Create the frontend application

Create a frontend app on the same project root directory. Here we use Vite and React to start a default project;
```
npm create vite@latest
```
Choose a name for the frontend project (such as app, which is what the examples later use), select the React framework, and select the Typescript language. If prompted, don't use the experimental version of Vite, and choose to not install and run immediately, because we have a few more settings to do below.
Run these commands to install the dependencies:
```
cd app
npm install
```

From the ./app folder, download some sample images for the frontend application:

wget -O public/chiefs.png https://github.com/trilitech/tutorial-applications/raw/main/etherlink-marketpulse/app/public/chiefs.png
wget -O public/lions.png https://github.com/trilitech/tutorial-applications/raw/main/etherlink-marketpulse/app/public/lions.png
wget -O public/graph.png https://github.com/trilitech/tutorial-applications/raw/main/etherlink-marketpulse/app/public/graph.png

Within your frontend ./app project, import the Viem library for blockchain interactions, thirdweb for the wallet connection and bignumber for calculations on large numbers:
```
npm i viem thirdweb bignumber.js
```
Add the typechain library to generate your contract structures and Typescript ABI classes from your ABI json file, that is your smart contract descriptor:
```
npm i -D typechain @typechain/ethers-v6
```
Add this line to the scripts section of the ./app/package.json file in the frontend application:
```
     "postinstall": "cp ../ignition/deployments/chain-127823/deployed_addresses.json ./src  &&  typechain --target=ethers-v6 --out-dir=./src/typechain-types --show-stack-traces ../artifacts/contracts/Marketpulse.sol/Marketpulse.json",
```
This script copies the output address of the last deployed contract into your source files and calls typechain to generate types from the ABI file from the Hardhat folders.
Run npm i to call the postinstall script automatically. You should see new files and folders in the ./src folder of the frontend application.

Create a utility file called app/src/DecodeEvmTransactionLogsArgs.ts to manage Viem errors (better than the technical defaults and not helpful ones), with this content:

import {
Abi,
BaseError,
ContractFunctionRevertedError,
decodeErrorResult,
} from "viem";

// Type-Safe Error Handling Interface
interface DetailedError {
type: "DecodedError" | "RawError" | "UnknownError";
message: string;
details?: string;
errorData?: any;
}

// Advanced Error Extraction Function
export function extractErrorDetails(error: unknown, abi: Abi): DetailedError {
// Type guard for BaseError
if (error instanceof BaseError) {
    // Type guard for ContractFunctionRevertedError
    if (error.walk() instanceof ContractFunctionRevertedError) {
    try {
        // Safe data extraction
        const revertError = error.walk() as ContractFunctionRevertedError;

        // Extract error data safely
        const errorData = (revertError as any).data;

        // Attempt to decode error
        if (errorData) {
        try {
            // Generic error ABI for decoding
            const errorAbi = abi;

            const decodedError = decodeErrorResult({
            abi: errorAbi,
            data: errorData,
            });

            return {
            type: "DecodedError",
            message: decodedError.errorName || "Contract function reverted",
            details: decodedError.args?.toString(),
            errorData,
            };
        } catch {
            // Fallback if decoding fails
            return {
            type: "RawError",
            message: "Could not decode error",
            errorData,
            };
        }
        }
    } catch (extractionError) {
        // Fallback error extraction
        return {
        type: "UnknownError",
        message: error.shortMessage || "Unknown contract error",
        details: error.message,
        };
    }
    }

    // Generic BaseError handling
    return {
    type: "RawError",
    message: error.shortMessage || "Base error occurred",
    details: error.message,
    };
}

// Fallback for non-BaseError
return {
    type: "UnknownError",
    message: "message" in (error as any) ? (error as any).message : String(error),
    details: error instanceof Error ? error.message : undefined,
};
}

