# Keep track of the best elements according to a distance value.
#
# ~~~
# var bests = new BestDistance[String](5)
# bests.update(10, "Too big")
# assert bests.best_items.is_empty
# bests.update(5, "Just fine")
# bests.update(5, "Another one")
# assert bests.best_items.has_exactly(["Just fine", "Another one"])
# bests.update(2, "A better one")
# bests.update(4, "Not good enough")
# assert bests.best_distance == 2
# assert bests.best_items.has_exactly(["A better one"])
# ~~~
class BestDistance[E]
	# Current smallest distance
	var best_distance: Int is writable

	# Known elements with the smallest distance
	var best_items = new Set[E] is writable

	# Register a `candidate` with a `distance`
	#
	# * To high, it is ignored.
	# * Equal to the current best, it is added
	# * Better that them, is is the new best element
	#
	# Return `true` if the candidate is kept (alone or with other)
	# returns `false` if the candidate is ignored.
	fun update(distance: Int, candidate: E): Bool
	do
		if distance > best_distance then return false
		if distance < best_distance then
			best_distance = distance
			best_items.clear
		end
		best_items.add candidate
		return true
	end
end