import { camelToDashCase } from './case';

export const attachEventProps = (node: HTMLElement, newProps: any, oldProps: any = {}) => {
  // add any classes in className to the class list
  const className = getClassName(node.classList, newProps, oldProps);
  if (className !== '') {
    node.className = className;
  }

  Object.keys(newProps).forEach(name => {
    if (name === 'children' || name === 'style' || name === 'ref' || name === 'class' || name === 'className' || name === 'forwardedRef') {
      return;
    }
    if (name.indexOf('on') === 0 && name[2] === name[2].toUpperCase()) {
      const eventName = name.substring(2);
      const eventNameLc = eventName[0].toLowerCase() + eventName.substring(1);

      if (!isCoveredByReact(eventNameLc)) {
        syncEvent(node, eventNameLc, newProps[name]);
      }
    } else {
      if (typeof newProps[name] === 'object') {
        (node as any)[name] = newProps[name];
      } else {
        node.setAttribute(camelToDashCase(name), newProps[name]);
      }
    }
  });
};

export const getClassName = (classList: DOMTokenList, newProps: any, oldProps: any) => {
  const newClassProp: string = newProps.className || newProps.class;
  const oldClassProp: string = oldProps.className || oldProps.class;
  // map the classes to Maps for performance
  const currentClasses = arrayToMap(classList);
  const incomingPropClasses = arrayToMap(newClassProp ? newClassProp.split(' ') : []);
  const oldPropClasses = arrayToMap(oldClassProp ? oldClassProp.split(' ') : []);
  const finalClassNames: string[] = [];
  // loop through each of the current classes on the component
  // to see if it should be a part of the classNames added
  currentClasses.forEach(currentClass => {
    if (incomingPropClasses.has(currentClass)) {
      // add it as its already included in classnames coming in from newProps
      finalClassNames.push(currentClass);
      incomingPropClasses.delete(currentClass);
    } else if (!oldPropClasses.has(currentClass)) {
      // add it as it has NOT been removed by user
      finalClassNames.push(currentClass);
    }
  });
  incomingPropClasses.forEach(s => finalClassNames.push(s));
  return finalClassNames.join(' ');
};

/**
 * Checks if an event is supported in the current execution environment.
 * @license Modernizr 3.0.0pre (Custom Build) | MIT
 */
export const isCoveredByReact = (eventNameSuffix: string, doc: Document = document) => {
  const eventName = 'on' + eventNameSuffix;
  let isSupported = eventName in doc;

  if (!isSupported) {
    const element = doc.createElement('div');
    element.setAttribute(eventName, 'return;');
    isSupported = typeof (element as any)[eventName] === 'function';
  }

  return isSupported;
};

export const syncEvent = (node: Element & {__events?: {[key: string]: ((e: Event) => any) | undefined}}, eventName: string, newEventHandler?: (e: Event) => any) => {
  const eventStore = node.__events || (node.__events = {});
  const oldEventHandler = eventStore[eventName];

  // Remove old listener so they don't double up.
  if (oldEventHandler) {
    node.removeEventListener(eventName, oldEventHandler);
  }

  // Bind new listener.
  node.addEventListener(eventName, eventStore[eventName] = function handler(e: Event) {
    if (newEventHandler) { newEventHandler.call(this, e); }
  });
};

const arrayToMap = (arr: string[] | DOMTokenList) => {
  const map = new Map<string, string>();
  (arr as string[]).forEach((s: string) => map.set(s, s));
  return map;
};