Edit ./app/src/main.tsx to add a Thirdweb provider around your application, by replacing its content with the one below. Then, replace on line 8 the placeholder <THIRDWEB_CLIENTID> (including the delimiters < and >!) with your own clientId configured on the Thirdweb dashboard here:

import { createRoot } from "react-dom/client";
import { createThirdwebClient } from "thirdweb";
import { ThirdwebProvider } from "thirdweb/react";
import App from "./App.tsx";
import "./index.css";

const client = createThirdwebClient({
clientId: "<THIRDWEB_CLIENTID>",
});

createRoot(document.getElementById("root")!).render(
<ThirdwebProvider>
    <App thirdwebClient={client} />
</ThirdwebProvider>
);

ThirdwebProvider encapsulates your application to inject account context and wrapped Viem functions

Edit ./app/src/App.tsx to have this code:

import { Marketpulse, Marketpulse__factory } from "./typechain-types";

import BigNumber from "bignumber.js";
import { useEffect, useState } from "react";
import "./App.css";

import {
  defineChain,
  getContract,
  prepareContractCall,
  readContract,
  sendTransaction,
  ThirdwebClient,
  waitForReceipt,
} from "thirdweb";
import { ConnectButton, useActiveAccount } from "thirdweb/react";
import { createWallet, inAppWallet } from "thirdweb/wallets";
import { parseEther } from "viem";
import { etherlinkShadownetTestnet } from "viem/chains";
import { extractErrorDetails } from "./DecodeEvmTransactionLogsArgs";
import CONTRACT_ADDRESS_JSON from "./deployed_addresses.json";

const wallets = [
  inAppWallet({
    auth: {
      options: ["google", "email", "passkey", "phone"],
    },
  }),
  createWallet("io.metamask"),
  createWallet("com.coinbase.wallet"),
  createWallet("io.rabby"),
  createWallet("com.trustwallet.app"),
  createWallet("global.safe"),
];

//copy pasta from Solidity code as Abi and Typechain does not export enum types
enum BET_RESULT {
  WIN = 0,
  DRAW = 1,
  PENDING = 2,
}

interface AppProps {
  thirdwebClient: ThirdwebClient;
}

export default function App({ thirdwebClient }: AppProps) {
  console.log("*************App");

  const marketPulseContract = {
    abi: Marketpulse__factory.abi,
    client: thirdwebClient,
    chain: defineChain(etherlinkShadownetTestnet.id),
    address: CONTRACT_ADDRESS_JSON["MarketpulseModule#Marketpulse"],
  }

  const account = useActiveAccount();

  const [options, setOptions] = useState<Map<string, bigint>>(new Map());

  const [error, setError] = useState<string>("");

  const [status, setStatus] = useState<BET_RESULT>(BET_RESULT.PENDING);
  const [winner, setWinner] = useState<string | undefined>(undefined);
  const [fees, setFees] = useState<number>(0);
  const [betKeys, setBetKeys] = useState<bigint[]>([]);
  const [_bets, setBets] = useState<Marketpulse.BetStruct[]>([]);

  const reload = async () => {
    if (!account?.address) {
      console.log("No address...");
    } else {
      const dataStatus = await readContract({
        contract: getContract(marketPulseContract),
        method: "status",
        params: [],
      });

      const dataWinner = await readContract({
        contract: getContract(marketPulseContract),
        method: "winner",
        params: [],
      });

      const dataFEES = await readContract({
        contract: getContract(marketPulseContract),
        method: "FEES",
        params: [],
      });

      const dataBetKeys = await readContract({
        contract: getContract(marketPulseContract),
        method: "getBetKeys",
        params: [],
      });

      setStatus(dataStatus as unknown as BET_RESULT);
      setWinner(dataWinner as unknown as string);
      setFees(Number(dataFEES as unknown as bigint) / 100);
      setBetKeys(dataBetKeys as unknown as bigint[]);

      console.log(
        "**********status, winner, fees, betKeys",
        status,
        winner,
        fees,
        betKeys
      );
    }
  };

