sharee.bike-App/TINKLib/Model/Connector/Filter/IntersectGroupFilterHelper.cs

using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace TINK.Model.Connector.Filter
{
    public static class IntersectGroupFilterHelper
    {
        /// <summary>
        /// Transforms a group (each element consists of an operator prefix and a numeric bike category) to bike category enumeration (numeric elements).
        /// </summary>
        /// <param name="group">Group to transform.</param>
        /// <returns>Enumeration of numeric bike categories.</returns>
        public static IEnumerable<string> ToBikeCategory(this IEnumerable<string> group)
            => group?.Select(x => x.GetBikeCategory())?.Where(x => !string.IsNullOrEmpty(x)) 
                ?? new List<string>();

        /// <summary>
        /// Extracts bike group category umber from a group string.
        /// </summary>
        /// <param name="group">Group to transform. Example KN_300101 (Stadtrad located in Konstanz), FR_300102 (Lastenrad located in Freiburg).</param>
        /// <returns>Enumeration of numeric bike categories.</returns>
        public static string GetBikeCategory(this string group)
            => Regex.Match(group, "[0-9]+")?.Value ?? string.Empty;

        /// <summary>
        /// Intersects two goups only taking into accout the numeric bike group category part.
        /// </summary>
        /// <param name="group">Group to filter.</param>
        /// <param name="filter">Filter to apply</param>
        public static IEnumerable<string> IntersectByGoupId(this IEnumerable<string> group, IEnumerable<string> filter)
            => group.Where(x => filter.ContainsGroupId(x));

        /// <summary>
        /// Gets if group contains a filter element.
        /// </summary>
        /// <param name="group"></param>
        /// <param name="filterElement"></param>
        /// <returns></returns>
        public static bool ContainsGroupId(this IEnumerable<string> group, string filterElement)
            => group.ToBikeCategory().Contains(filterElement.GetBikeCategory());
    }
}