import * as React from "react";

const { Component } = React;

export interface IAsyncComponentProps {}

export interface IAsyncComponentState {
  Component?: typeof Component
}

interface IGetComponent {
  (): Promise<typeof Component>;
}

export default function asyncComponent (getComponent: IGetComponent) {
  let ComponentCache: typeof Component = null;

  return class AsyncComponent extends Component<IAsyncComponentProps, IAsyncComponentState> {
    state: {
      Component?: typeof Component,
    };

    constructor(props: IAsyncComponentProps) {
      super(props);
      this.state = { Component: ComponentCache };
    }

    componentWillMount() {
      if (!this.state.Component) {
        getComponent().then((Component) => {
          ComponentCache = Component;

          this.setState({ Component });
        });
      }
    }

    render() {
      const { Component } = this.state;

      if (Component) {
        return <Component {...this.props} />;
      }
      return null;
    }
  };
}