  //first call to load data
  useEffect(() => {
    (() => reload())();
  }, [account?.address]);

  //fetch bets

  useEffect(() => {
    (async () => {
      if (!betKeys || betKeys.length === 0) {
        console.log("no dataBetKeys");
        setBets([]);
      } else {
        const bets = await Promise.all(
          betKeys.map(
            async (betKey) =>
              (await readContract({
                contract: getContract(marketPulseContract),
                method: "getBets",
                params: [betKey],
              })) as unknown as Marketpulse.BetStruct
          )
        );
        setBets(bets);

        //fetch options
        let newOptions = new Map();
        setOptions(newOptions);
        bets.forEach((bet) => {
          if (newOptions.has(bet!.option)) {
            newOptions.set(
              bet!.option,
              newOptions.get(bet!.option)! + bet!.amount
            ); //acc
          } else {
            newOptions.set(bet!.option, bet!.amount);
          }
        });
        setOptions(newOptions);
        console.log("options", newOptions);
      }
    })();
  }, [betKeys]);

  const Ping = () => {
    // Comprehensive error handling
    const handlePing = async () => {
      try {
        const preparedContractCall = await prepareContractCall({
          contract: getContract(marketPulseContract),
          method: "ping",
          params: [],
        });

        console.log("preparedContractCall", preparedContractCall);

        const transaction = await sendTransaction({
          transaction: preparedContractCall,
          account: account!,
        });

        //wait for tx to be included on a block
        const receipt = await waitForReceipt({
          client: thirdwebClient,
          chain: defineChain(etherlinkShadownetTestnet.id),
          transactionHash: transaction.transactionHash,
        });

        console.log("receipt:", receipt);

        setError("");
      } catch (error) {
        const errorParsed = extractErrorDetails(
          error,
          Marketpulse__factory.abi
        );
        setError(errorParsed.message);
      }
    };

    return (
      <span style={{ alignContent: "center", paddingLeft: 100 }}>
        <button onClick={handlePing}>Ping</button>
        {!error || error === "" ? <>&#128994;</> : <>&#128308;</>}
      </span>
    );
  };

  const BetFunction = () => {
    const [amount, setAmount] = useState<BigNumber>(BigNumber(0)); //in Ether decimals
    const [option, setOption] = useState("chiefs");

    const runFunction = async () => {
      try {
        const contract = getContract(marketPulseContract);

        const preparedContractCall = await prepareContractCall({
          contract,
          method: "bet",
          params: [option, parseEther(amount.toString(10))],
          value: parseEther(amount.toString(10)),
        });

        const transaction = await sendTransaction({
          transaction: preparedContractCall,
          account: account!,
        });

        //wait for tx to be included on a block
        const receipt = await waitForReceipt({
          client: thirdwebClient,
          chain: defineChain(etherlinkShadownetTestnet.id),
          transactionHash: transaction.transactionHash,
        });

        console.log("receipt:", receipt);

        await reload();

        setError("");
      } catch (error) {
        const errorParsed = extractErrorDetails(
          error,
          Marketpulse__factory.abi
        );
        console.log("ERROR", error);
        setError(errorParsed.message);
      }
    };

    const calculateOdds = (option: string, amount?: bigint): BigNumber => {
      //check option exists
      if (!options.has(option)) return new BigNumber(0);

      console.log(
        "actuel",
        options && options.size > 0
          ? new BigNumber(options.get(option)!.toString()).toString()
          : 0,
        "total",
        new BigNumber(
          [...options.values()]
            .reduce((acc, newValue) => acc + newValue, amount ? amount : 0n)
            .toString()
        ).toString()
      );

      return options && options.size > 0
        ? new BigNumber(options.get(option)!.toString(10))
            .plus(
              amount ? new BigNumber(amount.toString(10)) : new BigNumber(0)
            )
            .div(
              new BigNumber(
                [...options.values()]
                  .reduce(
                    (acc, newValue) => acc + newValue,
                    amount ? amount : 0n
                  )
                  .toString(10)
              )
            )
            .plus(1)
            .minus(fees)
        : new BigNumber(0);
    };

    return (
      <span style={{ alignContent: "center", width: "100%" }}>
        {status && status === BET_RESULT.PENDING ? (
          <>
            <h3>Choose team</h3>

