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<?php
/*
** Zabbix
** Copyright (C) 2001-2023 Zabbix SIA
**
** 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 2 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, write to the Free Software
** Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
**/
class CConditionFormula {
// possible parsing states
const STATE_AFTER_OPEN_BRACE = 0;
const STATE_AFTER_OPERATOR = 1;
const STATE_AFTER_CLOSE_BRACE = 2;
const STATE_AFTER_CONSTANT = 3;
const STATE_AFTER_NOT_OPERATOR = 4;
/**
* Set to true of the formula is valid.
*
* @var bool
*/
public $isValid;
/**
* Error message if the formula is invalid.
*
* @var string
*/
public $error;
/**
* The parsed formula.
*
* @var string
*/
public $formula;
/**
* Array of unique constants used in the formula.
*
* @var array
*/
public $constants = [];
/**
* Array of supported operators.
*
* @var array
*/
protected $allowedOperators = ['and', 'or'];
/**
* Current position on a parsed element.
*
* @var integer
*/
private $pos;
/**
* Parses the given condition formula.
*
* @param string $formula
*
* @return bool true if the formula is valid
*/
public function parse($formula) {
$this->isValid = true;
$this->error = '';
$this->constants = [];
$this->pos = 0;
$this->formula = $formula;
$state = self::STATE_AFTER_OPEN_BRACE;
$afterSpace = false;
$level = 0;
while (isset($this->formula[$this->pos])) {
if ($this->formula[$this->pos] === ' ') {
$afterSpace = true;
$this->pos++;
continue;
}
switch ($state) {
case self::STATE_AFTER_OPEN_BRACE:
switch ($this->formula[$this->pos]) {
case '(':
$state = self::STATE_AFTER_OPEN_BRACE;
$level++;
break;
default:
if ($this->parseConstant()) {
$state = self::STATE_AFTER_CONSTANT;
}
elseif ($this->parseNotOperator()) {
$state = self::STATE_AFTER_NOT_OPERATOR;
}
else {
break 3;
}
}
break;
case self::STATE_AFTER_OPERATOR:
switch ($this->formula[$this->pos]) {
case '(':
$state = self::STATE_AFTER_OPEN_BRACE;
$level++;
break;
default:
if (!$afterSpace) {
break 3;
}
if ($this->parseConstant()) {
$state = self::STATE_AFTER_CONSTANT;
}
elseif ($this->parseNotOperator()) {
$state = self::STATE_AFTER_NOT_OPERATOR;
}
else {
break 3;
}
}
break;
case self::STATE_AFTER_NOT_OPERATOR:
switch ($this->formula[$this->pos]) {
case '(':
$state = self::STATE_AFTER_OPEN_BRACE;
$level++;
break;
default:
if (!$afterSpace) {
break 3;
}
if ($this->parseConstant()) {
$state = self::STATE_AFTER_CONSTANT;
}
else {
break 3;
}
}
break;
case self::STATE_AFTER_CLOSE_BRACE:
switch ($this->formula[$this->pos]) {
case ')':
if ($level == 0) {
break 3;
}
$level--;
break;
default:
if ($this->parseOperator()) {
$state = self::STATE_AFTER_OPERATOR;
}
else {
break 3;
}
}
break;
case self::STATE_AFTER_CONSTANT:
switch ($this->formula[$this->pos]) {
case ')':
$state = self::STATE_AFTER_CLOSE_BRACE;
if ($level == 0) {
break 3;
}
$level--;
break;
default:
if (!$afterSpace) {
break 3;
}
if ($this->parseOperator()) {
$state = self::STATE_AFTER_OPERATOR;
}
else {
break 3;
}
}
break;
}
$afterSpace = false;
$this->pos++;
}
if ($this->pos == 0) {
$this->error = _('expression is empty');
$this->isValid = false;
}
if ($level != 0 || isset($this->formula[$this->pos]) || $state == self::STATE_AFTER_OPERATOR) {
$this->error = _s('incorrect syntax near "%1$s"',
substr($this->formula, $this->pos == 0 ? 0 : $this->pos - 1)
);
$this->isValid = false;
}
return $this->isValid;
}
/**
* Parses a constant and advances the position to its last character.
*
* @return bool
*/
protected function parseConstant() {
$start = $this->pos;
while (isset($this->formula[$this->pos]) && $this->isConstantChar($this->formula[$this->pos])) {
$this->pos++;
}
// empty constant
if ($start == $this->pos) {
return false;
}
$constant = substr($this->formula, $start, $this->pos - $start);
$this->constants[] = [
'value' => $constant,
'pos' => $start
];
$this->pos--;
return true;
}
/**
* Parses a keyword and advances the position to its last character.
*
* @return bool
*/
protected function parseNotOperator() {
if (substr($this->formula, $this->pos, 3) !== 'not') {
return false;
}
$this->pos += 2;
return true;
}
/**
* Parses an operator and advances the position to its last character.
*
* @return bool
*/
protected function parseOperator() {
$start = $this->pos;
while (isset($this->formula[$this->pos]) && $this->isOperatorChar($this->formula[$this->pos])) {
$this->pos++;
}
// empty operator
if ($start == $this->pos) {
return false;
}
$operator = substr($this->formula, $start, $this->pos - $start);
// check if this is a valid operator
if (!in_array($operator, $this->allowedOperators)) {
$this->pos = $start;
return false;
}
$this->pos--;
return true;
}
/**
* Returns true if the given character is a valid constant character.
*
* @param string $c
*
* @return bool
*/
protected function isConstantChar($c) {
return ($c >= 'A' && $c <= 'Z');
}
/**
* Returns true if the given character is a valid operator character.
*
* @param string $c
*
* @return bool
*/
protected function isOperatorChar($c) {
return ($c >= 'a' && $c <= 'z');
}
}