
         "value": {
           "id": 0.4738564640040104,
-          "price": 33.81343161111086,
-          "amount": 13.419040444697291,
+          "price": 34,
+          "amount": 13,
           "side": "buy",
           "status": "open",
           "user": "bob"
@@ -1868,8 +1719,8 @@ application/json
         "transactionID": "0.10559463277980186",
         "value": {
           "id": 0.7290001299502329,
-          "price": 88.46443462042551,
-          "amount": 40.73829142445539,
+          "price": 88,
+          "amount": 41,
           "side": "buy",
           "status": "open",
           "user": "bob"
@@ -1881,8 +1732,8 @@ application/json
         "transactionID": "0.3051861941862723",
         "value": {
           "id": 0.2643711262050747,
-          "price": 43.23453176136551,
-          "amount": 3.453515426678132,
+          "price": 43,
+          "amount": 3,
           "side": "buy",
           "status": "open",
           "user": "bob"
@@ -1894,8 +1745,8 @@ application/json
         "transactionID": "0.2855238856612927",
         "value": {
           "id": 0.7999519010073989,
-          "price": 26.76166373003429,
-          "amount": 62.511260865732346,
+          "price": 27,
+          "amount": 63,
           "side": "sell",
           "status": "open",
           "user": "bob"
@@ -1907,8 +1758,8 @@ application/json
         "transactionID": "0.7916017969060706",
         "value": {
           "id": 0.45140223107431293,
-          "price": 18.17019928076323,
-          "amount": 66.58643243516464,
+          "price": 18,
+          "amount": 67,
           "side": "sell",
           "status": "open",
           "user": "bob"
@@ -1920,8 +1771,8 @@ application/json
         "transactionID": "0.7173019593742694",
         "value": {
           "id": 0.694033415703134,
-          "price": 85.92259589202943,
-          "amount": 26.732071281161225,
+          "price": 86,
+          "amount": 27,
           "side": "buy",
           "status": "open",
           "user": "bob"
@@ -1933,8 +1784,8 @@ application/json
         "transactionID": "0.619620117004607",
         "value": {
           "id": 0.9553094734021551,
-          "price": 9.207850982628624,
-          "amount": 7.188029221434173,
+          "price": 9,
+          "amount": 7,
           "side": "sell",
           "status": "open",
           "user": "bob"
@@ -1946,8 +1797,8 @@ application/json
         "transactionID": "0.8863198197319357",
         "value": {
           "id": 0.37721112405621554,
-          "price": 45.103340684532505,
-          "amount": 40.76546099108221,
+          "price": 45,
+          "amount": 41,
           "side": "sell",
           "status": "open",
           "user": "bob"
@@ -1959,8 +1810,8 @@ application/json
         "transactionID": "0.787366886890835",
         "value": {
           "id": 0.2752696380720191,
-          "price": 10.674027689429026,
-          "amount": 34.3256187013589,
+          "price": 11,
+          "amount": 34,
           "side": "sell",
           "status": "open",
           "user": "bob"
@@ -1972,8 +1823,8 @@ application/json
         "transactionID": "0.4568127481795966",
         "value": {
           "id": 0.6518629055021916,
-          "price": 99.47066749396795,
-          "amount": 6.253315281358842,
+          "price": 99,
+          "amount": 6,
           "side": "buy",
           "status": "open",
           "user": "bob"
@@ -1985,8 +1836,8 @@ application/json
         "transactionID": "0.8598554999193694",
         "value": {
           "id": 0.5913882414730156,
-          "price": 5.453274869782175,
-          "amount": 70.84580550049041,
+          "price": 5,
+          "amount": 71,
           "side": "sell",
           "status": "open",
           "user": "bob"
@@ -1998,8 +1849,8 @@ application/json
         "transactionID": "0.46217763466963324",
         "value": {
           "id": 0.8195101016382781,
-          "price": 18.463462328969932,
-          "amount": 14.30466250917377,
+          "price": 18,
