Merge branch 'flutter-upgrade' of https://github.com/cake-tech/cake_wallet into cake-phone

cw_core/lib/crypto_currency.dart

@@ -51,6 +51,23 @@ class CryptoCurrency extends EnumerableItem<int> with Serializable<int> {
     CryptoCurrency.zec,
     CryptoCurrency.zen,
     CryptoCurrency.xvg,
+    CryptoCurrency.usdcpoly,
+    CryptoCurrency.dcr,
+    CryptoCurrency.husd,
+    CryptoCurrency.kmd,
+    CryptoCurrency.mana,
+    CryptoCurrency.maticpoly,
+    CryptoCurrency.matic,
+    CryptoCurrency.mkr,
+    CryptoCurrency.near,
+    CryptoCurrency.oxt,
+    CryptoCurrency.paxg,
+    CryptoCurrency.pivx,
+    CryptoCurrency.rune,
+    CryptoCurrency.rvn,
+    CryptoCurrency.scrt,
+    CryptoCurrency.uni,
+    CryptoCurrency.stx,
   ];
 
   static const xmr = CryptoCurrency(title: 'XMR', iconPath: 'assets/images/monero_icon.png', name: 'Monero', raw: 0);
@@ -102,6 +119,26 @@ class CryptoCurrency extends EnumerableItem<int> with Serializable<int> {
   static const zen = CryptoCurrency(title: 'ZEN', iconPath: 'assets/images/zen_icon.png', raw: 44);
   static const xvg = CryptoCurrency(title: 'XVG', name: 'Verge', iconPath: 'assets/images/xvg_icon.png', raw: 45);
 
+  static const usdcpoly = CryptoCurrency(title: 'USDC', iconPath: 'assets/images/usdc_icon.png', tag: 'POLY', raw: 46);
+  static const dcr = CryptoCurrency(title: 'DCR', iconPath: 'assets/images/dcr_icon.png', raw: 47);
+  static const husd = CryptoCurrency(title: 'HUSD', iconPath: 'assets/images/husd_icon.png', tag: 'ETH', raw: 48);
+  static const kmd = CryptoCurrency(title: 'KMD', iconPath: 'assets/images/kmd_icon.png', raw: 49);
+  static const mana = CryptoCurrency(title: 'MANA', iconPath: 'assets/images/mana_icon.png', tag: 'ETH', raw: 50);
+  static const maticpoly = CryptoCurrency(title: 'MATIC', iconPath: 'assets/images/matic_icon.png', tag: 'POLY', raw: 51);
+  static const matic = CryptoCurrency(title: 'MATIC', iconPath: 'assets/images/matic_icon.png', tag: 'ETH', raw: 52);
+  static const mkr = CryptoCurrency(title: 'MKR', iconPath: 'assets/images/mkr_icon.png', tag: 'ETH', raw: 53);
+  static const near = CryptoCurrency(title: 'NEAR', iconPath: 'assets/images/near_icon.png', raw: 54);
+  static const oxt = CryptoCurrency(title: 'OXT', iconPath: 'assets/images/oxt_icon.png', tag: 'ETH', raw: 55);
+  static const paxg = CryptoCurrency(title: 'PAXG', iconPath: 'assets/images/paxg_icon.png', tag: 'ETH', raw: 56);
+  static const pivx = CryptoCurrency(title: 'PIVX', iconPath: 'assets/images/pivx_icon.png', raw: 57);
+  static const rune = CryptoCurrency(title: 'RUNE', iconPath: 'assets/images/rune_icon.png', raw: 58);
+  static const rvn = CryptoCurrency(title: 'RVN', iconPath: 'assets/images/rvn_icon.png', raw: 59);
+  static const scrt = CryptoCurrency(title: 'SCRT', iconPath: 'assets/images/scrt_icon.png', raw: 60);
