Fee estimation

cw_bitcoin/lib/electrum.dart

@@ -331,14 +331,19 @@ class ElectrumClient {
   //   "height": 520481,
   //   "hex": "00000020890208a0ae3a3892aa047c5468725846577cfcd9b512b50000000000000000005dc2b02f2d297a9064ee103036c14d678f9afc7e3d9409cf53fd58b82e938e8ecbeca05a2d2103188ce804c4"
   // }
-  Future<int?> getCurrentBlockChainTip() =>
-      call(method: 'blockchain.headers.subscribe').then((result) {
-        if (result is Map<String, dynamic>) {
-          return result["height"] as int;
-        }
+  BehaviorSubject<Map<String, dynamic>>? tipListener;
+  int? currentTip;
 
-        return null;
-      });
+  Future<int?> getCurrentBlockChainTip() async {
+    final method = 'blockchain.headers.subscribe';
+    final cb = (result) => currentTip = result['height'] as int;
+    if (tipListener == null) {
+      tipListener = subscribe(id: method, method: method);
+      tipListener?.listen(cb);
+      cb(await call(method: method));
+    }
+    return currentTip;
+  }
 
   BehaviorSubject<Object>? scripthashUpdate(String scripthash) {
     _id += 1;
@@ -424,6 +429,12 @@ class ElectrumClient {
 
   void _methodHandler({required String method, required Map<String, dynamic> request}) {
     switch (method) {
+      case 'blockchain.headers.subscribe':
+        final params = request['params'] as List<dynamic>;
+        final id = 'blockchain.headers.subscribe';
+
+        _tasks[id]?.subject?.add(params.last);
+        break;
       case 'blockchain.scripthash.subscribe':
         final params = request['params'] as List<dynamic>;
         final scripthash = params.first as String?;

cw_bitcoin/lib/electrum_wallet.dart

@@ -392,24 +392,13 @@ abstract class ElectrumWalletBase
       value: BigInt.from(amountLeftForChangeAndFee),
     ));
 
-    int estimatedSize;
-    if (network is BitcoinCashNetwork) {
-      estimatedSize = ForkedTransactionBuilder.estimateTransactionSize(
-        utxos: utxos,
-        outputs: outputs,
-        network: network as BitcoinCashNetwork,
-        memo: memo,
-      );
-    } else {
-      estimatedSize = BitcoinTransactionBuilder.estimateTransactionSize(
-        utxos: utxos,
-        outputs: outputs,
-        network: network,
-        memo: memo,
-      );
-    }
-
-    int fee = feeAmountWithFeeRate(feeRate, 0, 0, size: estimatedSize);
+    int fee = await calcFee(
+      utxos: utxos,
+      outputs: outputs,
+      network: network,
+      memo: memo,
+      feeRate: feeRate,
+    );
 
     if (fee == 0) {
       throw BitcoinTransactionNoFeeException();
@@ -499,6 +488,33 @@ abstract class ElectrumWalletBase
     );
   }
 
+  Future<int> calcFee({
+      required List<UtxoWithAddress> utxos,
+      required List<BitcoinBaseOutput> outputs,
+      required BasedUtxoNetwork network,
+      String? memo,
+      required int feeRate}) async {
+
+    int estimatedSize;
+    if (network is BitcoinCashNetwork) {
+      estimatedSize = ForkedTransactionBuilder.estimateTransactionSize(
+        utxos: utxos,
+        outputs: outputs,
+        network: network,
+        memo: memo,
+      );
+    } else {
+      estimatedSize = BitcoinTransactionBuilder.estimateTransactionSize(
+        utxos: utxos,
+        outputs: outputs,
+        network: network,
+        memo: memo,
+      );
+    }
+
+    return feeAmountWithFeeRate(feeRate, 0, 0, size: estimatedSize);
+  }
+
   @override
   Future<PendingTransaction> createTransaction(Object credentials) async {
     try {

cw_bitcoin/lib/litecoin_wallet.dart

@@ -1,12 +1,15 @@
 import 'dart:async';
+import 'dart:math';
 import 'package:convert/convert.dart';
 import 'package:crypto/crypto.dart';
+import 'package:fixnum/fixnum.dart';
 import 'package:bitcoin_base/bitcoin_base.dart';
 import 'package:cw_bitcoin/bitcoin_mnemonic.dart';
 import 'package:cw_bitcoin/bitcoin_transaction_priority.dart';
 import 'package:cw_bitcoin/bitcoin_unspent.dart';
 import 'package:cw_bitcoin/electrum_transaction_info.dart';
 import 'package:cw_core/crypto_currency.dart';
+import 'package:cw_core/pending_transaction.dart';
 import 'package:cw_core/sync_status.dart';
 import 'package:cw_core/transaction_direction.dart';
 import 'package:cw_core/unspent_coins_info.dart';
@@ -279,4 +282,45 @@ abstract class LitecoinWalletBase extends ElectrumWallet with Store {
 
