/// <summary>
/// Initialise the in-memory cache using the delegates and caching period provided
/// </summary>
/// <param name="clonerFactory">An instance of the cloner factory to be used in cloning cache items</param>
/// <param name="asyncRetrievalDelegate">The async delegate to await for retrieval of the object, e.g. from a database</param>
/// <param name="syncRetrievalDelegate">The syncnronous delegate for retrieval of the object, e.g. from a database</param>
/// <param name="cachingPeriod">The period for which caching is to be performed</param>
/// <param name="initialRetrievalTimeout">The number of milliseconds to wait before timing out the first retrieval before returning the default</param>
/// <param name="repeatRetrievalTimeout">The number of milliseconds to wait before timing out on repeat retrievals before returning stale data</param>
/// <remarks>Either async or sync delegate may be null, but not both</remarks>
public InMemoryItemCache(IDeepClonerFactory <T> clonerFactory,
Func <Task <T> > asyncRetrievalDelegate, Func <T> syncRetrievalDelegate, TimeSpan cachingPeriod,
int initialRetrievalTimeout = int.MaxValue, int repeatRetrievalTimeout = 100)
{
if (asyncRetrievalDelegate is null && syncRetrievalDelegate is null)
{
throw new ArgumentException("Either a synchronous or asynchronous delegate must be provided as a minimum!", "Delegates");
}
_asyncRetrievalDelegate = asyncRetrievalDelegate;
_syncRetrievalDelegate = syncRetrievalDelegate;
_cachingPeriod = cachingPeriod;
_repeatRetrievalTimeout = repeatRetrievalTimeout;
// Create an instance of the default object cloner, for use when returning objects
_clonerFactory = clonerFactory;
// Create a default cache entry so that no null reference exceptions are encountered on first use
// This item is marked as immediately expiring, so that it always triggers a request to the source
_cacheEntry = new CacheEntry <T>(default(T), DateTime.MinValue, initialRetrievalTimeout);
}
/// <summary>
/// Create a new instance for use in caching some data
/// </summary>
/// <param name="logger">A logger to use for reporting issues with loading</param>
/// <param name="clonerFactory">The factory for the cloner to in cloning the cached item prior to return</param>
/// <param name="asyncLoadDelegate">The delegate that is used to load data</param>
/// <param name="initialValue">The initial value to place into the cache, before loading is complete</param>
/// <param name="refreshPeriod">The period between cache refreshes - the maxmimum data staleness</param>
/// <param name="loadTimeout">The timeout for the load operation - defaults to Timeout.InfiniteTimeSpan</param>
/// <exception cref="ArgumentException">One of the parameters was invalid</exception>
public AutoRefreshingItemCache(ILogger logger, IDeepClonerFactory <T> clonerFactory,
Func <CancellationToken, Task <T> > asyncLoadDelegate, T initialValue,
TimeSpan refreshPeriod, TimeSpan?loadTimeout = null)
{
if (loadTimeout.HasValue && loadTimeout.Value.TotalMilliseconds < 0)
{
throw new ArgumentException(nameof(loadTimeout));
}
if (refreshPeriod.TotalMilliseconds < 10)
{
throw new ArgumentException(nameof(refreshPeriod));
}
_logger = logger;
_clonerFactory = clonerFactory;
_asyncLoadDelegate = asyncLoadDelegate;
if (loadTimeout is null)
{
loadTimeout = Timeout.InfiniteTimeSpan;
}
_loadTimeout = loadTimeout.Value;
_refreshPeriod = refreshPeriod;
_cacheItem = new CacheItem <T>(initialValue);
}