/// <summary>
/// Gets a collection from the cache
/// </summary>
/// <param name="collectionIdentifier"></param>
/// <returns></returns>
private async Task <IonCollection> getCollectionFromCacheAsync(CollectionCacheIndex cacheIndex, bool serverCallAsBackup)
{
string collectionURL = PagesURLs.getCollectionURL(_config);
// retrieve from memory cache
IonCollection collection = _memoryCache.collection;
if (collection != null)
{
return(collection);
}
// try to load collection from isolated storage
try
{
collection = await StorageUtils.loadCollectionFromIsolatedStorageAsync(_config).ConfigureAwait(false);
// Add collection to memory cache
if (collection != null)
{
_memoryCache.collection = collection;
}
}
catch (Exception e)
{
IonLogging.log("Error getting collection from isolated storage. Message: " + e.Message, IonLogMessageTypes.ERROR);
}
return(collection);
}
/// <summary>
/// Used to get a page with a desired identifier
/// </summary>
/// <param name="pageIdentifier"></param>
/// <returns>Already parsed IonPage</returns>
public async Task <IonPage> getPageAsync(string pageIdentifier)
{
string pageURL = PagesURLs.getPageURL(_config, pageIdentifier);
PageCacheIndex pageCacheIndex = await PageCacheIndex.retrieve(pageURL, _config).ConfigureAwait(false);
bool isNetworkConnected = NetworkUtils.isOnline();
if (pageCacheIndex == null)
{
if (isNetworkConnected)
{
IonLogging.log("Loading page \"" + pageIdentifier + "\" from server.", IonLogMessageTypes.SUCCESS);
return(await getPageFromServerAsync(pageIdentifier).ConfigureAwait(false));
}
else
{
IonLogging.log("Error getting page \"" + pageIdentifier + "\" from server or cache.", IonLogMessageTypes.ERROR);
throw new PageNotAvailableException();
}
}
// Get collection
IonCollection collection = await getCollectionAsync().ConfigureAwait(false);
// Get last changed of the page from collection
DateTime pageLastChanged = collection.getPageLastChanged(pageIdentifier);
// Estimate, if the page is outdated or not
bool isOutdated = pageCacheIndex.isOutdated(pageLastChanged);
if (!isOutdated)
{
IonLogging.log("Loading page \"" + pageIdentifier + "\" from cache.", IonLogMessageTypes.SUCCESS);
return(await getPageFromCacheAsync(pageIdentifier).ConfigureAwait(false));
}
else
{
if (isNetworkConnected)
{
// Download page from server
IonLogging.log("Loading newer version of page \"" + pageIdentifier + "\" from server.", IonLogMessageTypes.SUCCESS);
return(await getPageFromServerAsync(pageIdentifier).ConfigureAwait(false));
}
else
{
// get old version from cache
IonLogging.log("Loading potentially old version of page \"" + pageIdentifier + "\" from cache.", IonLogMessageTypes.WARNING);
return(await getPageFromCacheAsync(pageIdentifier).ConfigureAwait(false));
}
}
}
/// <summary>
/// Used to get the collection of the class
/// </summary>
/// <returns>The collection of this pages</returns>
public async Task <IonCollection> getCollectionAsync()
{
string collectionURL = PagesURLs.getCollectionURL(_config);
CollectionCacheIndex cacheIndex = await CollectionCacheIndex.retrieve(collectionURL, _config).ConfigureAwait(false);
// Check if there is a not outdated cacheIndex avialible
bool currentCacheEntry = cacheIndex != null && !cacheIndex.isOutdated(_config);
bool networkConnected = NetworkUtils.isOnline();
if (currentCacheEntry)
{
// retrieve current version from cache
IonLogging.log("Loading collection \"" + _config.collectionIdentifier + "\" from cache.", IonLogMessageTypes.SUCCESS);
return(await getCollectionFromCacheAsync(cacheIndex, false).ConfigureAwait(false));
}
else
{
if (networkConnected)
{
// download collection or check for modifications
IonLogging.log("Loading collection \"" + _config.collectionIdentifier + "\" from server.", IonLogMessageTypes.SUCCESS);
return(await getCollectionFromServerAsync(cacheIndex, false).ConfigureAwait(false));
}
else
{
if (cacheIndex != null)
{
// no network: use potential old version from cache
IonLogging.log("Using potentially old version of collection \"" + _config.collectionIdentifier + "\" from cache, because there is no internet connection.", IonLogMessageTypes.WARNING);
return(await getCollectionFromCacheAsync(cacheIndex, false).ConfigureAwait(false));
}
else
{
// Collection can neither be downloaded nor be found in cache
IonLogging.log("Couldn't get collection \"" + _config.collectionIdentifier + "\" either from server or cache.", IonLogMessageTypes.ERROR);
throw new CollectionNotAvailableException();
}
}
}
}
