"use client";

import { createContext, PropsWithChildren, useContext, useMemo, useState } from "react";
import { AccessLevel, SessionState } from "@/lib/types";

interface AuthContextValue {
  session: SessionState;
  loginAs: (name?: string) => void;
  logout: () => void;
  setAccessLevel: (level: AccessLevel) => void;
}

const STORAGE_KEY = "download_nova_session";

const defaultSession: SessionState = {
  isLoggedIn: false,
  accessLevel: "guest",
};

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

function readSession(): SessionState {
  if (typeof window === "undefined") return defaultSession;
  const raw = localStorage.getItem(STORAGE_KEY);
  if (!raw) return defaultSession;
  try {
    return { ...defaultSession, ...JSON.parse(raw) } as SessionState;
  } catch {
    return defaultSession;
  }
}

export function AuthProvider({ children }: PropsWithChildren) {
  const [session, setSession] = useState<SessionState>(() => readSession());

  const persist = (next: SessionState) => {
    setSession(next);
    if (typeof window !== "undefined") {
      localStorage.setItem(STORAGE_KEY, JSON.stringify(next));
    }
  };

  const value = useMemo<AuthContextValue>(
    () => ({
      session,
      loginAs: (name = "Nova 用户") =>
        persist({
          ...session,
          isLoggedIn: true,
          userName: name,
          accessLevel: session.accessLevel === "guest" ? "unlocked" : session.accessLevel,
        }),
      logout: () => persist(defaultSession),
      setAccessLevel: (level) => persist({ ...session, isLoggedIn: true, accessLevel: level }),
    }),
    [session],
  );

  return <AuthContext.Provider value={value}>{children}</AuthContext.Provider>;
}

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