import { getRuntimePlatform, isIosDevice, isWechatDevTools } from './env';
import { ensureJssdkReady } from './jssdk';
import type { WeixinSdkConfig } from './types';

function delay(ms: number): Promise<void> {
  return new Promise((resolve) => window.setTimeout(resolve, ms));
}

/** 将微信 scanQRCode fail 的 errMsg 转为用户可读文案（避免误判为系统相机权限） */
export function formatScanFailMessage(errMsg: string): string {
  const msg = errMsg.trim() || '扫码失败';
  if (/cancel/i.test(msg)) return '';

  // iOS 常见：JSSDK 权限离线校验尚未完成，并非系统相机权限
  if (/offline verifying|permission value is offline/i.test(msg)) {
    return '微信权限验证中，请稍候再试或刷新页面后重新扫码';
  }

  if (/invalid signature|config:fail|signature/i.test(msg)) {
    return '微信 JSSDK 签名校验失败，请刷新页面后重试';
  }

  // 系统级相机权限（iPhone 设置 → 隐私 → 相机 → 微信）
  if (/system.*camera|NotAllowedError|camera.*not.*allowed|无法访问相机|无相机权限/i.test(msg)) {
    return '相机权限未开启，请在 iPhone「设置 → 隐私与安全性 → 相机」中允许微信使用摄像头';
  }

  // JSSDK 接口授权失败（含 permission，但不等于相机权限）
  if (/permission|auth|denied|授权|拒绝/i.test(msg)) {
    return `微信扫码接口未就绪（${msg}），请刷新页面后重试`;
  }

  return msg;
}

function invokeScanQrCode(): Promise<string | null> {
  return new Promise((resolve, reject) => {
    window.wx!.scanQRCode!({
      needResult: 1,
      scanType: ['qrCode', 'barCode'],
      success: (res) => resolve(res.resultStr || null),
      fail: (res) => {
        const msg = res.errMsg || '扫码失败';
        if (/cancel/i.test(msg)) {
          resolve(null);
          return;
        }
        const formatted = formatScanFailMessage(msg);
        reject(new Error(formatted || msg));
      },
    });
  });
}

/** 调起扫码（返回二维码/条码内容，失败返回 null） */
export async function scanQrCode(config: WeixinSdkConfig): Promise<string | null> {
  const platform = getRuntimePlatform();

  if (platform === 'mini' && window.wx?.scanCode) {
    return new Promise((resolve) => {
      window.wx!.scanCode!({
        onlyFromCamera: true,
        scanType: ['qrCode', 'barCode'],
        success: (res) => resolve(res.result || null),
        fail: () => resolve(null),
      });
    });
  }

  if (platform === 'wechat-h5') {
    await ensureJssdkReady({
      apiBase: config.apiBase ?? '/api/v1',
      clientApp: config.clientApp,
      getAccessToken: config.getAccessToken,
    });
    if (!window.wx?.scanQRCode) {
      throw new Error('当前微信版本不支持扫码，请升级微信后重试');
    }

    // iOS 在 wx.ready 后立即调 scanQRCode 可能触发 offline verifying
    if (isIosDevice() && !isWechatDevTools()) {
      await delay(500);
    }

    const maxAttempts = 2;
    let lastError: Error | null = null;
    for (let attempt = 0; attempt < maxAttempts; attempt++) {
      if (attempt > 0) {
        await delay(800);
      }
      try {
        return await invokeScanQrCode();
      } catch (e) {
        lastError = e instanceof Error ? e : new Error('扫码失败');
        const raw = lastError.message;
        const retryable = /offline verifying|权限验证中|接口未就绪/i.test(raw);
        if (attempt < maxAttempts - 1 && retryable) continue;
        throw lastError;
      }
    }
    throw lastError ?? new Error('扫码失败');
  }

  throw new Error('请在微信内打开以使用扫码核销');
}