/// <summary>
/// Visit the given context and return a collection of the resultant contexts.
/// </summary>
/// <returns>Zero or more <see cref="IRenderingContext"/> instances, determined by the outcome of this visit.</returns>
/// <param name="context">The rendering context to visit.</param>
public override IRenderingContext[] Visit(IRenderingContext context)
{
if(context == null)
{
throw new ArgumentNullException(nameof(context));
}
IZptAttribute attrib;
if((attrib = context.GetMetalAttribute(ZptConstants.Metal.DefineMacroAttribute)) != null)
{
context.MetalModel.AddGlobal(attrib.Value, context.Element);
}
return new [] { _macroExpander.ExpandMacros(context) };
}
/// <summary>
/// Examines the given <see cref="IZptElement"/> and - if it has an attribute referencing another macro - gets that
/// macro from the given <see cref="Model"/>.
/// </summary>
/// <returns>Either an <see cref="IZptElement"/> instance representing the referenced macro, or a <c>null</c> reference.</returns>
/// <param name="context">The rendering context.</param>
/// <param name="attributeName">The name of the desired attribute, which references a macro if present.</param>
private IZptElement GetReferencedMacro(IRenderingContext context, string attributeName)
{
if(context == null)
{
throw new ArgumentNullException(nameof(context));
}
IZptElement output;
var attrib = context.GetMetalAttribute(attributeName);
if(attrib != null)
{
ExpressionResult result;
try
{
result = context.MetalModel.Evaluate(attrib.Value, context);
output = result.GetValue<IZptElement>().Clone();
}
catch(Exception ex)
{
string message = String.Format(Resources.ExceptionMessages.UnexpectedExceptionGettingMacro,
attributeName,
attrib.Value,
context.Element.GetFullFilePathAndLocation());
throw new RenderingException(message, ex);
}
if(output == null)
{
string message = String.Format(Resources.ExceptionMessages.CannotFindMacro,
attributeName,
attrib.Value,
context.Element.GetFullFilePathAndLocation());
throw new MacroNotFoundException(message);
}
}
else
{
output = null;
}
return output;
}