Fixed rate for changenow.

lib/exchange/changenow/changenow_exchange_provider.dart

@@ -16,7 +16,8 @@ import 'package:cake_wallet/exchange/trade_not_created_exeption.dart';
 
 class ChangeNowExchangeProvider extends ExchangeProvider {
   ChangeNowExchangeProvider()
-      : super(
+      : _lastUsedRateId = '',
+        super(
             pairList: CryptoCurrency.all
                 .map((i) => CryptoCurrency.all
                     .map((k) => ExchangePair(from: i, to: k, reverse: true))
@@ -24,13 +25,13 @@ class ChangeNowExchangeProvider extends ExchangeProvider {
                 .expand((i) => i)
                 .toList());
 
-  static const apiUri = 'https://changenow.io/api/v1';
   static const apiKey = secrets.changeNowApiKey;
-  static const _exchangeAmountUriSufix = '/exchange-amount/';
-  static const _transactionsUriSufix = '/transactions/';
-  static const _minAmountUriSufix = '/min-amount/';
-  static const _marketInfoUriSufix = '/market-info/';
-  static const _fixedRateUriSufix = 'fixed-rate/';
+  static const apiAuthority = 'api.changenow.io';
+  static const createTradePath = '/v2/exchange';
+  static const findTradeByIdPath = '/v2/exchange/by-id';
+  static const estimatedAmountPath = '/v2/exchange/estimated-amount';
+  static const rangePath = '/v2/exchange/range';
+  static const apiHeaderKey = 'x-changenow-api-key';
 
   @override
   String get title => 'ChangeNOW';
@@ -45,68 +46,74 @@ class ChangeNowExchangeProvider extends ExchangeProvider {
   @override
   Future<bool> checkIsAvailable() async => true;
 
+  String _lastUsedRateId;
+
+  static String getFlow(bool isFixedRate) => isFixedRate ? 'fixed-rate' : 'standard';
+
   @override
   Future<Limits> fetchLimits({CryptoCurrency from, CryptoCurrency to,
     bool isFixedRateMode}) async {
-    final fromTitle = defineCurrencyTitle(from);
-    final toTitle = defineCurrencyTitle(to);
-    final symbol = fromTitle + '_' + toTitle;
-    final url = isFixedRateMode
-        ? apiUri + _marketInfoUriSufix + _fixedRateUriSufix + apiKey
-        : apiUri + _minAmountUriSufix + symbol;
-    final response = await get(url);
+    final headers = {apiHeaderKey: apiKey};
+    final normalizedFrom = normalizeCryptoCurrency(from);
+    final normalizedTo = normalizeCryptoCurrency(to);
+    final flow = getFlow(isFixedRateMode);
+    final params = <String, String>{
+      'fromCurrency': normalizedFrom,
+      'toCurrency': normalizedTo,
+      'flow': flow};
+    final uri = Uri.https(apiAuthority, rangePath, params);
+    final response = await get(uri, headers: headers);
     
-    if (isFixedRateMode) {
-      final responseJSON = json.decode(response.body) as List<dynamic>;
-
-      for (var elem in responseJSON) {
-        final elemFrom = elem["from"] as String;
-        final elemTo = elem["to"] as String;
-
-        if ((elemFrom == fromTitle) && (elemTo == toTitle)) {
-          final min = elem["min"] as double;
-          final max = elem["max"] as double;
-
-          return Limits(min: min, max: max);
-        }
-      }
-      return Limits(min: 0, max: 0);
-    } else {
+    if (response.statusCode == 400) {
       final responseJSON = json.decode(response.body) as Map<String, dynamic>;
-      final min = responseJSON['minAmount'] as double;
-
-      return Limits(min: min, max: null);
+      final error = responseJSON['error'] as String;
+      final message = responseJSON['message'] as String;
+      throw Exception('${error}\n$message');
     }
+
+    if (response.statusCode != 200) {
+      return null;
+    }
+
+    final responseJSON = json.decode(response.body) as Map<String, dynamic>;
+    return Limits(
+      min: responseJSON['minAmount'] as double,
+      max: responseJSON['maxAmount'] as double);
   }
 
