Consider latency when getting next send time from DB.

bramble-api/src/main/java/org/briarproject/bramble/api/db/DatabaseComponent.java

@@ -541,15 +541,18 @@ public interface DatabaseComponent extends TransactionManager {
 	 */
 	long getNextCleanupDeadline(Transaction txn) throws DbException;
 
-	/*
+	/**
 	 * Returns the next time (in milliseconds since the Unix epoch) when a
-	 * message is due to be sent to the given contact. The returned value may
+	 * message is due to be sent to the given contact over a transport with
-	 * be zero if a message is due to be sent immediately, or Long.MAX_VALUE if
+	 * the given latency.
-	 * no messages are scheduled to be sent.
+	 * <p>
+	 * The returned value may be zero if a message is due to be sent
+	 * immediately, or Long.MAX_VALUE if no messages are scheduled to be sent.
 	 * <p/>
 	 * Read-only.
 	 */
-	long getNextSendTime(Transaction txn, ContactId c) throws DbException;
+	long getNextSendTime(Transaction txn, ContactId c, long maxLatency)
+			throws DbException;
 
 	/**
 	 * Returns the pending contact with the given ID.

bramble-core/src/main/java/org/briarproject/bramble/db/Database.java

@@ -587,13 +587,16 @@ interface Database<T> {
 
 	/**
 	 * Returns the next time (in milliseconds since the Unix epoch) when a
-	 * message is due to be sent to the given contact. The returned value may
+	 * message is due to be sent to the given contact over a transport with
-	 * be zero if a message is due to be sent immediately, or Long.MAX_VALUE
+	 * the given latency.
-	 * if no messages are scheduled to be sent.
+	 * <p>
+	 * The returned value may be zero if a message is due to be sent
+	 * immediately, or Long.MAX_VALUE if no messages are scheduled to be sent.
 	 * <p/>
 	 * Read-only.
 	 */
-	long getNextSendTime(T txn, ContactId c) throws DbException;
+	long getNextSendTime(T txn, ContactId c, long maxLatency)
+			throws DbException;
 
 	/**
 	 * Returns the pending contact with the given ID.

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseComponentImpl.java

@@ -814,10 +814,10 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	}
 
 	@Override
-	public long getNextSendTime(Transaction transaction, ContactId c)
+	public long getNextSendTime(Transaction transaction, ContactId c,
-			throws DbException {
+			long maxLatency) throws DbException {
 		T txn = unbox(transaction);
-		return db.getNextSendTime(txn, c);
+		return db.getNextSendTime(txn, c, maxLatency);
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/db/JdbcDatabase.java

@@ -2490,12 +2490,28 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public long getNextSendTime(Connection txn, ContactId c)
+	public long getNextSendTime(Connection txn, ContactId c, long maxLatency)
 			throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT expiry FROM statuses"
+			// Are any messages sendable immediately?
+			String sql = "SELECT NULL FROM statuses"
+					+ " WHERE contactId = ? AND state = ?"
+					+ " AND groupShared = TRUE AND messageShared = TRUE"
+					+ " AND deleted = FALSE AND seen = FALSE"
+					+ " AND (maxLatency IS NULL OR ? < maxLatency)";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, c.getInt());
+			ps.setInt(2, DELIVERED.getValue());
+			ps.setLong(3, maxLatency);
+			rs = ps.executeQuery();
+			boolean found = rs.next();
+			rs.close();
+			ps.close();
+			if (found) return 0;
+			// When is the earliest expiry time (could be in the past)?
+			sql = "SELECT expiry FROM statuses"
 					+ " WHERE contactId = ? AND state = ?"
 					+ " AND groupShared = TRUE AND messageShared = TRUE"
 					+ " AND deleted = FALSE AND seen = FALSE"

bramble-core/src/main/java/org/briarproject/bramble/sync/DuplexOutgoingSession.java

@@ -313,7 +313,8 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 							Collection<Message> batch =
 									db.generateRequestedBatch(txn, contactId,
 											BATCH_CAPACITY, maxLatency);
-							setNextSendTime(db.getNextSendTime(txn, contactId));
+							setNextSendTime(db.getNextSendTime(txn, contactId,
+									maxLatency));
 							return batch;
 						});
 				if (LOG.isLoggable(INFO))
@@ -356,7 +357,8 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 				Offer o = db.transactionWithNullableResult(false, txn -> {
 					Offer offer = db.generateOffer(txn, contactId,
 							MAX_MESSAGE_IDS, maxLatency);
-					setNextSendTime(db.getNextSendTime(txn, contactId));
+					setNextSendTime(db.getNextSendTime(txn, contactId,
+							maxLatency));
 					return offer;
 				});
 				if (LOG.isLoggable(INFO))

bramble-core/src/test/java/org/briarproject/bramble/db/JdbcDatabaseTest.java

@@ -2020,37 +2020,51 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.addMessage(txn, message, UNKNOWN, false, false, null);
 
