API.dart

import 'dart:async';
import 'dart:convert';
import 'dart:io';
import 'dart:typed_data';

import 'package:bitcoin_flutter/bitcoin_flutter.dart';
import 'package:bitcoin_flutter/bitcoin_flutter.dart' as bitf;
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:http/http.dart' as http;
import 'package:shared_preferences/shared_preferences.dart';
import 'package:flutter_dotenv/flutter_dotenv.dart';
import 'package:versacoin/Utils.dart';
// import 'package:bitbox/bitbox.dart' as Bitbox;
import 'package:web3dart/web3dart.dart';
import 'package:web3dart/web3dart.dart' as w3d;
import 'package:convert/convert.dart';

class API extends ChangeNotifier {

  // ParaSwap

  Future<dynamic> paraSwapGetTokens() async {
    var res = await http.get(Uri.parse("https://apiv4.paraswap.io/v2/tokens/3"),
      headers: {
        'Content-Type': 'application/json',
      },).catchError((onError) {
      print("paraSwapGetTokens response >> failure: " + onError.toString());
    });

    print("paraSwapGetTokens response >> " + res.body);

    if (res.statusCode == 200) {
      return jsonDecode(res.body);
    } else {
      // Fluttertoast.showToast(toastLength: Toast.LENGTH_LONG, msg: jsonDecode(res.body)["responseMsg"]);
      return jsonDecode(res.body);
    }
  }

  Future<dynamic> paraSwapGetPairPrice(String ethAddress, String toTokenAddress, String fromTokenAddress, String amountInWei) async {
    print("amountInWei: $amountInWei");

    var res = await http.get(Uri.parse("https://apiv4.paraswap.io/v2/prices?"
        "userAddress=$ethAddress"
        "&from=$fromTokenAddress"
        "&to=$toTokenAddress"
        "&amount=$amountInWei"
        "&side=SELL"
        "&network=3"),
      headers: {
        'Content-Type': 'application/json',
      },).catchError((onError) {
      print("paraSwapGetPairPrice response >> failure: " + onError.toString());
    });

    print("paraSwapGetPairPrice response >> " + res.body);

    if (res.statusCode == 200) {
      return jsonDecode(res.body);
    } else {
      // Fluttertoast.showToast(toastLength: Toast.LENGTH_LONG, msg: jsonDecode(res.body)["responseMsg"]);
      return jsonDecode(res.body);
    }
  }

  Future<dynamic> paraSwapBuildTransaction(String privateKey, int toDecimals, int fromDecimals, String ethAddress, dynamic priceRouteJson, String toTokenAddress, String fromTokenAddress, String topriceWithSlippage, String fromAmountInWei) async {
    var approveRes = await paraSwapApproveTransaction(privateKey, ethAddress, toTokenAddress, fromTokenAddress, topriceWithSlippage, fromAmountInWei);
    print("approveRes: $approveRes");
    var body = json.encode({
      "toDecimals": toDecimals,
      "fromDecimals": fromDecimals,
      "referrer": 'chucknorris',
      "userAddress": ethAddress,
      "destAmount": topriceWithSlippage,
      "srcAmount": fromAmountInWei,
      "destToken": toTokenAddress,
      "srcToken": fromTokenAddress,
      "priceRoute": priceRouteJson,
    });

    print("body: $body");

    var res = await http.post(Uri.parse("https://apiv4.paraswap.io/v2/transactions/3"),
        headers: {
          'Content-Type': 'application/json',
        }, body: body).catchError((onError) {
      print("paraSwapBuildTransaction response >> failure: " + onError.toString());
    });

    print("paraSwapBuildTransaction response >> " + res.body);

    if (res.statusCode == 200) {
      return jsonDecode(res.body);
    } else {
      // Fluttertoast.showToast(toastLength: Toast.LENGTH_LONG, msg: jsonDecode(res.body)["responseMsg"]);
      return jsonDecode(res.body);
    }
  }

