public async Task <PagingResultObject> GetLatestNews(int pageNum, int pageSize)
{
try
{
if (pageNum < 1)
{
pageNum = 0;
}
//this is a purposefully inconsisten handling of validation. see assumptions.component.html for details
if (pageSize < 1 || pageSize > 100)
{
//Ideally this would be returning a proper HTTP response code...such as 422
throw new ValidationException("Page size must be greater than or equal to 1 and cannot exceed 100");
}
//if an error occurs, we can log it and return an empty array.
//or, if hackerNews is down, perhaps we should return an error response 500 or something
int[] latestNewsIdsArray = await _service.GetIdsAsync();
PagingResultObject pageResult;
if (latestNewsIdsArray == null || latestNewsIdsArray.Length == 0)
{
//presumably this is a valid scenario and so we're not going to return an error response. Just make sure the caller handles this.
pageResult = new PagingResultObject
{
PageSize = pageSize,
PageNum = 0,
NumItemsTotal = 0,
NumPagesTotal = 0
};
}
else
{
int numPages = this.CalculateNumPages(latestNewsIdsArray, pageSize);
int actualPageNum = this.CalculateRealPageNumber(latestNewsIdsArray, pageNum, pageSize);
int pageStartIndex = this.CalculatePageStartIndex(latestNewsIdsArray, actualPageNum, pageSize);
int pageEndIndex = this.CalculatePageEndIndex(latestNewsIdsArray, actualPageNum, pageSize);
pageResult = new PagingResultObject
{
PageSize = pageSize,
PageNum = actualPageNum,
NumItemsTotal = latestNewsIdsArray.Length,
NumPagesTotal = numPages,
PageStartItemNum = pageStartIndex + 1,
PageEndItemNum = pageEndIndex + 1,
PageIds = latestNewsIdsArray.Skip(pageStartIndex).Take(pageEndIndex - pageStartIndex).ToArray()
};
//some sort of c# map => Promise => promise.all would be better here
List <NewsArticle> pageArticles = new List <NewsArticle>();
for (int i = 0; i < pageResult.PageIds.Length; i++)
{
int articleId = pageResult.PageIds[i];
NewsArticle article = await _service.GetItemByIdAsync(articleId);
//I have seen some Ids come back with null responses. I have double-checked by hitting their api directly.
//seems like overkill to prevent the page from loading because one of the items has an issue,
//so we'll just create a dummy entry and make sure the caller handles it..
if (article == null)
{
article = new NewsArticle
{
Id = articleId,
Title = "<Error, Item not found>",
By = "?",
Url = null
};
}
pageArticles.Add(article);
}
pageResult.PageItems = pageArticles.ToArray();
}
return(pageResult);
}
catch (Exception ex)
{
throw;
}
}
