# Substrings of a Rope (i.e. Postfix iterator on leaves)
private class RopeSubstrings
	super IndexedIterator[FlatString]

	# Visit Stack
	var iter: RopeCharIteratorPiece is noinit
	# Position in `Rope`
	var pos: Int is noinit
	# Maximum position in `Rope` (i.e. length - 1)
	var max: Int is noinit

	# Current leaf
	var str: FlatString is noinit

	init from(root: Concat, pos: Int) do
		var r = new RopeCharIteratorPiece(root, true, false, null)
		max = root.length - 1
		var rnod: String = root
		var off = pos
		loop
			if rnod isa Concat then
				if off >= rnod._left.length then
					r.rdone = true
					off -= rnod._left.length
					rnod = rnod._right
					r = new RopeCharIteratorPiece(rnod, true, false, r)
				else
					rnod = rnod._left
					r = new RopeCharIteratorPiece(rnod, true, false, r)
				end
			else
				str = rnod.as(FlatString)
				r.rdone = true
				iter = r
				self.pos = pos - off
				break
			end
		end
	end

	redef fun item do return str

	redef fun is_ok do return pos <= max

	redef fun index do return pos

	redef fun next do
		pos += str.length
		if pos > max then return
		var it = iter.prev.as(not null)
		var rnod = it.node
		loop
			if not rnod isa Concat then
				it.ldone = true
				it.rdone = true
				str = rnod.as(FlatString)
				iter = it
				break
			end
			if not it.ldone then
				rnod = rnod._left
				it.ldone = true
				it = new RopeCharIteratorPiece(rnod, false, false, it)
			else if not it.rdone then
				it.rdone = true
				rnod = rnod._right
				it = new RopeCharIteratorPiece(rnod, false, false, it)
			else
				it = it.prev.as(not null)
				rnod = it.node
				continue
			end
		end
	end
end