DXCDT-548: Serve prompt data on demand (#868)

internal/cli/universal_login_customize.go

@@ -2,6 +2,7 @@ package cli
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"net"
 	"net/http"
@@ -19,7 +20,12 @@ import (
 	"github.com/auth0/auth0-cli/internal/display"
 )
 
-const webAppURL = "http://localhost:5173"
+const (
+	webAppURL               = "http://localhost:5173"
+	loadBrandingMessageType = "LOAD_BRANDING"
+	fetchPromptMessageType  = "FETCH_PROMPT"
+	saveBrandingMessageType = "SAVE_BRANDING"
+)
 
 type (
 	universalLoginBrandingData struct {
@@ -40,7 +46,7 @@ type (
 	promptData struct {
 		Language   string                            `json:"language"`
 		Prompt     string                            `json:"prompt"`
-		CustomText map[string]map[string]interface{} `json:"custom_text"`
+		CustomText map[string]map[string]interface{} `json:"custom_text,omitempty"`
 	}
 
 	webSocketHandler struct {
@@ -49,6 +55,11 @@ type (
 		api          *auth0.API
 		brandingData *universalLoginBrandingData
 	}
+
+	webSocketMessage struct {
+		Type    string          `json:"type"`
+		Payload json.RawMessage `json:"payload"`
+	}
 )
 
 func customizeUniversalLoginCmd(cli *cli) *cobra.Command {
@@ -314,18 +325,77 @@ func (h *webSocketHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 	connection, err := upgrader.Upgrade(w, r, nil)
 	if err != nil {
-		h.display.Errorf("error accepting WebSocket connection: %v", err)
+		h.display.Errorf("failed to upgrade the connection to the WebSocket protocol: %v", err)
 		h.shutdown()
 		return
 	}
 
 	connection.SetReadLimit(1e+6) // 1 MB.
 
-	if err = connection.WriteJSON(h.brandingData); err != nil {
-		h.display.Errorf("failed to write json message: %v", err)
+	payload, err := json.Marshal(&h.brandingData)
+	if err != nil {
+		h.display.Errorf("failed to encode the branding data to json: %v", err)
+		h.shutdown()
+		return
+	}
+
+	loadBrandingMsg := webSocketMessage{
+		Type:    loadBrandingMessageType,
+		Payload: payload,
+	}
+
+	if err = connection.WriteJSON(loadBrandingMsg); err != nil {
+		h.display.Errorf("failed to send branding data message: %v", err)
 		h.shutdown()
 		return
 	}
+
+	for {
+		var message webSocketMessage
+		if err := connection.ReadJSON(&message); err != nil {
+			h.display.Errorf("failed to read WebSocket message: %v", err)
+			continue
+		}
+
+		switch message.Type {
+		case fetchPromptMessageType:
+			var promptToFetch promptData
+			if err := json.Unmarshal(message.Payload, &promptToFetch); err != nil {
+				h.display.Errorf("failed to unmarshal fetch prompt payload: %v", err)
+				continue
+			}
+
+			promptToSend, err := fetchPromptCustomTextWithDefaults(
+				r.Context(),
+				h.api,
+				promptToFetch.Prompt,
+				promptToFetch.Language,
+			)
+			if err != nil {
+				h.display.Errorf("failed to fetch custom text for prompt: %v", err)
+				continue
+			}
+
+			payload, err := json.Marshal(promptToSend)
+			if err != nil {
+				h.display.Errorf("failed to encode the branding data to json: %v", err)
+				h.shutdown()
+				return
+			}
+
+			fetchPromptMsg := webSocketMessage{
+				Type:    fetchPromptMessageType,
+				Payload: payload,
+			}
+
+			if err = connection.WriteJSON(fetchPromptMsg); err != nil {
+				h.display.Errorf("failed to send prompt data message: %v", err)
+				continue
+			}
+		case saveBrandingMessageType:
+			h.display.Warnf("not yet implemented")
+		}
+	}
 }
 
 func checkOriginFunc(r *http.Request) bool {