enable electrum rpc batching on mempool-electrs servers

src/main/java/com/sparrowwallet/sparrow/net/BatchedElectrumServerRpc.java

@@ -25,13 +25,11 @@ public class BatchedElectrumServerRpc implements ElectrumServerRpc {
     static final int RETRY_DELAY_SECS = 1;
 
     private final AtomicLong idCounter;
+    private final int maxTargetBlocks;
 
-    public BatchedElectrumServerRpc() {
+    public BatchedElectrumServerRpc(long idCounterValue, int maxTargetBlocks) {
-        this.idCounter = new AtomicLong();
-    }
-
-    public BatchedElectrumServerRpc(long idCounterValue) {
         this.idCounter = new AtomicLong(idCounterValue);
+        this.maxTargetBlocks = maxTargetBlocks;
     }
 
     @Override
@@ -222,11 +220,19 @@ public class BatchedElectrumServerRpc implements ElectrumServerRpc {
     public Map<Integer, Double> getFeeEstimates(Transport transport, List<Integer> targetBlocks) {
         PagedBatchRequestBuilder<Integer, Double> batchRequest = PagedBatchRequestBuilder.create(transport, idCounter).keysType(Integer.class).returnType(Double.class);
         for(Integer targetBlock : targetBlocks) {
-            batchRequest.add(targetBlock, "blockchain.estimatefee", targetBlock);
+            if(targetBlock <= maxTargetBlocks) {
+                batchRequest.add(targetBlock, "blockchain.estimatefee", targetBlock);
+            }
         }
 
         try {
-            return batchRequest.execute();
+            Map<Integer, Double> result = batchRequest.execute();
+            for(Integer targetBlock : targetBlocks) {
+                if(targetBlock > maxTargetBlocks) {
+                    result.put(targetBlock, result.values().stream().mapToDouble(v -> v).min().orElse(0.0001d));
+                }
+            }
+            return result;
         } catch(JsonRpcBatchException e) {
             throw new ElectrumServerRpcException("Error getting fee estimates from connected server: " + e.getErrors(), e);
         } catch(Exception e) {

src/main/java/com/sparrowwallet/sparrow/net/ElectrumServer.java

@@ -47,6 +47,8 @@ public class ElectrumServer {
 
     private static final Version FULCRUM_MIN_BATCHING_VERSION = new Version("1.6.0");
 
+    private static final Version MEMPOOL_ELECTRS_MIN_BATCHING_VERSION = new Version("3.1.0");
+
     public static final String CORE_ELECTRUM_HOST = "127.0.0.1";
 
     private static final int MINIMUM_BROADCASTS = 2;
@@ -1021,15 +1023,15 @@ public class ElectrumServer {
         existingStatuses.add(status);
     }
 
-    public static boolean supportsBatching(List<String> serverVersion) {
+    public static ServerCapability getServerCapability(List<String> serverVersion) {
-        if(serverVersion.size() > 0) {
+        if(!serverVersion.isEmpty()) {
-            String server = serverVersion.get(0).toLowerCase(Locale.ROOT);
+            String server = serverVersion.getFirst().toLowerCase(Locale.ROOT);
             if(server.contains("electrumx")) {
-                return true;
+                return new ServerCapability(true);
             }
 
             if(server.startsWith("cormorant")) {
-                return true;
+                return new ServerCapability(true);
             }
 
