ich-lerne-deutsch/data/firestore-rules.txt

service cloud.firestore {
  match /databases/{database}/documents {
    function isAuthenticated() {
      return request.auth.uid != null;
    }
      
    function isAdmin() {
      return isAuthenticated()
        && get(/databases/$(database)/documents/userData/$(request.auth.uid)).data.isAdmin == true;
    }
      
    match /articles/{document=**} {
      allow read: if true;
      allow write: if isAdmin();
    }
      
    match /articleParts/{document=**} {
      allow read: if isAuthenticated()
        && get(/databases/$(database)/documents/userData/$(request.auth.uid))
          .data
          .articles[resource.data.articleId] != null;
      allow write: if isAdmin();
    }
      
    match /userData/{userId} {
      allow read, write: if isAuthenticated() || isAdmin();
    }
  }
}