   @override
   Future<Trade> createTrade({TradeRequest request, bool isFixedRateMode}) async {
-    final url = isFixedRateMode
-    ? apiUri + _transactionsUriSufix + _fixedRateUriSufix + apiKey
-    : apiUri + _transactionsUriSufix + apiKey;
     final _request = request as ChangeNowRequest;
-    final fromTitle = defineCurrencyTitle(_request.from);
-    final toTitle = defineCurrencyTitle(_request.to);
-    final body = {
-      'from': fromTitle,
-      'to': toTitle,
+    final headers = {
+      apiHeaderKey: apiKey,
+      'Content-Type': 'application/json'};
+    final flow = getFlow(isFixedRateMode);
+    final body = <String, String>{
+      'fromCurrency': normalizeCryptoCurrency(_request.from), 
+      'toCurrency': normalizeCryptoCurrency(_request.to), 
+      'fromAmount': _request.fromAmount, 
+      'toAmount': _request.toAmount, 
       'address': _request.address,
-      'amount': _request.amount,
+      'flow': flow,
       '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);
+    if (isFixedRateMode) {
+      body['rateId'] = _lastUsedRateId;
     }
 
-      throw TradeNotCreatedException(description);
+    final uri = Uri.https(apiAuthority, createTradePath);
+    final response = await post(uri, headers: headers, body: json.encode(body));
+    
+    if (response.statusCode == 400) {
+      final responseJSON = json.decode(response.body) as Map<String, dynamic>;
+      final error = responseJSON['error'] as String;
+      final message = responseJSON['message'] as String;
+      throw Exception('${error}\n$message');
+    }
+
+    if (response.statusCode != 200) {
+      return null;
     }
 
     final responseJSON = json.decode(response.body) as Map<String, dynamic>;
@@ -124,16 +131,21 @@ class ChangeNowExchangeProvider extends ExchangeProvider {
         refundAddress: refundAddress,
         extraId: extraId,
         createdAt: DateTime.now(),
-        amount: _request.amount,
+        amount: _request.fromAmount,
         state: TradeState.created);
   }
 
   @override
   Future<Trade> findTradeById({@required String id}) async {
-    final url = apiUri + _transactionsUriSufix + id + '/' + apiKey;
-    final response = await get(url);
+    final headers = {apiHeaderKey: apiKey};
+    final params = <String, String>{'id': id};
+    final uri = Uri.https(apiAuthority,findTradeByIdPath, params);
+    final response = await get(uri, headers: headers);
+
+    if (response.statusCode == 404) {
+      throw TradeNotFoundException(id, provider: description);
+    }
 
-    if (response.statusCode != 200) {
     if (response.statusCode == 400) {
       final responseJSON = json.decode(response.body) as Map<String, dynamic>;
       final error = responseJSON['message'] as String;
@@ -142,7 +154,8 @@ class ChangeNowExchangeProvider extends ExchangeProvider {
           provider: description, description: error);
     }
 
-      throw TradeNotFoundException(id, provider: description);
+    if (response.statusCode != 200) {
+      return null;
     }
 
