fix: Resolve merge conflicts and fix TimeUnit ambiguity

- Resolve merge conflicts from trunk merge (buildFlightClient extraction)
- Fix TimeUnit import ambiguity: fully qualify java.util.concurrent.TimeUnit
  at keepAlive call sites to avoid conflict with Arrow's TimeUnit
- Add closed guard to reset() — throws IllegalStateException after close()
- Make close() idempotent with early return on already-closed client
- Update testResetAfterClose to expect IllegalStateException

Author: lukekim

src/main/java/ai/spice/SpiceClient.java

@@ -39,7 +39,6 @@ of this software and associated documentation files (the "Software"), to deal
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ExecutionException;
-import java.util.concurrent.TimeUnit;
 
 import org.apache.arrow.adbc.core.AdbcConnection;
 import org.apache.arrow.adbc.core.AdbcDatabase;
@@ -154,6 +153,7 @@ public class SpiceClient implements AutoCloseable {
     private FlightSqlClient flightClient;
     private CredentialCallOption authCallOptions = null;
     private BufferAllocator allocator;
+    private boolean closed = false;
 
     // Cached retryers (immutable, thread-safe)
     private Retryer<ArrowReader> adbcRetryer;
@@ -268,8 +268,8 @@ private synchronized void buildFlightClient() {
         }
         channelBuilder
                 // HTTP/2 keep-alive to detect dead/idle connections behind load balancers
-                .keepAliveTime(30, TimeUnit.SECONDS)
-                .keepAliveTimeout(10, TimeUnit.SECONDS)
+                .keepAliveTime(30, java.util.concurrent.TimeUnit.SECONDS)
+                .keepAliveTimeout(10, java.util.concurrent.TimeUnit.SECONDS)
                 .keepAliveWithoutCalls(true)
                 .maxInboundMessageSize(Integer.MAX_VALUE)
                 .maxInboundMetadataSize(Integer.MAX_VALUE);
@@ -347,6 +347,9 @@ private synchronized void ensureFlightClient() {
      * }</pre>
      */
     public synchronized void reset() {
+        if (closed) {
+            throw new IllegalStateException("Cannot reset a closed SpiceClient");
+        }
         logger.info("Resetting SpiceClient transport");
 
         // Close ADBC resources (they maintain a separate Flight connection)
@@ -1011,6 +1014,10 @@ private boolean shouldRetry(CallStatus status) {
 
     @Override
     public void close() throws Exception {
+        if (closed) {
+            return;
+        }
+        closed = true;
         logger.debug("Closing SpiceClient");
         List<Exception> exceptions = new ArrayList<>();
 

src/test/java/ai/spice/ResetTest.java

@@ -170,14 +170,17 @@ public void testResetQueryResetQueryCycle() throws Exception {
     }
 
     /**
-     * reset() after close() should not throw.
-     * (The flight client is already null after close, reset handles that.)
+     * reset() after close() should throw IllegalStateException.
      */
     public void testResetAfterClose() throws Exception {
         SpiceClient client = SpiceClient.builder().build();
         client.close();
-        // reset on an already-closed client should be safe
-        client.reset();
+        try {
+            client.reset();
+            fail("Expected IllegalStateException when resetting a closed client");
+        } catch (IllegalStateException e) {
+            assertTrue(e.getMessage().contains("closed"));
+        }
     }
 
     /**