<?php
/**
 * SPDX-FileCopyrightText: 2016 Nextcloud GmbH and Nextcloud contributors
 * SPDX-License-Identifier: AGPL-3.0-or-later
 */
namespace OCA\WorkflowEngine\Check;

use OCP\IL10N;
use OCP\IRequest;
use OCP\WorkflowEngine\ICheck;

class RequestRemoteAddress implements ICheck {

	/**
	 * @param IL10N $l
	 * @param IRequest $request
	 */
	public function __construct(
		protected IL10N $l,
		protected IRequest $request,
	) {
	}

	/**
	 * @param string $operator
	 * @param string $value
	 * @return bool
	 */
	public function executeCheck($operator, $value) {
		$actualValue = $this->request->getRemoteAddress();
		$decodedValue = explode('/', $value);

		if ($operator === 'matchesIPv4') {
			return $this->matchIPv4($actualValue, $decodedValue[0], $decodedValue[1]);
		} elseif ($operator === '!matchesIPv4') {
			return !$this->matchIPv4($actualValue, $decodedValue[0], $decodedValue[1]);
		} elseif ($operator === 'matchesIPv6') {
			return $this->matchIPv6($actualValue, $decodedValue[0], $decodedValue[1]);
		} else {
			return !$this->matchIPv6($actualValue, $decodedValue[0], $decodedValue[1]);
		}
	}

	/**
	 * @param string $operator
	 * @param string $value
	 * @throws \UnexpectedValueException
	 */
	public function validateCheck($operator, $value) {
		if (!in_array($operator, ['matchesIPv4', '!matchesIPv4', 'matchesIPv6', '!matchesIPv6'])) {
			throw new \UnexpectedValueException($this->l->t('The given operator is invalid'), 1);
		}

		$decodedValue = explode('/', $value);
		if (count($decodedValue) !== 2) {
			throw new \UnexpectedValueException($this->l->t('The given IP range is invalid'), 2);
		}

		if (in_array($operator, ['matchesIPv4', '!matchesIPv4'])) {
			if (!filter_var($decodedValue[0], FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
				throw new \UnexpectedValueException($this->l->t('The given IP range is not valid for IPv4'), 3);
			}
			if ($decodedValue[1] > 32 || $decodedValue[1] <= 0) {
				throw new \UnexpectedValueException($this->l->t('The given IP range is not valid for IPv4'), 4);
			}
		} else {
			if (!filter_var($decodedValue[0], FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) {
				throw new \UnexpectedValueException($this->l->t('The given IP range is not valid for IPv6'), 3);
			}
			if ($decodedValue[1] > 128 || $decodedValue[1] <= 0) {
				throw new \UnexpectedValueException($this->l->t('The given IP range is not valid for IPv6'), 4);
			}
		}
	}

	/**
	 * Based on https://stackoverflow.com/a/594134
	 * @param string $ip
	 * @param string $rangeIp
	 * @param int $bits
	 * @return bool
	 */
	protected function matchIPv4($ip, $rangeIp, $bits) {
		$rangeDecimal = ip2long($rangeIp);
		$ipDecimal = ip2long($ip);
		$mask = -1 << (32 - $bits);
		return ($ipDecimal & $mask) === ($rangeDecimal & $mask);
	}

	/**
	 * Based on https://stackoverflow.com/a/7951507
	 * @param string $ip
	 * @param string $rangeIp
	 * @param int $bits
	 * @return bool
	 */
	protected function matchIPv6($ip, $rangeIp, $bits) {
		$ipNet = inet_pton($ip);
		$binaryIp = $this->ipv6ToBits($ipNet);
		$ipNetBits = substr($binaryIp, 0, $bits);

		$rangeNet = inet_pton($rangeIp);
		$binaryRange = $this->ipv6ToBits($rangeNet);
		$rangeNetBits = substr($binaryRange, 0, $bits);

		return $ipNetBits === $rangeNetBits;
	}

	/**
	 * Based on https://stackoverflow.com/a/7951507
	 * @param string $packedIp
	 * @return string
	 */
	protected function ipv6ToBits($packedIp) {
		$unpackedIp = unpack('A16', $packedIp);
		$unpackedIp = str_split($unpackedIp[1]);
		$binaryIp = '';
		foreach ($unpackedIp as $char) {
			$binaryIp .= str_pad(decbin(ord($char)), 8, '0', STR_PAD_LEFT);
		}
		return str_pad($binaryIp, 128, '0', STR_PAD_RIGHT);
	}

	/**
	 * returns a list of Entities the checker supports. The values must match
	 * the class name of the entity.
	 *
	 * An empty result means the check is universally available.
	 *
	 * @since 18.0.0
	 */
	public function supportedEntities(): array {
		return [];
	}

	/**
	 * returns whether the operation can be used in the requested scope.
	 *
	 * Scope IDs are defined as constants in OCP\WorkflowEngine\IManager. At
	 * time of writing these are SCOPE_ADMIN and SCOPE_USER.
	 *
	 * For possibly unknown future scopes the recommended behaviour is: if
	 * user scope is permitted, the default behaviour should return `true`,
	 * otherwise `false`.
	 *
	 * @since 18.0.0
	 */
	public function isAvailableForScope(int $scope): bool {
		return true;
	}
}
