/**
 * 主题 token 远端覆写运行时
 *
 * 设计原则(与 lang.js 完全同构):
 *   1) 后端只存"对要个性化的 token"做覆写 KV,前端拿本地 style_color.js + 远端覆写 合并
 *   2) 三态机: unknown / ok / fail
 *   3) 多租户 × 多端平台 × 多模式(brand/light/dark)三维隔离缓存
 *   4) 失败归一: timeout / network / http / parse / exception
 *   5) 失败时使用本地 style_color.js 兜底
 *   6) 不修改 Vuex.themeStyle / themeColorSet / 页面 wrapper,只把"合并后的 token map"
 *      提供给 store/index.js 的 applyThemeWithRemote action 使用
 *
 * 暴露的 API:
 *   ThemeOverride.boot()              首屏阻塞拉取 + 缓存预热(失败静默)
 *   ThemeOverride.refresh(force)      重新拉取 + 重新应用
 *   ThemeOverride.getByTheme(theme)   取单个模式桶(brand/light/dark)的合并 KV
 *   ThemeOverride.getAll()            { brand, light, dark }
 *   ThemeOverride.onUniacidChange()   切租户后清旧缓存
 *   ThemeOverride.getRemoteStatus()   'unknown' | 'ok' | 'fail'
 *   ThemeOverride.onRemoteStatusChange(fn)  订阅状态变化
 *   ThemeOverride.__debug_cache       内部缓存(测试用)
 *
 * 关键: 一次 boot 只发一次 HTTP 请求,后端 getAllByTenant 一次出 brand/light/dark 三桶
 *       避免对每个 theme 单独请求造成的 3 倍带宽浪费
 */

import { themeConfig } from './config-external.js';
import Config from './config.js';
import http from './http.js';
import { Platform } from './platform.js';

const THEMES = ['brand', 'light', 'dark'];

// 远端覆写:内存缓存
//  shape: { [theme]: { version, map, ts, global_version } }
const overrideCache = {};

// 远端覆写:并发去重(以"全量拉取"为粒度)
let allInflight = null;

// 远端可用性三态机
let remoteStatus = 'unknown';
let remoteStatusAt = 0;
const remoteStatusListeners = [];

// 配置项缓存
const REMOTE = (themeConfig && themeConfig.overrideRemote) || {};

/**
 * 校验 source 配置:只接受 local / remote / hybrid,其它一律视为 remote(安全默认)
 */
function normalizeSource(s) {
	return ['local', 'remote', 'hybrid'].includes(s) ? s : 'remote';
}
const SOURCE = normalizeSource(REMOTE.source || 'remote');

/**
 * 远端失败原因归一
 */
function normalizeReason(s) {
	const allow = ['timeout', 'network', 'http', 'parse', 'exception', 'unknown'];
	return allow.includes(s) ? s : 'unknown';
}

/**
 * 远端成功/失败状态机
 */
function setRemoteStatus(s, detail) {
	if (remoteStatus === s) return;
	const prev = remoteStatus;
	remoteStatus = s;
	remoteStatusAt = Date.now();
	const safeDetail = {
		reason: normalizeReason(detail && detail.reason),
		theme:  detail && detail.theme,
	};
	remoteStatusListeners.forEach(fn => {
		try { fn(s, safeDetail); } catch (e) { /* 忽略监听器异常 */ }
	});
	try { uni.$emit && uni.$emit('theme:remote-status', { from: prev, to: s, ...safeDetail }); } catch (e) {}
	if (s === 'fail') {
		try { uni.$emit && uni.$emit('theme:fallback', { reason: safeDetail.reason }); } catch (e) {}
	}
}

/**
 * 获得当前租户 id
 */
function getCurrentUniacid() {
	const u = uni.getStorageSync('uniacid');
	return u ? parseInt(u, 10) || Config.uniacid : Config.uniacid;
}

/**
 * 当前平台类型
 */
function getCurrentAppType() {
	try { return Platform.getAppType() || '*'; } catch (e) { return '*'; }
}

/**
 * 持久化 key: <prefix><uniacid>_<appType>_<theme>
 */
function getOverrideStorageKey(theme) {
	const u = getCurrentUniacid();
	const a = getCurrentAppType();
	return `${REMOTE.storagePrefix || 'THEME_OVR_'}${u}_${a}_${theme}`;
}