            <select
              name="options"
              onChange={(e) => setOption(e.target.value)}
              value={option}
            >
              <option value="chiefs"> Chiefs</option>
              <option value="lions">Lions </option>
            </select>
            <h3>Amount</h3>
            <input
              type="number"
              id="amount"
              name="amount"
              required
              onChange={(e) => {
                if (e.target.value && !isNaN(Number(e.target.value))) {
                  //console.log("e.target.value",e.target.value)
                  setAmount(new BigNumber(e.target.value));
                }
              }}
            />

            <hr />
            {account?.address ? <button onClick={runFunction}>Bet</button> : ""}

            <table style={{ fontWeight: "normal", width: "100%" }}>
              <tbody>
                <tr>
                  <td style={{ textAlign: "left" }}>Avg price (decimal)</td>
                  <td style={{ textAlign: "right" }}>
                    {options && options.size > 0
                      ? calculateOdds(option, parseEther(amount.toString(10)))
                          .toFixed(3)
                          .toString()
                      : 0}
                  </td>
                </tr>

                <tr>
                  <td style={{ textAlign: "left" }}>Potential return</td>
                  <td style={{ textAlign: "right" }}>
                    XTZ{" "}
                    {amount
                      ? calculateOdds(option, parseEther(amount.toString(10)))
                          .multipliedBy(amount)
                          .toFixed(6)
                          .toString()
                      : 0}{" "}
                    (
                    {options && options.size > 0
                      ? calculateOdds(option, parseEther(amount.toString(10)))
                          .minus(new BigNumber(1))
                          .multipliedBy(100)
                          .toFixed(2)
                          .toString()
                      : 0}
                    %)
                  </td>
                </tr>
              </tbody>
            </table>
          </>
        ) : (
          <>
            <span style={{ color: "#2D9CDB", fontSize: "1.125rem" }}>
              Outcome: {BET_RESULT[status]}
            </span>
            {winner ? <div style={{ color: "#858D92" }}>{winner}</div> : ""}
          </>
        )}
      </span>
    );
  };

  const resolve = async (option: string) => {
    try {
      const preparedContractCall = await prepareContractCall({
        contract: getContract(marketPulseContract),
        method: "resolveResult",
        params: [option, BET_RESULT.WIN],
      });

      console.log("preparedContractCall", preparedContractCall);

      const transaction = await sendTransaction({
        transaction: preparedContractCall,
        account: account!,
      });

      //wait for tx to be included on a block
      const receipt = await waitForReceipt({
        client: thirdwebClient,
        chain: defineChain(etherlinkShadownetTestnet.id),
        transactionHash: transaction.transactionHash,
      });

      console.log("receipt:", receipt);

      await reload();

      setError("");
    } catch (error) {
      const errorParsed = extractErrorDetails(error, Marketpulse__factory.abi);
      setError(errorParsed.message);
    }
  };

  return (
    <>
      <header>
        <span style={{ display: "flex" }}>
          <h1>Market Pulse</h1>

          <div className="flex items-center gap-4">
            <ConnectButton
              client={thirdwebClient}
              wallets={wallets}
              connectModal={{ size: "compact" }}
              chain={defineChain(etherlinkShadownetTestnet.id)}
            />
          </div>
        </span>
      </header>

      <div id="content" style={{ display: "flex", paddingTop: 10 }}>
        <div style={{ width: "calc(66vw - 4rem)" }}>
          <img
            style={{ maxHeight: "40vh" }}
            src="graph.png"
          />
          <hr />

