From 079ef5b3c09ad6b97013f890cf79da9906674dc6 Mon Sep 17 00:00:00 2001
From: akwizgran <michael@briarproject.org>
Date: Tue, 16 Aug 2022 15:11:53 +0100
Subject: [PATCH] Add helper method for checking client/server compatibility.

---
 .../bramble/api/mailbox/MailboxHelper.java             |  9 +++++++++
 .../bramble/mailbox/MailboxClientManager.java          | 10 +++++-----
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxHelper.java b/bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxHelper.java
index 42740156a..304fded5e 100644
--- a/bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxHelper.java
+++ b/bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxHelper.java
@@ -35,4 +35,13 @@ public class MailboxHelper {
 		return API_SERVER_TOO_OLD;
 	}
 
+	/**
+	 * Returns true if a client and server with the given API versions can
+	 * communicate with each other (ie, have any major API versions in common).
+	 */
+	public static boolean isClientCompatibleWithServer(
+			List<MailboxVersion> client, List<MailboxVersion> server) {
+		int common = getHighestCommonMajorVersion(client, server);
+		return common != API_CLIENT_TOO_OLD && common != API_SERVER_TOO_OLD;
+	}
 }
diff --git a/bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxClientManager.java b/bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxClientManager.java
index 7f23024c5..fe91f1b32 100644
--- a/bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxClientManager.java
+++ b/bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxClientManager.java
@@ -46,7 +46,7 @@ import javax.inject.Inject;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.mailbox.MailboxConstants.CLIENT_SUPPORTS;
-import static org.briarproject.bramble.api.mailbox.MailboxHelper.getHighestCommonMajorVersion;
+import static org.briarproject.bramble.api.mailbox.MailboxHelper.isClientCompatibleWithServer;
 import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
 import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
 import static org.briarproject.bramble.api.plugin.TorConstants.ID;
@@ -627,8 +627,8 @@ class MailboxClientManager implements Service, EventListener {
 	 */
 	private boolean isMailboxUsable(List<MailboxVersion> contactClient,
 			List<MailboxVersion> server) {
-		return getHighestCommonMajorVersion(contactClient, server) >= 0
-				&& getHighestCommonMajorVersion(CLIENT_SUPPORTS, server) >= 0;
+		return isClientCompatibleWithServer(contactClient, server)
+				&& isClientCompatibleWithServer(CLIENT_SUPPORTS, server);
 	}
 
 	/**
@@ -637,8 +637,8 @@ class MailboxClientManager implements Service, EventListener {
 	 */
 	@SuppressWarnings("BooleanMethodIsAlwaysInverted")
 	private boolean isOwnMailboxUsable(MailboxProperties ownProperties) {
-		return getHighestCommonMajorVersion(CLIENT_SUPPORTS,
-				ownProperties.getServerSupports()) >= 0;
+		return isClientCompatibleWithServer(CLIENT_SUPPORTS,
+				ownProperties.getServerSupports());
 	}
 
 	/**