using System;

namespace BCG {
   public class AddColumnsStream : ViewStream {
      public static Tuple<string, Type, object> parse_exp(string exp) {
         string[] toks = exp.Split(':');
         string col_name = toks[0];
         string col_value = toks[1];
         Tuple<Type, object> tup = BlueDataUtility.guess_type(col_value);
         return Tuple.Create(col_name, tup.Item1, tup.Item2);
      }

      private Tuple<string, Type, object> _new_col;
      private IBlueTableSchema _out_schema;

      public AddColumnsStream(ViewStream vs, string col_def) {
         _new_col = parse_exp(col_def);
         ViewStream rs = new MapStream(vs, (IBlueTableSchema s) => _get_schema(s), (IBlueRow r) => _map(r));
         mySetRealSource(rs);
      }

      private IBlueTableSchema _get_schema(IBlueTableSchema input_schema) {
         if (_out_schema == null)
            _out_schema = BlueDataUtility.add_column(input_schema, _new_col.Item1, _new_col.Item2);
         return _out_schema;
      }

      private IBlueRow _map(IBlueRow r) {
         MutableBlueRow rv = new MutableBlueRow(_get_schema(r.schema), r);
         rv.setValue(_new_col.Item1, _new_col.Item3);
         return rv;
      }
   }
}