+  static const uni = CryptoCurrency(title: 'UNI', iconPath: 'assets/images/uni_icon.png', tag: 'ETH', raw: 61);
+  static const stx = CryptoCurrency(title: 'STX', iconPath: 'assets/images/stx_icon.png', raw: 62);
+
+
+
   static CryptoCurrency deserialize({required int raw}) {
     switch (raw) {
       case 0:
@@ -196,6 +233,40 @@ class CryptoCurrency extends EnumerableItem<int> with Serializable<int> {
         return CryptoCurrency.zen;
       case 45:
         return CryptoCurrency.xvg;
+      case 46:
+        return CryptoCurrency.usdcpoly;
+      case 47:
+        return CryptoCurrency.dcr;
+      case 48:
+        return CryptoCurrency.husd;
+      case 49:
+        return CryptoCurrency.kmd;
+      case 50:
+        return CryptoCurrency.mana;
+      case 51:
+        return CryptoCurrency.maticpoly;
+      case 52:
+        return CryptoCurrency.matic;
+      case 53:
+        return CryptoCurrency.mkr;
+      case 54:
+        return CryptoCurrency.near;
+      case 55:
+        return CryptoCurrency.oxt;
+      case 56:
+        return CryptoCurrency.paxg;
+      case 57:
+        return CryptoCurrency.pivx;
+      case 58:
+        return CryptoCurrency.rune;
+      case 59:
+        return CryptoCurrency.rvn;
+      case 60:
+        return CryptoCurrency.scrt;
+      case 61:
+        return CryptoCurrency.uni;
+      case 62:
+        return CryptoCurrency.stx;
       default:
         throw Exception('Unexpected token: $raw for CryptoCurrency deserialize');
     }
@@ -295,6 +366,40 @@ class CryptoCurrency extends EnumerableItem<int> with Serializable<int> {
         return CryptoCurrency.zen;
       case 'xvg':
         return CryptoCurrency.xvg;
+      case 'usdcpoly':
+        return CryptoCurrency.usdcpoly;
+      case 'dcr':
+        return CryptoCurrency.dcr;
+      case 'husd':
+        return CryptoCurrency.husd;
+      case 'kmd':
+        return CryptoCurrency.kmd;
+      case 'mana':
+        return CryptoCurrency.mana;
+      case 'maticpoly':
+        return CryptoCurrency.maticpoly;
+      case 'matic':
+        return CryptoCurrency.matic;
+      case 'mkr':
+        return CryptoCurrency.mkr;
+      case 'near':
+        return CryptoCurrency.near;
+      case 'oxt':
+        return CryptoCurrency.oxt;
+      case 'paxg':
+        return CryptoCurrency.paxg;
+      case 'pivx':
+        return CryptoCurrency.pivx;
+      case 'rune':
+        return CryptoCurrency.rune;
+      case 'rvn':
+        return CryptoCurrency.rvn;
+      case 'scrt':
+        return CryptoCurrency.scrt;
+      case 'uni':
+        return CryptoCurrency.uni;
+      case 'stx':
+        return CryptoCurrency.stx;
       default:
         throw Exception('Unexpected token: $raw for CryptoCurrency fromString');
     }

