/// <summary>
/// Stores news items in the cache
/// </summary>
public static void SetCachedNews(List <NewsItem> news)
{
NewsCacheEntity entity = GetOrCreateEntity();
entity.News = news;
entity.Save(); // sets the UpdatedAt value to "now" automatically
}
/// <summary>
/// Finds the cache entity in the database or creates and saves new one
/// </summary>
private static NewsCacheEntity GetOrCreateEntity()
{
var entity = DB.First <NewsCacheEntity>();
if (entity == null)
{
entity = new NewsCacheEntity();
entity.Save();
}
return(entity);
}
/// <summary>
/// Returns the latest news, prepared for display
/// </summary>
public List <NewsItem> GetLatestNews()
{
// === try to get news from the cache first ===
var cachedNews = NewsCacheEntity.GetCachedNews();
if (cachedNews != null)
{
return(cachedNews);
}
// === only then query all the news sources to build the news ===
var news = BuildTheNews();
NewsCacheEntity.SetCachedNews(news);
return(news);
}
/// <summary>
/// Returns the cached news, or null if there's nothing cached
/// </summary>
public static List <NewsItem> GetCachedNews()
{
NewsCacheEntity entity = GetOrCreateEntity();
// nothing cached
if (entity.News == null || entity.News.Count == 0)
{
return(null);
}
// cached, but expired
double age = (DateTime.UtcNow - entity.UpdatedAt).TotalMinutes;
if (age > CacheExpiryMinutes)
{
return(null);
}
return(entity.News);
}