             if(server.startsWith("electrs/")) {
@@ -1041,7 +1043,7 @@ public class ElectrumServer {
                 try {
                     Version version = new Version(electrsVersion);
                     if(version.compareTo(ELECTRS_MIN_BATCHING_VERSION) >= 0) {
-                        return true;
+                        return new ServerCapability(true);
                     }
                 } catch(Exception e) {
                     //ignore
@@ -1057,7 +1059,26 @@ public class ElectrumServer {
                 try {
                     Version version = new Version(fulcrumVersion);
                     if(version.compareTo(FULCRUM_MIN_BATCHING_VERSION) >= 0) {
-                        return true;
+                        return new ServerCapability(true);
+                    }
+                } catch(Exception e) {
+                    //ignore
+                }
+            }
+
+            if(server.startsWith("mempool-electrs")) {
+                String mempoolElectrsVersion = server.substring("mempool-electrs".length()).trim();
+                int dashIndex = mempoolElectrsVersion.indexOf('-');
+                String mempoolElectrsSuffix = "";
+                if(dashIndex > -1) {
+                    mempoolElectrsSuffix = mempoolElectrsVersion.substring(dashIndex);
+                    mempoolElectrsVersion = mempoolElectrsVersion.substring(0, dashIndex);
+                }
+                try {
+                    Version version = new Version(mempoolElectrsVersion);
+                    if(version.compareTo(MEMPOOL_ELECTRS_MIN_BATCHING_VERSION) > 0 ||
+                            (version.compareTo(MEMPOOL_ELECTRS_MIN_BATCHING_VERSION) == 0 && (!mempoolElectrsSuffix.contains("dev") || mempoolElectrsSuffix.contains("dev-249848d")))) {
+                        return new ServerCapability(true, 25);
                     }
                 } catch(Exception e) {
                     //ignore
@@ -1065,7 +1086,7 @@ public class ElectrumServer {
             }
         }
 
-        return false;
+        return new ServerCapability(false);
     }
 
     public static class ServerVersionService extends Service<List<String>> {
@@ -1196,9 +1217,10 @@ public class ElectrumServer {
                         firstCall = false;
 
                         //If electrumx is detected, we can upgrade to batched RPC. Electrs/EPS do not support batching.
-                        if(supportsBatching(serverVersion)) {
+                        ServerCapability serverCapability = getServerCapability(serverVersion);
+                        if(serverCapability.supportsBatching()) {
                             log.debug("Upgrading to batched JSON-RPC");
-                            electrumServerRpc = new BatchedElectrumServerRpc(electrumServerRpc.getIdCounterValue());
+                            electrumServerRpc = new BatchedElectrumServerRpc(electrumServerRpc.getIdCounterValue(), serverCapability.getMaxTargetBlocks());
                         }
 
                         BlockHeaderTip tip;

src/main/java/com/sparrowwallet/sparrow/net/ServerCapability.java

@@ -0,0 +1,26 @@
+package com.sparrowwallet.sparrow.net;
+
+import com.sparrowwallet.sparrow.AppServices;
+
+public class ServerCapability {
+    private final boolean supportsBatching;
+    private final int maxTargetBlocks;
+
+    public ServerCapability(boolean supportsBatching) {
+        this.supportsBatching = supportsBatching;
+        this.maxTargetBlocks = AppServices.TARGET_BLOCKS_RANGE.getLast();
+    }
+
+    public ServerCapability(boolean supportsBatching, int maxTargetBlocks) {
+        this.supportsBatching = supportsBatching;
+        this.maxTargetBlocks = maxTargetBlocks;
+    }
+
+    public boolean supportsBatching() {
+        return supportsBatching;
+    }
+
+    public int getMaxTargetBlocks() {
+        return maxTargetBlocks;
+    }
+}

src/main/java/com/sparrowwallet/sparrow/preferences/ServerPreferencesController.java

@@ -603,7 +603,8 @@ public class ServerPreferencesController extends PreferencesDetailController {
         testConnection.setGraphic(getGlyph(FontAwesome5.Glyph.CHECK_CIRCLE, "success"));
         if(serverVersion != null) {
             testResults.setText("Connected to " + serverVersion.get(0) + " on protocol version " + serverVersion.get(1));
-            if(ElectrumServer.supportsBatching(serverVersion)) {
+            ServerCapability serverCapability = ElectrumServer.getServerCapability(serverVersion);
+            if(serverCapability.supportsBatching()) {
                 testResults.setText(testResults.getText() + "\nBatched RPC enabled.");
             }
         }

src/main/java/com/sparrowwallet/sparrow/terminal/preferences/ServerTestDialog.java

@@ -168,7 +168,8 @@ public class ServerTestDialog extends DialogWindow {
         testStatus.setText("Success");
         if(serverVersion != null) {
             testResults.setText("Connected to " + serverVersion.get(0) + " on protocol version " + serverVersion.get(1));
-            if(ElectrumServer.supportsBatching(serverVersion)) {
+            ServerCapability serverCapability = ElectrumServer.getServerCapability(serverVersion);
+            if(serverCapability.supportsBatching()) {
                 testResults.setText(testResults.getText() + "\nBatched RPC enabled.");
             }
         }