/**
 * 内存 cache key: <uniacid>_<appType>_<theme>
 */
function getOverrideMemKey(theme) {
	return `${getCurrentUniacid()}_${getCurrentAppType()}_${theme}`;
}

/**
 * 从 storage 预热单个 theme 桶到内存(首屏兜底)
 * 仅在内存还没有该 key 时才读 storage,避免覆盖更新值
 */
function preheatFromStorage(theme) {
	const mk = getOverrideMemKey(theme);
	if (overrideCache[mk]) return;
	try {
		const cached = uni.getStorageSync(getOverrideStorageKey(theme));
		if (cached && cached.map) {
			overrideCache[mk] = {
				version: cached.version || 0,
				map: cached.map || {},
				ts: cached.ts || 0,
				global_version: cached.global_version || 0,
			};
			return;
		}
	} catch (e) { /* 忽略 */ }
	overrideCache[mk] = { version: 0, map: {}, ts: 0, global_version: 0 };
}

/**
 * 把"单次 HTTP 响应"按 by_theme 拆到 3 个内存桶 + 持久化
 */
function applyRemoteResponse(d) {
	const byTheme = (d && d.by_theme && typeof d.by_theme === 'object') ? d.by_theme : {};
	const gv = (d && d.global_version) || 0;
	const ts = Date.now();

	THEMES.forEach(theme => {
		const remoteMap = (byTheme[theme] && typeof byTheme[theme] === 'object') ? byTheme[theme] : {};
		const mk = getOverrideMemKey(theme);
		const baseCache = overrideCache[mk] || { version: 0, map: {}, ts: 0, global_version: 0 };
		const merged = Object.assign({}, baseCache.map, remoteMap);
		overrideCache[mk] = {
			version: gv,
			map: merged,
			ts,
			global_version: gv,
		};
		try { uni.setStorageSync(getOverrideStorageKey(theme), overrideCache[mk]); } catch (e) {}
	});
}

/**
 * 取"3 个桶里最大的 global_version"(穿透缓存用)
 */
function maxCachedGlobalVersion() {
	let gv = 0;
	THEMES.forEach(t => {
		const mk = getOverrideMemKey(t);
		const c = overrideCache[mk];
		if (c && c.global_version > gv) gv = c.global_version;
	});
	return gv;
}

/**
 * 一次 HTTP 拉齐 3 个 theme 桶
 * 这是 boot() / refresh() / onUniacidChange() 共用的"拉取入口"
 *
 * 关键: 1 次 HTTP, 拆 3 桶,避免对每个 theme 单独请求造成 3 倍浪费
 *
 * @returns {Promise<{ source:'cache'|'remote'|'local', ok:boolean, reason?:string, themes:string[] }>}
 */
async function loadAllOverrides() {
	if (SOURCE === 'local') return { source: 'local', ok: true, themes: THEMES };

	// 并发去重:同一刻只允许一个在飞
	if (allInflight) return allInflight;

	allInflight = (async () => {
		// 1) 先预热 storage 兜底
		THEMES.forEach(preheatFromStorage);

		// 2) 一次 HTTP 拉齐 3 桶
		try {
			const res = await Promise.race([
				http.sendRequest({
					url: REMOTE.overridesUrl || '/api/theme/overrides',
					data: {
						global_version: maxCachedGlobalVersion(),
					},
					async: false,
				}),
				new Promise((r) => setTimeout(() => r({ code: -1, message: 'timeout' }), REMOTE.requestTimeout || 4000)),
			]);

			if (!res || res.code !== 0 || !res.data) {
				const reason = !res ? 'network' : (res.code === -1 ? 'timeout' : (res.message || 'bad-response'));
				setRemoteStatus('fail', { reason, theme: 'all' });
				return { source: 'local', ok: false, reason, themes: THEMES };
			}

			applyRemoteResponse(res.data);
			setRemoteStatus('ok', { theme: 'all' });
			emitUpdated('all');
			return { source: 'remote', ok: true, themes: THEMES };
		} catch (e) {
			setRemoteStatus('fail', { reason: 'exception', error: String(e && e.message || e), theme: 'all' });
			return { source: 'local', ok: false, reason: 'exception', themes: THEMES };
		}
	})();

	try {
		return await allInflight;
	} finally {
		allInflight = null;
	}
}

/**
 * 触发"主题已更新"事件
 * 注意:Vuex 的 themeColorSet action 已经在 setThemeStyle 后跑过,
 *       CSS 变量已挂到页面 wrapper 上,组件会自动刷新。
 *       这里只发通知,方便业务代码(如自定义 JS 直读 themeStyle 的页面)主动 re-render。
 */
function emitUpdated(theme) {
	try { uni.$emit && uni.$emit('theme:updated', { theme }); } catch (e) {}
}