lib/core/address_validator.dart

@@ -17,39 +17,25 @@ class AddressValidator extends TextValidator {
       case CryptoCurrency.ada:
         return '^[0-9a-zA-Z]{59}\$|^[0-9a-zA-Z]{92}\$|^[0-9a-zA-Z]{104}\$'
             '|^[0-9a-zA-Z]{105}\$|^addr1[0-9a-zA-Z]{98}\$';
-      case CryptoCurrency.ape:
-        return '0x[0-9a-zA-Z]';
-      case CryptoCurrency.avaxc:
-        return '0x[0-9a-zA-Z]';
-      case CryptoCurrency.bch:
-        return '[0-9a-zA-Z]';
-      case CryptoCurrency.bnb:
-        return '[0-9a-zA-Z]';
       case CryptoCurrency.btc:
         return '^1[0-9a-zA-Z]{32}\$|^1[0-9a-zA-Z]{33}\$|^3[0-9a-zA-Z]{32}\$'
             '|^3[0-9a-zA-Z]{33}\$|^bc1[0-9a-zA-Z]{39}\$|^bc1[0-9a-zA-Z]{59}\$';
-      case CryptoCurrency.dai:
-        return '[0-9a-zA-Z]';
-      case CryptoCurrency.dash:
-        return '[0-9a-zA-Z]';
-      case CryptoCurrency.eos:
-        return '[0-9a-zA-Z]';
-      case CryptoCurrency.eth:
-        return '0x[0-9a-zA-Z]';
-      case CryptoCurrency.ltc:
-        return '[0-9a-zA-Z]';
       case CryptoCurrency.nano:
         return '[0-9a-zA-Z_]';
-      case CryptoCurrency.trx:
-        return '[0-9a-zA-Z]';
       case CryptoCurrency.usdc:
+      case CryptoCurrency.usdcpoly:
+      case CryptoCurrency.husd:
+      case CryptoCurrency.ape:
+      case CryptoCurrency.avaxc:
+      case CryptoCurrency.eth:
+      case CryptoCurrency.mana:
+      case CryptoCurrency.matic:
+      case CryptoCurrency.maticpoly:
+      case CryptoCurrency.mkr:
+      case CryptoCurrency.oxt:
+      case CryptoCurrency.paxg:
+      case CryptoCurrency.uni:
         return '0x[0-9a-zA-Z]';
-      case CryptoCurrency.usdt:
-        return '[0-9a-zA-Z]';
-      case CryptoCurrency.usdterc20:
-        return '[0-9a-zA-Z]';
-      case CryptoCurrency.xlm:
-        return '[0-9a-zA-Z]';
       case CryptoCurrency.xrp:
         return '^[0-9a-zA-Z]{34}\$|^X[0-9a-zA-Z]{46}\$';
       case CryptoCurrency.xhv:
@@ -67,6 +53,16 @@ class AddressValidator extends TextValidator {
       case CryptoCurrency.xnok:
       case CryptoCurrency.xnzd:
       case CryptoCurrency.xusd:
+      case CryptoCurrency.usdt:
+      case CryptoCurrency.usdterc20:
+      case CryptoCurrency.xlm:
+      case CryptoCurrency.trx:
+      case CryptoCurrency.dai:
+      case CryptoCurrency.dash:
+      case CryptoCurrency.eos:
+      case CryptoCurrency.ltc:
+      case CryptoCurrency.bch:
+      case CryptoCurrency.bnb:
         return '[0-9a-zA-Z]';
       case  CryptoCurrency.hbar:
         return '[0-9a-zA-Z.]';
@@ -74,6 +70,22 @@ class AddressValidator extends TextValidator {
         return '^zs[0-9a-zA-Z]{75}';
       case CryptoCurrency.zec:
         return '^t1[0-9a-zA-Z]{33}\$|^t3[0-9a-zA-Z]{33}\$';
+      case CryptoCurrency.dcr:
+        return 'D[ksecS]([0-9a-zA-Z])+';
+      case CryptoCurrency.rvn:
+        return '[Rr]([1-9a-km-zA-HJ-NP-Z]){33}';
+      case CryptoCurrency.near:
+        return '[0-9a-f]{64}';
+      case CryptoCurrency.rune:
+        return 'thor1[0-9a-z]{38}';
+      case CryptoCurrency.scrt:
+        return 'secret1[0-9a-z]{38}';
+      case CryptoCurrency.stx:
+        return 'S[MP][0-9a-zA-Z]+';
+      case CryptoCurrency.kmd:
+        return 'R[0-9a-zA-Z]{33}';
+      case CryptoCurrency.pivx:
+        return 'D([1-9a-km-zA-HJ-NP-Z]){33}';
       default:
         return '[0-9a-zA-Z]';
     }
@@ -160,6 +172,30 @@ class AddressValidator extends TextValidator {
         return null;
       case CryptoCurrency.zec:
         return null;
+      case CryptoCurrency.kmd:
+      case CryptoCurrency.pivx:
+      case CryptoCurrency.rvn:
+        return [34];
+      case CryptoCurrency.dcr:
+        return [35];
+      case CryptoCurrency.stx:
+        return [40, 41, 42];
+      case CryptoCurrency.usdcpoly:
+      case CryptoCurrency.husd:
+      case CryptoCurrency.mana:
+      case CryptoCurrency.matic:
+      case CryptoCurrency.maticpoly:
+      case CryptoCurrency.mkr:
+      case CryptoCurrency.oxt:
+      case CryptoCurrency.paxg:
+      case CryptoCurrency.uni:
+        return [42];
+      case CryptoCurrency.rune:
+        return [43];
+      case CryptoCurrency.scrt:
+        return [45];
+      case CryptoCurrency.near:
+        return [64];
       default:
         return [];
     }

lib/exchange/sideshift/sideshift_exchange_provider.dart

@@ -16,16 +16,7 @@ import 'package:flutter/foundation.dart';
 import 'package:http/http.dart';
 
 class SideShiftExchangeProvider extends ExchangeProvider {
-  SideShiftExchangeProvider()
-      : super(
-            pairList: CryptoCurrency.all
-                .where((i) => i != CryptoCurrency.xhv)
-                .map((i) => CryptoCurrency.all
-                    .where((i) => i != CryptoCurrency.xhv)
-                    .map((k) => ExchangePair(from: i, to: k, reverse: true))
-                    .where((c) => c != null))
-                .expand((i) => i)
-                .toList());
+  SideShiftExchangeProvider() : super(pairList: _supportedPairs());
 
   static const affiliateId = secrets.sideShiftAffiliateId;
   static const apiBaseUrl = 'https://sideshift.ai/api';
@@ -34,6 +25,35 @@ class SideShiftExchangeProvider extends ExchangeProvider {
   static const quotePath = '/v1/quotes';
   static const permissionPath = '/v1/permissions';
 
