Ombi/src/Ombi.Helpers/PaginationHelper.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace Ombi.Helpers
{
    public static class PaginationHelper
    {
        public static List<PagesToLoad> GetNextPages(int currentlyLoaded, int toTake, int maxItemsPerPage)
        {
            var result = new List<PagesToLoad>();

            var firstPage = currentlyLoaded / maxItemsPerPage + 1;
            var startPos = currentlyLoaded % maxItemsPerPage + 1;

            var lastItemIndex = currentlyLoaded + toTake - 1;
            var lastPage = lastItemIndex / maxItemsPerPage + 1;
            var stopPos = lastItemIndex % maxItemsPerPage + 1;

            while (currentlyLoaded >= maxItemsPerPage)
            {
                currentlyLoaded -= maxItemsPerPage;
            }
            if ((currentlyLoaded % maxItemsPerPage) == 0 && (currentlyLoaded % toTake) == 0)
            {
                currentlyLoaded = 0;
            }

            var page1 = new PagesToLoad { Page = firstPage, Skip = currentlyLoaded, Take = toTake };

            if (toTake + startPos - 1 > maxItemsPerPage)
            {
                page1.Take = maxItemsPerPage - startPos + 1;
                result.Add(page1);

                for (var i = firstPage + 1; i < lastPage; i++)
                {
                    var nextPage = new PagesToLoad { Page = i, Skip = 0, Take = maxItemsPerPage };
                    result.Add(nextPage);
                }

                var pageN = new PagesToLoad { Page = lastPage, Skip = 0, Take = stopPos };
                result.Add(pageN);
            }
            else
            {
                if (page1.Skip + page1.Take > maxItemsPerPage)
                {
                    page1.Skip = 0;
                }
                result.Add(page1);
            }

            return result;
        }
    }

    public class PagesToLoad
    {
        public int Page { get; set; }
        public int Take { get; set; }
        public int Skip { get; set; }
    }
}