<?php
	namespace Juju\Data;

	class Encryption {
		private static $methods = null;
		private static $instances = [];
		private $method = null;
		private function __construct(string $method){
			$this->method = $method;
		}
		public function __get(string $name){
			switch($name){
				case 'method':
					return $this->method;
				default:
					throw new \Exception("Property {$name} does not exist");
			}
		}
		public static function methods(){
			if(is_null(self::$methods)){
				$methods = openssl_get_cipher_methods(true);
				$methods = array_map('StrToLower', $methods);
				$methods = array_intersect_key(
					$methods,
					array_unique($methods)
				);
				$methods = array_diff($methods, [
					'aes-128-ccm',
					'aes-128-gcm',
					'aes-128-xts',
					'aes-192-ccm',
					'aes-192-gcm',
					'aes-256-ccm',
					'aes-256-gcm',
					'aes-256-xts',
					'id-aes128-ccm',
					'id-aes128-gcm',
					'id-aes128-wrap',
					'id-aes192-ccm',
					'id-aes192-gcm',
					'id-aes192-wrap',
					'id-aes256-ccm',
					'id-aes256-gcm',
					'id-aes256-wrap',
					'id-smime-alg-cms3deswrap'
				]);
				self::$methods = array_values(array_unique($methods));
			}
			return self::$methods;
		}
		public static function from(string $method){
			if(!in_array($method, self::methods())){
				throw new \Exception("Unsupported OpenSSL method: {$method}");
			}
			if(!isset(Encryption::$instances[$method])){
				Encryption::$instances[$method] = new Encryption($method);
			}
			return Encryption::$instances[$method];
		}
		public function __toString(){
			return $this->method.'';
		}
		public function iv_len(){
			return openssl_cipher_iv_length($this->method);
		}
		public function encrypt(string $data, string $key, string $iv){
			$ret = openssl_encrypt($data, $this->method, $key, \OPENSSL_RAW_DATA, $iv);
			if($ret === false){
				throw new \Exception("Encryption ({$this->method}) failed: ".openssl_error_string());
			}
			return $ret;
		}
		public function decrypt(string $data, string $key, string $iv){
			$ret = openssl_decrypt($data, $this->method, $key, \OPENSSL_RAW_DATA, $iv);
			if($ret === false){
				throw new \Exception("Decryption ({$this->method}) failed: ".openssl_error_string());
			}
			return $ret;
		}
	}
?>