fix(txsubmission): handle client MsgDone in server agent to avoid mempool stall

core/src/main/java/com/bloxbean/cardano/yaci/core/protocol/txsubmission/TxSubmissionServerAgent.java

@@ -114,11 +114,25 @@ public void processResponse(Message message) {
             handleReplyTxIds((ReplyTxIds) message);
         } else if (message instanceof ReplyTxs) {
             handleReplyTxs((ReplyTxs) message);
+        } else if (message instanceof MsgDone) {
+            handleDone();
         } else {
             log.warn("Unexpected message type: {}", message.getClass().getSimpleName());
         }
     }
 
+    /**
+     * The client terminated the tx-submission protocol with MsgDone. The state machine has already
+     * advanced to {@link TxSubmissionState#Done} (see {@link TxSubmissionState}), so the inbound
+     * handler stops routing to this agent and the session can be torn down; a fresh agent is created
+     * when the peer reconnects. Drop any in-flight bookkeeping so nothing leaks.
+     */
+    private void handleDone() {
+        log.info("Received MsgDone from client - tx-submission protocol terminated, agent is Done");
+        outstandingTxIds.clear();
+        pendingRequest = null;
+    }
+
     private void handleInit() {
         log.info("Received Init message from client - transitioning to Idle state");
 

core/src/main/java/com/bloxbean/cardano/yaci/core/protocol/txsubmission/TxSubmissionState.java

@@ -2,6 +2,7 @@
 
 import com.bloxbean.cardano.yaci.core.protocol.Message;
 import com.bloxbean.cardano.yaci.core.protocol.State;
+import com.bloxbean.cardano.yaci.core.protocol.txsubmission.messges.MsgDone;
 import com.bloxbean.cardano.yaci.core.protocol.txsubmission.messges.ReplyTxIds;
 import com.bloxbean.cardano.yaci.core.protocol.txsubmission.messges.ReplyTxs;
 import com.bloxbean.cardano.yaci.core.protocol.txsubmission.messges.RequestTxIds;
@@ -44,6 +45,8 @@ public boolean hasAgency(boolean isClient) {
         public State nextState(Message message) {
             if (message instanceof ReplyTxIds)
                 return Idle;
+            else if (message instanceof MsgDone)
+                return Done;
             else
                 return this;
         }
@@ -58,6 +61,8 @@ public boolean hasAgency(boolean isClient) {
         public State nextState(Message message) {
             if (message instanceof ReplyTxIds)
                 return Idle;
+            else if (message instanceof MsgDone) // defensive: honour client termination
+                return Done;
             else
                 return this;
         }
@@ -72,6 +77,8 @@ public boolean hasAgency(boolean isClient) {
         public State nextState(Message message) {
             if (message instanceof ReplyTxs)
                 return Idle;
+            else if (message instanceof MsgDone) // defensive: honour client termination
+                return Done;
             else
                 return this;
         }

core/src/test/java/com/bloxbean/cardano/yaci/core/protocol/txsubmission/TxSubmissionServerAgentTest.java

@@ -332,6 +332,33 @@ void testEmptyReplyTxIds() {
         assertEquals(0, requestTxIds.getAckTxIds()); // No transactions to acknowledge
     }
 
+    @Test
+    void testMsgDoneFromTxIdsBlockingTransitionsToDone() {
+        // Move to Idle, then have the server send a blocking RequestTxIds so we land in TxIdsBlocking
+        agent.receiveResponse(new Init());
+        assertEquals(TxSubmissionState.Idle, agent.getCurrentState());
+
+        agent.sendRequest(new RequestTxIds(true, (short) 0, (short) 10));
+        assertEquals(TxSubmissionState.TxIdsBlocking, agent.getCurrentState());
+        assertFalse(agent.isDone());
+
+        // Client terminates the protocol with MsgDone while we are blocking-waiting.
+        // Before the fix the agent stayed wedged in TxIdsBlocking forever; now it must reach Done.
+        agent.receiveResponse(new MsgDone());
+
+        assertEquals(TxSubmissionState.Done, agent.getCurrentState());
+        assertTrue(agent.isDone());
+        assertEquals(0, agent.getOutstandingTxCount());
+    }
+
+    @Test
+    void testMsgDoneStateTransitionsForAllClientAgencyStates() {
+        // The terminal MsgDone transition must hold for every state where the client has agency.
+        assertEquals(TxSubmissionState.Done, TxSubmissionState.TxIdsBlocking.nextState(new MsgDone()));
+        assertEquals(TxSubmissionState.Done, TxSubmissionState.TxIdsNonBlocking.nextState(new MsgDone()));
+        assertEquals(TxSubmissionState.Done, TxSubmissionState.Txs.nextState(new MsgDone()));
+    }
+
     @Test
     void testConfigurationValidation() {
         // Valid config should not log warnings