     final responseJSON = json.decode(response.body) as Map<String, dynamic>;
@@ -151,7 +164,7 @@ class ChangeNowExchangeProvider extends ExchangeProvider {
     final toCurrency = responseJSON['toCurrency'] as String;
     final to = CryptoCurrency.fromString(toCurrency);
     final inputAddress = responseJSON['payinAddress'] as String;
-    final expectedSendAmount = responseJSON['expectedSendAmount'].toString();
+    final expectedSendAmount = responseJSON['expectedAmountFrom'].toString();
     final status = responseJSON['status'] as String;
     final state = TradeState.deserialize(raw: status);
     final extraId = responseJSON['payinExtraId'] as String;
@@ -181,68 +194,46 @@ class ChangeNowExchangeProvider extends ExchangeProvider {
       double amount,
       bool isFixedRateMode,
       bool isReceiveAmount}) async {
-    if (isReceiveAmount && isFixedRateMode) {
-      final url = apiUri + _marketInfoUriSufix + _fixedRateUriSufix + apiKey;
-      final response = await get(url);
-      final responseJSON = json.decode(response.body) as List<dynamic>;
-      final fromTitle = defineCurrencyTitle(from);
-      final toTitle = defineCurrencyTitle(to);
-      var rate = 0.0;
-      var fee = 0.0;
-
-      for (var elem in responseJSON) {
-        final elemFrom = elem["from"] as String;
-        final elemTo = elem["to"] as String;
-
-        if ((elemFrom == toTitle) && (elemTo == fromTitle)) {
-          rate = elem["rate"] as double;
-          fee = elem["minerFee"] as double;
-          break;
-        }
+    try {
+      if (amount == 0) {
+        return 0.0;
       }
 
-      final estimatedAmount = (amount == 0.0)||(rate == 0.0) ? 0.0
-          : (amount + fee)/rate;
+      final headers = {apiHeaderKey: apiKey};
+      final isReverse = isReceiveAmount;
+      final type = isReverse ? 'reverse' : 'direct';
+      final flow = getFlow(isFixedRateMode);
+      final params = <String, String>{
+        'fromCurrency': isReverse ? normalizeCryptoCurrency(to) : normalizeCryptoCurrency(from),
+        'toCurrency': isReverse ? normalizeCryptoCurrency(from) : normalizeCryptoCurrency(to) ,
+        'type': type,
+        'flow': flow};
 
-      return estimatedAmount;
+      if (isReverse) {
+        params['toAmount'] = amount.toString();
       } else {
-      final url = defineUrlForCalculatingAmount(from, to, amount, isFixedRateMode);
-      final response = await get(url);
+        params['fromAmount'] = amount.toString();
+      }
+      
+      final uri = Uri.https(apiAuthority, estimatedAmountPath, params);
+      final response = await get(uri, headers: headers);
       final responseJSON = json.decode(response.body) as Map<String, dynamic>;
-      final estimatedAmount = responseJSON['estimatedAmount'] as double;
+      final fromAmount = double.parse(responseJSON['fromAmount'].toString());
+      final toAmount =  double.parse(responseJSON['toAmount'].toString());
+      final rateId = responseJSON['rateId'] as String ?? '';
 
-      return estimatedAmount;
+      if (rateId.isNotEmpty) {
+        _lastUsedRateId = rateId;
+      }
+
+      return isReverse ? fromAmount : toAmount;
+    } catch(e) {
+      print(e.toString());
+      return 0.0;
     }
   }
 
-  static String defineUrlForCalculatingAmount(
-      CryptoCurrency from,
-      CryptoCurrency to,
-      double amount,
-      bool isFixedRateMode) {
-    final fromTitle = defineCurrencyTitle(from);
-    final toTitle = defineCurrencyTitle(to);
-
-    return isFixedRateMode
-        ? apiUri +
-        _exchangeAmountUriSufix +
-        _fixedRateUriSufix +
-        amount.toString() +
-        '/' +
-        fromTitle +
-        '_' +
-        toTitle +
-        '?api_key=' + apiKey
-        : apiUri +
-        _exchangeAmountUriSufix +
-        amount.toString() +
-        '/' +
-        fromTitle +
-        '_' +
-        toTitle;
-  }
-
-  static String defineCurrencyTitle(CryptoCurrency currency) {
+  static String normalizeCryptoCurrency(CryptoCurrency currency) {
     const bnbTitle = 'bnbmainnet';
     final currencyTitle = currency == CryptoCurrency.bnb
         ? bnbTitle : currency.title.toLowerCase();

lib/exchange/changenow/changenow_request.dart

@@ -7,12 +7,16 @@ class ChangeNowRequest extends TradeRequest {
       {@required this.from,
       @required this.to,
       @required this.address,
-      @required this.amount,
-      @required this.refundAddress});
+      @required this.fromAmount,
+      @required this.toAmount,
+      @required this.refundAddress,
+      @required this.isReverse});
 
