gradio-webrtc/frontend/shared/webrtc_utils.ts

export function createPeerConnection(pc, node) {
	// register some listeners to help debugging
	pc.addEventListener(
		"icegatheringstatechange",
		() => {
			console.debug(pc.iceGatheringState);
		},
		false
	);

	pc.addEventListener(
		"iceconnectionstatechange",
		() => {
			console.debug(pc.iceConnectionState);
		},
		false
	);

	pc.addEventListener(
		"signalingstatechange",
		() => {
			console.debug(pc.signalingState);
		},
		false
	);

	// connect audio / video from server to local
	pc.addEventListener("track", (evt) => {
		console.debug("track event listener");
		if (node.srcObject !== evt.streams[0]) {
			console.debug("streams", evt.streams);
			node.srcObject = evt.streams[0];
			console.debug("node.srcOject", node.srcObject);
			if (evt.track.kind === 'audio') {
				node.volume = 1.0;  // Ensure volume is up
				node.muted = false;
				node.autoplay = true;
				
				// Attempt to play (needed for some browsers)
				node.play().catch(e => console.debug("Autoplay failed:", e));
			}
		}
	});

	return pc;
}

export async function start(stream, pc: RTCPeerConnection, node, server_fn, webrtc_id, modality: "video" | "audio" = "video") {
	pc = createPeerConnection(pc, node);
	if (stream) {
		stream.getTracks().forEach((track) => {
			track.applyConstraints({ frameRate: { max: 30 } });

			console.debug("Track stream callback", track);
			pc.addTrack(track, stream);
		});
	} else {
		console.debug("Creating transceiver!");
		pc.addTransceiver(modality, { direction: "recvonly" });
	}

	await negotiate(pc, server_fn, webrtc_id);
	return pc;
}

function make_offer(server_fn: any, body): Promise<object> {
    return new Promise((resolve, reject) => {
        server_fn(body).then((data) => {
            console.debug("data", data)
            if(data?.status === "failed") {
                console.debug("rejecting")
                reject("error")
            }
            resolve(data);
        })
    })
}

async function negotiate(
	pc: RTCPeerConnection,
	server_fn: any,
    webrtc_id: string,
): Promise<void> {
	return pc
		.createOffer()
		.then((offer) => {
			return pc.setLocalDescription(offer);
		})
		.then(() => {
			// wait for ICE gathering to complete
			return new Promise<void>((resolve) => {
				console.debug("ice gathering state", pc.iceGatheringState);
				if (pc.iceGatheringState === "complete") {
					resolve();
				} else {
					const checkState = () => {
						if (pc.iceGatheringState === "complete") {
							console.debug("ice complete");
							pc.removeEventListener("icegatheringstatechange", checkState);
							resolve();
						}
					};
					pc.addEventListener("icegatheringstatechange", checkState);
				}
			});
		})
		.then(() => {
			var offer = pc.localDescription;
			return make_offer(
                server_fn,
				{
					sdp: offer.sdp,
					type: offer.type,
                    webrtc_id: webrtc_id
				},
			);
		})
		.then((response) => {
			return response;
		})
		.then((answer) => {
			return pc.setRemoteDescription(answer);
		})
}

export function stop(pc: RTCPeerConnection) {
	console.debug("Stopping peer connection");
	// close transceivers
	if (pc.getTransceivers) {
		pc.getTransceivers().forEach((transceiver) => {
			if (transceiver.stop) {
				transceiver.stop();
			}
		});
	}

	// close local audio / video
	if (pc.getSenders()) {
		pc.getSenders().forEach((sender) => {
			if (sender.track && sender.track.stop) sender.track.stop();
		});
	}

	// close peer connection
	setTimeout(() => {
		pc.close();
	}, 500);
}