const getKeysFromOptions = options => [
  ...Object.keys((options.data && options.data()) || {}),
  ...Object.keys(options.props || {})
];

const defineDescriptor = (src, dest, name) => {
  if (!dest.hasOwnProperty(name)) {
    const descriptor = Object.getOwnPropertyDescriptor(src, name);
    Object.defineProperty(dest, name, descriptor);
  }
};

const merge = objs => {
  const res = {};
  objs.forEach(obj => {
    obj &&
      Object.getOwnPropertyNames(obj).forEach(name =>
        defineDescriptor(obj, res, name)
      );
  });
  return res;
};

const buildFromProps = (obj, props) => {
  const res = {};
  props.forEach(prop => defineDescriptor(obj, res, prop));
  return res;
};

export default {
  props: {
    template: String
  },
  render(h) {
    if (this.template) {
      const { $data, $props, $options } = this.$parent;

      const methodKeys = Object.keys($options.methods || {});
      const allKeys = getKeysFromOptions($options).concat(methodKeys);
      const methods = buildFromProps(this.$parent, methodKeys);
      const props = merge([$data, $props, methods]);

      const dynamic = {
        template: this.template || "<div></div>",
        props: allKeys,
        computed: $options.computed,
        components: $options.components
      };

      return h(dynamic, {
        props
      });
    }
  }
};