   CryptoCurrency from;
   CryptoCurrency to;
   String address;
-  String amount;
+  String fromAmount;
+  String toAmount;
   String refundAddress;
+  bool isReverse;
 }

lib/src/screens/exchange/exchange_page.dart

@@ -1,5 +1,6 @@
 import 'dart:ui';
 import 'package:cake_wallet/entities/parsed_address.dart';
+import 'package:cake_wallet/utils/debounce.dart';
 import 'package:cw_core/sync_status.dart';
 import 'package:cw_core/wallet_type.dart';
 import 'package:cake_wallet/entities/parse_address_from_domain.dart';
@@ -44,6 +45,8 @@ class ExchangePage extends BasePage {
   final _depositAddressFocus = FocusNode();
   final _receiveAmountFocus = FocusNode();
   final _receiveAddressFocus = FocusNode();
+  final _receiveAmountDebounce = Debounce(Duration(milliseconds: 500));
+  final _depositAmountDebounce = Debounce(Duration(milliseconds: 500));
   var _isReactionsSet = false;
 
   @override
@@ -99,6 +102,7 @@ class ExchangePage extends BasePage {
         .addPostFrameCallback((_) => _setReactions(context, exchangeViewModel));
 
     return KeyboardActions(
+        disableScroll: true,
         config: KeyboardActionsConfig(
             keyboardActionsPlatform: KeyboardActionsPlatform.IOS,
             keyboardBarColor:
@@ -113,7 +117,6 @@ class ExchangePage extends BasePage {
                   toolbarButtons: [(_) => KeyboardDoneButton()])
             ]),
         child: Container(
-          height: 1,
           color: Theme.of(context).backgroundColor,
           child: Form(
               key: _formKey,
@@ -314,6 +317,21 @@ class ExchangePage extends BasePage {
                         ],
                       ),
                     ),
+                    Padding(
+                        padding: EdgeInsets.only(top: 12, left: 24),
+                        child: Row(
+                          mainAxisAlignment: MainAxisAlignment.start,
+                          children: [
+                            StandardCheckbox(
+                              key: checkBoxKey,
+                              value: exchangeViewModel.isFixedRateMode,
+                              caption: S.of(context).fixed_rate,
+                              onChanged: (value) =>
+                              exchangeViewModel.isFixedRateMode = value,
+                            ),
+                          ],
+                        )
+                    ),
                     Padding(
                       padding: EdgeInsets.only(top: 30, left: 24, bottom: 24),
                       child: Row(
@@ -548,7 +566,9 @@ class ExchangePage extends BasePage {
       final max = limitsState.limits.max != null
           ? limitsState.limits.max.toString()
           : null;
-      final key = depositKey;
+      final key = exchangeViewModel.isFixedRateMode
+        ? receiveKey
+        : depositKey;
       key.currentState.changeLimits(min: min, max: max);
     }
 
@@ -656,8 +676,13 @@ class ExchangePage extends BasePage {
         max = '...';
       }
 
+      if (exchangeViewModel.isFixedRateMode) {
+        depositKey.currentState.changeLimits(min: null, max: null);
+        receiveKey.currentState.changeLimits(min: min, max: max);
+      } else {
         depositKey.currentState.changeLimits(min: min, max: max);
         receiveKey.currentState.changeLimits(min: null, max: null);
+      }
     });
 
     depositAddressController.addListener(
@@ -665,9 +690,11 @@ class ExchangePage extends BasePage {
 
     depositAmountController.addListener(() {
       if (depositAmountController.text != exchangeViewModel.depositAmount) {
+        _depositAmountDebounce.run(() { 
           exchangeViewModel.changeDepositAmount(
               amount: depositAmountController.text);
           exchangeViewModel.isReceiveAmountEntered = false;
+        });
       }
     });
 
