Adds support for json offer and answer then also in json

Signed-off-by: Jerzy Kołosowski <jerzy@kolosowscy.pl>

cmd/webrtc/webrtc.go

@@ -1,6 +1,7 @@
 package webrtc
 
 import (
+	"encoding/json"
 	"errors"
 	"github.com/AlexxIT/go2rtc/cmd/api"
 	"github.com/AlexxIT/go2rtc/cmd/app"
@@ -9,10 +10,16 @@ import (
 	pion "github.com/pion/webrtc/v3"
 	"github.com/rs/zerolog"
 	"io"
+	"mime"
 	"net"
 	"net/http"
 )
 
+type jsonSdp struct {
+	Type string `json:"type"`
+	Sdp  string `json:"sdp"`
+}
+
 func Init() {
 	var cfg struct {
 		Mod struct {
@@ -145,25 +152,76 @@ func syncHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	mediaType, err := DetermineMediaType(r)
+	if err != nil {
+		log.Error().Err(err).Caller().Msg("DetermineMediaType")
+		return
+	}
+
 	// get offer
-	offer, err := io.ReadAll(r.Body)
+	body, err := io.ReadAll(r.Body)
 	if err != nil {
 		log.Error().Err(err).Caller().Msg("ioutil.ReadAll")
 		return
 	}
 
-	answer, err := ExchangeSDP(stream, string(offer), r.UserAgent())
+	offer, err := DeserializeOffer(mediaType, body)
+	if err != nil {
+		log.Error().Err(err).Caller().Msg("DeserializeOffer")
+		return
+	}
+
+	answer, err := ExchangeSDP(stream, offer, r.UserAgent())
 	if err != nil {
 		log.Error().Err(err).Caller().Msg("ExchangeSDP")
 		return
 	}
 
+	response, err := SerializeAnswer(mediaType, answer)
+	if err != nil {
+		log.Error().Err(err).Caller().Msg("SerializeAnswer")
+		return
+	}
+
 	// send SDP to client
-	if _, err = w.Write([]byte(answer)); err != nil {
+	if _, err = w.Write(response); err != nil {
 		log.Error().Err(err).Caller().Msg("w.Write")
 	}
 }
 
+func DetermineMediaType(r *http.Request) (mediaType string, err error) {
+	contentType := r.Header.Get("Content-Type")
+	if contentType != "" {
+		mediaType, _, err = mime.ParseMediaType(contentType)
+		if err != nil {
+			log.Error().Err(err).Caller().Msg("mime.ParseMediaType")
+			return
+		}
+	} else {
+		mediaType = "text/plain"
+	}
+	return
+}
+
+func DeserializeOffer(mediaType string, body []byte) (offer string, err error) {
+	switch mediaType {
+	case "application/json":
+		var jsonOffer jsonSdp
+		err = json.Unmarshal(body, &jsonOffer)
+		if err != nil {
+			log.Error().Err(err).Caller().Msg("json.Unmarshal")
+			return
+		}
+
+		offer = jsonOffer.Sdp
+		break
+	default:
+		offer = string(body)
+		break
+	}
+	return
+}
+
 func ExchangeSDP(
 	stream *streams.Stream, offer string, userAgent string,
 ) (answer string, err error) {
@@ -216,3 +274,23 @@ func ExchangeSDP(
 
 	return
 }
+
+func SerializeAnswer(mediaType string, answer string) (response []byte, err error) {
+	switch mediaType {
+	case "application/json":
+		jsonAnswer := jsonSdp{
+			Sdp:  answer,
+			Type: "answer",
+		}
+		response, err = json.Marshal(jsonAnswer)
+		if err != nil {
+			log.Error().Err(err).Caller().Msg("json.Marshal")
+			return
+		}
+		break
+	default:
+		response = []byte(answer)
+		break
+	}
+	return
+}