     static let algoVirus:String = "algoVirus"
     static let algoAid:String = "algoAid"
     static let harvest:String = "harvest"
-    private let reference:FIRDatabaseReference
+    private let reference:DatabaseReference
     
     init()
     {
-        reference = FIRDatabase.database().reference()
+        reference = Database.database().reference()
     }
     
     //MARK: public

        path:String,
        json:Any)
    {
        let childReference:FIRDatabaseReference = reference.child(path)
        childReference.setValue(json)
    }
    
    func removeChild(path:String)
    {
        let childReference:FIRDatabaseReference = reference.child(path)
        childReference.removeValue()
    }
    

        path:String,
        handler:UInt)
    {
        let pathReference:DatabaseReference = reference.child(path)
        pathReference.removeObserver(withHandle:handler)
    }
    
    func transaction(
        path:String,
        transactionBlock:@escaping((MutableData) -> (TransactionResult)))
    {
        let childReference:DatabaseReference = reference.child(path)
        childReference.runTransactionBlock(transactionBlock)
    }
}
