/// <summary>
/// Un-decorates <see cref="LessEngine" /> from <paramref name="engine" />. Can process only
/// <see cref="CacheDecorator" /> and <see cref="ParameterDecorator" />, otherwise raises exception.
/// </summary>
/// <param name="engine">Possibly decorated <see cref="ILessEngine" /></param>
/// <exception cref="ArgumentException">Unexpected type of <paramref name="engine" /></exception>
/// <returns><see cref="LessEngine" /> instance.</returns>
internal static LessEngine ResolveLessEngine(this ILessEngine engine)
{
if (engine == null)
{
throw new ArgumentNullException("engine");
}
while (true)
{
var lessEngine = engine as LessEngine;
if (lessEngine != null)
{
return(lessEngine);
}
var cacheDecorator = engine as CacheDecorator;
if (cacheDecorator != null)
{
engine = cacheDecorator.Underlying;
}
else
{
var parameterDecorator = engine as ParameterDecorator;
if (parameterDecorator == null)
{
throw new ArgumentException(string.Format("Cannot resolve {0} to LessEngine", engine.GetType()));
}
engine = parameterDecorator.Underlying;
}
}
}