feat: bridge OnIceSelectedCandidatePairChanged to Java observers (#247)

Author: SendableMetatype

webrtc-jni/src/main/cpp/include/api/PeerConnectionObserver.h

@@ -47,6 +47,7 @@ namespace jni
 			void OnIceCandidateError(const std::string & address, int port, const std::string & url, int error_code, const std::string & error_text) override;
 			void OnIceCandidatesRemoved(const std::vector<webrtc::Candidate> & candidates) override;
 			void OnIceConnectionReceivingChange(bool receiving) override;
+			void OnIceSelectedCandidatePairChanged(const webrtc::CandidatePairChangeEvent & event) override;
 
 		private:
 			class JavaPeerConnectionObserverClass : public JavaClass
@@ -67,6 +68,7 @@ namespace jni
 					jmethodID onIceCandidateError;
 					jmethodID onIceCandidatesRemoved;
 					jmethodID onIceConnectionReceivingChange;
+					jmethodID onSelectedCandidatePairChanged;
 			};
 
 		private:

webrtc-jni/src/main/cpp/src/api/PeerConnectionObserver.cpp

@@ -24,6 +24,7 @@
 #include "JavaEnums.h"
 #include "JavaFactories.h"
 #include "JavaRuntimeException.h"
+#include "JavaString.h"
 #include "JavaUtils.h"
 #include "JNI_WebRTC.h"
 
@@ -193,6 +194,27 @@ namespace jni
 		ExceptionCheck(env);
 	}
 
+	void PeerConnectionObserver::OnIceSelectedCandidatePairChanged(const webrtc::CandidatePairChangeEvent & event)
+	{
+		JNIEnv * env = AttachCurrentThread();
+
+		const webrtc::Candidate & remote = event.selected_candidate_pair.remote_candidate();
+
+		std::string ip = remote.address().ipaddr().ToString();
+		int port = remote.address().port();
+
+		const auto typeName = remote.type_name();
+		std::string type(typeName.data(), typeName.size());
+
+		JavaLocalRef<jstring> jAddress = JavaString::toJava(env, ip);
+		JavaLocalRef<jstring> jType = JavaString::toJava(env, type);
+
+		env->CallVoidMethod(observer, javaClass->onSelectedCandidatePairChanged,
+			jAddress.get(), static_cast<jint>(port), jType.get());
+
+		ExceptionCheck(env);
+	}
+
 	PeerConnectionObserver::JavaPeerConnectionObserverClass::JavaPeerConnectionObserverClass(JNIEnv * env)
 	{
 		jclass cls = FindClass(env, PKG"PeerConnectionObserver");
@@ -210,5 +232,6 @@ namespace jni
 		onIceCandidateError = GetMethod(env, cls, "onIceCandidateError", "(L" PKG "RTCPeerConnectionIceErrorEvent;)V");
 		onIceCandidatesRemoved = GetMethod(env, cls, "onIceCandidatesRemoved", "([L" PKG "RTCIceCandidate;)V");
 		onIceConnectionReceivingChange = GetMethod(env, cls, "onIceConnectionReceivingChange", "(Z)V");
+		onSelectedCandidatePairChanged = GetMethod(env, cls, "onSelectedCandidatePairChanged", "(Ljava/lang/String;ILjava/lang/String;)V");
 	}
 }

webrtc/src/main/java/dev/onvoid/webrtc/PeerConnectionObserver.java

@@ -170,4 +170,20 @@ default void onRemoveTrack(RTCRtpReceiver receiver) {
 	default void onTrack(RTCRtpTransceiver transceiver) {
 	}
 
+	/**
+	 * ICE has selected (or later re-selected) a candidate pair for this
+	 * connection. Fires once connectivity checks nominate a pair, which is
+	 * before DTLS and SCTP are established and before data channels open, so
+	 * the remote transport address is known before the connection becomes
+	 * usable. May fire again if ICE re-nominates mid session.
+	 *
+	 * @param remoteAddress The remote candidate's IP address. For a relayed
+	 *                      connection this is the TURN relay's address.
+	 * @param remotePort    The remote candidate's port.
+	 * @param candidateType The remote candidate type: "host", "srflx",
+	 *                      "prflx", or "relay".
+	 */
+	default void onSelectedCandidatePairChanged(String remoteAddress, int remotePort, String candidateType) {
+	}
+
 }