Add discovery methods to plugin API.

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/DiscoveryHandler.java

@@ -0,0 +1,18 @@
+package org.briarproject.bramble.api.plugin;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.properties.TransportProperties;
+
+/**
+ * An interface for handling peers discovered by transport plugins.
+ */
+@NotNullByDefault
+public interface DiscoveryHandler {
+
+	/**
+	 * Handles a peer discovered by a transport plugin.
+	 *
+	 * @param p A set of properties describing the discovered peer.
+	 */
+	void handleDevice(TransportProperties p);
+}

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/Plugin.java

@@ -5,7 +5,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.settings.SettingsManager;
 
-import java.util.Collection;
+import java.util.List;
 
 @NotNullByDefault
 public interface Plugin {
@@ -106,6 +106,5 @@ public interface Plugin {
 	 * Attempts to create connections using the given transport properties,
 	 * passing any created connections to the corresponding handlers.
 	 */
-	void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
+	void poll(List<Pair<TransportProperties, ConnectionHandler>> properties);
-			properties);
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/duplex/DuplexPlugin.java

@@ -1,14 +1,18 @@
 package org.briarproject.bramble.api.plugin.duplex;
 
+import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.DiscoveryHandler;
 import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
 import org.briarproject.bramble.api.rendezvous.RendezvousEndpoint;
 
+import java.util.List;
+
 import javax.annotation.Nullable;
 
 /**
@@ -58,4 +62,16 @@ public interface DuplexPlugin extends Plugin {
 	@Nullable
 	RendezvousEndpoint createRendezvousEndpoint(KeyMaterialSource k,
 			boolean alice, ConnectionHandler incoming);
+
+	/**
+	 * Returns true if the plugin supports peer discovery.
+	 */
+	boolean supportsDiscovery();
+
+	/**
+	 * Attempts to discover peers using the given transport properties, passing
+	 * any discovered peers to the corresponding handlers.
+	 */
+	void discoverPeers(List<Pair<TransportProperties, DiscoveryHandler>>
+			properties);
 }

bramble-core/src/main/java/org/briarproject/bramble/plugin/PollerImpl.java

@@ -32,6 +32,7 @@ import java.security.SecureRandom;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.concurrent.Executor;
@@ -216,8 +217,8 @@ class PollerImpl implements Poller, EventListener {
 					transportPropertyManager.getRemoteProperties(t);
 			Collection<ContactId> connected =
 					connectionRegistry.getConnectedContacts(t);
-			Collection<Pair<TransportProperties, ConnectionHandler>>
+			List<Pair<TransportProperties, ConnectionHandler>> properties =
-					properties = new ArrayList<>();
+					new ArrayList<>();
 			for (Entry<ContactId, TransportProperties> e : remote.entrySet()) {
 				ContactId c = e.getKey();
 				if (!connected.contains(c))

bramble-core/src/main/java/org/briarproject/bramble/plugin/bluetooth/BluetoothPlugin.java

@@ -15,6 +15,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.DiscoveryHandler;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.PluginException;
 import org.briarproject.bramble.api.plugin.TransportId;
@@ -31,7 +32,7 @@ import org.briarproject.bramble.api.settings.event.SettingsUpdatedEvent;
 
 import java.io.IOException;
 import java.security.SecureRandom;
-import java.util.Collection;
+import java.util.List;
 import java.util.UUID;
 import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -266,8 +267,8 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	}
 
 	@Override
-	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
+	public void poll(
-			properties) {
+			List<Pair<TransportProperties, ConnectionHandler>> properties) {
 		if (getState() != ACTIVE) return;
 		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
@@ -411,6 +412,17 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		throw new UnsupportedOperationException();
 	}
 
+	@Override
+	public boolean supportsDiscovery() {
+		return false;
+	}
+
+	@Override
+	public void discoverPeers(
+			List<Pair<TransportProperties, DiscoveryHandler>> properties) {
+		throw new UnsupportedOperationException();
+	}
+
 	@Override
 	public void eventOccurred(Event e) {
 		if (e instanceof EnableBluetoothEvent) {

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/TcpPlugin.java

@@ -2,16 +2,15 @@ package org.briarproject.bramble.plugin.tcp;
 
 import org.briarproject.bramble.PoliteExecutor;
 import org.briarproject.bramble.api.Pair;
-import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventListener;
-import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.DiscoveryHandler;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
@@ -221,8 +220,8 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 	}
 
 	@Override
-	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
+	public void poll(
-			properties) {
+			List<Pair<TransportProperties, ConnectionHandler>> properties) {
 		if (getState() != ACTIVE) return;
 		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
@@ -323,22 +322,6 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 		}
 	}
 
