/// <summary>
/// Gets the pagination token
/// </summary>
/// <param name="criteria">Criteria of the pagination token</param>
/// <param name="currentPage">Current page</param>
/// <returns>Pagination token or null if there is no pagination</returns>
protected string GetPaginationToken(FetchCriteria <TModel> criteria, int currentPage = 0)
{
var pageSize = criteria?.PageSize;
if (!pageSize.HasValue || pageSize.Value == 0)
{
return(null);
}
return(PaginationTokenManager.CreateToken(new PaginationTokenInfo <TModel> {
Criteria = criteria,
CurrentPage = currentPage
}));
}
/// <inheritdoc />
public virtual Task <FetchResult <TModel> > FetchNext(string paginationToken)
{
if (string.IsNullOrEmpty(paginationToken))
{
throw new ArgumentNullException(nameof(paginationToken));
}
var paginationInfo = (PaginationTokenInfo <TModel>)PaginationTokenManager.DecodeToken(paginationToken);
if (paginationInfo == null)
{
throw new ApplicationException($"Pagination token is not valid. Current value is '{paginationToken}'");
}
Logger.LogDebug("Loading next page for file {FileName}, pagination token {PaginationToken}", FileName, paginationToken);
var criteria = paginationInfo.Criteria;
var items = FetchAll();
var count = items.Count;
items = ApplyCriteria(items, criteria);
var criteriaCount = items.Count;
var currentPage = paginationInfo.CurrentPage.GetValueOrDefault() + 1;
items = ApplyPagination(items, criteria.PageSize, currentPage);
var paginatedCount = items.Count;
var token = GetPaginationToken(criteria, currentPage);
Logger.LogDebug("Read {RecordCount} records, where {CriteriaCount} match criteria, returned {PaginatedCount} after pagination, " +
"new pagination token {Token}",
count, criteriaCount, paginatedCount, token);
return(Task.FromResult(new FetchResult <TModel> (items, token)));
}