+  static const List<CryptoCurrency> _notSupported = [
+    CryptoCurrency.xhv,
+    CryptoCurrency.dcr,
+    CryptoCurrency.husd,
+    CryptoCurrency.kmd,
+    CryptoCurrency.mkr,
+    CryptoCurrency.near,
+    CryptoCurrency.oxt,
+    CryptoCurrency.paxg,
+    CryptoCurrency.pivx,
+    CryptoCurrency.rune,
+    CryptoCurrency.rvn,
+    CryptoCurrency.scrt,
+    CryptoCurrency.stx,
+  ];
+
+  static List<ExchangePair> _supportedPairs() {
+    final supportedCurrencies = CryptoCurrency.all
+        .where((element) => !_notSupported.contains(element))
+        .toList();
+
+    return supportedCurrencies
+        .map((i) => supportedCurrencies
+            .map((k) => ExchangePair(from: i, to: k, reverse: true))
+            .where((c) => c != null))
+        .expand((i) => i)
+        .toList();
+  }
+
   @override
   ExchangeProviderDescription get description =>
       ExchangeProviderDescription.sideShift;
@@ -270,6 +290,14 @@ class SideShiftExchangeProvider extends ExchangeProvider {
         return currency.tag!.toLowerCase();
       case CryptoCurrency.usdterc20:
         return 'usdtErc20';
+      case CryptoCurrency.usdttrc20:
+        return 'usdtTrc20';
+      case CryptoCurrency.usdcpoly:
+        return 'usdcpolygon';
+      case CryptoCurrency.usdcsol:
+        return 'usdcsol';
+      case CryptoCurrency.maticpoly:
+        return 'polygon';
       default:
         return currency.title.toLowerCase();
     }

lib/exchange/simpleswap/simpleswap_exchange_provider.dart

@@ -17,8 +17,11 @@ class SimpleSwapExchangeProvider extends ExchangeProvider {
   SimpleSwapExchangeProvider()
       : super(
             pairList: CryptoCurrency.all
-                .map((i) =>
-                    CryptoCurrency.all.map((k) => ExchangePair(from: i, to: k, reverse: true)).where((c) => c != null))
+                .where((i) => i != CryptoCurrency.zaddr)
+                .map((i) => CryptoCurrency.all
+                    .where((i) => i != CryptoCurrency.zaddr)
+                    .map((k) => ExchangePair(from: i, to: k, reverse: true))
+                    .where((c) => c != null))
                 .expand((i) => i)
                 .toList());
 
@@ -56,7 +59,7 @@ class SimpleSwapExchangeProvider extends ExchangeProvider {
       final uri = Uri.https(apiAuthority, getEstimatePath, params);
       final response = await get(uri);
 
-      if (response.body == null) return 0.00;
+      if (response.body == null || response.body == "null") return 0.00;
       final data = json.decode(response.body) as String;
     
       return double.parse(data);
@@ -151,8 +154,8 @@ class SimpleSwapExchangeProvider extends ExchangeProvider {
     }
 
     final responseJSON = json.decode(response.body) as Map<String, dynamic>;
-    final min =  responseJSON['min'] != null ?  double.tryParse(responseJSON['min'] as String) : null;
-    final max = responseJSON['max'] != null ?  double.parse(responseJSON['max'] as String) : null;
+    final min = double.tryParse(responseJSON['min'] as String? ?? '');
+    final max = double.tryParse(responseJSON['max'] as String? ?? '');
 
     return Limits(min: min, max: max);
   }
@@ -217,7 +220,13 @@ class SimpleSwapExchangeProvider extends ExchangeProvider {
       case CryptoCurrency.bnb:
         return currency.tag!.toLowerCase();
       case CryptoCurrency.usdterc20:
-        return 'usdterc';
+        return 'usdterc20';
+      case CryptoCurrency.usdttrc20:
+        return 'usdttrc20';
+      case CryptoCurrency.usdcpoly:
+        return 'usdcpoly';
+      case CryptoCurrency.usdcsol:
+        return 'usdcspl';
       default:
         return currency.title.toLowerCase();
     }

lib/src/screens/exchange/exchange_page.dart

@@ -179,6 +179,7 @@ class ExchangePage extends BasePage {
                             padding: EdgeInsets.fromLTRB(24, 100, 24, 32),
                             child: Observer(
                               builder: (_) => ExchangeCard(
+                                onDispose: disposeBestRateSync,
                                 hasAllAmount: exchangeViewModel.hasAllAmount,
                                 allAmount: exchangeViewModel.hasAllAmount
                                     ? () => exchangeViewModel
@@ -265,6 +266,7 @@ class ExchangePage extends BasePage {
                             EdgeInsets.only(top: 29, left: 24, right: 24),
                             child: Observer(
                                 builder: (_) => ExchangeCard(
+                                  onDispose: disposeBestRateSync,
                                   amountFocusNode: _receiveAmountFocus,
                                   addressFocusNode: _receiveAddressFocus,
                                   key: receiveKey,
@@ -743,13 +745,13 @@ class ExchangePage extends BasePage {
       if (_receiveAmountFocus.hasFocus) {
         exchangeViewModel.isFixedRateMode = true;
       }
-      exchangeViewModel.changeReceiveAmount(amount: receiveAmountController.text);
+      // exchangeViewModel.changeReceiveAmount(amount: receiveAmountController.text);
     });
 
