firestore.rules

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    // ===============================================================
    // Helper Functions
    // ===============================================================
    function isAuthenticated() {
      return request.auth != null;
    }

    function isOwner(userId) {
      return isAuthenticated() && request.auth.uid == userId;
    }

    function isValidUser(data) {
      return data.keys().hasAll(['uid', 'email']) &&
             data.uid is string &&
             data.email is string &&
             (!('solvedQuestionIds' in data) || data.solvedQuestionIds is list);
    }

    // ===============================================================
    // Rules
    // ===============================================================
    match /users/{userId} {
      allow read: if isOwner(userId);
      allow create: if isOwner(userId) && isValidUser(request.resource.data);
      allow update: if isOwner(userId) && isValidUser(request.resource.data);
    }
  }
}