import { useState, useEffect, useRef, type ReactNode } from 'react';
import { AuthContext, type AuthState, type AuthUser } from './useAuth';
import { setTokenGetter, setPreviewTokenGetter, invalidateAuthenticatedRequests, fetchPreviewControl } from './api-client';

const AUTH_API = '/api/auth';

export default function AuthProvider({ children }: { children: ReactNode }) {
  const [state, setState] = useState<AuthState>({
    isLoading: true,
    isAuthenticated: false,
    user: null,
    error: null,
  });
  const tokenRef = useRef<string | null>(null);
  const authStarted = useRef(false);
  const previewTokenRef = useRef<string | null>(null);
  const actorRef = useRef<AuthUser | null>(null);
  const transitionRef = useRef(0);
  const [identityVersion, setIdentityVersion] = useState(0);
  const [preview, setPreview] = useState<{ user: AuthUser; expiresAt: string } | null>(null);
  const [canPreview, setCanPreview] = useState(false);
  const [previewNotice, setPreviewNotice] = useState<string | null>(null);

  function resetPreview(message: string | null = null) {
    transitionRef.current += 1;
    previewTokenRef.current = null;
    sessionStorage.removeItem('bi_preview_token');
    invalidateAuthenticatedRequests();
    setIdentityVersion(v => v + 1);
    setPreview(null);
    setPreviewNotice(message);
  }

  async function loadPreviewContext(user: AuthUser | null) {
    actorRef.current = user;
    try {
      const context = await fetchPreviewControl<{ canPreview: boolean; actor: AuthUser }>('context');
      actorRef.current = context.actor;
      setCanPreview(context.canPreview);
      if (context.canPreview) {
        const savedPreview = sessionStorage.getItem('bi_preview_token');
        if (savedPreview) {
          previewTokenRef.current = savedPreview;
          try {
            const current = await fetchPreviewControl<{ user: AuthUser; expiresAt: string }>('current', undefined, true);
            setPreview(current);
          } catch {
            resetPreview('上次权限视角已失效，已返回本人视角。');
          }
        }
      } else {
        resetPreview();
      }
    } catch {
      resetPreview();
      setCanPreview(false);
    }
  }

  async function finishAuthentication(user: AuthUser | null) {
    await loadPreviewContext(user);
    if (!tokenRef.current) return;
    setState({ isLoading: false, isAuthenticated: true, user: actorRef.current, error: null });
  }

  async function startPreview(userId: string) {
    const transition = ++transitionRef.current;
    const next = await fetchPreviewControl<{ previewToken: string; user: AuthUser; expiresAt: string }>('start', {
      method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ userId }),
    });
    if (transition !== transitionRef.current) return;
    invalidateAuthenticatedRequests();
    previewTokenRef.current = next.previewToken;
    sessionStorage.setItem('bi_preview_token', next.previewToken);
    setPreview({ user: next.user, expiresAt: next.expiresAt });
    setIdentityVersion(v => v + 1);
    setPreviewNotice(null);
  }

  async function stopPreview() {
    const stopping = fetchPreviewControl('stop', { method: 'POST' }, true);
    resetPreview();
    await stopping.catch(() => { setPreviewNotice('已退出本地预览；服务端凭证将自动到期。'); });
  }

  useEffect(() => {
    if (!preview) return;
    const token = previewTokenRef.current;
    const validate = async () => {
      try {
        const current = await fetchPreviewControl<{ user: AuthUser; expiresAt: string }>('current', undefined, true);
        if (token !== previewTokenRef.current) return;
        if (JSON.stringify(current.user) !== JSON.stringify(preview.user)) {
          invalidateAuthenticatedRequests();
          setPreview(current);
          setIdentityVersion(v => v + 1);
        }
      } catch {
        if (token === previewTokenRef.current) resetPreview('权限视角验证失败，已返回本人视角，请重新选择。');
      }
    };
    const timer = window.setInterval(validate, 60_000);
    const expiry = window.setTimeout(() => resetPreview('权限视角已到期，已返回本人视角。'), Math.max(0, Date.parse(preview.expiresAt) - Date.now()));
    window.addEventListener('focus', validate);
    return () => { clearInterval(timer); clearTimeout(expiry); window.removeEventListener('focus', validate); };
  }, [preview]);

  useEffect(() => {
    // 设置全局 token getter
    setTokenGetter(() => tokenRef.current);

    setPreviewTokenGetter(() => previewTokenRef.current);