+          "amount": 14,
           "side": "buy",
           "status": "open",
           "user": "bob"
@@ -2011,8 +1862,8 @@ application/json
         "transactionID": "0.5062796468904983",
         "value": {
           "id": 0.04202915219779047,
-          "price": 14.714031819919155,
-          "amount": 26.07334524027383,
+          "price": 15,
+          "amount": 26,
           "side": "sell",
           "status": "open",
           "user": "bob"
@@ -2024,8 +1875,8 @@ application/json
         "transactionID": "0.3839684854112272",
         "value": {
           "id": 0.3583391274868875,
-          "price": 0.08381153464672299,
-          "amount": 35.15202494817974,
+          "price": 0,
+          "amount": 35,
           "side": "buy",
           "status": "open",
           "user": "bob"
@@ -2037,8 +1888,8 @@ application/json
         "transactionID": "0.6057206938096514",
         "value": {
           "id": 0.34770394428419316,
-          "price": 85.3441100896747,
-          "amount": 68.30995084560472,
+          "price": 85,
+          "amount": 68,
           "side": "sell",
           "status": "open",
           "user": "bob"
@@ -2050,8 +1901,8 @@ application/json
         "transactionID": "0.8601966894792362",
         "value": {
           "id": 0.3257611713612091,
-          "price": 82.06709235167791,
-          "amount": 72.08794352792943,
+          "price": 82,
+          "amount": 72,
           "side": "buy",
           "status": "open",
           "user": "bob"
@@ -2063,8 +1914,8 @@ application/json
         "transactionID": "0.06801234424860435",
         "value": {
           "id": 0.08347707994606074,
-          "price": 51.974749287566866,
-          "amount": 84.354850635263,
+          "price": 52,
+          "amount": 84,
           "side": "buy",
           "status": "open",
           "user": "bob"
@@ -2076,8 +1927,8 @@ application/json
         "transactionID": "0.9992898264893236",
         "value": {
           "id": 0.06411381118382682,
-          "price": 15.311881075903663,
-          "amount": 72.79795987792123,
+          "price": 15,
+          "amount": 73,
           "side": "buy",
           "status": "open",
           "user": "bob"
diff --git a/apps/actors/systems/kvSync/examples/commodityMarket/index.ts b/apps/actors/systems/kvSync/examples/commodityMarket/index.ts
new file mode 100644
index 00000000..95d41d8d
--- /dev/null
+++ b/apps/actors/systems/kvSync/examples/commodityMarket/index.ts
@@ -0,0 +1,17 @@
+import { KVApp } from "../types";
+import { choose } from "./choose";
+import { matchOrders, mutations } from "./mutations";
+import { MarketUI } from "./ui";
+
+export const commodityMarket: KVApp = {
+  name: "Commodity Market",
+  mutations,
+  ui: MarketUI,
+  triggers: [
+    {
+      prefix: "/orders/",
+      fn: matchOrders,
+    },
+  ],
+  choose,
+};
diff --git a/apps/actors/systems/kvSync/examples/commodityMarket/mutations.ts b/apps/actors/systems/kvSync/examples/commodityMarket/mutations.ts
new file mode 100644
index 00000000..8b80035c
--- /dev/null
+++ b/apps/actors/systems/kvSync/examples/commodityMarket/mutations.ts
@@ -0,0 +1,86 @@
+import { MutationCtx, TSMutationDefns, WriteOp } from "../../types";
+import { Order, readOrder } from "./types";
+
+export const mutations: TSMutationDefns = {
+  Order: (ctx, [price, amount, side]) => {
+    const id = ctx.rand();
+    ctx.write(`/orders/${id}`, {
+      id,
+      price,
+      amount,
+      side,
+      status: "open",
+      user: ctx.curUser,
+    });
+  },
+};
+
+export function matchOrders(ctx: MutationCtx, evt: WriteOp) {
+  // Prevent us from going on forever
+  if (evt.desc.type !== "Insert") {
+    return;
+  }
+
+  const orders = ctx.scan("/orders/").map(readOrder);
+
+  const buys = orders
+    .filter((order) => order.side === "buy" && order.status === "open")
+    .sort((a, b) => b.price - a.price);
+  const sells = orders
+    .filter((order) => order.side === "sell" && order.status === "open")
+    .sort((a, b) => a.price - b.price);
+
