/**
 * 跳转目标高亮：目标区域先铺主题色浅底（--accent-soft）再渐隐。
 * 供评论深链定位与文章目录树跳转共用；样式见 globals.css 的 .j13-flash-target。
 */
import { scrollBehavior } from "@/lib/motion";

const FLASH_MS = 1800;
const CLEANUP_MS = FLASH_MS + 300;

const timers = new WeakMap<HTMLElement, ReturnType<typeof setTimeout>>();

export function flashElement(el: HTMLElement | null | undefined) {
  if (!el) return;
  el.classList.remove("j13-flash-target");
  // 强制重排，支持连续触发同一元素
  void el.offsetWidth;
  el.classList.add("j13-flash-target");
  const prev = timers.get(el);
  if (prev) clearTimeout(prev);
  timers.set(
    el,
    setTimeout(() => {
      el.classList.remove("j13-flash-target");
      timers.delete(el);
    }, CLEANUP_MS)
  );
}

/** 滚动到目标（尊重平滑滚动开关与 scroll-margin）并高亮渐隐 */
export function scrollFlashTo(el: HTMLElement | null | undefined, block: ScrollLogicalPosition = "start") {
  if (!el) return;
  el.scrollIntoView({ behavior: scrollBehavior(), block });
  flashElement(el);
}