ua-labels: derive source from User-Agent, persist peerID in localStorage

Server now parses the User-Agent header on /api/send when no explicit
source is provided, producing labels like 'iphone-safari',
'macos-chrome', 'windows-firefox' so the feed shows where messages
came from at a glance.

Browser-side peerID is now stored in localStorage instead of being
freshly random on each page load — refreshing or reopening the tab
keeps the same identity for the same browser profile.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

go.mod

@@ -12,6 +12,7 @@ require (
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/google/uuid v1.6.0 // indirect
+	github.com/mileusna/useragent v1.3.5 // indirect
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/pion/datachannel v1.6.0 // indirect
 	github.com/pion/dtls/v3 v3.1.2 // indirect

go.sum

@@ -18,6 +18,8 @@ github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/kylelemons/godebug v1.1.0 h1:RPNrshWIDI6G2gRW9EHilWtl7Z6Sb1BR0xunSBf0SNc=
 github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+fNqagV/RAw=
+github.com/mileusna/useragent v1.3.5 h1:SJM5NzBmh/hO+4LGeATKpaEX9+b4vcGg2qXGLiNGDws=
+github.com/mileusna/useragent v1.3.5/go.mod h1:3d8TOmwL/5I8pJjyVDteHtgDGcefrFUX4ccGOMKNYYc=
 github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq1c1nUAm88MOHcQC9l5mIlSMApZMrHA=
 github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=
 github.com/pion/datachannel v1.6.0 h1:XecBlj+cvsxhAMZWFfFcPyUaDZtd7IJvrXqlXD/53i0=

server/main.go

@@ -31,11 +31,45 @@ import (
 	"sync"
 	"time"
 
+	"github.com/mileusna/useragent"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
+// labelFromUA returns a short, human-friendly platform label like
+// "iphone-safari", "macos-chrome", "windows-firefox". Falls back to "web".
+func labelFromUA(uaStr string) string {
+	ua := useragent.Parse(uaStr)
+	platform := strings.ToLower(ua.OS)
+	switch {
+	case ua.IsIOS() && strings.Contains(strings.ToLower(ua.Device), "ipad"):
+		platform = "ipad"
+	case ua.IsIOS():
+		platform = "iphone"
+	case ua.IsAndroid():
+		platform = "android"
+	case ua.IsMacOS():
+		platform = "macos"
+	case ua.IsWindows():
+		platform = "windows"
+	case ua.IsLinux():
+		platform = "linux"
+	}
+	browser := strings.ToLower(ua.Name)
+	browser = strings.ReplaceAll(browser, " ", "")
+	if platform == "" && browser == "" {
+		return "web"
+	}
+	if browser == "" {
+		return platform
+	}
+	if platform == "" {
+		return browser
+	}
+	return platform + "-" + browser
+}
+
 //go:embed web
 var webFS embed.FS
 
@@ -251,7 +285,7 @@ func main() {
 		if m.Source == "" {
 			m.Source = r.Header.Get("X-Tether-Source")
 			if m.Source == "" {
-				m.Source = "web"
+				m.Source = labelFromUA(r.Header.Get("User-Agent"))
 			}
 		}
 		m.TS = time.Now().UnixMilli()

server/web/index.html

@@ -151,7 +151,12 @@
   if (!roomMatch) { window.location.replace("/"); }
   const room = roomMatch ? roomMatch[1] : "";
   const fullUrl = window.location.origin + "/r/" + room;
-  const peerID = "browser-" + Array.from(crypto.getRandomValues(new Uint8Array(6))).map(b=>b.toString(16).padStart(2,"0")).join("");
+  // Stable per-device id — persists across reloads (unless cleared).
+  let peerID = localStorage.getItem("tether-peerID");
+  if (!peerID) {
+    peerID = "browser-" + Array.from(crypto.getRandomValues(new Uint8Array(6))).map(b=>b.toString(16).padStart(2,"0")).join("");
+    localStorage.setItem("tether-peerID", peerID);
+  }
 
   $("roomTag").textContent = room;
   $("sessionUrl").textContent = fullUrl;
@@ -218,16 +223,16 @@
       const r = await fetch("/api/send?room=" + room, {
         method: "POST",
         headers: { "Content-Type": "application/json" },
-        body: JSON.stringify({ type: "clipboard", text, source: "web", from: peerID, room }),
+        body: JSON.stringify({ type: "clipboard", text, from: peerID, room }),
       });
       status(r.ok ? "delivered ✓" : "server returned " + r.status, r.ok ? "ok" : "err");
     } catch (e) { status("network error", "err"); }
   });
 
   // ── Signaling ─────────────────────────────────────────────────────────
+  // Let the server fill in source from User-Agent unless caller specifies.
   async function postMessage(m) {
     m.from = m.from || peerID;
-    m.source = m.source || "web";
     m.room = room;
     await fetch("/api/send?room=" + room, {
       method: "POST",