Ported snowflake client to work with pion/webrtc

Modified the snowflake client to use pion/webrtc as the webrtc library.
This involved a few small changes to match function signatures as well
as several larger ones:
- OnNegotiationNeeded is no longer supported, so CreateOffer and
SetLocalDescription have been moved to a go routine called after the
other peer connection callbacks are set
- We need our own deserialize/serialize functions
- We need to use a SettingEngine in order to access the
OnICEGatheringStateChange callback

client/lib/util.go

@@ -1,23 +1,17 @@
 package lib
 
 import (
-	"fmt"
+	"encoding/json"
 	"log"
 	"time"
 
-	"github.com/keroserene/go-webrtc"
+	"github.com/pion/webrtc"
 )
 
 const (
 	LogTimeInterval = 5
 )
 
-type IceServerList []webrtc.ConfigurationOption
-
-func (i *IceServerList) String() string {
-	return fmt.Sprint(*i)
-}
-
 type BytesLogger interface {
 	Log()
 	AddOutbound(int)
@@ -93,3 +87,52 @@ func (b *BytesSyncLogger) AddInbound(amount int) {
 	}
 	b.InboundChan <- amount
 }
+func deserializeSessionDescription(msg string) *webrtc.SessionDescription {
+	var parsed map[string]interface{}
+	err := json.Unmarshal([]byte(msg), &parsed)
+	if nil != err {
+		log.Println(err)
+		return nil
+	}
+	if _, ok := parsed["type"]; !ok {
+		log.Println("Cannot deserialize SessionDescription without type field.")
+		return nil
+	}
+	if _, ok := parsed["sdp"]; !ok {
+		log.Println("Cannot deserialize SessionDescription without sdp field.")
+		return nil
+	}
+
+	var stype webrtc.SDPType
+	switch parsed["type"].(string) {
+	default:
+		log.Println("Unknown SDP type")
+		return nil
+	case "offer":
+		stype = webrtc.SDPTypeOffer
+	case "pranswer":
+		stype = webrtc.SDPTypePranswer
+	case "answer":
+		stype = webrtc.SDPTypeAnswer
+	case "rollback":
+		stype = webrtc.SDPTypeRollback
+	}
+
+	if err != nil {
+		log.Println(err)
+		return nil
+	}
+	return &webrtc.SessionDescription{
+		Type: stype,
+		SDP:  parsed["sdp"].(string),
+	}
+}
+
+func serializeSessionDescription(desc *webrtc.SessionDescription) string {
+	bytes, err := json.Marshal(*desc)
+	if nil != err {
+		log.Println(err)
+		return ""
+	}
+	return string(bytes)
+}