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228 lines (182 loc) · 6.71 KB
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using System;
using System.Collections.Generic;
using System.Linq;
namespace Bitdiff.Utils
{
public class PaginationHelper
{
private readonly PaginationDefaults _paginationDefaults;
public int RecordsPerPage { get; private set; }
public long TotalRecords { get; private set; }
public int CurrentPageNumber { get; private set; }
public PaginationHelper(long totalRecords, int currentPage)
: this(totalRecords, currentPage, PaginationDefaults.DefaultRecordsPerPage) { }
public PaginationHelper(long totalRecords, int currentPage, int recordsPerPage)
: this(totalRecords, currentPage, recordsPerPage, new PaginationDefaults(PaginationDefaults.DefaultPagesToShow, PaginationDefaults.DefaultNumberOfPagesLeftOfCurrent, PaginationDefaults.DefaultNumberOfPagesRightOfCurrent)) { }
public PaginationHelper(long totalRecords, int currentPage, int recordsPerPage, PaginationDefaults paginationDefaults)
{
TotalRecords = totalRecords;
RecordsPerPage = recordsPerPage;
_paginationDefaults = paginationDefaults;
SetCurrentPage(currentPage);
}
// Default url builder returns the page number as the link.
private Func<int, string> _linkBuilder = page => page.ToString();
// Default url text returns the page number as the text.
private Func<int, string> _linkTextBuilder = page => page.ToString();
public PaginationHelper Link(Func<int, string> linkBuilder)
{
_linkBuilder = linkBuilder;
return this;
}
private void SetCurrentPage(int pageNumber)
{
if (pageNumber < 1)
pageNumber = 1;
if (pageNumber > LastPageNumber && pageNumber != FirstPageNumber)
pageNumber = LastPageNumber;
CurrentPageNumber = pageNumber;
}
public PaginationHelper LinkText(Func<int, string> linkTextBuilder)
{
_linkTextBuilder = linkTextBuilder;
return this;
}
public string GetLink(int pageNumber)
{
return _linkBuilder(pageNumber);
}
public string GetLinkText(int pageNumber)
{
return _linkTextBuilder(pageNumber);
}
public bool HasNextPage
{
get { return CurrentPageNumber < TotalNumberOfPages; }
}
public bool HasPreviousPage
{
get { return CurrentPageNumber > 1; }
}
public int PreviousPageNumber
{
get { return CurrentPageNumber - 1; }
}
public VisiblePage PreviousVisiblePage
{
get { return GetPageToShow(PreviousPageNumber); }
}
private VisiblePage GetPageToShow(int pageNumber)
{
return new VisiblePage(pageNumber, _linkBuilder(pageNumber),
_linkTextBuilder(pageNumber), pageNumber == CurrentPageNumber);
}
public int NextPageNumber
{
get { return CurrentPageNumber + 1; }
}
public VisiblePage NextVisiblePage
{
get { return GetPageToShow(NextPageNumber); }
}
public VisiblePage FirstVisiblePage
{
get { return GetPageToShow(FirstPageNumber); }
}
public VisiblePage LastVisiblePage
{
get { return GetPageToShow(LastPageNumber); }
}
public int FirstPageNumber
{
get { return 1; }
}
public int LastPageNumber
{
get { return TotalNumberOfPages; }
}
public int TotalNumberOfPages
{
get { return (int)Math.Ceiling(((double)TotalRecords) / RecordsPerPage); }
}
public List<VisiblePage> PagesToShow
{
get
{
int numberOfPages = TotalNumberOfPages;
if (TotalNumberOfPages == 1)
{
return new List<VisiblePage>();
}
if (numberOfPages <= _paginationDefaults.NumberOfPagesToShow)
{
return BuildPageList(1, numberOfPages);
}
if (CurrentPageNumber <= _paginationDefaults.NumberOfPagesLeftOfCurrent)
{
return BuildFirstPage();
}
if (CurrentPageNumber + _paginationDefaults.NumberOfPagesRightOfCurrent > numberOfPages)
{
return BuildLastPage(numberOfPages);
}
return BuildPageList(CurrentPageNumber - _paginationDefaults.NumberOfPagesLeftOfCurrent,
CurrentPageNumber + _paginationDefaults.NumberOfPagesRightOfCurrent);
}
}
public bool HasFirstPage
{
get { return !HasPageNumber(1) && PagesToShow.Count > 0; }
}
public bool HasLastPage
{
get { return !HasPageNumber(TotalNumberOfPages) && PagesToShow.Count > 0; }
}
private List<VisiblePage> BuildLastPage(int numberOfPages)
{
return BuildPageList((numberOfPages - _paginationDefaults.NumberOfPagesToShow) + 1, numberOfPages);
}
private List<VisiblePage> BuildFirstPage()
{
return BuildPageList(1, _paginationDefaults.NumberOfPagesToShow);
}
private bool HasPageNumber(int pageNumber)
{
return PagesToShow.Exists(pageToShow => pageToShow.PageNumber == pageNumber);
}
private List<VisiblePage> BuildPageList(int startPage, int endPage)
{
var result = new List<VisiblePage>();
for (int i = startPage; i <= endPage; i++)
{
result.Add(GetPageToShow(i));
}
return result;
}
public static int CalculateSkip(int currentPageNumber, int recordsPerPage)
{
return (currentPageNumber - 1) * recordsPerPage;
}
public int NumberOfRecordsFromBeginningToSkip
{
get { return CalculateSkip(CurrentPageNumber, RecordsPerPage); }
}
public long FirstVisibleResult
{
get { return NumberOfRecordsFromBeginningToSkip + 1; }
}
public long LastVisibleResult
{
get
{
if (HasNextPage)
return CurrentPageNumber * RecordsPerPage;
return TotalRecords;
}
}
public IEnumerable<T> PopulateAsNecessary<T>(IEnumerable<T> items)
{
return items.Skip(NumberOfRecordsFromBeginningToSkip).Take(RecordsPerPage);
}
}
}