@@ -676,9 +703,11 @@ class ExchangePage extends BasePage {
 
     receiveAmountController.addListener(() {
       if (receiveAmountController.text != exchangeViewModel.receiveAmount) {
+        _receiveAmountDebounce.run(() {
           exchangeViewModel.changeReceiveAmount(
               amount: receiveAmountController.text);
           exchangeViewModel.isReceiveAmountEntered = true;
+        });
       }
     });
 

lib/utils/debounce.dart

@@ -0,0 +1,14 @@
+import 'dart:async';
+import 'package:flutter/foundation.dart';
+
+class Debounce {
+  Debounce(this.duration);
+  
+  final Duration duration;
+  Timer _timer;
+  
+  void run(VoidCallback action) {
+    _timer?.cancel();
+    _timer = Timer(duration, action);
+  }
+}

lib/view_model/exchange/exchange_view_model.dart

@@ -57,10 +57,14 @@ abstract class ExchangeViewModelBase with Store {
     receiveCurrencies = CryptoCurrency.all
       .where((cryptoCurrency) => !excludeCurrencies.contains(cryptoCurrency))
       .toList();
-    _defineIsReceiveAmountEditable();
+    isReverse = false;
     isFixedRateMode = false;
     isReceiveAmountEntered = false;
+    _defineIsReceiveAmountEditable();
     loadLimits();
+    reaction(
+      (_) => isFixedRateMode,
+      (Object _) => _defineIsReceiveAmountEditable());
   }
 
   final WalletBase wallet;
@@ -129,6 +133,8 @@ abstract class ExchangeViewModelBase with Store {
 
   Limits limits;
 
+  bool isReverse;
+
   NumberFormat _cryptoNumberFormat;
 
   SettingsStore _settingsStore;
@@ -164,6 +170,7 @@ abstract class ExchangeViewModelBase with Store {
   @action
   void changeReceiveAmount({String amount}) {
     receiveAmount = amount;
+    isReverse = true;
 
     if (amount == null || amount.isEmpty) {
       depositAmount = '';
@@ -190,6 +197,7 @@ abstract class ExchangeViewModelBase with Store {
   @action
   void changeDepositAmount({String amount}) {
     depositAmount = amount;
+    isReverse = false;
 
     if (amount == null || amount.isEmpty) {
       depositAmount = '';
@@ -217,9 +225,15 @@ abstract class ExchangeViewModelBase with Store {
     limitsState = LimitsIsLoading();
 
     try {
+      final from = isFixedRateMode
+        ? receiveCurrency
+        : depositCurrency;
+      final to = isFixedRateMode
+        ? depositCurrency
+        : receiveCurrency;
       limits = await provider.fetchLimits(
-          from: depositCurrency,
-          to: receiveCurrency,
+          from: from,
+          to: to,
           isFixedRateMode: isFixedRateMode);
       limitsState = LimitsLoadedSuccessfully(limits: limits);
     } catch (e) {
@@ -250,10 +264,12 @@ abstract class ExchangeViewModelBase with Store {
       request = ChangeNowRequest(
           from: depositCurrency,
           to: receiveCurrency,
-          amount: depositAmount?.replaceAll(',', '.'),
+          fromAmount: depositAmount?.replaceAll(',', '.'),
+          toAmount: receiveAmount?.replaceAll(',', '.'),
           refundAddress: depositAddress,
-          address: receiveAddress);
-      amount = depositAmount;
+          address: receiveAddress,
+          isReverse: isReverse);
+      amount = isReverse ? receiveAmount : depositAmount;
       currency = depositCurrency;
     }
 
@@ -422,6 +438,7 @@ abstract class ExchangeViewModelBase with Store {
     } else {
       isReceiveAmountEditable = false;
     }*/
-    isReceiveAmountEditable = false;
+    //isReceiveAmountEditable = false;
+    isReceiveAmountEditable = (isFixedRateMode ?? false) && provider is ChangeNowExchangeProvider;
   }
 }