var querySelectorAll;
// multiple scoped selector not supported yet. e.g. ">embed,>object"

(function () {
  var toArray = function (nodes) {
    return [].slice.call(nodes, 0);
  };
  var squeezers = {
    ">": function (node) {
      return toArray(node.children);
    },
    "+": function (node) {
      var next = node.nextElementSibling;
      return next ? [next] : [];
    },
    "~": function (node) {
      var nodes = [], n;
      for (n = node.nextElementSibling; n; n = n.nextElementSibling)
        nodes.push(n);
      return nodes;
    }
  };

  querySelectorAll = function (selector, context) {
    var scoped = /^\s*([>+~])(.*)/;
    var match = selector.match(scoped); // [all, type, selector] or null
    if (match) {
      return squeezers[match[1]](context).filter(function (node) {
        return node.webkitMatchesSelector(match[2]);
      });
    }
    return toArray(context.querySelectorAll(selector));
  }
})();

/*

function like(a, b) {
  var p = a.every(function (x, i) { return x == b[i] });
  console.assert(p, "test failed: %s != %s", a, b);
}

like(
  querySelectorAll("a", document.body),
  document.body.querySelectorAll("a")
);

like(
  querySelectorAll("+ a", document.body),
  document.querySelectorAll("body > a")
);

like(
  querySelectorAll("+ *", document.head),
  document.querySelectorAll("head + *")
);

like(
  querySelectorAll("~ *", document.head),
  document.querySelectorAll("head ~ *")
);

*/