  Future<dynamic> paraSwapApproveTransaction(String privateKey, String ethAddress, String toTokenAddress, String fromTokenAddress, String topriceWithSlippage, String fromAmountInWei) async {
    http.Client httpClient = http.Client();
    // Web3Client ethClient = Web3Client('https://mainnet.infura.io/v3/976f66afa6ee4b25ac3b40bbdb17dc47', httpClient);
    Web3Client ethClient = Web3Client('https://ropsten.infura.io/v3/976f66afa6ee4b25ac3b40bbdb17dc47', httpClient);
    // var res = await submit(ethClient, privateKey, 'transferFrom', [EthereumAddress.fromHex(toTokenAddress), EthereumAddress.fromHex(ethAddress), EthereumAddress.fromHex(ethAddress), BigInt.from(num.parse(topriceWithSlippage))]);
    // return res;
    var allowAndApproveRes = await allowAndApprove(ethClient, privateKey, ethAddress, toTokenAddress, fromTokenAddress, topriceWithSlippage, fromAmountInWei);
    print('allowAndApproveRes: $allowAndApproveRes');
    return allowAndApproveRes;
  }

  Future<DeployedContract> loadContract(String contractAddress) async {
    String abiCode = await rootBundle.loadString("assets/erc20.json");
    final contract = DeployedContract(ContractAbi.fromJson(abiCode, "ERC20"), EthereumAddress.fromHex(contractAddress));
    return contract;
  }


  Future<List<dynamic>> query(Web3Client ethClient, String tokenAddress, String functionName, List<dynamic> args) async {
    DeployedContract contract = await loadContract(tokenAddress);
    final ethFunction = contract.function(functionName);
    final data = await ethClient.call(contract: contract, function: ethFunction, params: args);
    return data;
  }

  Future<String> submit(Web3Client ethClient, String privateKey, String tokenAddress, String functionName, List<dynamic> args) async {
    EthPrivateKey credentials = EthPrivateKey.fromHex(privateKey);
    DeployedContract contract = await loadContract(tokenAddress);
    final ethFunction = contract.function(functionName);
    var result = await ethClient.sendTransaction(
      credentials,
      w3d.Transaction.callContract(
        contract: contract,
        function: ethFunction,
        parameters: args,
      ),
    );
    return result;
  }



  Future<dynamic> allowAndApprove(Web3Client ethClient, String privateKey, String ethAddress, String toTokenAddress, String fromTokenAddress, String topriceWithSlippage, String fromAmountInWei) async {
    try {
      // String AUGUSTUS_SPENDER = '0xb70Bc06D2c9Bf03b3373799606dc7d39346c06B3'; //from augustus.getTokenTransferProxy()
      String AUGUSTUS_SPENDER = '0xDb28dc14E5Eb60559844F6f900d23Dce35FcaE33'; // ropsten.

      BigInt srcAmount = BigInt.parse(fromAmountInWei);

      BigInt balance = BigInt.parse((await query(ethClient, fromTokenAddress, 'balanceOf', [EthereumAddress.fromHex(ethAddress)])).toString().replaceAll("[", "").replaceAll("]", ""));

      if (balance<srcAmount) {
        return '$balance isLessThan srcAmount $srcAmount';
      }

      print('balance: '+ balance.toString());
      print('srcAmount: '+ srcAmount.toString());

      if (fromTokenAddress != "0xeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee") {
        BigInt allowance = BigInt.parse((await query(ethClient, fromTokenAddress, 'allowance', [EthereumAddress.fromHex(ethAddress), EthereumAddress.fromHex(AUGUSTUS_SPENDER)])).toString().replaceAll("[", "").replaceAll("]", ""));
        print('allowance: '+ allowance.toString());

        if (allowance<srcAmount) {
          print('Approval needed, allowance = '+ allowance.toString());

          var res = await submit(ethClient, privateKey, fromTokenAddress, 'approve', [EthereumAddress.fromHex(AUGUSTUS_SPENDER), srcAmount]);//Can also approve  ps.approve(from.address, srcAmount) but it has to be called on each tx
          print('approved: $res');
        }
      }

      return 'allowance & approval done';
    } catch (error) {
      print('error'+ error.toString());
    }
  }

}