path /visits/{visit_id} is Visit {
  read() { canManageSpace(this.spaceId) }
  write() { canManageSpace(this.spaceId) }
}

path /spaceVisits/{space_id}/{visit_id} is Visit {
  read() { canManageSpace(space_id) }
}

path /memberVisits/{member_id}/{visit_id} is Visit {
  read() { canManageSpace(this.spaceId) }
}

type Visit {
  duration: UnsignedNumber | Null,
  in: UnsignedNumber,
  memberId: String,
  out: UnsignedNumber | Null,
  spaceId: String,

  validate() {
    (this.out === null || this.duration === (this.out - this.in))
  }
}

type UnsignedNumber extends Number {
  validate() { this >= 0 }
}

// Returns `true` if the value is initialized to init, or if it retains it's prior value, otherwise `false`
isSignedIn() { auth !== null }
isCurrentUser(uid) { isSignedIn() && auth.uid === uid }
canManageSpace(id) {
  // Check that the user has proper credentials in your own logic
  isSignedIn()
}