using System.Collections;

namespace Core.GIS.NetTopologySuite.Utilities
{
    /// <summary>
    /// Executes a transformation function on each element of a collection
    /// and returns the results in a new List.
    /// </summary>
    public class CollectionUtil
    {
        /// <summary>
        /// 
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="obj"></param>
        /// <returns></returns>
        public delegate T FunctionDelegate<T>(T obj);

        /// <summary>
        /// Executes a function on each item in a <see cref="ICollection" />
        /// and returns the results in a new <see cref="IList" />.
        /// </summary>
        /// <param name="coll"></param>
        /// <param name="func"></param>
        /// <returns></returns>
        public static IList Transform(ICollection coll, FunctionDelegate<object> func)
        {
            IList result = new ArrayList();
            IEnumerator i = coll.GetEnumerator();
            foreach (object obj in coll)
            {
                result.Add(func(obj));
            }
            return result;
        }

        /// <summary>
        /// Executes a function on each item in a <see cref="ICollection" /> 
        /// but does not accumulate the result.
        /// </summary>
        /// <param name="coll"></param>
        /// <param name="func"></param>
        public static void Apply(ICollection coll, FunctionDelegate<object> func)
        {
            foreach (object obj in coll)
            {
                func(obj);
            }
        }

        /// <summary>
        /// Executes a function on each item in a <see cref="ICollection" />
        /// and collects all the entries for which the result
        /// of the function is equal to <c>true</c>.
        /// </summary>
        /// <param name="coll"></param>
        /// <param name="func"></param>
        /// <returns></returns>
        public static IList Select(ICollection coll, FunctionDelegate<object> func)
        {
            IList result = new ArrayList();
            foreach (object obj in coll)
            {
                if (true.Equals(func(obj)))
                {
                    result.Add(obj);
                }
            }
            return result;
        }
    }
}