<?php

/*
 *
 *  ____            _        _   __  __ _                  __  __ ____
 * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
 * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
 * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
 * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * @author PocketMine Team
 * @link http://www.pocketmine.net/
 *
 *
*/

declare(strict_types=1);

namespace pocketmine\network\mcpe\encryption;

use pocketmine\network\mcpe\JwtUtils;
use pocketmine\scheduler\AsyncTask;
use pocketmine\utils\AssumptionFailedError;
use function igbinary_serialize;
use function igbinary_unserialize;
use function openssl_error_string;
use function openssl_free_key;
use function openssl_pkey_get_details;
use function openssl_pkey_new;
use function random_bytes;

class PrepareEncryptionTask extends AsyncTask{

	private const TLS_KEY_ON_COMPLETION = "completion";

	/** @var resource|null */
	private static $SERVER_PRIVATE_KEY = null;

	/** @var string */
	private $serverPrivateKey;

	/** @var string|null */
	private $aesKey = null;
	/** @var string|null */
	private $handshakeJwt = null;
	/** @var string */
	private $clientPub;

	/**
	 * @phpstan-param \Closure(string $encryptionKey, string $handshakeJwt) : void $onCompletion
	 */
	public function __construct(string $clientPub, \Closure $onCompletion){
		if(self::$SERVER_PRIVATE_KEY === null){
			$serverPrivateKey = openssl_pkey_new(["ec" => ["curve_name" => "secp384r1"]]);
			if($serverPrivateKey === false){
				throw new \RuntimeException("openssl_pkey_new() failed: " . openssl_error_string());
			}
			self::$SERVER_PRIVATE_KEY = $serverPrivateKey;
		}

		$this->serverPrivateKey = igbinary_serialize(openssl_pkey_get_details(self::$SERVER_PRIVATE_KEY));
		$this->clientPub = $clientPub;
		$this->storeLocal(self::TLS_KEY_ON_COMPLETION, $onCompletion);
	}

	public function onRun() : void{
		/** @var mixed[] $serverPrivDetails */
		$serverPrivDetails = igbinary_unserialize($this->serverPrivateKey);
		$serverPriv = openssl_pkey_new($serverPrivDetails);
		if($serverPriv === false) throw new AssumptionFailedError("Failed to restore server signing key from details");
		$clientPub = JwtUtils::parseDerPublicKey($this->clientPub);
		$sharedSecret = EncryptionUtils::generateSharedSecret($serverPriv, $clientPub);

		$salt = random_bytes(16);
		$this->aesKey = EncryptionUtils::generateKey($sharedSecret, $salt);
		$this->handshakeJwt = EncryptionUtils::generateServerHandshakeJwt($serverPriv, $salt);

		openssl_free_key($serverPriv);
		openssl_free_key($clientPub);
	}

	public function onCompletion() : void{
		/**
		 * @var \Closure $callback
		 * @phpstan-var \Closure(string $encryptionKey, string $handshakeJwt) : void $callback
		 */
		$callback = $this->fetchLocal(self::TLS_KEY_ON_COMPLETION);
		if($this->aesKey === null || $this->handshakeJwt === null){
			throw new AssumptionFailedError("Something strange happened here ...");
		}
		$callback($this->aesKey, $this->handshakeJwt);
	}
}