ftx: define subscribed msg

pkg/exchange/ftx/websocket_messages.go

@@ -1,5 +1,7 @@
 package ftx
 
+import "encoding/json"
+
 type operation string
 
 const subscribe operation = "subscribe"
@@ -17,3 +19,44 @@ type SubscribeRequest struct {
 	Channel   channel   `json:"channel"`
 	Market    string    `json:"market"`
 }
+
+type respType string
+
+const errRespType respType = "error"
+const subscribedRespType respType = "subscribed"
+const unsubscribedRespType respType = "unsubscribed"
+const infoRespType respType = "info"
+const partialRespType respType = "partial"
+const updateRespType respType = "update"
+
+type mandatoryFields struct {
+	Type respType `json:"type"`
+
+	// Channel is mandatory
+	Channel channel `json:"channel"`
+
+	// Market is mandatory
+	Market string `json:"market"`
+}
+
+// doc: https://docs.ftx.com/#response-format
+type rawResponse struct {
+	mandatoryFields
+
+	// The following fields are optional.
+	// Example 1: {"type": "error", "code": 404, "msg": "No such market: BTCUSDT"}
+	Code    int64                      `json:"code"`
+	Message string                     `json:"msg"`
+	Data    map[string]json.RawMessage `json:"data"`
+}
+
+func (r rawResponse) toSubscribedResp() subscribedResponse {
+	return subscribedResponse{
+		mandatoryFields: r.mandatoryFields,
+	}
+}
+
+// {"type": "subscribed", "channel": "orderbook", "market": "BTC/USDT"}
+type subscribedResponse struct {
+	mandatoryFields
+}

pkg/exchange/ftx/websocket_messages_test.go

@@ -0,0 +1,18 @@
+package ftx
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_rawResponse_toSubscribedResp(t *testing.T) {
+	input := `{"type": "subscribed", "channel": "orderbook", "market": "BTC/USDT"}`
+	var m rawResponse
+	assert.NoError(t, json.Unmarshal([]byte(input), &m))
+	r := m.toSubscribedResp()
+	assert.Equal(t, subscribedRespType, r.Type)
+	assert.Equal(t, orderbook, r.Channel)
+	assert.Equal(t, "BTC/USDT", r.Market)
+}