import crypto from 'node:crypto';
import { getConfig } from './config.js';

const SESSION_TTL_MS = 7 * 24 * 60 * 60 * 1000; // 7 days

interface Session {
  username: string;
  expiresAt: number;
}

const sessions = new Map<string, Session>();

function verifyPassword(password: string, stored: string): boolean {
  if (stored.startsWith('scrypt$')) {
    const [, salt, hash] = stored.split('$');
    const derived = crypto.scryptSync(password, salt, 64).toString('hex');
    return derived === hash;
  }
  return false;
}

export function login(username: string, password: string): string | null {
  const config = getConfig();
  const stored = config.users?.[username];
  if (!stored || !verifyPassword(password, stored)) return null;

  const token = crypto.randomBytes(32).toString('hex');
  sessions.set(token, { username, expiresAt: Date.now() + SESSION_TTL_MS });
  return token;
}

export function validateSession(token: string): string | null {
  const session = sessions.get(token);
  if (!session) return null;
  if (Date.now() > session.expiresAt) {
    sessions.delete(token);
    return null;
  }
  return session.username;
}

export function logout(token: string): void {
  sessions.delete(token);
}

export function generatePasswordHash(password: string): string {
  const salt = crypto.randomBytes(16).toString('hex');
  const hash = crypto.scryptSync(password, salt, 64).toString('hex');
  return `scrypt$${salt}$${hash}`;
}