cake_wallet/lib/exchange/changenow/changenow_exchange_provider.dart

import 'dart:convert';
import 'package:cake_wallet/exchange/trade_not_found_exeption.dart';
import 'package:flutter/foundation.dart';
import 'package:http/http.dart';
import 'package:cake_wallet/.secrets.g.dart' as secrets;
import 'package:cake_wallet/entities/crypto_currency.dart';
import 'package:cake_wallet/exchange/exchange_pair.dart';
import 'package:cake_wallet/exchange/exchange_provider.dart';
import 'package:cake_wallet/exchange/limits.dart';
import 'package:cake_wallet/exchange/trade.dart';
import 'package:cake_wallet/exchange/trade_request.dart';
import 'package:cake_wallet/exchange/trade_state.dart';
import 'package:cake_wallet/exchange/changenow/changenow_request.dart';
import 'package:cake_wallet/exchange/exchange_provider_description.dart';
import 'package:cake_wallet/exchange/trade_not_created_exeption.dart';

class ChangeNowExchangeProvider extends ExchangeProvider {
  ChangeNowExchangeProvider()
      : super(
            pairList: CryptoCurrency.all
                .map((i) {
                  return CryptoCurrency.all.map((k) {
                    if (i == CryptoCurrency.btc && k == CryptoCurrency.xmr) {
                      return ExchangePair(from: i, to: k, reverse: false);
                    }

                    if (i == CryptoCurrency.xmr && k == CryptoCurrency.btc) {
                      return null;
                    }

                    return ExchangePair(from: i, to: k, reverse: true);
                  }).where((c) => c != null);
                })
                .expand((i) => i)
                .toList());

  static const apiUri = 'https://changenow.io/api/v1';
  static const apiKey = secrets.change_now_api_key;
  static const _exchangeAmountUriSufix = '/exchange-amount/';
  static const _transactionsUriSufix = '/transactions/';
  static const _minAmountUriSufix = '/min-amount/';

  @override
  String get title => 'ChangeNOW';

  @override
  ExchangeProviderDescription get description =>
      ExchangeProviderDescription.changeNow;

  @override
  Future<Limits> fetchLimits({CryptoCurrency from, CryptoCurrency to}) async {
    final symbol = from.toString() + '_' + to.toString();
    final url = apiUri + _minAmountUriSufix + symbol;
    final response = await get(url);
    final responseJSON = json.decode(response.body) as Map<String, dynamic>;
    final min = responseJSON['minAmount'] as double;

    return Limits(min: min, max: null);
  }

  @override
  Future<Trade> createTrade({TradeRequest request}) async {
    const url = apiUri + _transactionsUriSufix + apiKey;
    final _request = request as ChangeNowRequest;
    final body = {
      'from': _request.from.toString(),
      'to': _request.to.toString(),
      'address': _request.address,
      'amount': _request.amount,
      'refundAddress': _request.refundAddress
    };

    final response = await post(url,
        headers: {'Content-Type': 'application/json'}, body: json.encode(body));

    if (response.statusCode != 200) {
      if (response.statusCode == 400) {
        final responseJSON = json.decode(response.body) as Map<String, dynamic>;
        final error = responseJSON['message'] as String;

        throw TradeNotCreatedException(description, description: error);
      }

      throw TradeNotCreatedException(description);
    }

    final responseJSON = json.decode(response.body) as Map<String, dynamic>;
    final id = responseJSON['id'] as String;
    final inputAddress = responseJSON['payinAddress'] as String;
    final refundAddress = responseJSON['refundAddress'] as String;
    final extraId = responseJSON['payinExtraId'] as String;

    return Trade(
        id: id,
        from: _request.from,
        to: _request.to,
        provider: description,
        inputAddress: inputAddress,
        refundAddress: refundAddress,
        extraId: extraId,
        createdAt: DateTime.now(),
        amount: _request.amount,
        state: TradeState.created);
  }

  @override
  Future<Trade> findTradeById({@required String id}) async {
    final url = apiUri + _transactionsUriSufix + id + '/' + apiKey;
    final response = await get(url);

    if (response.statusCode != 200) {
      if (response.statusCode == 400) {
        final responseJSON = json.decode(response.body) as Map<String, dynamic>;
        final error = responseJSON['message'] as String;

        throw TradeNotFoundException(id,
            provider: description, description: error);
      }

      throw TradeNotFoundException(id, provider: description);
    }

    final responseJSON = json.decode(response.body) as Map<String, dynamic>;
    final fromCurrency = responseJSON['fromCurrency'] as String;
    final from = CryptoCurrency.fromString(fromCurrency);
    final toCurrency = responseJSON['toCurrency'] as String;
    final to = CryptoCurrency.fromString(toCurrency);
    final inputAddress = responseJSON['payinAddress'] as String;
    final expectedSendAmount = responseJSON['expectedSendAmount'].toString();
    final status = responseJSON['status'] as String;
    final state = TradeState.deserialize(raw: status);
    final extraId = responseJSON['payinExtraId'] as String;
    final outputTransaction = responseJSON['payoutHash'] as String;

    return Trade(
        id: id,
        from: from,
        to: to,
        provider: description,
        inputAddress: inputAddress,
        amount: expectedSendAmount,
        state: state,
        extraId: extraId,
        outputTransaction: outputTransaction);
  }

  @override
  Future<double> calculateAmount(
      {CryptoCurrency from, CryptoCurrency to, double amount}) async {
    final url = apiUri +
        _exchangeAmountUriSufix +
        amount.toString() +
        '/' +
        from.toString() +
        '_' +
        to.toString();
    final response = await get(url);
    final responseJSON = json.decode(response.body) as Map<String, dynamic>;
    final estimatedAmount = responseJSON['estimatedAmount'] as double;

    return estimatedAmount;
  }
}