namespace BCG {
    using System.Collections.Generic;

    public class KeyValueToRelationalStream : ViewStream {
        private readonly ViewStream _kv_str;
        private readonly string _doc_id_col, _key_col, _val_col;
        public KeyValueToRelationalStream(ViewStream kv_str, string doc_id_col, string key_col, string val_col) {
            _kv_str = kv_str;
            _doc_id_col = doc_id_col;
            _key_col = key_col;
            _val_col = val_col;
        }

        protected override void myOnFirstSubscriber() {
            _kv_str.onChange += _on_str_update;
        }

        protected override void myOnLastSubscriber() {
            _kv_str.onChange -= _on_str_update;
        }

        private void _on_str_update(object dp_obj) {
            DataPacket dp = dp_obj as DataPacket;
            var rows = dp.newRows;
            var rv = BlueDataUtility.keyvalue_to_relational<string>(rows, _doc_id_col, _key_col, _val_col);
            var dp_out = BlueDataUtility.build_dp_inc(rv, myLastValue as DataPacket, true);
            myFireEvent(dp_out);
        }

    }
}