private IFeatureFilter GetFeatureFilter(string filterName)
{
const string filterSuffix = "filter";
IFeatureFilter filter = _filterCache.GetOrAdd(
filterName,
(_) => {
IEnumerable <IFeatureFilter> matchingFilters = _featureFilters.Where(f =>
{
Type t = f.GetType();
string name = ((FilterAliasAttribute)Attribute.GetCustomAttribute(t, typeof(FilterAliasAttribute)))?.Alias;
if (name == null)
{
name = t.Name.EndsWith(filterSuffix, StringComparison.OrdinalIgnoreCase) ? t.Name.Substring(0, t.Name.Length - filterSuffix.Length) : t.Name;
}
//
// Feature filters can have namespaces in their alias
// If a feature is configured to use a filter without a namespace such as 'MyFilter', then it can match 'MyOrg.MyProduct.MyFilter' or simply 'MyFilter'
// If a feature is configured to use a filter with a namespace such as 'MyOrg.MyProduct.MyFilter' then it can only match 'MyOrg.MyProduct.MyFilter'
if (filterName.Contains('.'))
{
//
// The configured filter name is namespaced. It must be an exact match.
return(string.Equals(name, filterName, StringComparison.OrdinalIgnoreCase));
}
else
{
//
// We take the simple name of a filter, E.g. 'MyFilter' for 'MyOrg.MyProduct.MyFilter'
string simpleName = name.Contains('.') ? name.Split('.').Last() : name;
return(string.Equals(simpleName, filterName, StringComparison.OrdinalIgnoreCase));
}
});
if (matchingFilters.Count() > 1)
{
throw new InvalidOperationException($"Multiple feature filters match the configured filter named '{filterName}'.");
}
return(matchingFilters.FirstOrDefault());
}
);
return(filter);
}
public bool IsEnabled(string feature)
{
foreach (ISessionManager sessionManager in _sessionManagers)
{
if (sessionManager.TryGet(feature, out bool cachedEnabled))
{
return(cachedEnabled);
}
}
bool enabled = false;
IFeatureSettings settings = _settingsProvider.TryGetFeatureSettings(feature);
if (settings != null)
{
//
// Check if feature is always on
// If it is, result is true, goto: cache
if (settings.EnabledFor.Any(featureFilter => string.Equals(featureFilter.Name, "AlwaysOn", StringComparison.OrdinalIgnoreCase)))
{
enabled = true;
}
else
{
//
// For all enabling filters listed in the feature's state calculate if they return true
// If any executed filters return true, return true
foreach (IFeatureFilterSettings featureFilterSettings in settings.EnabledFor)
{
IFeatureFilter filter = GetFeatureFilter(featureFilterSettings.Name);
if (filter == null)
{
_logger.LogWarning($"Feature filter '{featureFilterSettings.Name}' specified for feature '{feature}' was not found.");
continue;
}
var context = new FeatureFilterEvaluationContext()
{
FeatureName = feature,
Parameters = featureFilterSettings.Parameters
};
if (filter.Evaluate(context))
{
enabled = true;
break;
}
}
}
}
foreach (ISessionManager sessionManager in _sessionManagers)
{
sessionManager.Set(feature, enabled);
}
return(enabled);
}