+  for (const buy of buys) {
+    // TODO: keep buying while there's more to buy
+    for (const sell of sells) {
+      if (sell.status === "sold") {
+        continue;
+      }
+
+      if (buy.price >= sell.price) {
+        const amount = Math.min(buy.amount, sell.amount);
+        const price = (buy.price + sell.price) / 2;
+
+        // Execute the trade
+        const newBuyAmount = buy.amount - amount;
+        const newBuyStatus = newBuyAmount === 0 ? "sold" : "open";
+        const newBuy: Order = {
+          ...buy,
+          amount: newBuyAmount,
+          status: newBuyStatus,
+        };
+        ctx.write(`/orders/${buy.id}`, newBuy);
+
+        const newSellAmount = sell.amount - amount;
+        const newSellStatus = newSellAmount === 0 ? "sold" : "open";
+        const newSell: Order = {
+          ...sell,
+          amount: newSellAmount,
+          status: newSellStatus,
+        };
+        ctx.write(`/orders/${sell.id}`, newSell);
+
+        // for future loops
+        buy.amount = newBuyAmount;
+        buy.status = newBuyStatus;
+        sell.amount = newSellAmount;
+        sell.status = newSellStatus;
+
+        // console.log("matchOrders", { newBuy, newSell });
+
+        const tradeID = ctx.rand();
+        ctx.write(`/trades/${tradeID}`, {
+          id: tradeID,
+          buyOrder: buy.id,
+          sellOrder: sell.id,
+          amount,
+          price,
+        });
+
+        if (newBuyAmount === 0) {
+          break;
+        }
+      }
+    }
+  }
+}
diff --git a/apps/actors/systems/kvSync/examples/commodityMarket/types.ts b/apps/actors/systems/kvSync/examples/commodityMarket/types.ts
new file mode 100644
index 00000000..39214dc6
--- /dev/null
+++ b/apps/actors/systems/kvSync/examples/commodityMarket/types.ts
@@ -0,0 +1,48 @@
+import { Json } from "../../../../../../util/json";
+import { TransactionState } from "../../client";
+
+export type OfferStatus = "open" | "sold";
+
+export type OrderSide = "sell" | "buy";
+
+export type Order = {
+  id: number;
+  price: number;
+  amount: number;
+  side: OrderSide;
+  user: string;
+  status: OfferStatus;
+};
+
+export function readOrder(rawOrder: Json): Order {
+  const order = rawOrder as any;
+  return {
+    id: order.id as number,
+    price: order.price as number,
+    amount: order.amount as number,
+    status: order.status as OfferStatus,
+    side: order.side as OrderSide,
+    user: order.user as string,
+  };
+}
+
+export type Trade = {
+  id: number;
+  price: number;
+  amount: number;
+  buyOrder: number;
+  sellOrder: number;
+};
+
+export function readTrade(rawTrade: Json): Trade {
+  const trade = rawTrade as any;
+  return {
+    id: trade.id as number,
+    price: trade.price as number,
+    amount: trade.amount as number,
+    buyOrder: trade.buyOrder as number,
+    sellOrder: trade.sellOrder as number,
+  };
+}
+
+export type OrderWithState = Order & { state: TransactionState };
diff --git a/apps/actors/systems/kvSync/examples/commodityMarket/ui.tsx b/apps/actors/systems/kvSync/examples/commodityMarket/ui.tsx
new file mode 100644
index 00000000..05eee140
--- /dev/null
+++ b/apps/actors/systems/kvSync/examples/commodityMarket/ui.tsx
@@ -0,0 +1,170 @@
+import React, { useState } from "react";
+import { UIProps } from "../../../../types";
+import { ClientState, QueryStatus } from "../../client";
+import { Client, makeClient, useLiveQuery } from "../../hooks";
+import { UserInput } from "../../types";
+import { LoginWrapper } from "../../uiCommon/loginWrapper";
+import { LoggedInHeader } from "../../uiCommon/loggedInHeader";
+import { Table } from "../../../../../../uiCommon/generic/table";
+import {
+  Order,
+  OrderSide,
+  OrderWithState,
+  readOrder,
+  readTrade,
+  Trade,
+} from "./types";
+import { Inspector } from "../../uiCommon/inspector";
+
+export function MarketUI(props: UIProps<ClientState, UserInput>) {
+  const client = makeClient(props);
+
+  return (
+    <LoginWrapper
+      client={client}
+      loggedIn={(user) => <MarketInner client={client} user={user} />}
