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

interface User {
  id: number;
  username: string;
  email: string;
  created_at: string;
}

interface AuthContextType {
  user: User | null;
  token: string | null;
  isLoading: boolean;
  login: (email: string, password: string) => Promise<void>;
  register: (username: string, email: string, password: string) => Promise<void>;
  logout: () => void;
}

const AuthContext = createContext<AuthContextType | null>(null);

const API_BASE = "";

export function AuthProvider({ children }: { children: React.ReactNode }) {
  const [user, setUser] = useState<User | null>(null);
  const [token, setToken] = useState<string | null>(() => localStorage.getItem("pettalk_token"));
  const [isLoading, setIsLoading] = useState(true);

  const fetchMe = useCallback(async (t: string) => {
    try {
      const res = await fetch("/api/me", {
        headers: { Authorization: `Bearer ${t}` },
      });
      if (res.ok) {
        const data = await res.json();
        setUser(data.user);
      } else {
        localStorage.removeItem("pettalk_token");
        setToken(null);
      }
    } catch {
      // Network error — keep token but mark as loaded
    }
  }, []);

  useEffect(() => {
    if (token) {
      fetchMe(token).finally(() => setIsLoading(false));
    } else {
      setIsLoading(false);
    }
  }, [token, fetchMe]);

  const login = async (email: string, password: string) => {
    const res = await fetch("/api/login", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ email, password }),
    });
    const data = await res.json();
    if (!res.ok) {
      throw new Error(data.error || "Login failed");
    }
    localStorage.setItem("pettalk_token", data.token);
    setToken(data.token);
    setUser(data.user);
  };

  const register = async (username: string, email: string, password: string) => {
    const res = await fetch("/api/register", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ username, email, password }),
    });
    const data = await res.json();
    if (!res.ok) {
      throw new Error(data.error || "Registration failed");
    }
    localStorage.setItem("pettalk_token", data.token);
    setToken(data.token);
    setUser(data.user);
  };

  const logout = () => {
    localStorage.removeItem("pettalk_token");
    setToken(null);
    setUser(null);
  };

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

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

/** Helper to get auth headers for fetch calls */
export function getAuthHeaders(): Record<string, string> {
  const token = localStorage.getItem("pettalk_token");
  if (!token) return {};
  return { Authorization: `Bearer ${token}` };
}