feat: runtime config, Matomo analytics, chat accounts, DM history/search, and Prometheus retention

backend/chat/src/auth/auth.go

@@ -137,4 +137,52 @@ func RequireAdmin(store *SessionStore, cookieName string) func(http.HandlerFunc)
 			next(w, r)
 		}
 	}
+}
+
+// UserSessionStore maps user session tokens to usernames with expiry.
+type UserSessionStore struct {
+	mu       sync.Mutex
+	sessions map[string]userSession
+}
+
+type userSession struct {
+	Username  string
+	ExpiresAt time.Time
+}
+
+// NewUserSessionStore creates a new user session store.
+func NewUserSessionStore() *UserSessionStore {
+	return &UserSessionStore{sessions: make(map[string]userSession)}
+}
+
+// Add stores a user session token with username and expiry.
+func (s *UserSessionStore) Add(token, username string, expiresAt time.Time) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.sessions[token] = userSession{Username: username, ExpiresAt: expiresAt}
+}
+
+// Username returns the username for a valid, unexpired token.
+func (s *UserSessionStore) Username(token string) (string, bool) {
+	if token == "" {
+		return "", false
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	sess, ok := s.sessions[token]
+	if !ok {
+		return "", false
+	}
+	if time.Now().After(sess.ExpiresAt) {
+		delete(s.sessions, token)
+		return "", false
+	}
+	return sess.Username, true
+}
+
+// Remove deletes a user session token.
+func (s *UserSessionStore) Remove(token string) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	delete(s.sessions, token)
 }

backend/chat/src/auth/auth_test.go

@@ -245,4 +245,33 @@ func TestRequireAdmin(t *testing.T) {
 	if w3.Code != http.StatusUnauthorized {
 		t.Errorf("status = %d, want 401", w3.Code)
 	}
+}
+
+func TestUserSessionStore(t *testing.T) {
+	store := NewUserSessionStore()
+
+	if _, ok := store.Username(""); ok {
+		t.Error("Username(\"\") = true, want false")
+	}
+
+	token, _ := GenerateToken()
+	store.Add(token, "alice", time.Now().Add(1*time.Hour))
+
+	username, ok := store.Username(token)
+	if !ok || username != "alice" {
+		t.Errorf("Username() = %q, %v; want alice, true", username, ok)
+	}
+
+	// Expired session
+	expired, _ := GenerateToken()
+	store.Add(expired, "bob", time.Now().Add(-1*time.Hour))
+	if _, ok := store.Username(expired); ok {
+		t.Error("Username(expired) = true, want false")
+	}
+
+	// Remove
+	store.Remove(token)
+	if _, ok := store.Username(token); ok {
+		t.Error("Username after Remove = true, want false")
+	}
 }