export type WecomCsSessionContext = {
  orderId?: string;
  orderNo?: string;
  from?: string;
};

type OpenCsChatOption = {
  extInfo: { url: string };
  corpId: string;
  showMessageCard?: boolean;
  sendMessageTitle?: string;
  sendMessagePath?: string;
};

type WxCsFail = { errMsg?: string; errCode?: number };

type WxCsChat = {
  openCustomerServiceChat?: (
    option: OpenCsChatOption & {
      success?: () => void;
      fail?: (err: WxCsFail) => void;
    },
  ) => void;
};

/**
 * 取小程序原生 wx.openCustomerServiceChat。
 * 官方不支持 Promise 风格；Taro 模块作用域下也可能读不到全局 wx。
 */
function getWxOpenCsChat(): WxCsChat['openCustomerServiceChat'] | null {
  if (process.env.TARO_ENV !== 'weapp') return null;

  const candidates: Array<WxCsChat | null | undefined> = [];
  try {
    // eslint-disable-next-line no-undef
    if (typeof wx !== 'undefined') candidates.push(wx as WxCsChat);
  } catch {
    /* ignore */
  }
  candidates.push((globalThis as typeof globalThis & { wx?: WxCsChat }).wx);
  try {
    const fromRuntime = new Function(
      'return typeof wx !== "undefined" ? wx : null',
    )() as WxCsChat | null;
    candidates.push(fromRuntime);
  } catch {
    /* ignore */
  }

  for (const api of candidates) {
    if (api && typeof api.openCustomerServiceChat === 'function') {
      return api.openCustomerServiceChat.bind(api);
    }
  }
  return null;
}

function rawCsError(err: unknown): string {
  if (err instanceof Error) return err.message;
  if (typeof err === 'string') return err;
  if (err && typeof err === 'object' && 'errMsg' in err) {
    return String((err as WxCsFail).errMsg || '');
  }
  return '';
}

/** 把微信 fail 转成可读提示；用户取消返回空串，调用方不 toast */
export function formatOpenCsError(err: unknown): string {
  const raw = rawCsError(err);
  if (/cancel/i.test(raw)) return '';
  if (/not bind|not bound/i.test(raw)) {
    return '企业ID未绑定当前小程序。请到微信公众平台「功能 → 客服 → 微信客服」填写同一企业ID';
  }
  if (!raw || /openCustomerServiceChat:fail$/i.test(raw.trim())) {
    return '无法打开微信客服。开发者工具模拟器通常不可用，请用真机预览';
  }
  return raw;
}

/** 小程序调起企业微信「微信客服」会话 */
export async function openWecomCustomerServiceChat(params: {
  url: string;
  corpId: string;
  session?: WecomCsSessionContext;
}): Promise<void> {
  const url = params.url.trim();
  const corpId = params.corpId.trim();
  if (!url || !corpId) {
    throw new Error('企微客服未配置');
  }

  const wxApi = getWxOpenCsChat();
  if (!wxApi) {
    throw new Error('当前微信版本不支持企业微信客服');
  }

  const option: OpenCsChatOption = {
    extInfo: { url },
    corpId,
  };
  if (params.session?.orderNo || params.session?.orderId) {
    option.showMessageCard = true;
    option.sendMessageTitle = params.session.orderNo
      ? `订单 ${params.session.orderNo}`
      : '订单咨询';
    if (params.session.orderId) {
      option.sendMessagePath = `pages/order-detail/index?id=${params.session.orderId}`;
    }
  }

  await new Promise<void>((resolve, reject) => {
    wxApi({
      ...option,
      success: () => resolve(),
      fail: (err) => reject(err),
    });
  });
}