'use strict';

var value    = require('../../object/valid-value')
  , aFrom    = require('../from')
  , toArray  = require('../to-array')
  , contains = require('./contains')
  , byLength = require('./_compare-by-length')

  , filter = Array.prototype.filter, push = Array.prototype.push;

module.exports = function (/*…lists*/) {
	var lists, seen, result;
	if (!arguments.length) return aFrom(this);
	push.apply(lists = [this], arguments);
	lists.forEach(value);
	seen = [];
	result = [];
	lists.sort(byLength).forEach(function (list) {
		result = result.filter(function (item) {
			return !contains.call(list, item);
		}).concat(filter.call(list, function (x) {
			return !contains.call(seen, x);
		}));
		push.apply(seen, toArray(list));
	});
	return result;
};