# Abuser iterator for sorting array, see `sort_fa`
# Implements a sort by permutation
private class SortAbuserIterator[E]
	super Iterator[CompareQuery[E]]
	# The index of the big loop
	var i: Int = 0
	# The index of the small loop
	var j: Int = 0
	# The array to sort
	var array: Array[E]
	# The query used to communicate with the user.
	# For ecological concerns, a unique CompareQuery is instatiated.
	var query: nullable CompareQuery[E] = null
	redef fun item do return query.as(not null)
	init
	do
		# Initialize the algorithm, see `next` for the rest
		if not is_ok then return
		query = new CompareQuery[E](array[i], array[j])
	end
	redef fun is_ok do return i < array.length - 1
	redef fun next
	do
		# Process the last query
		if item.res > 0 then
			var tmp = array[i]
			array[i] = array[j]
			array[j] = tmp
		end
		# Get the next iteration
		j += 1
		if j >= array.length then
			# End of small loop
			i += 1
			j = i + 1
		end
		if not is_ok then return
		# Prepare the next query
		item.a = array[i]
		item.b = array[j]
		item.res = 0
	end
end