     _depositAmountFocus.addListener(() {
       exchangeViewModel.isFixedRateMode = false;
-      exchangeViewModel.changeDepositAmount(
-        amount: depositAmountController.text);
+      // exchangeViewModel.changeDepositAmount(
+      //   amount: depositAmountController.text);
     });
 
     _isReactionsSet = true;
@@ -791,4 +793,6 @@ class ExchangePage extends BasePage {
     final address = await extractAddressFromParsed(context, parsedAddress);
     return address;
   }
+
+  void disposeBestRateSync() => exchangeViewModel.bestRateSync?.cancel();
 }

lib/src/screens/exchange/widgets/exchange_card.dart

@@ -37,7 +37,8 @@ class ExchangeCard extends StatefulWidget {
       this.addressFocusNode,
       this.allAmount,
       this.onPushPasteButton,
-      this.onPushAddressBookButton})
+      this.onPushAddressBookButton,
+      this.onDispose})
       : super(key: key);
 
   final List<CryptoCurrency> currencies;
@@ -63,6 +64,7 @@ class ExchangeCard extends StatefulWidget {
   final VoidCallback? allAmount;
   final void Function(BuildContext context)? onPushPasteButton;
   final void Function(BuildContext context)? onPushAddressBookButton;
+  final Function()? onDispose;
 
   @override
   ExchangeCardState createState() => ExchangeCardState();
@@ -106,6 +108,13 @@ class ExchangeCardState extends State<ExchangeCard> {
     super.initState();
   }
 
+  @override
+  void dispose() {
+    widget.onDispose?.call();
+
+    super.dispose();
+  }
+
   void changeLimits({String? min, String? max}) {
     setState(() {
       _min = min;

lib/view_model/exchange/exchange_view_model.dart

@@ -1,3 +1,4 @@
+import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 
@@ -59,12 +60,12 @@ abstract class ExchangeViewModelBase with Store {
       receiveCurrency = wallet.currency,
       depositCurrency = wallet.currency,
       providerList = [ChangeNowExchangeProvider(), SideShiftExchangeProvider(), SimpleSwapExchangeProvider()],
-      selectedProviders = ObservableList<ExchangeProvider>(),
-      currentTradeAvailableProviders = SplayTreeMap<double, ExchangeProvider>() {
+      selectedProviders = ObservableList<ExchangeProvider>() {
     const excludeDepositCurrencies = [CryptoCurrency.btt, CryptoCurrency.nano];
     const excludeReceiveCurrencies = [CryptoCurrency.xlm, CryptoCurrency.xrp,
       CryptoCurrency.bnb, CryptoCurrency.btt, CryptoCurrency.nano];
     _initialPairBasedOnWallet();
+
     final Map<String, dynamic> exchangeProvidersSelection = json
         .decode(sharedPreferences.getString(PreferencesKey.exchangeProvidersSelection) ?? "{}") as Map<String, dynamic>;
 
@@ -76,6 +77,11 @@ abstract class ExchangeViewModelBase with Store {
             : (exchangeProvidersSelection[element.title] as bool))
         .toList());
 
+    _setAvailableProviders();
+    _calculateBestRate();
+
+    bestRateSync = Timer.periodic(Duration(seconds: 10), (timer) => _calculateBestRate());
+
     isDepositAddressEnabled = !(depositCurrency == wallet.currency);
     isReceiveAddressEnabled = !(receiveCurrency == wallet.currency);
     depositAmount = '';
@@ -119,8 +125,15 @@ abstract class ExchangeViewModelBase with Store {
   /// Maps in dart are not sorted by default
   /// SplayTreeMap is a map sorted by keys
   /// will use it to sort available providers
-  /// depending on the amount they yield for the current trade
-  SplayTreeMap<double, ExchangeProvider> currentTradeAvailableProviders;
+  /// based on the rate they yield for the current trade
+  ///
+  ///
+  /// initialize with descending comparator
+  /// since we want largest rate first
+  final SplayTreeMap<double, ExchangeProvider> _sortedAvailableProviders =
+          SplayTreeMap<double, ExchangeProvider>((double a, double b) => b.compareTo(a));
+
+  final List<ExchangeProvider> _tradeAvailableProviders = [];
 
   @observable
   ObservableList<ExchangeProvider> selectedProviders;
@@ -191,6 +204,10 @@ abstract class ExchangeViewModelBase with Store {
 
   final SettingsStore _settingsStore;
 
