// Go subscription to CodeB Signal WebSocket events (ops dashboards).
// European Digital Identity Wallet-enabled tenants use the same signalling.
// [realtime-events-cookbook 2026-07-23]
//   go get github.com/gorilla/websocket
//
// Endpoint: wss://<tenant>/signal.ashx?room=<room>&name=<peerName>

package main

import (
	"encoding/json"
	"log"
	"net/url"
	"os"
	"time"

	"github.com/gorilla/websocket"
)

type frame struct {
	Type    string          `json:"type"`
	Message string          `json:"message,omitempty"`
	Mode    string          `json:"mode,omitempty"`
	Room    string          `json:"room,omitempty"`
	Peer    json.RawMessage `json:"peer,omitempty"`
}

func main() {
	host := envOr("CODEB_TENANT_HOST", "phone.example.tld")
	room := envOr("ROOM", "lobby")
	name := envOr("NAME", "ops-dashboard")

	u := url.URL{Scheme: "wss", Host: host, Path: "/signal.ashx",
		RawQuery: "room=" + url.QueryEscape(room) + "&name=" + url.QueryEscape(name)}

	backoff := time.Second
	for {
		c, _, err := websocket.DefaultDialer.Dial(u.String(), nil)
		if err != nil {
			log.Printf("[ws] dial: %v; retry in %s", err, backoff)
			time.Sleep(backoff)
			if backoff < 30*time.Second {
				backoff *= 2
			}
			continue
		}
		backoff = time.Second
		log.Printf("[ws] open %s", u.String())
		for {
			_, buf, err := c.ReadMessage()
			if err != nil {
				log.Printf("[ws] read: %v", err)
				break
			}
			var f frame
			if json.Unmarshal(buf, &f) != nil {
				continue
			}
			switch f.Type {
			case "welcome":
				log.Printf("[welcome] mode=%s room=%s", f.Mode, f.Room)
			case "peer-joined":
				log.Printf("[peer-joined] %s", f.Peer)
			case "peer-left":
				log.Printf("[peer-left] %s", f.Peer)
			case "mode-changed":
				log.Printf("[mode-changed] mode=%s", f.Mode)
			case "error":
				log.Printf("[server error] %s", f.Message)
			default:
				log.Printf("[event] %s", f.Type)
			}
		}
		c.Close()
	}
}

func envOr(k, d string) string {
	if v := os.Getenv(k); v != "" {
		return v
	}
	return d
}