const generateKey = () => Math.random().toString(36).slice(2, 8);

// Exported only for test
export type WindowInternal = Window & {
  CustomEvent?: new <T>(typeArg: string, eventInitDict?: CustomEventInit<T>) => CustomEvent<T>;
  Event: typeof Event;
};

type IPrototype = {
  prototype: any;
};

type InitCustomEventParams<T = any> = {
  bubbles: boolean;
  cancelable: boolean;
  detail: T;
};

// IE Polyfill for CustomEvent
export const CreateEvent =
  (windowInternal: WindowInternal, documentInternal: Document) =>
  (event: string, params: InitCustomEventParams): CustomEvent => {
    if (typeof windowInternal.CustomEvent === 'function') {
      return new windowInternal.CustomEvent(event, params);
    }
    const paramsToFunction = params || { bubbles: false, cancelable: false, detail: undefined };
    const evt: CustomEvent = documentInternal.createEvent('CustomEvent');
    evt.initCustomEvent(
      event,
      paramsToFunction.bubbles,
      paramsToFunction.cancelable,
      paramsToFunction.detail,
    );
    (evt as CustomEvent & IPrototype).prototype = windowInternal.Event.prototype;
    return evt;
  };

type WindowHistoryState = typeof window.history.state;

export interface ReactOidcHistory {
  replaceState: (url?: string | null, stateHistory?: WindowHistoryState) => void;
}

export type CustomHistory = {
  replaceState(url?: string | null, stateHistory?: WindowHistoryState): void;
};

const getHistory = (
  windowInternal: WindowInternal,
  CreateEventInternal: (event: string, params?: InitCustomEventParams) => CustomEvent,
  generateKeyInternal: typeof generateKey,
): CustomHistory => {
  return {
    replaceState: (url?: string | null, stateHistory?: WindowHistoryState): void => {
      const key = generateKeyInternal();
      const state = stateHistory || windowInternal.history.state;
      windowInternal.history.replaceState({ key, state }, null, url);
      windowInternal.dispatchEvent(CreateEventInternal('popstate'));
    },
  };
};

export const getCustomHistory = () =>
  getHistory(window, CreateEvent(window, document), generateKey);