-	@Override
-	public boolean supportsKeyAgreement() {
-		return false;
-	}
-
-	@Override
-	public KeyAgreementListener createKeyAgreementListener(byte[] commitment) {
-		throw new UnsupportedOperationException();
-	}
-
-	@Override
-	public DuplexTransportConnection createKeyAgreementConnection(
-			byte[] commitment, BdfList descriptor) {
-		throw new UnsupportedOperationException();
-	}
-
 	@Override
 	public boolean supportsRendezvous() {
 		return false;
@@ -350,6 +333,17 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 		throw new UnsupportedOperationException();
 	}
 
+	@Override
+	public boolean supportsDiscovery() {
+		return false;
+	}
+
+	@Override
+	public void discoverPeers(
+			List<Pair<TransportProperties, DiscoveryHandler>> properties) {
+		throw new UnsupportedOperationException();
+	}
+
 	List<InterfaceAddress> getLocalInterfaceAddresses() {
 		List<InterfaceAddress> addrs = new ArrayList<>();
 		for (NetworkInterface iface : getNetworkInterfaces()) {

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/WanTcpPlugin.java

@@ -1,10 +1,13 @@
 package org.briarproject.bramble.plugin.tcp;
 
+import org.briarproject.bramble.api.data.BdfList;
+import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportProperties;
 
 import java.net.Inet4Address;
@@ -42,6 +45,22 @@ class WanTcpPlugin extends TcpPlugin {
 		return ID;
 	}
 
+	@Override
+	public boolean supportsKeyAgreement() {
+		return false;
+	}
+
+	@Override
+	public KeyAgreementListener createKeyAgreementListener(byte[] commitment) {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public DuplexTransportConnection createKeyAgreementConnection(
+			byte[] commitment, BdfList descriptor) {
+		throw new UnsupportedOperationException();
+	}
+
 	@Override
 	protected List<InetSocketAddress> getLocalSocketAddresses() {
 		// Use the same address and port as last time if available

bramble-core/src/main/java/org/briarproject/bramble/plugin/tor/TorPlugin.java

@@ -19,6 +19,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.DiscoveryHandler;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.PluginException;
 import org.briarproject.bramble.api.plugin.TorConstants;
@@ -549,8 +550,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	@Override
-	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
+	public void poll(
-			properties) {
+			List<Pair<TransportProperties, ConnectionHandler>> properties) {
 		if (getState() != ACTIVE) return;
 		backoff.increment();
 		for (Pair<TransportProperties, ConnectionHandler> p : properties) {
@@ -684,6 +685,17 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 	}
 
+	@Override
+	public boolean supportsDiscovery() {
+		return false;
+	}
+
+	@Override
+	public void discoverPeers(
+			List<Pair<TransportProperties, DiscoveryHandler>> properties) {
+		throw new UnsupportedOperationException();
+	}
+
 	@Override
 	public void circuitStatus(String status, String id, String path) {
 		if (status.equals("BUILT") &&

bramble-core/src/test/java/org/briarproject/bramble/plugin/PollerImplTest.java

@@ -38,7 +38,7 @@ import static java.util.Collections.emptyList;
 import static java.util.Collections.singletonList;
 import static java.util.Collections.singletonMap;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
-import static org.briarproject.bramble.test.CollectionMatcher.collectionOf;
+import static org.briarproject.bramble.test.ListMatcher.listOf;
 import static org.briarproject.bramble.test.PairMatcher.pairOf;
 import static org.briarproject.bramble.test.TestUtils.getContactId;
 import static org.briarproject.bramble.test.TestUtils.getTransportId;
@@ -357,8 +357,8 @@ public class PollerImplTest extends BrambleMockTestCase {
 			oneOf(connectionRegistry).getConnectedContacts(transportId);
 			will(returnValue(emptyList()));
 			// Poll the plugin
-			oneOf(plugin).poll(with(collectionOf(
+			oneOf(plugin).poll(with(listOf(pairOf(
-					pairOf(equal(properties), any(ConnectionHandler.class)))));
+					equal(properties), any(ConnectionHandler.class)))));
 		}});
 
 		poller.eventOccurred(new TransportActiveEvent(transportId));

bramble-core/src/test/java/org/briarproject/bramble/rendezvous/RendezvousPollerImplTest.java

