import { Injectable } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import * as crypto from 'crypto';

@Injectable()
export class EncryptionService {
  private readonly algorithm = 'aes-256-cbc';
  private readonly key: Buffer;

  constructor(private readonly configService: ConfigService) {
    const keyString = this.configService.get<string>('ENCRYPTION_KEY') || 'f2d7a2287c8052445b2bb5e8e3d09a25';
    // Ensure the key is 32 bytes
    this.key = Buffer.from(keyString, 'hex');
    if (this.key.length !== 32) {
      this.key = crypto.scryptSync(keyString, 'salt', 32);
    }
  }

  encrypt(text: string): string {
    const iv = crypto.randomBytes(16);
    const cipher = crypto.createCipheriv(this.algorithm, this.key, iv);
    let encrypted = cipher.update(text, 'utf8', 'hex');
    encrypted += cipher.final('hex');
    return `${iv.toString('hex')}:${encrypted}`;
  }

  decrypt(encryptedText: string): string {
    const parts = encryptedText.split(':');
    if (parts.length !== 2) {
      throw new Error('Invalid encrypted format');
    }
    const iv = Buffer.from(parts[0], 'hex');
    const encrypted = parts[1];
    const decipher = crypto.createDecipheriv(this.algorithm, this.key, iv);
    let decrypted = decipher.update(encrypted, 'hex', 'utf8');
    decrypted += decipher.final('utf8');
    return decrypted;
  }

  encryptJson(data: any): string {
    return this.encrypt(JSON.stringify(data));
  }

  decryptJson<T>(encryptedText: string): T {
    return JSON.parse(this.decrypt(encryptedText)) as T;
  }
}