/**
 * 全站动画策略：系统「减少动态效果」优先；站点总开关/子开关可进一步关闭。
 * 新增性能相关动画时：CSS 挂 j13-reduce-*，JS 走 allowMotion / scrollBehavior。
 */

export type MotionKind = "codeFold" | "smoothScroll" | "chrome";

export type MotionSiteConfig = {
  /** 界面动画总开关 */
  ui_animations: boolean;
  /** 代码折叠高度与跟滚 */
  anim_code_fold: boolean;
  /** 平滑滚动 */
  anim_smooth_scroll: boolean;
  /** 装饰入场：列表/Toast/点赞/脉冲等 */
  anim_chrome: boolean;
};

export const DEFAULT_MOTION_CONFIG: MotionSiteConfig = {
  ui_animations: true,
  anim_code_fold: true,
  anim_smooth_scroll: true,
  anim_chrome: true,
};

let siteConfig: MotionSiteConfig = { ...DEFAULT_MOTION_CONFIG };

export function getMotionSiteConfig(): MotionSiteConfig {
  return siteConfig;
}

export function motionConfigFromSettings(s: {
  ui_animations?: boolean;
  anim_code_fold?: boolean;
  anim_smooth_scroll?: boolean;
  anim_chrome?: boolean;
}): MotionSiteConfig {
  return {
    ui_animations: s.ui_animations !== false,
    anim_code_fold: s.anim_code_fold !== false,
    anim_smooth_scroll: s.anim_smooth_scroll !== false,
    anim_chrome: s.anim_chrome !== false,
  };
}

export function osPrefersReducedMotion(): boolean {
  return (
    typeof window !== "undefined" &&
    window.matchMedia("(prefers-reduced-motion: reduce)").matches
  );
}

/** 是否允许指定类动画（OS reduce 或总开关关闭则一律否） */
export function allowMotion(kind: MotionKind = "chrome"): boolean {
  if (osPrefersReducedMotion()) return false;
  if (!siteConfig.ui_animations) return false;
  switch (kind) {
    case "codeFold":
      return siteConfig.anim_code_fold;
    case "smoothScroll":
      return siteConfig.anim_smooth_scroll;
    case "chrome":
      return siteConfig.anim_chrome;
    default:
      return true;
  }
}

export function scrollBehavior(): ScrollBehavior {
  return allowMotion("smoothScroll") ? "smooth" : "auto";
}

/** 同步 documentElement class，供 CSS 与 SSR 初值一致 */
export function syncMotionHtmlClasses(cfg: MotionSiteConfig = siteConfig): void {
  if (typeof document === "undefined") return;
  const root = document.documentElement;
  root.classList.toggle("j13-reduce-motion", !cfg.ui_animations);
  root.classList.toggle(
    "j13-reduce-chrome",
    cfg.ui_animations && !cfg.anim_chrome
  );
}

/** 应用站点动画配置（SSR 初值 / WS 热更新） */
export function applyMotionSiteConfig(cfg: MotionSiteConfig): MotionSiteConfig {
  siteConfig = motionConfigFromSettings(cfg);
  syncMotionHtmlClasses(siteConfig);
  return siteConfig;
}