/**
 * 本文件由 YschTheme scripts/gen-theme.mjs 从 assets-src/pc/theme-core.js 生成（版本 20261006-2013-75c1d10），勿手改。
 * 分发方式：YschTheme `npm run sync` 拷进各端 src/utils/theme.ts（与 ThemeSwitcher.vue 配套，MD5 对齐报告）。
 * 运行时档位类名由 /static/js/yh-theme-init.js 在 <head> 内先行挂好，本模块只负责读写与切换。
 */
export type ThemeName = "blue" | "ocean" | "ink" | "violet" | "teal";

/** 定稿默认档：blue + side-deep + grad-on + 侧栏跟随（D1 拍板 deep） */
export interface ThemeState {
  theme: ThemeName;
  /** 侧栏深色（false=浅色档） */
  sideDeep: boolean;
  /** 顶栏渐变（联动侧栏竖向渐变） */
  gradOn: boolean;
  /** 侧栏颜色跟随顶栏品牌色（false=中性灰 side-plain） */
  sideFollow: boolean;
}

interface StorageLike {
  getItem(k: string): string | null;
  setItem(k: string, v: string): void;
}

export const THEME_NAMES: readonly ThemeName[] = ["blue", "ocean", "ink", "violet", "teal"];

export const THEME_STORAGE_KEY = "yh-theme";

/* 学校默认档存储键（UserHome 登录时写入；值格式与 yh-theme 完全相同，仅无"用户自选"语义） */
export const SCHOOL_DEFAULT_STORAGE_KEY = "yh-theme-sch-default";

export const DEFAULT_THEME_STATE: ThemeState = {
  theme: "blue",
  sideDeep: true,
  gradOn: true,
  sideFollow: true
};

/** 宽松解析：任一字段非法/缺失即回退默认档（脏数据不阻塞启动） */
export function parseThemeState(raw: string | null): ThemeState {
  if (!raw) return { ...DEFAULT_THEME_STATE };
  try {
    const o = JSON.parse(raw);
    if (!o || typeof o !== "object") return { ...DEFAULT_THEME_STATE };
    return {
      theme: THEME_NAMES.includes(o.theme) ? o.theme : DEFAULT_THEME_STATE.theme,
      sideDeep: typeof o.sideDeep === "boolean" ? o.sideDeep : DEFAULT_THEME_STATE.sideDeep,
      gradOn: typeof o.gradOn === "boolean" ? o.gradOn : DEFAULT_THEME_STATE.gradOn,
      sideFollow: typeof o.sideFollow === "boolean" ? o.sideFollow : DEFAULT_THEME_STATE.sideFollow
    };
  } catch {
    return { ...DEFAULT_THEME_STATE };
  }
}

/** 严格读取：四字段全部合法才返回状态，否则 null（合成链"值非法→回落下一级"用；用户键仍走宽松解析保现状） */
function readThemeStateOrNull(raw: string | null): ThemeState | null {
  if (!raw) return null;
  try {
    const o = JSON.parse(raw);
    if (!o || typeof o !== "object") return null;
    if (!THEME_NAMES.includes(o.theme)) return null;
    if (typeof o.sideDeep !== "boolean" || typeof o.gradOn !== "boolean" || typeof o.sideFollow !== "boolean") return null;
    return { theme: o.theme, sideDeep: o.sideDeep, gradOn: o.gradOn, sideFollow: o.sideFollow };
  } catch {
    return null;
  }
}

/** URL 覆盖参数（?yh-theme= / ?yh-side=deep|light / ?yh-grad=on|off）：仅预览/排障用，
    非法值忽略（对应字段不覆盖），且只影响"读哪一档"、绝不写回 localStorage。 */
function readThemeOverrides(): { theme?: ThemeName; sideDeep?: boolean; gradOn?: boolean } | null {
  let out = null;
  try {
    const search = (globalThis.location && globalThis.location.search) || "";
    const get = (name) => {
      const m = new RegExp("[?&]" + name + "=([^&]*)").exec(search);
      return m ? decodeURIComponent(m[1]) : null;
    };
    const t = get("yh-theme");
    if (t && THEME_NAMES.includes(t)) {
      out = out || {};
      out.theme = t;
    }
    const s = get("yh-side");
    if (s === "deep" || s === "light") {
      out = out || {};
      out.sideDeep = s === "deep";
    }
    const g = get("yh-grad");
    if (g === "on" || g === "off") {
      out = out || {};
      out.gradOn = g === "on";
    }
  } catch {
    /* 无 location 环境（测试/SSR）：无覆盖 */
  }
  return out;
}

/**
 * 生效档合成（唯一实现，init 启动段与 UserHome theme.ts 共用）：
 *   URL 覆盖 > localStorage["yh-theme"]（用户自选，存在即用——宽松修补，与历史行为一致）
 *   > localStorage["yh-theme-sch-default"]（学校默认，整体合法才生效）
 *   > DEFAULT_THEME_STATE。
 * 键不存在/解析失败/值非法均静默回落，不报错不阻塞首帧。
 */
export function resolveEffectiveThemeState(storage: StorageLike | undefined = globalThis.localStorage): ThemeState {
  let state = null;
  if (storage) {
    const userRaw = storage.getItem(THEME_STORAGE_KEY);
    if (userRaw) state = parseThemeState(userRaw);
    if (!state) state = readThemeStateOrNull(storage.getItem(SCHOOL_DEFAULT_STORAGE_KEY));
  }
  if (!state) state = { ...DEFAULT_THEME_STATE };
  const ov = readThemeOverrides();
  if (ov) {
    if (ov.theme) state = { ...state, theme: ov.theme };
    if (ov.sideDeep != null) state = { ...state, sideDeep: ov.sideDeep };
    if (ov.gradOn != null) state = { ...state, gradOn: ov.gradOn };
  }
  return state;
}

export function loadThemeState(storage: StorageLike | undefined = globalThis.localStorage): ThemeState {
  if (!storage) return { ...DEFAULT_THEME_STATE };
  return parseThemeState(storage.getItem(THEME_STORAGE_KEY));
}

export function saveThemeState(state: ThemeState, storage: StorageLike | undefined = globalThis.localStorage): void {
  try {
    storage?.setItem(THEME_STORAGE_KEY, JSON.stringify(state));
  } catch {
    /* 隐私模式/配额失败静默：仅丢持久化，不丢本次会话生效 */
  }
}

/** 把状态落到根元素档位类名（幂等：先清后挂），返回传入的 state 便于链式 */
export function applyThemeState(state: ThemeState, root: HTMLElement = document.documentElement): ThemeState {
  root.dataset.theme = state.theme;
  root.classList.toggle("side-deep", state.sideDeep);
  root.classList.toggle("side-light", !state.sideDeep);
  root.classList.toggle("grad-on", state.gradOn);
  root.classList.toggle("grad-off", !state.gradOn);
  root.classList.toggle("side-plain", !state.sideFollow);
  return state;
}

/** 启动引导：各端 main.ts（或本仓 init 脚本的启动段）于挂载前调用，消除首帧闪色 */
export function initTheme(): ThemeState {
  return applyThemeState(loadThemeState());
}