import React, { createContext, useContext, useState, useEffect, useCallback } from 'react';

const AuthContext = createContext(null);

export function AuthProvider({ children }) {
  const [user, setUser] = useState(null);
  const [token, setToken] = useState(localStorage.getItem('gilded-token'));
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    if (!token) {
      setLoading(false);
      return;
    }

    fetch('/api/auth/me', {
      headers: { Authorization: `Bearer ${token}` },
    })
      .then((res) => {
        if (!res.ok) throw new Error('Invalid token');
        return res.json();
      })
      .then((data) => {
        setUser(data.user || data);
      })
      .catch(() => {
        localStorage.removeItem('gilded-token');
        setToken(null);
        setUser(null);
      })
      .finally(() => setLoading(false));
  }, [token]);

  const login = useCallback(async (email, password) => {
    const res = await fetch('/api/auth/login', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ email, password }),
    });

    if (!res.ok) {
      const err = await res.json();
      throw new Error(err.message || 'Login failed');
    }

    const data = await res.json();
    localStorage.setItem('gilded-token', data.token);
    setToken(data.token);
    setUser(data.user);
    return data;
  }, []);

  const register = useCallback(async (username, email, password) => {
    const res = await fetch('/api/auth/register', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ username, email, password }),
    });

    if (!res.ok) {
      const err = await res.json();
      throw new Error(err.message || 'Registration failed');
    }

    const data = await res.json();
    localStorage.setItem('gilded-token', data.token);
    setToken(data.token);
    setUser(data.user);
    return data;
  }, []);

  const logout = useCallback(() => {
    localStorage.removeItem('gilded-token');
    setToken(null);
    setUser(null);
  }, []);

  const updateUser = useCallback((data) => {
    setUser((prev) => (prev ? { ...prev, ...data } : data));
  }, []);

  return (
    <AuthContext.Provider value={{ user, token, loading, login, register, logout, updateUser }}>
      {children}
    </AuthContext.Provider>
  );
}

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