Redo protocol for proxy--broker messages

Switch to containing all communication between the proxy and the broker
in the HTTP response body. This will make things easier if we ever use
something other than HTTP communicate between different actors in the
snowflake system.

Other changes to the protocol are as follows:
- requests are accompanied by a version number so the broker can be
backwards compatable if desired in the future
- all responses are 200 OK unless the request was badly formatted

common/messages/proxy_test.go

@@ -0,0 +1,161 @@
+package messages
+
+import (
+	"encoding/json"
+	"fmt"
+	"testing"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestDecodeProxyPollRequest(t *testing.T) {
+	Convey("Context", t, func() {
+		for _, test := range []struct {
+			sid  string
+			data string
+			err  error
+		}{
+			{
+				//Version 1.0 proxy message
+				"ymbcCMto7KHNGYlp",
+				`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.0"}`,
+				nil,
+			},
+			{
+				//Version 0.X proxy message:
+				"",
+				"ymbcCMto7KHNGYlp",
+				&json.SyntaxError{},
+			},
+			{
+				"",
+				`{"Sid":"ymbcCMto7KHNGYlp"}`,
+				fmt.Errorf(""),
+			},
+			{
+				"",
+				"{}",
+				fmt.Errorf(""),
+			},
+			{
+				"",
+				`{"Version":"1.0"}`,
+				fmt.Errorf(""),
+			},
+			{
+				"",
+				`{"Version":"2.0"}`,
+				fmt.Errorf(""),
+			},
+		} {
+			sid, err := DecodePollRequest([]byte(test.data))
+			So(sid, ShouldResemble, test.sid)
+			So(err, ShouldHaveSameTypeAs, test.err)
+		}
+
+	})
+}
+
+func TestEncodeProxyPollRequests(t *testing.T) {
+	Convey("Context", t, func() {
+		b, err := EncodePollRequest("ymbcCMto7KHNGYlp")
+		So(err, ShouldEqual, nil)
+		sid, err := DecodePollRequest(b)
+		So(sid, ShouldEqual, "ymbcCMto7KHNGYlp")
+		So(err, ShouldEqual, nil)
+	})
+}
+
+func TestDecodeProxyAnswerRequest(t *testing.T) {
+	Convey("Context", t, func() {
+		for _, test := range []struct {
+			answer string
+			sid    string
+			data   string
+			err    error
+		}{
+			{
+				"test",
+				"test",
+				`{"Version":"1.0","Sid":"test","Answer":"test"}`,
+				nil,
+			},
+			{
+				"",
+				"",
+				`{"type":"offer","sdp":"v=0\r\no=- 4358805017720277108 2 IN IP4 [scrubbed]\r\ns=-\r\nt=0 0\r\na=group:BUNDLE data\r\na=msid-semantic: WMS\r\nm=application 56688 DTLS/SCTP 5000\r\nc=IN IP4 [scrubbed]\r\na=candidate:3769337065 1 udp 2122260223 [scrubbed] 56688 typ host generation 0 network-id 1 network-cost 50\r\na=candidate:2921887769 1 tcp 1518280447 [scrubbed] 35441 typ host tcptype passive generation 0 network-id 1 network-cost 50\r\na=ice-ufrag:aMAZ\r\na=ice-pwd:jcHb08Jjgrazp2dzjdrvPPvV\r\na=ice-options:trickle\r\na=fingerprint:sha-256 C8:88:EE:B9:E7:02:2E:21:37:ED:7A:D1:EB:2B:A3:15:A2:3B:5B:1C:3D:D4:D5:1F:06:CF:52:40:03:F8:DD:66\r\na=setup:actpass\r\na=mid:data\r\na=sctpmap:5000 webrtc-datachannel 1024\r\n"}`,
+				fmt.Errorf(""),
+			},
+			{
+				"",
+				"",
+				`{"Version":"1.0","Answer":"test"}`,
+				fmt.Errorf(""),
+			},
+			{
+				"",
+				"",
+				`{"Version":"1.0","Sid":"test"}`,
+				fmt.Errorf(""),
+			},
+		} {
+			answer, sid, err := DecodeAnswerRequest([]byte(test.data))
+			So(answer, ShouldResemble, test.answer)
+			So(sid, ShouldResemble, test.sid)
+			So(err, ShouldHaveSameTypeAs, test.err)
+		}
+
+	})
+}
+
+func TestEncodeProxyAnswerRequest(t *testing.T) {
+	Convey("Context", t, func() {
+		b, err := EncodeAnswerRequest("test answer", "test sid")
+		So(err, ShouldEqual, nil)
+		answer, sid, err := DecodeAnswerRequest(b)
+		So(answer, ShouldEqual, "test answer")
+		So(sid, ShouldEqual, "test sid")
+		So(err, ShouldEqual, nil)
+	})
+}
+
+func TestDecodeProxyAnswerResponse(t *testing.T) {
+	Convey("Context", t, func() {
+		for _, test := range []struct {
+			success bool
+			data    string
+			err     error
+		}{
+			{
+				true,
+				`{"Status":"success"}`,
+				nil,
+			},
+			{
+				false,
+				`{"Status":"client gone"}`,
+				nil,
+			},
+			{
+				false,
+				`{"Test":"test"}`,
+				fmt.Errorf(""),
+			},
+		} {
+			success, err := DecodeAnswerResponse([]byte(test.data))
+			So(success, ShouldResemble, test.success)
+			So(err, ShouldHaveSameTypeAs, test.err)
+		}
+
+	})
+}
+
+func TestEncodeProxyAnswerResponse(t *testing.T) {
+	Convey("Context", t, func() {
+		b, err := EncodeAnswerResponse(true)
+		So(err, ShouldEqual, nil)
+		success, err := DecodeAnswerResponse(b)
+		So(success, ShouldEqual, true)
+		So(err, ShouldEqual, nil)
+	})
+}