+    />
+  );
+}
+
+function MarketInner(props: { client: Client; user: string }) {
+  const [orders, orderQueryStatus] = useOrders(props.client);
+  const [trades, tradeQueryStatus] = useTrades(props.client);
+
+  return (
+    <>
+      <LoggedInHeader user={props.user} client={props.client}>
+        <h2>Market</h2>
+      </LoggedInHeader>
+
+      <h3>Orders</h3>
+
+      {orderQueryStatus === "Loading" ? (
+        <em>Loading...</em>
+      ) : (
+        <Table<Order>
+          data={orders}
+          getKey={(order) => order.id.toString()}
+          columns={[
+            { name: "id", render: (order) => order.id },
+            { name: "price", render: (order) => `$${order.price}` },
+            { name: "amount", render: (order) => order.amount },
+            { name: "side", render: (order) => order.side },
+            { name: "user", render: (order) => order.user },
+            { name: "status", render: (order) => order.status },
+          ]}
+        />
+      )}
+
+      <h3>Create Order</h3>
+
+      <OrderForm client={props.client} />
+
+      <h3>Trades</h3>
+
+      {tradeQueryStatus === "Loading" ? (
+        <em>Loading...</em>
+      ) : (
+        <Table<Trade>
+          data={trades}
+          getKey={(trade) => trade.id.toString()}
+          columns={[
+            { name: "id", render: (trade) => trade.id },
+            { name: "price", render: (trade) => `$${trade.price}` },
+            { name: "amount", render: (trade) => trade.amount },
+            { name: "buy order", render: (trade) => trade.buyOrder },
+            { name: "sell order", render: (trade) => trade.sellOrder },
+          ]}
+        />
+      )}
+
+      <Inspector client={props.client} />
+    </>
+  );
+}
+
+function OrderForm(props: { client: Client }) {
+  const [price, setPrice] = useState(10);
+  const [amount, setAmount] = useState(100);
+  const [side, setSide] = useState<OrderSide>("buy");
+
+  return (
+    <form
+      onSubmit={(evt) => {
+        evt.preventDefault();
+
+        props.client.runMutation("Order", [price, amount, side]);
+      }}
+    >
+      Amount:{" "}
+      <input
+        type="number"
+        placeholder="Amount"
+        value={amount}
+        onChange={(evt) => setAmount(parseInt(evt.target.value))}
+      />{" "}
+      Price:{" "}
+      <input
+        type="number"
+        placeholder="Price"
+        value={price}
+        onChange={(evt) => setPrice(parseInt(evt.target.value))}
+      />
+      <div>
+        <label>
+          <input
+            type="radio"
+            value="buy"
+            checked={side === "buy"}
+            onChange={(evt) => setSide("buy")}
+          />
+          Buy
+        </label>
+        <label>
+          <input
+            type="radio"
+            value="sell"
+            checked={side === "sell"}
+            onChange={(evt) => setSide("sell")}
+          />
+          Sell
+        </label>
+      </div>
+      <button type="submit">Create Order</button>
+    </form>
+  );
+}
+
+function useOrders(client: Client): [OrderWithState[], QueryStatus] {
+  const [rawOrders, queryStatus] = useLiveQuery(client, "list-orders", {
+    prefix: "/orders/",
+  });
+
+  const cmpKey = (a: OrderWithState) => (a.side === "buy" ? a.price : -a.price);
+
+  const orders = Object.entries(rawOrders)
+    .map(([id, rawOrder]): OrderWithState => {
+      const order = rawOrder.value as any;
+      const mapped = readOrder(order);
+      return {
+        ...mapped,
+        state: client.state.transactions[rawOrder.transactionID]?.state,
+      };
+    })
+    .sort((a, b) => cmpKey(a) - cmpKey(b));
+
+  return [orders, queryStatus];
+}
+
+function useTrades(client: Client): [Trade[], QueryStatus] {
+  const [rawTrades, queryStatus] = useLiveQuery(client, "list-trades", {
+    prefix: "/trades/",
+  });
+
+  const trades = Object.entries(rawTrades).map(([id, rawTrade]): Trade => {
+    const trade = rawTrade.value as any;
+    return readTrade(trade);
+  });
+
+  return [trades, queryStatus];
+}