// 导出主体
export default {
	SOURCE,

	/**
	 * 阻塞式预热:App.onLaunch 在 Lang.boot 后调用
	 * 失败静默,不阻塞首屏
	 *
	 * @returns {Promise<{ok:boolean, source:'local'|'remote'|'cache'|'timeout', status:string, reason?:string, themes:string[]}>}
	 */
	async boot() {
		if (SOURCE === 'local') {
			return { ok: true, source: 'local', status: remoteStatus, themes: THEMES };
		}

		const bootTimeout = REMOTE.bootTimeout || 2000;
		const t = new Promise((r) => setTimeout(() => r({ __timeout: true }), bootTimeout));

		// 切租户检测
		const currentUid = getCurrentUniacid();
		try {
			const lastUid = uni.getStorageSync('theme_last_uniacid');
			if (lastUid && String(lastUid) !== String(currentUid)) {
				this.onUniacidChange();
			}
			uni.setStorageSync('theme_last_uniacid', currentUid);
		} catch (e) {}

		const result = await Promise.race([loadAllOverrides(), t]);
		if (result && result.__timeout) {
			return { ok: false, source: 'timeout', status: 'fail', reason: 'timeout', themes: THEMES };
		}
		return {
			ok: remoteStatus === 'ok',
			source: remoteStatus === 'ok' ? 'remote' : 'local',
			status: remoteStatus,
			themes: THEMES,
		};
	},

	/**
	 * 主动重新拉取(管理后台改了之后 EventBus 通知触发)
	 * @param {boolean} [force=false] true = 绕过缓存强刷
	 */
	async refresh(force = false) {
		if (force) {
			// 强刷:清掉内存 + 持久化缓存,逼 loadAllOverrides 走远端
			THEMES.forEach(t => {
				const mk = getOverrideMemKey(t);
				if (overrideCache[mk]) overrideCache[mk] = { version: 0, map: {}, ts: 0, global_version: 0 };
				try { uni.removeStorageSync(getOverrideStorageKey(t)); } catch (e) {}
			});
		}
		return loadAllOverrides();
	},

	/**
	 * 切租户后清旧缓存
	 */
	onUniacidChange() {
		if (SOURCE === 'local') return;
		if (REMOTE.refreshOnUniacidChange === false) return;
		THEMES.forEach(t => {
			const sk = getOverrideStorageKey(t);
			try { uni.removeStorageSync(sk); } catch (e) {}
			delete overrideCache[getOverrideMemKey(t)];
		});
		loadAllOverrides();
	},

	/**
	 * 取某个 theme 桶(同步:有缓存返缓存;无缓存时该桶返回 {})
	 * store/index.js 的 applyThemeWithRemote action 直接用
	 * @param {'brand'|'light'|'dark'} theme
	 * @returns {object}  扁平 KV  map (没有时返回 {})
	 */
	getByTheme(theme) {
		const mk = getOverrideMemKey(theme);
		const cached = overrideCache[mk];
		return (cached && cached.map) ? cached.map : {};
	},

	/**
	 * 取所有 theme 桶
	 * @returns {{ brand: object, light: object, dark: object }}
	 */
	getAll() {
		return {
			brand: this.getByTheme('brand'),
			light: this.getByTheme('light'),
			dark:  this.getByTheme('dark'),
		};
	},

	/**
	 * 当前远端状态
	 */
	getRemoteStatus() { return remoteStatus; },

	/**
	 * 订阅远端状态变化
	 * @param {(status:string, detail:object) => void} fn
	 * @returns {() => void} unsubscribe
	 */
	onRemoteStatusChange(fn) {
		if (typeof fn !== 'function') return () => {};
		remoteStatusListeners.push(fn);
		try { fn(remoteStatus, { at: remoteStatusAt, source: SOURCE }); } catch (e) {}
		return () => {
			const i = remoteStatusListeners.indexOf(fn);
			if (i >= 0) remoteStatusListeners.splice(i, 1);
		};
	},

	// 内部测试/调试用
	__debug_overrideCache: overrideCache,
	__debug_loadAllOverrides: loadAllOverrides,
}