using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Text.RegularExpressions;
using DataTable = System.Data.DataTable;

namespace Kreta.BusinessLogic.Utils
{
    /// <summary>
    /// Extensions for manipulating DataTables
    /// </summary>
    public static class DataTableExtensions
    {
        private static string suffixPattern = @"(_DNAME)|(_BNAME)|(_BOOL)";

        /// <summary>
        /// Replaces id columns with added _DNAME and _BNAME colums.
        /// </summary>
        /// <param name="table">DataTable returned by DataAccessBase.GetData.</param>
        public static DataTable ConsolidateColumns(this DataTable table)
        {
            //Reading all column names
            var columnNames = (table.Columns.Cast<DataColumn>().Select(column => column.ColumnName)).ToList();

            //Selecting the columns we need in the right order
            var orderedColumnNames = new List<string>();
            foreach (var name in columnNames)
            {
                if (Regex.IsMatch(name, suffixPattern))
                {
                    continue;
                }
                if (columnNames.Contains($"{name}_DNAME"))
                {
                    orderedColumnNames.Add($"{name}_DNAME");
                }
                else if (columnNames.Contains($"{name}_BNAME"))
                {
                    orderedColumnNames.Add($"{name}_BNAME");
                }
                else
                {
                    orderedColumnNames.Add(name);
                }
            }

            //Removing everything else
            var redundantColumnNames = columnNames.Except(orderedColumnNames);
            foreach (var name in redundantColumnNames)
            {
                table.Columns.Remove(name);
            }

            //Ordering columns
            var i = 0;
            foreach (var name in orderedColumnNames)
            {
                table.Columns[name].SetOrdinal(i++);
            }

            //Renaming columns
            var suffixedColumnNames = orderedColumnNames.Where(n => Regex.IsMatch(n, suffixPattern));
            foreach (var name in suffixedColumnNames)
            {
                table.Columns[name].ColumnName = Regex.Replace(name, suffixPattern, string.Empty);
            }

            return table;
        }
    }
}