+  double _bestRate = 0.0;
+
+  late Timer bestRateSync;
+
   @action
   void changeDepositCurrency({required CryptoCurrency currency}) {
     depositCurrency = currency;
@@ -210,68 +227,11 @@ abstract class ExchangeViewModelBase with Store {
   }
 
   @action
-  void changeReceiveAmount({required String amount}) {
+  Future<void> changeReceiveAmount({required String amount}) async {
     receiveAmount = amount;
     isReverse = true;
 
-    if (amount == null || amount.isEmpty) {
-      depositAmount = '';
-      receiveAmount = '';
-      return;
-    }
-
-    final _enteredAmount = double.parse(amount.replaceAll(',', '.')) ?? 0;
-
-    currentTradeAvailableProviders.clear();
-    for (var provider in selectedProviders) {
-      /// if this provider is not valid for the current pair, skip it
-      if (!providersForCurrentPair().contains(provider)) {
-        continue;
-      }
-      provider
-          .calculateAmount(
-              from: receiveCurrency,
-              to: depositCurrency,
-              amount: _enteredAmount,
-              isFixedRateMode: isFixedRateMode,
-              isReceiveAmount: true)
-          .then((amount) {
-
-        final from = isFixedRateMode
-            ? receiveCurrency
-            : depositCurrency;
-        final to = isFixedRateMode
-            ? depositCurrency
-            : receiveCurrency;
-
-        provider.fetchLimits(
-          from: from,
-          to: to,
-          isFixedRateMode: isFixedRateMode,
-        ).then((limits) {
-          /// if the entered amount doesn't exceed the limits of this provider
-          if ((limits?.max ?? double.maxFinite) >= _enteredAmount
-              && (limits?.min ?? 0) <= _enteredAmount) {
-            /// add this provider as its valid for this trade
-            /// will be sorted ascending already since
-            /// we seek the least deposit amount
-            currentTradeAvailableProviders[amount] = provider;
-          }
-          return amount;
-        }).then((amount) => depositAmount = _cryptoNumberFormat
-            .format(amount)
-            .toString()
-            .replaceAll(RegExp('\\,'), ''));
-      });
-    }
-  }
-
-  @action
-  void changeDepositAmount({required String amount}) {
-    depositAmount = amount;
-    isReverse = false;
-
-    if (amount == null || amount.isEmpty) {
+    if (amount.isEmpty) {
       depositAmount = '';
       receiveAmount = '';
       return;
@@ -279,93 +239,115 @@ abstract class ExchangeViewModelBase with Store {
 
     final _enteredAmount = double.tryParse(amount.replaceAll(',', '.')) ?? 0;
 
-    currentTradeAvailableProviders.clear();
-    for (var provider in selectedProviders) {
-      /// if this provider is not valid for the current pair, skip it
-      if (!providersForCurrentPair().contains(provider)) {
-        continue;
+    if (_bestRate == 0) {
+      depositAmount = S.current.fetching;
+
+      await _calculateBestRate();
+    }
+
+    depositAmount = _cryptoNumberFormat
+        .format(_enteredAmount / _bestRate)
+        .toString()
+        .replaceAll(RegExp('\\,'), '');
+  }
+
+  @action
+  Future<void> changeDepositAmount({required String amount}) async {
+    depositAmount = amount;
+    isReverse = false;
+
+    if (amount.isEmpty) {
+      depositAmount = '';
+      receiveAmount = '';
+      return;
+    }
+
+    final _enteredAmount = double.tryParse(amount.replaceAll(',', '.')) ?? 0;
+
+    /// in case the best rate was not calculated yet
+    if (_bestRate == 0) {
+      receiveAmount = S.current.fetching;
+
+      await _calculateBestRate();
+    }
+
+    receiveAmount = _cryptoNumberFormat
+        .format(_bestRate * _enteredAmount)
+        .toString()
+        .replaceAll(RegExp('\\,'), '');
+  }
+
+  Future<void> _calculateBestRate() async {
+    final result = await Future.wait<double>(
+        _tradeAvailableProviders
+            .map((element) => element.calculateAmount(
+                from: depositCurrency,
+                to: receiveCurrency,
+                amount: 1,
+                isFixedRateMode: isFixedRateMode,
+                isReceiveAmount: false))
+    );
+
+    _sortedAvailableProviders.clear();
+
+    for (int i=0;i<result.length;i++) {
+      if (result[i] != 0) {
+        /// add this provider as its valid for this trade
+        _sortedAvailableProviders[result[i]] = _tradeAvailableProviders[i];
       }
-      provider
-          .calculateAmount(
-              from: depositCurrency,
-              to: receiveCurrency,
-              amount: _enteredAmount,
-              isFixedRateMode: isFixedRateMode,
-              isReceiveAmount: false)
-          .then((amount) {
-
-        final from = isFixedRateMode
-            ? receiveCurrency
-            : depositCurrency;
-        final to = isFixedRateMode
-            ? depositCurrency
-            : receiveCurrency;
-
-        provider.fetchLimits(
-          from: from,
-          to: to,
-          isFixedRateMode: isFixedRateMode,
-        ).then((limits) {
-
-          /// if the entered amount doesn't exceed the limits of this provider
-          if ((limits?.max ?? double.maxFinite) >= _enteredAmount
-              && (limits?.min ?? 0) <= _enteredAmount) {
-            /// add this provider as its valid for this trade
-            /// subtract from maxFinite so the provider
-            /// with the largest amount would be sorted ascending
-            currentTradeAvailableProviders[double.maxFinite - amount] = provider;
-          }
-          return amount;
-        }).then((amount) => receiveAmount =
-            receiveAmount = _cryptoNumberFormat
-            .format(amount)
-            .toString()
-            .replaceAll(RegExp('\\,'), ''));
-      });
+    }
+    if (_sortedAvailableProviders.isNotEmpty) {
+      _bestRate = _sortedAvailableProviders.keys.first;
     }
   }
 
