using System;

using System.Collections.Generic;

using System.Linq;

​

namespace JW

{

    public class Pager

    {

        public Pager(

            int totalItems,

            int currentPage = 1,

            int pageSize = 10,

            int maxPages = 10)

        {

            // calculate total pages

            var totalPages = (int)Math.Ceiling((decimal)totalItems / (decimal)pageSize);

​

            // ensure current page isn't out of range

            if (currentPage < 1)

            {

                currentPage = 1;

            }

            else if (currentPage > totalPages)

            {

                currentPage = totalPages;

            }

​

            int startPage, endPage;

            if (totalPages <= maxPages) 

            {

                // total pages less than max so show all pages

                startPage = 1;

                endPage = totalPages;

            }

            else 

            {

                // total pages more than max so calculate start and end pages

                var maxPagesBeforeCurrentPage = (int)Math.Floor((decimal)maxPages / (decimal)2);

                var maxPagesAfterCurrentPage = (int)Math.Ceiling((decimal)maxPages / (decimal)2) - 1;

                if (currentPage <= maxPagesBeforeCurrentPage) 

                {

                    // current page near the start

                    startPage = 1;

                    endPage = maxPages;

                } 

                else if (currentPage + maxPagesAfterCurrentPage >= totalPages) 

                {

                    // current page near the end

                    startPage = totalPages - maxPages + 1;

                    endPage = totalPages;

                }

                else 

                {

                    // current page somewhere in the middle

                    startPage = currentPage - maxPagesBeforeCurrentPage;

                    endPage = currentPage + maxPagesAfterCurrentPage;

                }

            }

​

            // calculate start and end item indexes

            var startIndex = (currentPage - 1) * pageSize;

            var endIndex = Math.Min(startIndex + pageSize - 1, totalItems - 1);

​

            // create an array of pages that can be looped over

            var pages = Enumerable.Range(startPage, (endPage + 1) - startPage);

​

            // update object instance with all pager properties required by the view

            TotalItems = totalItems;

            CurrentPage = currentPage;

            PageSize = pageSize;

            TotalPages = totalPages;

            StartPage = startPage;

            EndPage = endPage;

            StartIndex = startIndex;

            EndIndex = endIndex;

            Pages = pages;

        }

​

        public int TotalItems { get; private set; }

        public int CurrentPage { get; private set; }

        public int PageSize { get; private set; }

        public int TotalPages { get; private set; }

        public int StartPage { get; private set; }

        public int EndPage { get; private set; }

        public int StartIndex { get; private set; }

        public int EndIndex { get; private set; }

        public IEnumerable<int> Pages { get; private set; }

        public static void main(string [] args) {

    Pager pg = new Pager() ;

            console. writeLine(pg) ;

        }

    }

}