Migrate BestOrders to mmrpc 2.0 (#110)

* Migrate BestOrders to mmrpc 2.0

Leaving the BestOrder and BestOrders attributes unchanged to minimise the impact

* Fix empty best orders list

ARRR has no `address_data` as it is a `Shielded` address, so we cannot use address to filter ARRR top orders.

lib/model/best_order.dart

@@ -12,11 +12,14 @@ class BestOrders {
     if (json['result'] == null) return bestOrders;
 
     final Market action = bestOrders.request.action;
+    final Map<String, dynamic> result = json['result'];
+    final Map<String, dynamic> resultOrders =
+        result['orders'] as Map<String, dynamic>;
 
-    json['result'].forEach((String ticker, dynamic items) {
+    resultOrders.forEach((String ticker, dynamic items) {
       bestOrders.result ??= {};
       final List<BestOrder> list = [];
-      for (dynamic item in items) {
+      for (final Map<String, dynamic> item in items) {
         item['action'] = action;
         item['other_coin'] =
             action == Market.SELL ? bestOrders.request.coin : ticker;
@@ -45,15 +48,24 @@ class BestOrder {
   });
 
   factory BestOrder.fromJson(Map<String, dynamic> json) {
+    final Map<String, dynamic> price = json['price'];
+    final Map<String, dynamic> address = json['address'];
+
+    // base_ max and min volume are used, as the base and rel coins are swapped
+    // for buy and sell orders, so the max volume is always the max volume of
+    // the base coin. The web wallet has a similar implementation.
+    final Map<String, dynamic> maxVolume = json['base_max_volume'];
+    final Map<String, dynamic> minVolume = json['base_min_volume'];
+
     return BestOrder(
-      price: fract2rat(json['price_fraction']) ?? Rational.parse(json['price']),
-      maxVolume: fract2rat(json['max_volume_fraction']) ??
-          Rational.parse(json['maxvolume']),
-      minVolume: fract2rat(json['min_volume_fraction']) ??
-          Rational.parse(json['min_volume']),
+      price: fract2rat(price['fraction']) ?? Rational.parse(price['decimal']),
+      maxVolume: fract2rat(maxVolume['fraction']) ??
+          Rational.parse(maxVolume['decimal']),
+      minVolume: fract2rat(minVolume['fraction']) ??
+          Rational.parse(minVolume['decimal']),
       coin: json['coin'],
       otherCoin: json['other_coin'],
-      address: json['address'],
+      address: address['address_data'],
       action: json['action'],
     );
   }

lib/model/get_best_orders.dart

@@ -8,25 +8,30 @@ class GetBestOrders {
   GetBestOrders({
     this.userpass,
     this.method = 'best_orders',
+    this.mmrpc = '2.0',
     this.coin,
     this.volume,
     this.action,
   });
 
   String userpass;
   String method;
+  String mmrpc;
   String coin;
   Rational volume;
   Market action;
 
   Map<String, dynamic> toJson() => <String, dynamic>{
         'method': method,
         'userpass': userpass,
-        'coin': coin,
-        'volume': {
-          'numer': volume.numerator.toString(),
-          'denom': volume.denominator.toString(),
-        },
-        'action': action == Market.BUY ? 'buy' : 'sell',
+        'mmrpc': mmrpc,
+        'params': {
+          'coin': coin,
+          'action': action == Market.BUY ? 'buy' : 'sell',
+          'request_by': {
+            'type': 'volume',
+            'value': volume.toDecimalString(),
+          }
+        }
       };
 }

lib/model/swap_constructor_provider.dart

@@ -332,11 +332,18 @@ class ConstructorProvider extends ChangeNotifier {
 
   BestOrder getTickerTopOrder(List<BestOrder> tickerOrdersList, Market type) {
     final List<BestOrder> sorted = List.from(tickerOrdersList);
+    // This code appears to remove orders placed by the current wallet
+    // so that the user doesn't trade with themselves
     sorted.removeWhere((BestOrder order) {
       final String coin =
           order.action == Market.SELL ? order.coin : order.otherCoin;
       final CoinBalance coinBalance = coinsBloc.getBalanceByAbbr(coin);
-      if (coinBalance == null) return false;
+
+      // ZHTLC address is null (Shielded), so we can't check it.
+      // This removes the protection against users taking their own maker orders
+      if (coinBalance == null || order.address == null) {
+        return false;
+      }
       return coinBalance.balance.address.toLowerCase() ==
           order.address.toLowerCase();
     });