# A macro is a special text command that is replaced by other content in a `TemplateString`.
private class TemplateMacro
	super Template
	# Macro name as found in the template.
	var name: String

	# Macro starting position in template.
	var start_pos: Int

	# Macro ending position in template.
	var end_pos: Int

	# Macro replacement if any.
	var replacement: nullable Writable = null

	# Does `self` already have a `replacement`?
	fun is_replaced: Bool do return replacement != null

	# Render `replacement` or else `name`.
	redef fun rendering do
		if is_replaced then
			add replacement.as(not null)
		else
			add "%{name}%"
		end
	end

	# Human readable location.
	fun location: String do return "({start_pos}:{end_pos})"
end