content: import React from 'react';
  import PropTypes from 'prop-types';
  import 'wicg-inert';
  import { createBrowserHistory } from 'history';
  import { multiply } from 'color-blend';
  
  export default class ModalRoot extends React.PureComponent {
  
    static contextTypes = {
      router: PropTypes.object,
    };
  
    static propTypes = {
      children: PropTypes.node,
      onClose: PropTypes.func.isRequired,
      backgroundColor: PropTypes.shape({
        r: PropTypes.number,
        g: PropTypes.number,
        b: PropTypes.number,
      }),
    };
  
    activeElement = this.props.children ? document.activeElement : null;
  
    handleKeyUp = (e) => {
      if ((e.key === 'Escape' || e.key === 'Esc' || e.keyCode === 27)
           && !!this.props.children) {
        this.props.onClose();
      }
    }
  
    handleKeyDown = (e) => {
      if (e.key === 'Tab') {
        const focusable = Array.from(this.node.querySelectorAll('button:not([disabled]), [href], input:not([disabled]), select:not([disabled]), textarea:not([disabled]), [tabindex]:not([tabindex="-1"])')).filter((x) => window.getComputedStyle(x).display !== 'none');
        const index = focusable.indexOf(e.target);
  
        let element;
  
        if (e.shiftKey) {
          element = focusable[index - 1] || focusable[focusable.length - 1];
        } else {
          element = focusable[index + 1] || focusable[0];
        }
  
        if (element) {
          element.focus();
          e.stopPropagation();
          e.preventDefault();
        }
      }
    }
  
    componentDidMount () {
      window.addEventListener('keyup', this.handleKeyUp, false);
      window.addEventListener('keydown', this.handleKeyDown, false);
      this.history = this.context.router ? this.context.router.history : createBrowserHistory();
    }
  
    componentWillReceiveProps (nextProps) {
      if (!!nextProps.children && !this.props.children) {
        this.activeElement = document.activeElement;
  
        this.getSiblings().forEach(sibling => sibling.setAttribute('inert', true));
      }
    }
  
    componentDidUpdate (prevProps) {
      if (!this.props.children && !!prevProps.children) {
        this.getSiblings().forEach(sibling => sibling.removeAttribute('inert'));
  
        // Because of the wicg-inert polyfill, the activeElement may not be
        // immediately selectable, we have to wait for observers to run, as
        // described in https://github.com/WICG/inert#performance-and-gotchas
        Promise.resolve().then(() => {
          this.activeElement.focus({ preventScroll: true });
          this.activeElement = null;
        }).catch(console.error);
  
        this._handleModalClose();
      }
      if (this.props.children && !prevProps.children) {
        this._handleModalOpen();
      }
      if (this.props.children) {
        this._ensureHistoryBuffer();
      }
    }
  
    componentWillUnmount () {
      window.removeEventListener('keyup', this.handleKeyUp);
      window.removeEventListener('keydown', this.handleKeyDown);
    }
  
    _handleModalOpen () {
      this._modalHistoryKey = Date.now();
      this.unlistenHistory = this.history.listen((_, action) => {
        if (action === 'POP') {
          this.props.onClose();
        }
      });
    }
  
    _handleModalClose () {
      if (this.unlistenHistory) {
        this.unlistenHistory();
      }
      const { state } = this.history.location;
      if (state && state.mastodonModalKey === this._modalHistoryKey) {
        this.history.goBack();
      }
    }
  
    _ensureHistoryBuffer () {
      const { pathname, state } = this.history.location;
      if (!state || state.mastodonModalKey !== this._modalHistoryKey) {
        this.history.push(pathname, { ...state, mastodonModalKey: this._modalHistoryKey });
      }
    }
  
    getSiblings = () => {
      return Array(...this.node.parentElement.childNodes).filter(node => node !== this.node);
    }
  
    setRef = ref => {
      this.node = ref;
    }
  
    render () {
      const { children, onClose } = this.props;
      const visible = !!children;
  
      if (!visible) {
        return (
          <div className='modal-root' ref={this.setRef} style={{ opacity: 0 }} />
        );
      }
  
      let backgroundColor = null;
  
      if (this.props.backgroundColor) {
        backgroundColor = multiply({ ...this.props.backgroundColor, a: 1 }, { r: 0, g: 0, b: 0, a: 0.7 });
      }
  
      return (
        <div className='modal-root' ref={this.setRef}>
          <div style={{ pointerEvents: visible ? 'auto' : 'none' }}>
            <div role='presentation' className='modal-root__overlay' onClick={onClose} style={{ backgroundColor: backgroundColor ? `rgba(${backgroundColor.r}, ${backgroundColor.g}, ${backgroundColor.b}, 0.7)` : null }} />
            <div role='dialog' className='modal-root__container'>{children}</div>
          </div>
        </div>
      );
    }
  
  }
  