<?php
// Own namespace
namespace Org\Mxchange\CoreFramework\Helper\Crypto;

// Import framework stuff
use Org\Mxchange\CoreFramework\Bootstrap\FrameworkBootstrap;
use Org\Mxchange\CoreFramework\Crypto\Cryptable;
use Org\Mxchange\CoreFramework\Crypto\RandomNumber\RandomNumberGenerator;
use Org\Mxchange\CoreFramework\Factory\Object\ObjectFactory;
use Org\Mxchange\CoreFramework\Object\BaseFrameworkSystem;

/**
 * A helper class for cryptographical things like hashing passwords and so on
 *
 * @author		Roland Haeder <webmaster@shipsimu.org>
 * @version		0.0.0
 * @copyright	Copyright (c) 2007, 2008 Roland Haeder, 2009 - 2023 Core Developer Team
 * @license		GNU GPL 3.0 or any newer version
 * @link		http://www.shipsimu.org
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
class CryptoHelper extends BaseFrameworkSystem implements Cryptable {
	// Exception constants
	const EXCEPTION_ENCRYPT_MISSING = 0x1f0;
	const EXCEPTION_ENCRYPT_INVALID = 0x1f1;

	/**
	 * An instance of this own clas
	 */
	private static $selfInstance = NULL;

	/**
	 * Instance of the crypto stream
	 */
	private $cryptoStreamInstance = NULL;

	/**
	 * Salt for hashing operations
	 */
	private $salt = '';

	/**
	 * Instance of a RNG
	 */
	private $rngInstance = NULL;

	/**
	 * Protected constructor
	 *
	 * @return	void
	 */
	private function __construct () {
		// Call parent constructor
		parent::__construct(__CLASS__);
	}

	/**
	 * Creates an instance of this class
	 *
	 * @return	$cryptoInstance		An instance of this crypto helper class
	 */
	public static final function createCryptoHelper () {
		// Get a new instance
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('CRYPTO-HELPER: CALLED!');
		$cryptoInstance = new CryptoHelper();

		// Initialize the hasher
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('CRYPTO-HELPER: Invoking cryptoInstance->initHasher() ...');
		$cryptoInstance->initHasher();

		// Attach a crypto stream
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('CRYPTO-HELPER: Invoking cryptoInstance->attachCryptoStream() ...');
		$cryptoInstance->attachCryptoStream();

		// Return the instance
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('CRYPTO-HELPER: cryptoInstance=%s - EXIT!', $cryptoInstance->__toString()));
		return $cryptoInstance;
	}

	/**
	 * Get a singleton instance of this class
	 *
	 * @return	$selfInstance	An instance of this crypto helper class
	 */
	public static final function getSelfInstance () {
		// Is no instance there?
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('CRYPTO-HELPER: self::selfInstance[]=%s - CALLED!', gettype(self::$selfInstance)));
		if (is_null(self::$selfInstance)) {
			// Then get a new one
			self::$selfInstance = self::createCryptoHelper();
		}

		// Return the instance
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage(sprintf('CRYPTO-HELPER: self::selfInstance=%s - EXIT!', self::$selfInstance->__toString()));
		return self::$selfInstance;
	}

	/**
	 * Setter for RNG instance
	 *
	 * @param	$rngInstance	An instance of a random number generator (RNG)
	 * @return	void
	 */
	protected final function setRngInstance (RandomNumberGenerator $rngInstance) {
		$this->rngInstance = $rngInstance;
	}

	/**
	 * Getter for RNG instance
	 *
	 * @return	$rngInstance	An instance of a random number generator (RNG)
	 */
	public final function getRngInstance () {
		return $this->rngInstance;
	}

	/**
	 * Attaches a crypto stream to this crypto helper by detecting loaded
	 * modules.
	 *
	 * @return	void
	 */
	protected function attachCryptoStream () {
		// @TODO Maybe rewrite this with DirectoryIterator, similar to Compressor thing?
		// Do we have openssl loaded?
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('CRYPTO-HELPER: CALLED!');
		if ($this->isPhpExtensionLoaded('openssl')) {
			// Then use it
			/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage('CRYPTO-HELPER: Attaching openssl crypto stream ...');
			$this->cryptoStreamInstance = ObjectFactory::createObjectByConfiguredName('crypto_openssl_stream_class', [$this->getRngInstance()]);
		} else {
			// If nothing works ...
			/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->debugMessage('CRYPTO-HELPER: Attaching NULL crypto stream ...');
			$this->cryptoStreamInstance = ObjectFactory::createObjectByConfiguredName('crypto_null_stream_class');
		}

