require "rexml/child"
require "rexml/source"

module REXML
	# Represents an XML Instruction; IE, <? ... ?>
	class Instruction < Child
		START = '<\?'
		START_RE = /\A<\?/u
		STOP = '\?>'
		STOP_RE = /\?>/u
		PATTERN = /#{START}(.*?)(\s+.*?)?#{STOP}/um

		# target is the "name" of the Instruction; IE, the "tag" in <?tag ...?>
		# content is everything else.
		attr_accessor :target, :content

		# Constructs a new Instruction
		# @param target can be one of a number of things.  If String, then 
		# the target of this instruction is set to this.  If an Instruction,
		# then the Instruction is shallowly cloned (target and content are
		# copied).  If a Source, then the source is scanned and parsed for
		# an Instruction declaration.
		# @param content Must be either a String, or a Parent.  Can only
		# be a Parent if the target argument is a Source.  Otherwise, this
		# String is set as the content of this instruction.
		def initialize(target, content=nil)
			if target.kind_of? Source
				super(content)
				md = target.match(PATTERN, true)
				@target, @content = md[1], md[2]
			elsif target.kind_of? String
				super()
				@target = target
				@content = content
			elsif target.kind_of? Instruction
				super(content)
				@target = target.target
				@content = target.content
			end
			@content.strip! if @content
		end

		def clone
			Instruction.new self
		end
		
		def write writer, indent=-1
			indent(writer, indent)
			writer << START.sub(/\\/u, '')
			writer << @target
			writer << ' '
			writer << @content
			writer << STOP.sub(/\\/u, '')
		end

		# @return true if other is an Instruction, and the content and target
		# of the other matches the target and content of this object.
		def ==( other )
			other.kind_of? Instruction and
			other.target == @target and
			other.content == @content
		end

		def Instruction.parse_stream source, listener
			md = source.match(PATTERN, true)
			listener.instruction md[1], md[2]
		end
	end
end
