/// <reference no-default-lib="true" />
/// <reference lib="esnext" />
/// <reference lib="dom" />

const eventHandlers: MutationCallback[] = [];
let cursorChangeObserver: MutationObserver | undefined;

export function addCursorChangeEventListener(callback: MutationCallback) {
  /**
   * 初期化用関数
   * @return {boolean} 成功したならtrue、失敗したらfalse
   */
  function init(): boolean {
    const cursor = document.querySelector(".cursor");
    if (cursor === null) return false;
    const options: MutationObserverInit = {
      attributes: true,
      attributeFilter: ["style"],
    };

    cursorChangeObserver = new MutationObserver((
      mutation: MutationRecord[],
      observer: MutationObserver,
    ) => eventHandlers.forEach((e) => e(mutation, observer)));
    cursorChangeObserver.observe(cursor, options);
    return true;
  }
  if (cursorChangeObserver === undefined) if (!init()) return;
  eventHandlers.push(callback);
}