    // 监听 401 事件
    const onUnauthorized = () => {
      resetPreview();
      setCanPreview(false);
      tokenRef.current = null;
      sessionStorage.removeItem('bi_jwt');
      sessionStorage.removeItem('bi_user');
      actorRef.current = null;
      setState({ isLoading: false, isAuthenticated: false, user: null, error: '会话已过期' });
    };
    window.addEventListener('auth:unauthorized', onUnauthorized);

    const onPreviewEnded = (event: Event) => {
      if ((event as CustomEvent).detail === 'PREVIEW_REVOKED') setCanPreview(false);
      resetPreview('预览权限已失效，已返回本人视角。');
    };
    const onReadOnly = () => setPreviewNotice('权限视角仅供查看数据，请退出预览后进行修改操作。');
    window.addEventListener('auth:preview-ended', onPreviewEnded);
    window.addEventListener('auth:preview-readonly', onReadOnly);
    // StrictMode 重新安装监听，但一次性 jumpToken 仅交换一次。
    if (!authStarted.current) { authStarted.current = true; void authenticate(); }
    return () => {
      window.removeEventListener('auth:unauthorized', onUnauthorized);
      window.removeEventListener('auth:preview-ended', onPreviewEnded);
      window.removeEventListener('auth:preview-readonly', onReadOnly);
    };
  }, []);

  async function authenticate() {
    // 本地开发免登录开关：.env 里设 VITE_DEV_BYPASS_AUTH=1 启用，仅 dev 生效
    if (import.meta.env.DEV && import.meta.env.VITE_DEV_BYPASS_AUTH === '1') {
      const devUser: AuthUser = {
        userId: 'dev-local',
        userName: '本地开发',
        permissionLevel: 'full',
        depName: '',
        roles: ['所有权限', 'BI-SCHEDULE-OPT', 'BI-ADMIN-FEEDBACK', 'BI-LEADER-ENERGY'],
      };
      // 预览授权仍由后端独立开发开关决定，不使用真实用户令牌。
      tokenRef.current = null;
      await loadPreviewContext(devUser);
      actorRef.current ||= devUser;
      setState({ isLoading: false, isAuthenticated: true, user: actorRef.current, error: null });
      return;
    }

    // 1. 检查 sessionStorage 中是否有 JWT
    const savedToken = sessionStorage.getItem('bi_jwt');
    if (savedToken) {
      tokenRef.current = savedToken;
      // 从受保护的身份接口验证 JWT；不使用本地缓存用户决定权限。
      try {
        const res = await fetch('/api/auth/me', {
          headers: { Authorization: `Bearer ${savedToken}` },
        });
        if (res.ok) {
          const verifiedUser: AuthUser = await res.json();
          if (!verifiedUser.userId) throw new Error('无效的用户身份');
          await finishAuthentication(verifiedUser);
          return;
        }
      } catch { /* token 无效，继续流程 */ }
      tokenRef.current = null;
      resetPreview();
      sessionStorage.removeItem('bi_jwt');
      sessionStorage.removeItem('bi_user');
    }

    // 2. 从 URL 提取 jumpToken
    const params = new URLSearchParams(window.location.search);
    const jumpToken = params.get('jumpToken');

    if (!jumpToken) {
      setState({ isLoading: false, isAuthenticated: false, user: null, error: '请从业务系统跳转访问' });
      return;
    }

    try {
      // 3. 一步完成：jumpToken → 用户信息 + JWT
      const res = await fetch(`${AUTH_API}/exchange?jumpToken=${encodeURIComponent(jumpToken)}`);
      const data = await res.json();

      if (!res.ok || !data.token) {
        setState({ isLoading: false, isAuthenticated: false, user: null, error: data.message || '跳转令牌无效或已过期' });
        return;
      }

      // 4. 存储 JWT
      tokenRef.current = data.token;
      sessionStorage.setItem('bi_jwt', data.token);
      sessionStorage.setItem('bi_user', JSON.stringify(data.user));

      // 6. 清除 URL 中的 jumpToken
      params.delete('jumpToken');
      const cleanUrl = params.toString()
        ? `${window.location.pathname}?${params.toString()}${window.location.hash}`
        : `${window.location.pathname}${window.location.hash}`;
      window.history.replaceState({}, '', cleanUrl);

      await finishAuthentication(data.user);
    } catch (e) {
      setState({ isLoading: false, isAuthenticated: false, user: null, error: '认证过程出错' });
    }
  }

  return (
    <AuthContext.Provider value={{ ...state, actor: actorRef.current || state.user,
      user: preview?.user || state.user, preview, canPreview, identityVersion, previewNotice,
      startPreview, stopPreview, clearPreviewNotice: () => setPreviewNotice(null) }}>
      {children}
    </AuthContext.Provider>
  );
}