          <table style={{ width: "inherit" }}>
            <thead>
              <tr>
                <th>Outcome</th>
                <th>% chance</th>
                <th>action</th>
              </tr>
            </thead>
            <tbody>
              {options && options.size > 0 ? (
                [...options.entries()].map(([option, amount]) => (
                  <tr key={option}>
                    <td className="tdTable">
                      <div className="picDiv">
                        <img
                          style={{ objectFit: "cover", height: "inherit" }}
                          src={
                            option +
                            ".png"
                          }
                        ></img>
                      </div>
                      {option}
                    </td>
                    <td>
                      {new BigNumber(amount.toString())
                        .div(
                          new BigNumber(
                            [...options.values()]
                              .reduce((acc, newValue) => acc + newValue, 0n)
                              .toString()
                          )
                        )
                        .multipliedBy(100)
                        .toFixed(2)}
                      %
                    </td>

                    <td>
                      {status && status === BET_RESULT.PENDING ? (
                        <button onClick={() => resolve(option)}>Winner</button>
                      ) : (
                        ""
                      )}
                    </td>
                  </tr>
                ))
              ) : (
                <></>
              )}
            </tbody>
          </table>
        </div>

        <div
          style={{
            width: "calc(33vw - 4rem)",
            boxShadow: "",
            margin: "1rem",
            borderRadius: "12px",
            border: "1px solid #344452",
            padding: "1rem",
          }}
        >
          <span className="tdTable">{<BetFunction />}</span>
        </div>
      </div>

      <footer>
        <h3>Errors</h3>

        <textarea
          readOnly
          rows={10}
          style={{ width: "100%" }}
          value={error}
        ></textarea>

        {account?.address ? <Ping /> : ""}
      </footer>
    </>
  );
}

Explanations:

import { Marketpulse, Marketpulse__factory } from "./typechain-types";: Imports the contract ABI and contract structures
import CONTRACT_ADDRESS_JSON from "./deployed_addresses.json";: Imports the address of the last deployed contract automatically
const wallets = [inAppWallet(...),createWallet(...)}: Configures the Thirdweb wallet connection. Look at the Thirdweb playground and play with the generator.
useActiveAccount: Uses Thirdweb React hooks and functions as a wrapper over the Viem library to get the active account.
const reload = async () => {: Refreshes the smart contract storage (status, winner, fees and mapping keys).
useEffect...[betKeys]);: React effect that reloads all bets from the storage when betKeys is updated.
const Ping = () => {: Checks that the smart contract interaction works. It can be removed in production deployments.
const BetFunction = () => {: Sends your bet to the smart contract, passing along the correct amount of XTZ.
const calculateOdds = (option: string, amount?: bigint): BigNumber => {: Calculates the odds, similar to the onchain function in the smart contract.

To fix the CSS for the page styling, replace the ./app/src/App.css file with this code:

#root {
  margin: 0 auto;
  padding: 2rem;
  text-align: center;

  width: 100vw;
  height: calc(100vh - 4rem);
}

.logo {
  height: 6em;
  padding: 1.5em;
  will-change: filter;
  transition: filter 300ms;
}

.logo:hover {
  filter: drop-shadow(0 0 2em #646cffaa);
}

.logo.react:hover {
  filter: drop-shadow(0 0 2em #61dafbaa);
}

@keyframes logo-spin {
  from {
    transform: rotate(0deg);
  }

  to {
    transform: rotate(360deg);
  }
}

@media (prefers-reduced-motion: no-preference) {
  a:nth-of-type(2) .logo {
    animation: logo-spin infinite 20s linear;
  }
}

header {
  border-bottom: 1px solid #2c3f4f;
  height: 100px;
}

footer {
  border-top: 1px solid #2c3f4f;
}

hr {
  color: #2c3f4f;
  height: 1px;
}

.tdTable {
  align-items: center;
  gap: 1rem;
  width: 100%;
  flex: 3 1 0%;
  display: flex;
  font-weight: bold;
}