 		// There should be no messages to send
-		assertEquals(Long.MAX_VALUE, db.getNextSendTime(txn, contactId));
+		assertEquals(Long.MAX_VALUE,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// Share the group with the contact - still no messages to send
 		db.addGroupVisibility(txn, contactId, groupId, true);
-		assertEquals(Long.MAX_VALUE, db.getNextSendTime(txn, contactId));
+		assertEquals(Long.MAX_VALUE,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// Set the message's state to DELIVERED - still no messages to send
 		db.setMessageState(txn, messageId, DELIVERED);
-		assertEquals(Long.MAX_VALUE, db.getNextSendTime(txn, contactId));
+		assertEquals(Long.MAX_VALUE,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// Share the message - now it should be sendable immediately
 		db.setMessageShared(txn, messageId, true);
-		assertEquals(0, db.getNextSendTime(txn, contactId));
+		assertEquals(0, db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// Mark the message as requested - it should still be sendable
 		db.raiseRequestedFlag(txn, contactId, messageId);
-		assertEquals(0, db.getNextSendTime(txn, contactId));
+		assertEquals(0, db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// Update the message's expiry time as though we sent it - now the
 		// message should be sendable after one round-trip
-		db.updateRetransmissionData(txn, contactId, messageId, 1000);
+		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
-		assertEquals(now + 2000, db.getNextSendTime(txn, contactId));
+		assertEquals(now + MAX_LATENCY * 2,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
+
+		// The message should be sendable immediately over a transport with
+		// lower latency
+		assertEquals(0L, db.getNextSendTime(txn, contactId, MAX_LATENCY - 1));
 
 		// Update the message's expiry time again - now it should be sendable
 		// after two round-trips
-		db.updateRetransmissionData(txn, contactId, messageId, 1000);
+		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
-		assertEquals(now + 4000, db.getNextSendTime(txn, contactId));
+		assertEquals(now + MAX_LATENCY * 4,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
+
+		// The message should be sendable immediately over a transport with
+		// lower latency
+		assertEquals(0L, db.getNextSendTime(txn, contactId, MAX_LATENCY - 1));
 
 		// Delete the message - there should be no messages to send
 		db.deleteMessage(txn, messageId);
-		assertEquals(Long.MAX_VALUE, db.getNextSendTime(txn, contactId));
+		assertEquals(Long.MAX_VALUE,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		db.commitTransaction(txn);
 		db.close();
@@ -2115,7 +2129,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
 
 		// The message should expire after 2 * MAX_LATENCY
-		assertEquals(now + MAX_LATENCY * 2, db.getNextSendTime(txn, contactId));
+		assertEquals(now + MAX_LATENCY * 2,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// Time: now + MAX_LATENCY * 2 - 1
 		// The message should not yet be sendable
@@ -2158,7 +2173,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
 
 		// The message should expire after 2 * MAX_LATENCY
-		assertEquals(now + MAX_LATENCY * 2, db.getNextSendTime(txn, contactId));
+		assertEquals(now + MAX_LATENCY * 2,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// The message should not be sendable via the same transport
 		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
@@ -2205,7 +2221,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.updateRetransmissionData(txn, contactId, messageId, MAX_LATENCY);
 
 		// The message should expire after 2 * MAX_LATENCY
-		assertEquals(now + MAX_LATENCY * 2, db.getNextSendTime(txn, contactId));
+		assertEquals(now + MAX_LATENCY * 2,
+				db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// Time: now + MAX_LATENCY * 2 - 1
 		// The message should not yet be sendable
@@ -2216,8 +2233,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		// Reset the retransmission times
 		db.resetUnackedMessagesToSend(txn, contactId);
 
-		// The message should have infinitely short expiry
+		// The message should be sendable immediately
-		assertEquals(0, db.getNextSendTime(txn, contactId));
+		assertEquals(0, db.getNextSendTime(txn, contactId, MAX_LATENCY));
 
 		// The message should be sendable
 		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);