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LangGraph CloudTutorial: Stockbroker

Part 3: Approval UI

Background: LangGraph implementation details

LangChain LangGraph

Our LangGraph backend interrupts the purchase_stock tool execution in order to ensure the user confirms the purchase. The user confirms the purchase by submitting a tool message with the approve field set to true.

assistant-ui-stockbroker/backend/src/index.ts
const purchaseApproval = async (state: typeof GraphAnnotation.State) => {
  const { messages } = state;
  const lastMessage = messages[messages.length - 1];
  if (!(lastMessage instanceof ToolMessage)) {
    // Interrupt the node to request permission to execute the purchase.
    throw new NodeInterrupt("Please confirm the purchase before executing.");
  }
};
 
const shouldExecutePurchase = (state: typeof GraphAnnotation.State) => {
  const { messages } = state;
  const lastMessage = messages[messages.length - 1];
  if (!(lastMessage instanceof ToolMessage)) {
    // Interrupt the node to request permission to execute the purchase.
    throw new NodeInterrupt("Please confirm the purchase before executing.");
  }
 
  const { approve } = JSON.parse(lastMessage.content as string);
  return approve ? "execute_purchase" : "agent";
};
 
const workflow = new StateGraph(GraphAnnotation)
  .addNode("agent", callModel)
  .addEdge(START, "agent")
  .addNode("tools", toolNode)
  .addNode("prepare_purchase_details", preparePurchaseDetails)
  .addNode("purchase_approval", purchaseApproval)
  .addNode("execute_purchase", executePurchase)
  .addEdge("prepare_purchase_details", "purchase_approval")
  .addEdge("execute_purchase", END)
  .addEdge("tools", "agent")
  .addConditionalEdges("purchase_approval", shouldExecutePurchase, [
    "agent",
    "execute_purchase",
  ])
  .addConditionalEdges("agent", shouldContinue, [
    "tools",
    END,
    "prepare_purchase_details",
  ]);

Add approval UI

We create a new file under /components/tools/purchase-stock/PurchaseStockTool.tsx to define the tool.

First, we define the tool arguments and result types:

@/components/tools/purchase-stock/PurchaseStockTool.tsx
type PurchaseStockArgs = {
  ticker: string;
  companyName: string;
  quantity: number;
  maxPurchasePrice: number;
};
 
type PurchaseStockResult = {
  approve?: boolean;
  cancelled?: boolean;
  error?: string;
};

Then we use makeAssistantToolUI to define the tool UI:

@/components/tools/purchase-stock/PurchaseStockTool.tsx
"use client";
 
import { TransactionConfirmationPending } from "./transaction-confirmation-pending";
import { TransactionConfirmationFinal } from "./transaction-confirmation-final";
import { makeAssistantToolUI } from "@assistant-ui/react";
import { updateState } from "@/lib/chatApi";
 
export const PurchaseStockTool = makeAssistantToolUI<PurchaseStockArgs, string>(
  {
    toolName: "purchase_stock",
    render: function PurchaseStockUI({ args, result, status, addResult }) {
      const handleReject = async () => {
        addResult({ approve: false });
      };
 
      const handleConfirm = async () => {
        addResult({ approve: true });
      };
 
      return (
        <div className="mb-4 flex flex-col items-center gap-2">
          <div>
            <pre className="whitespace-pre-wrap break-all text-center">
              purchase_stock({JSON.stringify(args)})
            </pre>
          </div>
          {!result && status.type !== "running" && (
            <TransactionConfirmationPending
              {...args}
              onConfirm={handleConfirm}
              onReject={handleReject}
            />
          )}
        </div>
      );
    },
  },
);

Finally, we add a TransactionConfirmationPending component to ask for approval.

This requires shadcn/ui's Card and Button components. We will install them as a dependency.

npx shadcn@latest add card button

Then create a new file under /components/tools/purchase-stock/transaction-confirmation-pending.tsx to define the approval UI.

@/components/tools/purchase-stock/transaction-confirmation-pending.tsx
"use client";
 
import { CheckIcon, XIcon } from "lucide-react";
 
import { Button } from "@/components/ui/button";
import {
  Card,
  CardContent,
  CardFooter,
  CardHeader,
  CardTitle,
} from "@/components/ui/card";
 
type TransactionConfirmation = {
  ticker: string;
  companyName: string;
  quantity: number;
  maxPurchasePrice: number;
  onConfirm: () => void;
  onReject: () => void;
};
 
export function TransactionConfirmationPending(props: TransactionConfirmation) {
  const {
    ticker,
    companyName,
    quantity,
    maxPurchasePrice,
    onConfirm,
    onReject,
  } = props;
 
  return (
    <Card className="mx-auto w-full max-w-md">
      <CardHeader>
        <CardTitle className="text-2xl font-bold">
          Confirm Transaction
        </CardTitle>
      </CardHeader>
      <CardContent className="space-y-4">
        <div className="grid grid-cols-2 gap-2">
          <p className="text-muted-foreground text-sm font-medium">Ticker:</p>
          <p className="text-sm font-bold">{ticker}</p>
          <p className="text-muted-foreground text-sm font-medium">Company:</p>
          <p className="text-sm">{companyName}</p>
          <p className="text-muted-foreground text-sm font-medium">Quantity:</p>
          <p className="text-sm">{quantity} shares</p>
          <p className="text-muted-foreground text-sm font-medium">
            Max Purchase Price:
          </p>
          <p className="text-sm">${maxPurchasePrice?.toFixed(2)}</p>
        </div>
        <div className="bg-muted rounded-md p-3">
          <p className="text-sm font-medium">Total Maximum Cost:</p>
          <p className="text-lg font-bold">
            ${(quantity * maxPurchasePrice)?.toFixed(2)}
          </p>
        </div>
      </CardContent>
      <CardFooter className="flex justify-end">
        <Button variant="outline" onClick={onReject}>
          <XIcon className="mr-2 h-4 w-4" />
          Reject
        </Button>
        <Button onClick={onConfirm}>
          <CheckIcon className="mr-2 h-4 w-4" />
          Confirm
        </Button>
      </CardFooter>
    </Card>
  );
}

