import { Database } from 'sqlite3';
import jwt from 'jsonwebtoken';
import crypto from 'crypto';

export interface VapidKeys {
  publicKey: string;
  privateKey: string;
}

export class VapidService {
  private db: Database;

  constructor() {
    this.db = new Database('vapidKeys.db');
    this.initializeDatabase();
  }

  private initializeDatabase(): void {
    this.db.run(`CREATE TABLE IF NOT EXISTS vapid (id INTEGER PRIMARY KEY, publicKey TEXT, privateKey TEXT)`);
  }

  private generateVAPIDKeys(): VapidKeys {
    const ecdh = crypto.createECDH('prime256v1');
    ecdh.generateKeys();
    
    return {
      publicKey: ecdh.getPublicKey().toString('base64'),
      privateKey: ecdh.getPrivateKey().toString('base64')
    };
  }

  async getVapidKeys(): Promise<VapidKeys> {
    return new Promise((resolve, reject) => {
      this.db.get('SELECT publicKey, privateKey FROM vapid WHERE id = ?', [1], (err, row: VapidKeys) => {
        if (err) reject(err);

        if (row) {
          resolve({ publicKey: row.publicKey, privateKey: row.privateKey });
        } else {
          const keys = this.generateVAPIDKeys();
          this.db.run('INSERT INTO vapid (publicKey, privateKey) VALUES (?, ?)', [keys.publicKey, keys.privateKey], (err) => {
            if (err) reject(err);
            resolve(keys);
          });
        }
      });
    });
  }

  async createVapidAuthHeader(endpoint: string, expiration: number, subject: string): Promise<{ 'Authorization': string, 'Crypto-Key': string }> {
    const { publicKey, privateKey } = await this.getVapidKeys();

    const jwtInfo = {
      aud: new URL(endpoint).origin,
      exp: Math.floor((Date.now() / 1000) + expiration),
      sub: subject
    };

    const jwtToken = jwt.sign(jwtInfo, privateKey, { algorithm: 'ES256' });

    return {
      'Authorization': `vapid t=${jwtToken}, k=${publicKey}`,
      'Crypto-Key': publicKey
    };
  }
}