using BCG;

using System.Collections;
using System.Collections.Generic;
using System.Linq;

using ZstdSharp.Unsafe;

namespace bts {
    public class RowDiffStream : ViewStream {
        private ViewStream _vs;
        private readonly string _order_col, _col_1, _col_2;
        private readonly int _diff;
        private IBlueTableSchema _out_schema;
        private readonly string _diff_col_name;
        public RowDiffStream(ViewStream vs, string order_col, string col_1, string col_2, int diff, string diff_col_name) {
            _vs = vs;
            _order_col = order_col;
            _col_1 = col_1;
            _col_2 = col_2;
            _diff = diff;
            _diff_col_name = diff_col_name;
        }

        private string _diff_col_name_perc {
            get {
                return $"{_diff_col_name}_percentage";
            }
        }

        protected override void myOnFirstSubscriber() {
            _vs.onChange += _handle_vs;
        }

        protected override void myOnLastSubscriber() {
            _vs.onChange -= _handle_vs;
        }

        private void _handle_vs(object dp_obj) {
            var dp = dp_obj as DataPacket;
            IBlueRowCollection nrows = dp.newRows;
            _out_schema = BlueDataUtility.add_column(nrows.schema, _diff_col_name, typeof(double));
            _out_schema = BlueDataUtility.add_column(_out_schema, _diff_col_name_perc, typeof(double));
            List<IBlueRow> row_list = new List<IBlueRow>();
            foreach (IBlueRow r in nrows)
                row_list.Add(r);
            //OrderBy sorts in ascedning order
            var sorted_rows = row_list.OrderBy(r => r[_order_col]).ToList();
            var sorted_row_array = sorted_rows.ToArray();
            // reverse it to make it descending    
            sorted_rows.Reverse();
            //sort rows so we can do the diff
            OrderedBlueTable rv = new OrderedBlueTable(_out_schema);
            int i = 0;
            foreach (IBlueRow r in sorted_rows) {
                MutableBlueRow nr = new MutableBlueRow(_out_schema, r);
                //So, in the expression "x - y," where y is subtracted from x, x is the minuend, and y is the subtrahend.
                // we assume x - y, and name variables like that
                double x = r.get<double>(_col_1);
                int y_row_idx = i + _diff;
                double diff = System.Double.NaN;
                double perc = System.Double.NaN;
                if (y_row_idx < sorted_rows.Count()) {
                    var y = sorted_rows[y_row_idx].get<double>(_col_2);
                    diff = x - y;
                    perc = 100.0 * diff / y;
                }
                nr.setValue(_diff_col_name, diff);
                nr.setValue(_diff_col_name_perc, perc);
                rv.addRow(nr);
                i++;
            }

            var dp_out = BlueDataUtility.build_dp_inc(new_rows: rv, myLastValue as DataPacket, true);
            myFireEvent(dp_out);

        }
    }
}