Migrate OkHttp to bramble-core

bramble-core/src/main/java/org/briarproject/bramble/io/IoModule.java

@@ -1,18 +1,49 @@
 package org.briarproject.bramble.io;
 
+import org.briarproject.bramble.api.WeakSingletonProvider;
 import org.briarproject.bramble.api.io.TimeoutMonitor;
 
+import javax.annotation.Nonnull;
 import javax.inject.Singleton;
+import javax.net.SocketFactory;
 
 import dagger.Module;
 import dagger.Provides;
+import okhttp3.Dns;
+import okhttp3.OkHttpClient;
+
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
 
 @Module
 public class IoModule {
 
+	private static final int CONNECT_TIMEOUT = 60_000; // Milliseconds
+
 	@Provides
 	@Singleton
 	TimeoutMonitor provideTimeoutMonitor(TimeoutMonitorImpl timeoutMonitor) {
 		return timeoutMonitor;
 	}
+
+	// Share an HTTP client instance between requests where possible, while
+	// allowing the client to be garbage-collected between requests. The
+	// provider keeps a weak reference to the last client instance and reuses
+	// the instance until it gets garbage-collected. See
+	// https://medium.com/@leandromazzuquini/if-you-are-using-okhttp-you-should-know-this-61d68e065a2b
+	@Provides
+	@Singleton
+	WeakSingletonProvider<OkHttpClient> provideOkHttpClientProvider(
+			SocketFactory torSocketFactory, Dns noDnsLookups) {
+		return new WeakSingletonProvider<OkHttpClient>() {
+			@Override
+			@Nonnull
+			public OkHttpClient createInstance() {
+				return new OkHttpClient.Builder()
+						.socketFactory(torSocketFactory)
+						.dns(noDnsLookups) // Don't make local DNS lookups
+						.connectTimeout(CONNECT_TIMEOUT, MILLISECONDS)
+						.build();
+			}
+		};
+	}
 }