var h = require('./h');

function copyToThunk(vnode, thunk) {
  thunk.elm = vnode.elm;
  vnode.data.fn = thunk.data.fn;
  vnode.data.args = thunk.data.args;
  thunk.data = vnode.data;
  thunk.children = vnode.children;
  thunk.text = vnode.text;
  thunk.elm = vnode.elm;
}

function init(thunk) {
  var i, cur = thunk.data;
  var vnode = cur.fn.apply(undefined, cur.args);
  copyToThunk(vnode, thunk);
}

function prepatch(oldVnode, thunk) {
  var i, old = oldVnode.data, cur = thunk.data, vnode;
  var oldArgs = old.args, args = cur.args;
  if (old.fn !== cur.fn || oldArgs.length !== args.length) {
    copyToThunk(cur.fn.apply(undefined, args), thunk);
  }
  for (i = 0; i < args.length; ++i) {
    if (oldArgs[i] !== args[i]) {
      copyToThunk(cur.fn.apply(undefined, args), thunk);
      return;
    }
  }
  copyToThunk(oldVnode, thunk);
}

module.exports = function(sel, key, fn, args) {
  if (args === undefined) {
    args = fn;
    fn = key;
    key = undefined;
  }
  return h(sel, {
    key: key,
    hook: {init: init, prepatch: prepatch},
    fn: fn,
    args: args
  });
};