   @action
-  Future loadLimits() async {
+  Future<void> loadLimits() async {
     if (selectedProviders.isEmpty) {
       return;
     }
 
     limitsState = LimitsIsLoading();
 
-    try {
-      final from = isFixedRateMode
+    final from = isFixedRateMode
         ? receiveCurrency
         : depositCurrency;
-      final to = isFixedRateMode
+    final to = isFixedRateMode
         ? depositCurrency
         : receiveCurrency;
 
-      limits = await selectedProviders.first.fetchLimits(
-          from: from,
-          to: to,
-          isFixedRateMode: isFixedRateMode);
+    double lowestMin = double.maxFinite;
+    double? highestMax = 0.0;
 
-      /// if the first provider limits is bounded then check with other providers
-      /// for the highest maximum limit
-      if (limits.max != null) {
-        for (int i = 1;i < selectedProviders.length;i++) {
-          final Limits tempLimits = await selectedProviders[i].fetchLimits(
-              from: from,
-              to: to,
-              isFixedRateMode: isFixedRateMode);
-
-          /// set the limits with the maximum provider limit
-          /// if there is a provider with null max then it's the maximum limit
-          if ((tempLimits.max ?? double.maxFinite) > limits.max!) {
-            limits = tempLimits;
-          }
-        }
+    for (var provider in selectedProviders) {
+      /// if this provider is not valid for the current pair, skip it
+      if (!providersForCurrentPair().contains(provider)) {
+        continue;
       }
 
+      try {
+        final tempLimits = await provider.fetchLimits(
+            from: from,
+            to: to,
+            isFixedRateMode: isFixedRateMode);
+
+        if (tempLimits.min != null && tempLimits.min! < lowestMin) {
+          lowestMin = tempLimits.min!;
+        }
+        if (highestMax != null && (tempLimits.max ?? double.maxFinite) > highestMax) {
+          highestMax = tempLimits.max;
+        }
+      } catch (e) {
+        continue;
+      }
+    }
+
+    if (lowestMin < double.maxFinite) {
+      limits = Limits(min: lowestMin, max: highestMax);
+
       limitsState = LimitsLoadedSuccessfully(limits: limits);
-    } catch (e) {
-      limitsState = LimitsLoadedFailure(error: e.toString());
+    } else {
+      limitsState = LimitsLoadedFailure(error: 'Limits loading failed');
     }
   }
 
@@ -374,7 +356,7 @@ abstract class ExchangeViewModelBase with Store {
     TradeRequest? request;
     String amount = '';
 
