var raf = (typeof window !== 'undefined' && window.requestAnimationFrame) || setTimeout;
var nextFrame = function(fn) { raf(function() { raf(fn); }); };

function setNextFrame(obj, prop, val) {
  nextFrame(function() { obj[prop] = val; });
}

function updateStyle(oldVnode, vnode) {
  var cur, name, elm = vnode.elm,
      oldStyle = oldVnode.data.style,
      style = vnode.data.style;

  if (!oldStyle && !style) return;
  oldStyle = oldStyle || {};
  style = style || {};
  var oldHasDel = 'delayed' in oldStyle;

  for (name in oldStyle) {
    if (!style[name]) {
      elm.style[name] = '';
    }
  }
  for (name in style) {
    cur = style[name];
    if (name === 'delayed') {
      for (name in style.delayed) {
        cur = style.delayed[name];
        if (!oldHasDel || cur !== oldStyle.delayed[name]) {
          setNextFrame(elm.style, name, cur);
        }
      }
    } else if (name !== 'remove' && cur !== oldStyle[name]) {
      elm.style[name] = cur;
    }
  }
}

function applyDestroyStyle(vnode) {
  var style, name, elm = vnode.elm, s = vnode.data.style;
  if (!s || !(style = s.destroy)) return;
  for (name in style) {
    elm.style[name] = style[name];
  }
}

function applyRemoveStyle(vnode, rm) {
  var s = vnode.data.style;
  if (!s || !s.remove) {
    rm();
    return;
  }
  var name, elm = vnode.elm, idx, i = 0, maxDur = 0,
      compStyle, style = s.remove, amount = 0, applied = [];
  for (name in style) {
    applied.push(name);
    elm.style[name] = style[name];
  }
  compStyle = getComputedStyle(elm);
  var props = compStyle['transition-property'].split(', ');
  for (; i < props.length; ++i) {
    if(applied.indexOf(props[i]) !== -1) amount++;
  }
  elm.addEventListener('transitionend', function(ev) {
    if (ev.target === elm) --amount;
    if (amount === 0) rm();
  });
}

module.exports = {create: updateStyle, update: updateStyle, destroy: applyDestroyStyle, remove: applyRemoveStyle};