/// <summary>
/// Fetches hackernews' top posts and returns a formated JSON string
/// containing N posts.
/// </summary>
/// <param name="n">Number of posts to return</param>
/// <returns>JSON string with hacker news posts</returns>
public async Task <string> GetPostsJson(int n)
{
int[] ids;
try
{
ids = await GetTopPostsIdsAsync();
}
catch (Exception e)
{
return($"Exception when trying to get top posts: {e.Message}");
}
if (ids == null || ids.Count() == 0)
{
return("Unable to find any posts.");
}
var posts = new List <Post>();
foreach (var id in ids)
{
HackerNewsPostResponse post = null;
try
{
post = await GetPostById(id);
}
catch (Exception ex)
{
return($"Exception when trying to get post with id={id}: {ex.Message}");
}
if (post == null || PostIsInvalid(post))
{
continue;
}
posts.Add(new Post
{
title = post.title,
author = post.by,
uri = post.url,
points = post.score,
comments = post.descendants,
rank = posts.Count() + 1 // rank is updated as we add to list
});
if (posts.Count() == n)
{
break;
}
}
var json = JsonConvert.SerializeObject(posts, Formatting.Indented);
return(json);
}
/// <summary>
/// Checks whether post is invalid.
/// </summary>
/// <param name="post"></param>
/// <returns></returns>
public bool PostIsInvalid(HackerNewsPostResponse post)
{
if (string.IsNullOrEmpty(post.title) || post.title.Length > 256 ||
string.IsNullOrEmpty(post.by) || post.by.Length > 256 ||
!Uri.TryCreate(post.url, UriKind.Absolute, out _) ||
post.score < 0 || post.descendants < 0)
{
return(true);
}
return(false);
}