		// Trace message
		/* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__, __LINE__)->traceMessage('CRYPTO-HELPER: EXIT!');
	}

	/**
	 * Initializes the hasher for different purposes.
	 *
	 * @return	void
	 */
	protected function initHasher () {
		// Initialize the random number generator which is required by some crypto methods
		$this->setRngInstance(ObjectFactory::createObjectByConfiguredName('rng_class'));

		// Generate a salt for the hasher
		$this->generateSalt();
	}

	/**
	 * Generates the salt based on configured length
	 *
	 * @return	void
	 */
	private function generateSalt () {
		// Get a random string from the RNG
		$randomString = $this->getRngInstance()->randomString() . $this->createUuid();

		// Get config entry for salt length
		$length = FrameworkBootstrap::getConfigurationInstance()->getConfigEntry('salt_length');

		// Keep only defined number of characters
		$this->salt = substr(sha1($randomString), -$length, $length);
	}

	/**
	 * Returns a UUID (Universal Unique IDentifier) if PECL extension uuid was
	 * found or an empty string it not.
	 *
	 * @return	$uuid	UUID with leading dash or empty string
	 */
	public function createUuid () {
		// Init empty UUID
		$uuid = '';

		// Is the UUID extension loaded and enabled? (see pecl)
		if (FrameworkBootstrap::getConfigurationInstance()->getConfigEntry('extension_uuid_loaded') === true) {
			// Then add it as well
			$uuid = uuid_create();
		}

		// Return it
		return $uuid;
	}

	/**
	 * Hashes a string with salt and returns the hash. If an old previous hash
	 * is supplied the method will use the first X chars of that hash for hashing
	 * the password. This is useful if you want to check if password is identical
	 * for authorization purposes.
	 *
	 * @param	$str		Unhashed string
	 * @param	$oldHash	A hash from previous hashed string
	 * @param	$withFixed	Whether to include a fixed salt (not recommended in p2p applications)
	 * @return	$hashed		The hashed and salted string
	 */
	public function hashString (string $str, string $oldHash = '', bool $withFixed = true) {
		// Default is the default salt ;-)
		$salt = $this->salt;

		// Is the old password set?
		if (!empty($oldHash)) {
			// Use the salt from hash, first get length
			$length = FrameworkBootstrap::getConfigurationInstance()->getConfigEntry('salt_length');

			// Then extract the X first characters from the hash as our salt
			$salt = substr($oldHash, 0, $length);
		}

		// Hash the password with salt
		//* DEBUG: */ echo "salt=".$salt."/plain=".$str."<br />\n";
		if ($withFixed === true) {
			// Use additional fixed salt
			$hashed = $salt . md5(sprintf(FrameworkBootstrap::getConfigurationInstance()->getConfigEntry('hash_extra_mask'),
				$salt,
				$this->getRngInstance()->getFixedSalt(),
				$str
			));
		} else {
			// Use salt+string to hash
			$hashed = $salt . md5(sprintf(FrameworkBootstrap::getConfigurationInstance()->getConfigEntry('hash_normal_mask'),
				$salt,
				$str
			));
		}

		// And return it
		return $hashed;
	}

	/**
	 * Encrypt the string with fixed salt
	 *
	 * @param	$str		The unencrypted string
	 * @param	$key		Optional key, if none provided, a random key will be generated
	 * @return	$encrypted	Encrypted string
	 */
	public function encryptString (string $str, string $key = NULL) {
		// Encrypt the string through the stream
		$encrypted = $this->cryptoStreamInstance->encryptStream($str, $key);

		// Return the string
		return $encrypted;
	}

	/**
	 * Decrypt the string with fixed salt
	 *
	 * @param	$encrypted	Encrypted string
	 * @return	$str		The unencrypted string
	 */
	public function decryptString (string $encrypted) {
		// Encrypt the string through the stream
		$str = $this->cryptoStreamInstance->decryptStream($encrypted);

		// Return the string
		return $str;
	}

}