.picDiv {
  height: 40px;
  width: 40px;
  min-width: 40px;
  border-radius: 999px;
  position: relative;
  overflow: hidden;
}

.card {
  padding: 2em;
}

.read-the-docs {
  color: #888;
}

h1 {
  margin: unset;
}

Replace the ./app/src/index.css file with this code:

:root {
  font-family: Inter, system-ui, Avenir, Helvetica, Arial, sans-serif;
  line-height: 1.5;
  font-weight: 400;

  color-scheme: light dark;
  color: rgba(255, 255, 255, 0.87);
  background-color: #1D2B39;



  font-synthesis: none;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  font-weight: 500;
  color: #646cff;
  text-decoration: inherit;
}

a:hover {
  color: #535bf2;
}

body {
  margin: 0;
  display: flex;
  place-items: center;
  min-width: 320px;
  min-height: 100vh;

}

h1 {
  font-size: 3.2em;
  line-height: 1.1;
}

button {
  border-radius: 8px;
  border: 1px solid transparent;
  padding: 0.6em 1.2em;
  font-size: 1em;
  font-weight: 500;
  font-family: inherit;
  background-color: #2D9CDB;
  cursor: pointer;
  transition: border-color 0.25s;
}

button:hover {
  border-color: #646cff;
}

button:focus,
button:focus-visible {
  outline: 4px auto -webkit-focus-ring-color;
}

select {
  width: inherit;
  font-size: 0.875rem;
  color: #858D92;
  border-color: #344452;
  transition: color 0.2s;
  text-align: center;
  border-width: 1px;
  border-style: solid;
  align-self: center;
  padding: 1rem 1rem;
  background: #1D2B39;
  outline: none;
  outline-color: currentcolor;
  outline-style: none;
  outline-width: medium;
  border-radius: 8px;
}

input {
  width: calc(100% - 35px);
  font-size: 0.875rem;
  color: #858D92;
  border-color: #344452;
  transition: color 0.2s;
  text-align: center;
  border-width: 1px;
  border-style: solid;
  align-self: center;
  padding: 1rem 1rem;
  background: #1D2B39;
  outline: none;
  outline-color: currentcolor;
  outline-style: none;
  outline-width: medium;
  border-radius: 8px;
}

@media (prefers-color-scheme: light) {
  :root {
    color: #213547;
    background-color: #ffffff;
  }

  a:hover {
    color: #747bff;
  }

  button {
    background-color: #f9f9f9;
  }
}

Edit the file app/tsconfig.app.json to set both "verbatimModuleSyntax" and "erasableSyntaxOnly" to "false".
Build and run the application:
```
npm run build
npm run dev
```
In a web browser, click the Connect button to login with your wallet.
Click the Ping button at the bottom. It should stay green if you can interact with your smart contract with no error messages.
Run a betting scenario:
1. Select Chiefs on the select box on the right corner, choose a small amount like 0.00001 XTZ, and click the Bet button.
2. Confirm the transaction in your wallet. If you don't have enough XTZ in your account, the application shows an OutOfFund error.
3. Optional: Disconnect and connect with another account in your wallet. You can also use the same account to make a second bet.
4. Select Lions on the select box on the right corner, choose a small amount like 0.00001 XTZ, and click the Bet button.
5. Confirm the transaction in your wallet.
  
  Both teams have 50% of chance to win. Note: Default platform fees have been set to 10%, and the odds calculation takes those fees into account.
6. Connect as the account that you deployed the contract with (the admin) and click one of the Winner buttons to resolve the poll.
  
  The page's right-hand corner refreshes and displays the winner of the poll and the application automatically pays the winning bets.
7. Find your transaction resolveResult on the Etherlink Shadownet Testnet explorer at https://shadownet.explorer.etherlink.com. In the Transaction details>Internal txns tab, you should see, if you won something, the expected amount transferred to you from the smart contract address.