-    for (var provider in currentTradeAvailableProviders.values) {
+    for (var provider in _sortedAvailableProviders.values) {
       if (!(await provider.checkIsAvailable())) {
         continue;
       }
@@ -383,7 +365,7 @@ abstract class ExchangeViewModelBase with Store {
         request = SideShiftRequest(
           depositMethod: depositCurrency,
           settleMethod: receiveCurrency,
-          depositAmount: depositAmount?.replaceAll(',', '.') ?? '',
+          depositAmount: depositAmount.replaceAll(',', '.'),
           settleAddress: receiveAddress,
           refundAddress: depositAddress,
         );
@@ -394,7 +376,7 @@ abstract class ExchangeViewModelBase with Store {
         request = SimpleSwapRequest(
           from: depositCurrency,
           to: receiveCurrency,
-          amount: depositAmount?.replaceAll(',', '.') ?? '',
+          amount: depositAmount.replaceAll(',', '.'),
           address: receiveAddress,
           refundAddress: depositAddress,
         );
@@ -405,8 +387,8 @@ abstract class ExchangeViewModelBase with Store {
         request = XMRTOTradeRequest(
             from: depositCurrency,
             to: receiveCurrency,
-            amount: depositAmount?.replaceAll(',', '.') ?? '',
-            receiveAmount: receiveAmount?.replaceAll(',', '.') ?? '',
+            amount: depositAmount.replaceAll(',', '.'),
+            receiveAmount: receiveAmount.replaceAll(',', '.'),
             address: receiveAddress,
             refundAddress: depositAddress,
             isBTCRequest: isReceiveAmountEntered);
@@ -417,8 +399,8 @@ abstract class ExchangeViewModelBase with Store {
         request = ChangeNowRequest(
             from: depositCurrency,
             to: receiveCurrency,
-            fromAmount: depositAmount?.replaceAll(',', '.') ?? '',
-            toAmount: receiveAmount?.replaceAll(',', '.') ?? '',
+            fromAmount: depositAmount.replaceAll(',', '.'),
+            toAmount: receiveAmount.replaceAll(',', '.'),
             refundAddress: depositAddress,
             address: receiveAddress,
             isReverse: isReverse);
@@ -429,7 +411,7 @@ abstract class ExchangeViewModelBase with Store {
         request = MorphTokenRequest(
             from: depositCurrency,
             to: receiveCurrency,
-            amount: depositAmount?.replaceAll(',', '.') ?? '',
+            amount: depositAmount.replaceAll(',', '.'),
             refundAddress: depositAddress,
             address: receiveAddress);
         amount = depositAmount;
@@ -437,7 +419,7 @@ abstract class ExchangeViewModelBase with Store {
 
       amount = amount.replaceAll(',', '.');
 
-      if (limitsState is LimitsLoadedSuccessfully && amount != null) {
+      if (limitsState is LimitsLoadedSuccessfully) {
         if (double.parse(amount) < limits.min!) {
           continue;
         } else if (limits.max != null && double.parse(amount) > limits.max!) {
@@ -527,7 +509,7 @@ abstract class ExchangeViewModelBase with Store {
     final providers = providerList
         .where((provider) => provider.pairList
             .where((pair) =>
-                pair.from == (from ?? depositCurrency) && pair.to == (to ?? receiveCurrency))
+                pair.from == from && pair.to == to)
             .isNotEmpty)
         .toList();
 
@@ -537,6 +519,10 @@ abstract class ExchangeViewModelBase with Store {
   void _onPairChange() {
     depositAmount = '';
     receiveAmount = '';
+    loadLimits();
+    _setAvailableProviders();
+    _bestRate = 0;
+    _calculateBestRate();
   }
 
   void _initialPairBasedOnWallet() {
@@ -579,11 +565,15 @@ abstract class ExchangeViewModelBase with Store {
   @action
   void addExchangeProvider(ExchangeProvider provider) {
     selectedProviders.add(provider);
+    if (providersForCurrentPair().contains(provider)) {
+      _tradeAvailableProviders.add(provider);
+    }
   }
 
   @action
   void removeExchangeProvider(ExchangeProvider provider) {
     selectedProviders.remove(provider);
+    _tradeAvailableProviders.remove(provider);
   }
 
   @action
@@ -593,13 +583,14 @@ abstract class ExchangeViewModelBase with Store {
     isFixedRateMode = false;
     _defineIsReceiveAmountEditable();
     loadLimits();
+    _bestRate = 0;
+    _calculateBestRate();
 
     final Map<String, dynamic> exchangeProvidersSelection = json
         .decode(sharedPreferences.getString(PreferencesKey.exchangeProvidersSelection) ?? "{}") as Map<String, dynamic>;
 
-    exchangeProvidersSelection.updateAll((key, dynamic value) => false);
-    for (var provider in selectedProviders) {
-      exchangeProvidersSelection[provider.title] = true;
+    for (var provider in providerList) {
+      exchangeProvidersSelection[provider.title] = selectedProviders.contains(provider);
     }
 
     sharedPreferences.setString(
@@ -612,4 +603,12 @@ abstract class ExchangeViewModelBase with Store {
     final providersForPair = providersForCurrentPair();
     return selectedProviders.any((element) => element.isAvailable && providersForPair.contains(element));
   }
+
+  void _setAvailableProviders() {
+    _tradeAvailableProviders.clear();
+
+    _tradeAvailableProviders.addAll(
+        selectedProviders
+            .where((provider) => providersForCurrentPair().contains(provider)));
+  }
 }

lib/view_model/restore_from_backup_view_model.dart

@@ -64,7 +64,7 @@ abstract class RestoreFromBackupViewModelBase with Store {
     } catch (e) {
       var msg = e.toString();
 
-      if (msg == 'Message authentication code (MAC) is invalid') {
+      if (msg.toLowerCase().contains("message authentication code (mac)")) {
         msg = 'Incorrect backup password';
       }