import BaseService from "@Services/BaseService";
import { Service } from "typedi";
import { BackendVariables } from "@Common/config/variables/Variables";
import crypto from "crypto";

@Service()
export default class CryptoService extends BaseService {

	private static readonly CRYPTO_ALGORITHM = "aes-256-ctr";

	constructor(protected variables: BackendVariables) {
		super();
	}

	private getKey(key: string) {
		return crypto.createHash('sha256').update(String(key)).digest('base64').slice(0, 32);
	}

	/**
	 * @description : encrypt data
	 * @throws {Error} If data cannot be encrypted
	 */
	public async encrypt(buffer: Buffer, key: string): Promise<Buffer> {
		// Create an initialization vector
		const iv = crypto.randomBytes(16);
		// Create a new cipher using the algorithm, key, and iv
		const cipher = crypto.createCipheriv(CryptoService.CRYPTO_ALGORITHM, this.getKey(key), iv);
		// Create the new (encrypted) buffer
		const result = Buffer.concat([iv, cipher.update(buffer), cipher.final()]);
		return result;
	}
	
	/**
	 * @description : decrypt data with an initialization vector
	 * @throws {Error} If data cannot be decrypted
	 */
	public async decrypt(encrypted: Buffer, key: string): Promise<Buffer> {
		// Get the iv: the first 16 bytes
		const iv = encrypted.subarray(0, 16);
		// Get the rest
		encrypted = encrypted.subarray(16);
		// Create a decipher
		const decipher = crypto.createDecipheriv(CryptoService.CRYPTO_ALGORITHM, this.getKey(key), iv);
		// Actually decrypt it
		const result = Buffer.concat([decipher.update(encrypted), decipher.final()]);
		return result;
	}
}