call_write_function.dart

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:web3modal_flutter/web3modal_flutter.dart';

import 'package:walletconnect_flutter_v2/apis/sign_api/utils/custom_credentials.dart';
import 'package:http/http.dart' as http;

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  late W3MService _w3mService;

  @override
  void initState() {
    super.initState();
    _initWalletService();
  }

  void _initWalletService() async {
    // Sepolia has to be added in the chain lists so it can be approved
    W3MChainPresets.chains.putIfAbsent(_sepolia.chainId, () => _sepolia);
    _w3mService = W3MService(
      projectId: '....',
      metadata: const PairingMetadata(
        name: '....',
        description: '....',
        url: 'https://..../',
        icons: [],
        redirect: Redirect(
          native: '....://',
          universal: 'https://..../',
        ),
      ),
    );

    _w3mService.onModalConnect.subscribe(_onModalConnect);
    _w3mService.onModalDisconnect.subscribe(_onModalDisconnect);

    await _w3mService.init();
    setState(() {});
  }

  void _onModalConnect(ModalConnect? event) async {
    debugPrint('_onModalConnect($event)');
    setState(() {});
  }

  void _onModalDisconnect(ModalDisconnect? event) {
    debugPrint('_onModalDisconnect($event)');
    setState(() {});
  }

  Future<void> _callWriteFunction() async {
    final abi = await rootBundle.loadString('....abi.json');
    const contractAddress = '0x52....';
    _w3mService.launchConnectedWallet();
    try {
      final deployedContract = DeployedContract(
        ContractAbi.fromJson(abi, '....'),
        EthereumAddress.fromHex(contractAddress),
      );
      await requestWriteContract(
        topic: _w3mService.session?.topic ?? '',
        chainId: 'eip155:11155111',
        rpcUrl: 'https://ethereum-sepolia.publicnode.com',
        deployedContract: deployedContract,
        functionName: 'subscribe',
        parameters: [],
        transaction: Transaction(
          from: EthereumAddress.fromHex(_w3mService.session!.address!),
          value: EtherAmount.fromInt(EtherUnit.finney, 1),
        ),
      );
    } catch (e, s) {
      debugPrint('Error calling write function: $e, $s');
    }
  }

  Future<dynamic> requestWriteContract({
    required String topic,
    required String chainId,
    required String rpcUrl,
    required DeployedContract deployedContract,
    required String functionName,
    required Transaction transaction,
    String? method,
    List<dynamic> parameters = const [],
  }) async {
    final credentials = CustomCredentials(
      signEngine: _w3mService.web3App!.signEngine,
      topic: topic,
      chainId: chainId,
      address: transaction.from!,
      method: method,
    );
    final trx = Transaction.callContract(
      contract: deployedContract,
      function: deployedContract.function(functionName),
      from: credentials.address,
      value: transaction.value,
      parameters: parameters,
    );

    if (chainId.contains(':')) {
      chainId = chainId.split(':').last;
    }
    return await Web3Client(rpcUrl, http.Client()).sendTransaction(
      credentials,
      trx,
      chainId: int.parse(chainId),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: Center(
        child: ElevatedButton(
          onPressed: _w3mService.isConnected
              ? () {
                  _callWriteFunction();
                }
              : null,
          child: const Text('Call Write Function'),
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () async {
          _w3mService.openModal(context);
        },
        child: Icon(
          _w3mService.isConnected
              ? Icons.link_outlined
              : Icons.link_off_outlined,
          size: 30.0,
        ),
      ),
    );
  }
}

final _sepolia = W3MChainInfo(
  chainName: 'Sepolia Testnet',
  chainId: '11155111',
  namespace: 'eip155:11155111',
  tokenName: 'SEP',
  rpcUrl: 'https://eth-sepolia.g.alchemy.com/v2/kgakyspjgeajykfh',
  blockExplorer: W3MBlockExplorer(
    name: 'Sepolia Etherscan',
    url: 'https://sepolia.etherscan.io/',
  ),
);