Bind approval UI

@/app/page.tsx
import { PurchaseStockTool } from "@/components/tools/purchase-stock/PurchaseStockTool";
 
export default function Home() {
  return (
    <div className="flex h-full flex-col">
      <Thread
        ...
        tools={[PriceSnapshotTool, PurchaseStockTool]}
      />
    </div>
  );
}

Try it out!

Ask the assistant to buy 5 shares of Tesla. You should see the following appear:

Approval UI

Add TransactionConfirmationFinal to show approval result

We will add a component to display the approval result.

@/components/tools/purchase-stock/transaction-confirmation-final.tsx
"use client";
 
import { CheckCircle } from "lucide-react";
 
import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
 
type TransactionConfirmation = {
  ticker: string;
  companyName: string;
  quantity: number;
  maxPurchasePrice: number;
};
 
export function TransactionConfirmationFinal(props: TransactionConfirmation) {
  const { ticker, companyName, quantity, maxPurchasePrice } = props;
 
  return (
    <Card className="mx-auto w-full max-w-md">
      <CardHeader className="text-center">
        <CheckCircle className="mx-auto mb-4 h-16 w-16 text-green-500" />
        <CardTitle className="text-2xl font-bold text-green-700">
          Transaction Confirmed
        </CardTitle>
      </CardHeader>
      <CardContent className="space-y-4">
        <div className="rounded-md border border-green-200 bg-green-50 p-4">
          <h3 className="mb-2 text-lg font-semibold text-green-800">
            Purchase Summary
          </h3>
          <div className="grid grid-cols-2 gap-2 text-sm">
            <p className="font-medium text-green-700">Ticker:</p>
            <p className="font-bold text-green-900">{ticker}</p>
            <p className="font-medium text-green-700">Company:</p>
            <p className="text-green-900">{companyName}</p>
            <p className="font-medium text-green-700">Quantity:</p>
            <p className="text-green-900">{quantity} shares</p>
            <p className="font-medium text-green-700">Price per Share:</p>
            <p className="text-green-900">${maxPurchasePrice?.toFixed(2)}</p>
          </div>
        </div>
        <div className="rounded-md border border-green-300 bg-green-100 p-4">
          <p className="text-lg font-semibold text-green-800">Total Cost:</p>
          <p className="text-2xl font-bold text-green-900">
            ${(quantity * maxPurchasePrice)?.toFixed(2)}
          </p>
        </div>
        <p className="text-center text-sm text-green-600">
          Your purchase of {quantity} shares of {companyName} ({ticker}) has
          been successfully processed.
        </p>
      </CardContent>
    </Card>
  );
}

Update PurchaseStockTool

We will import the new <TransactionConfirmationFinal /> component and use it in the render function whenever an approval result is available.

@/components/tools/purchase-stock/PurchaseStockTool.tsx
"use client";
 
import { TransactionConfirmationPending } from "./transaction-confirmation-pending";
import { TransactionConfirmationFinal } from "./transaction-confirmation-final";
import { makeAssistantToolUI } from "@assistant-ui/react";
import { updateState } from "@/lib/chatApi";
 
type PurchaseStockArgs = {
  ticker: string;
  companyName: string;
  quantity: number;
  maxPurchasePrice: number;
};
 
type PurchaseStockResult = {
  approve?: boolean;
  cancelled?: boolean;
  error?: string;
};
 
export const PurchaseStockTool = makeAssistantToolUI<PurchaseStockArgs, string>(
  {
    toolName: "purchase_stock",
    render: function PurchaseStockUI({ args, result, status, addResult }) {
      let resultObj: PurchaseStockResult;
      try {
        resultObj = result ? JSON.parse(result) : {};
      } catch (e) {
        resultObj = { error: result! };
      }
 
      const handleReject = () => {
        addResult({ cancelled: true });
      };
 
      const handleConfirm = async () => {
        addResult({ approve: true });
      };
 
      return (
        <div className="mb-4 flex flex-col items-center gap-2">
          <div>
            <pre className="whitespace-pre-wrap break-all text-center">
              purchase_stock({JSON.stringify(args)})
            </pre>
          </div>
          {!result && status.type !== "running" && (
            <TransactionConfirmationPending
              {...args}
              onConfirm={handleConfirm}
              onReject={handleReject}
            />
          )}
          {resultObj.approve && <TransactionConfirmationFinal {...args} />}
          {resultObj.approve === false && (
            <pre className="font-bold text-red-600">User rejected purchase</pre>
          )}
          {resultObj.cancelled && (
            <pre className="font-bold text-red-600">Cancelled</pre>
          )}
        </div>
      );
    },
  },
);

Try it out!

Confirm the purchase of shares. You should see the approval confimration UI appear.

Approval result

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