"use client";

import { createContext, useContext, useState, useEffect, ReactNode, useCallback } from "react";

interface User {
  id: number;
  email: string;
  role: string;
}

interface AuthState {
  user: User | null;
  accessToken: string | null;
  loading: boolean;
  login: (email: string, password: string) => Promise<void>;
  register: (email: string, password: string, inviteCode: string) => Promise<void>;
  logout: () => void;
  isLoggedIn: boolean;
  isAdmin: boolean;
}

const AuthContext = createContext<AuthState | undefined>(undefined);

const API_BASE = process.env.NEXT_PUBLIC_API_URL ?? "";

export function AuthProvider({ children }: { children: ReactNode }) {
  const [user, setUser] = useState<User | null>(null);
  const [accessToken, setAccessToken] = useState<string | null>(null);
  const [loading, setLoading] = useState(true);

  // init from localStorage
  useEffect(() => {
    // [REVIEW] FE-P3-1 | Tokens 存储在 localStorage，存在 XSS 盗取风险
    // 任何能在页面执行的 JS（包括第三方依赖的供应链攻击）都能读取 localStorage
    // 对于交易系统建议改用 httpOnly Secure cookie（需后端配合 /api/auth/session 端点）
    const token = localStorage.getItem("access_token");
    const saved = localStorage.getItem("user");
    if (token && saved) {
      try {
        setAccessToken(token);
        setUser(JSON.parse(saved));
      } catch {}
    }
    setLoading(false);
  }, []);

  const saveAuth = (data: { access_token: string; refresh_token: string; user: User }) => {
    localStorage.setItem("access_token", data.access_token);
    localStorage.setItem("refresh_token", data.refresh_token);
    localStorage.setItem("user", JSON.stringify(data.user));
    setAccessToken(data.access_token);
    setUser(data.user);
  };

  const login = useCallback(async (email: string, password: string) => {
    const res = await fetch(`${API_BASE}/api/auth/login`, {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ email, password }),
    });
    if (!res.ok) {
      const err = await res.json().catch(() => ({}));
      throw new Error(err.detail || "Login failed");
    }
    const data = await res.json();
    saveAuth(data);
  }, []);

  const register = useCallback(async (email: string, password: string, inviteCode: string) => {
    const res = await fetch(`${API_BASE}/api/auth/register`, {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ email, password, invite_code: inviteCode }),
    });
    if (!res.ok) {
      const err = await res.json().catch(() => ({}));
      throw new Error(err.detail || "Registration failed");
    }
    const data = await res.json();
    saveAuth(data);
  }, []);

  const logout = useCallback(() => {
    localStorage.removeItem("access_token");
    localStorage.removeItem("refresh_token");
    localStorage.removeItem("user");
    setAccessToken(null);
    setUser(null);
  }, []);

  return (
    <AuthContext.Provider value={{
      user, accessToken, loading, login, register, logout,
      isLoggedIn: !!user, isAdmin: user?.role === "admin",
    }}>
      {children}
    </AuthContext.Provider>
  );
}

export function useAuth() {
  const ctx = useContext(AuthContext);
  if (!ctx) throw new Error("useAuth must be used within AuthProvider");
  return ctx;
}

// Authenticated fetch helper
export async function authFetch(path: string, options: RequestInit = {}): Promise<Response> {
  const token = localStorage.getItem("access_token");
  const headers = new Headers(options.headers);
  if (token) headers.set("Authorization", `Bearer ${token}`);
  
  let res = await fetch(`${API_BASE}${path}`, { ...options, headers });
  
  // try refresh on 401
  if (res.status === 401) {
    const refreshToken = localStorage.getItem("refresh_token");
    if (refreshToken) {
      // [REVIEW] FE-P1-1 | 并发刷新竞态：多个组件同时 401 时会并发调用此逻辑
      // 后端 refresh token 是单次使用（用完即 revoke），多个并发刷新请求中只有第一个成功
      // 其余请求的刷新会失败，进入 else 分支清除 localStorage，导致部分组件数据停止更新
      // 修复：用模块级 Promise 单例防止并发刷新
      //   let _refreshPromise: Promise<string|null> | null = null;
      //   if (!_refreshPromise) { _refreshPromise = doRefresh().finally(() => _refreshPromise = null); }
      //   const newToken = await _refreshPromise;
      const refreshRes = await fetch(`${API_BASE}/api/auth/refresh`, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ refresh_token: refreshToken }),
      });
      if (refreshRes.ok) {
        const data = await refreshRes.json();
        localStorage.setItem("access_token", data.access_token);
        localStorage.setItem("refresh_token", data.refresh_token);
        headers.set("Authorization", `Bearer ${data.access_token}`);
        res = await fetch(`${API_BASE}${path}`, { ...options, headers });
      } else {
        // [REVIEW] FE-P1-2 | 刷新失败后 React AuthContext 状态未同步
        // 这里清除了 localStorage 但没有调用 AuthContext.logout()（无法直接访问 Context）
        // 结果：React state 仍显示 isLoggedIn=true，user 对象仍存在
        // 用户 UI 看起来仍是登录状态，但所有后续 API 调用都会无声失败（catch{} 吞掉错误）
        // 修复方案A：抛出特定错误码，调用方 useEffect 中捕获并执行 logout()
        // 修复方案B：用 window.dispatchEvent(new CustomEvent("auth:logout")) 触发全局登出
        // refresh failed, clear auth
        localStorage.removeItem("access_token");
        localStorage.removeItem("refresh_token");
        localStorage.removeItem("user");
      }
    }
  }
  
  return res;
}