     return 0;
   }
+
+  @override
+  Future<int> calcFee({
+      required List<UtxoWithAddress> utxos,
+      required List<BitcoinBaseOutput> outputs,
+      required BasedUtxoNetwork network,
+      String? memo,
+      required int feeRate}) async {
+
+    final txb = BitcoinTransactionBuilder(utxos: utxos,
+        outputs: outputs, fee: BigInt.zero, network: network);
+    final scanSecret = mwebHd.derive(0x80000000).privKey!;
+    final spendSecret = mwebHd.derive(0x80000001).privKey!;
+    final stub = await CwMweb.stub();
+    final resp = await stub.create(CreateRequest(
+        rawTx: txb.buildTransaction((a, b, c, d) => '').toBytes(),
+        scanSecret: hex.decode(scanSecret),
+        spendSecret: hex.decode(spendSecret),
+        feeRatePerKb: Int64(feeRate * 1000),
+        dryRun: true));
+    final tx = BtcTransaction.fromRaw(hex.encode(resp.rawTx));
+    final posUtxos = utxos.where((utxo) => tx.inputs.any((input) =>
+        input.txId == utxo.utxo.txHash && input.txIndex == utxo.utxo.vout)).toList();
+    final preOutputSum = outputs.fold<int>(0, (acc, output) => acc + output.toOutput.amount.toInt());
+    final posOutputSum = tx.outputs.fold<int>(0, (acc, output) => acc + output.amount.toInt());
+    final mwebInputSum = utxos.sumOfUtxosValue() - posUtxos.sumOfUtxosValue();
+    final expectedPegin = max(0, preOutputSum - mwebInputSum.toInt());
+    var fee = posOutputSum - expectedPegin;
+    if (expectedPegin > 0) {
+      fee += await super.calcFee(utxos: posUtxos, outputs: tx.outputs.map((output) =>
+          BitcoinScriptOutput(script: output.scriptPubKey, value: output.amount)).toList(),
+          network: network, memo: memo, feeRate: feeRate) + feeRate * 41;
+    }
+    return fee;
+  }
+
+  @override
+  Future<PendingTransaction> createTransaction(Object credentials) async {
+    final tx = await super.createTransaction(credentials);
+    return tx;
+  }
 }

cw_mweb/android/src/main/kotlin/com/cakewallet/mweb/CwMwebPlugin.kt

@@ -17,6 +17,7 @@ class CwMwebPlugin: FlutterPlugin, MethodCallHandler {
   /// This local reference serves to register the plugin with the Flutter Engine and unregister it
   /// when the Flutter Engine is detached from the Activity
   private lateinit var channel : MethodChannel
+  private var port: Long? = null
 
   override fun onAttachedToEngine(@NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
     channel = MethodChannel(flutterPluginBinding.binaryMessenger, "cw_mweb")
@@ -26,7 +27,8 @@ class CwMwebPlugin: FlutterPlugin, MethodCallHandler {
   override fun onMethodCall(@NonNull call: MethodCall, @NonNull result: Result) {
     if (call.method == "start") {
       val dataDir = call.argument("dataDir") ?: ""
-      result.success(Mwebd.newServer("", dataDir, "").start(0))
+      port = port ?: Mwebd.newServer("", dataDir, "").start(0)
+      result.success(port)
     } else {
       result.notImplemented()
     }

cw_mweb/lib/cw_mweb.dart

@@ -4,13 +4,10 @@ import 'cw_mweb_platform_interface.dart';
 import 'mwebd.pbgrpc.dart';
 
 class CwMweb {
-  static Future<int?>? port;
-
   static Future<RpcClient> stub() async {
     final appDir = await getApplicationSupportDirectory();
-    port ??= CwMwebPlatform.instance.start(appDir.path);
     return RpcClient(ClientChannel('127.0.0.1',
-      port: await port ?? 0,
+      port: await CwMwebPlatform.instance.start(appDir.path) ?? 0,
       options: const ChannelOptions(
         credentials: ChannelCredentials.insecure())));
   }