@@ -49,7 +49,7 @@ import static org.briarproject.bramble.api.contact.PendingContactState.OFFLINE;
 import static org.briarproject.bramble.api.contact.PendingContactState.WAITING_FOR_CONNECTION;
 import static org.briarproject.bramble.rendezvous.RendezvousConstants.POLLING_INTERVAL_MS;
 import static org.briarproject.bramble.rendezvous.RendezvousConstants.RENDEZVOUS_TIMEOUT_MS;
-import static org.briarproject.bramble.test.CollectionMatcher.collectionOf;
+import static org.briarproject.bramble.test.ListMatcher.listOf;
 import static org.briarproject.bramble.test.PairMatcher.pairOf;
 import static org.briarproject.bramble.test.TestUtils.getAgreementPrivateKey;
 import static org.briarproject.bramble.test.TestUtils.getAgreementPublicKey;
@@ -196,7 +196,7 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 			oneOf(clock).currentTimeMillis();
 			will(returnValue(beforeExpiry));
 			oneOf(eventBus).broadcast(with(any(RendezvousPollEvent.class)));
-			oneOf(plugin).poll(with(collectionOf(pairOf(
+			oneOf(plugin).poll(with(listOf(pairOf(
 					equal(transportProperties),
 					any(ConnectionHandler.class)))));
 		}});
@@ -248,7 +248,7 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 			oneOf(clock).currentTimeMillis();
 			will(returnValue(beforeExpiry));
 			oneOf(eventBus).broadcast(with(any(RendezvousPollEvent.class)));
-			oneOf(plugin).poll(with(collectionOf(pairOf(
+			oneOf(plugin).poll(with(listOf(pairOf(
 					equal(transportProperties),
 					any(ConnectionHandler.class)))));
 		}});

bramble-core/src/test/java/org/briarproject/bramble/test/ListMatcher.java

@@ -5,24 +5,24 @@ import org.hamcrest.BaseMatcher;
 import org.hamcrest.Description;
 import org.hamcrest.Matcher;
 
-import java.util.Collection;
+import java.util.List;
 
 import javax.annotation.Nullable;
 
 @NotNullByDefault
-public class CollectionMatcher<T> extends BaseMatcher<Collection<T>> {
+public class ListMatcher<T> extends BaseMatcher<List<T>> {
 
 	private final Matcher<T> elementMatcher;
 
-	public CollectionMatcher(Matcher<T> elementMatcher) {
+	public ListMatcher(Matcher<T> elementMatcher) {
 		this.elementMatcher = elementMatcher;
 	}
 
 	@Override
 	public boolean matches(@Nullable Object item) {
-		if (!(item instanceof Collection)) return false;
+		if (!(item instanceof List)) return false;
-		Collection collection = (Collection) item;
+		List list = (List) item;
-		for (Object element : collection) {
+		for (Object element : list) {
 			if (!elementMatcher.matches(element)) return false;
 		}
 		return true;
@@ -33,7 +33,7 @@ public class CollectionMatcher<T> extends BaseMatcher<Collection<T>> {
 		description.appendText("matches a collection");
 	}
 
-	public static <T> CollectionMatcher<T> collectionOf(Matcher<T> t) {
+	public static <T> ListMatcher<T> listOf(Matcher<T> t) {
-		return new CollectionMatcher<>(t);
+		return new ListMatcher<>(t);
 	}
 }

bramble-java/src/main/java/org/briarproject/bramble/plugin/modem/ModemPlugin.java

@@ -7,6 +7,7 @@ import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.ConnectionHandler;
+import org.briarproject.bramble.api.plugin.DiscoveryHandler;
 import org.briarproject.bramble.api.plugin.PluginCallback;
 import org.briarproject.bramble.api.plugin.PluginException;
 import org.briarproject.bramble.api.plugin.TransportId;
@@ -20,7 +21,7 @@ import org.briarproject.bramble.api.rendezvous.RendezvousEndpoint;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
-import java.util.Collection;
+import java.util.List;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.logging.Logger;
 
@@ -136,8 +137,8 @@ class ModemPlugin implements DuplexPlugin, Modem.Callback {
 	}
 
 	@Override
-	public void poll(Collection<Pair<TransportProperties, ConnectionHandler>>
+	public void poll(
-			properties) {
+			List<Pair<TransportProperties, ConnectionHandler>> properties) {
 		throw new UnsupportedOperationException();
 	}
 
@@ -213,6 +214,17 @@ class ModemPlugin implements DuplexPlugin, Modem.Callback {
 		throw new UnsupportedOperationException();
 	}
 
+	@Override
+	public boolean supportsDiscovery() {
+		return false;
+	}
+
+	@Override
+	public void discoverPeers(
+			List<Pair<TransportProperties, DiscoveryHandler>> properties) {
+		throw new UnsupportedOperationException();
+	}
+
 	@Override
 	public void incomingCallConnected() {
 		LOG.info("Incoming call connected");