class.ilDclExpressionParser.php

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<?php

class ilDclExpressionParser {

        const N_DECIMALS = 1;
        const SCIENTIFIC_NOTATION_UPPER = 1000000000000;
        const SCIENTIFIC_NOTATION_LOWER = 0.000000001;
        protected $record;
        protected $field;
        protected $expression;
        protected static $operators = array(
                '+' => array( 'precedence' => 1 ),
                '-' => array( 'precedence' => 1 ),
                '*' => array( 'precedence' => 2 ),
                '/' => array( 'precedence' => 2 ),
                '^' => array( 'precedence' => 3 ),
        );
        protected static $cache_tokens = array();
        protected static $cache_fields = array();
        protected static $cache_math_tokens = array();
        protected static $cache_math_function_tokens = array();
        protected static $functions = array(
                'SUM',
                'AVERAGE',
                'MIN',
                'MAX',
        );


        public function __construct($expression, ilDataCollectionRecord $record, ilDataCollectionField $field) {
                $this->expression = $expression;
                $this->record = $record;
                $this->field = $field;
        }


        public function parse() {
                if (isset(self::$cache_tokens[$this->field->getId()])) {
                        $tokens = self::$cache_tokens[$this->field->getId()];
                } else {
                        $tokens = ilDclTokenizer::getTokens($this->expression);
                        self::$cache_tokens[$this->field->getId()] = $tokens;
                }
                //                      ilUtil::sendInfo( "<pre>" . print_r($tokens, 1) . "</pre>");
                $parsed = '';
                foreach ($tokens as $token) {
                        if (empty($token)) {
                                continue;
                        }
                        if ($this->isMathToken($token)) {
                                $token = $this->calculateFunctions($token);
                                $math_tokens = ilDclTokenizer::getMathTokens($token);
                                $value = $this->parseMath($this->substituteFieldValues($math_tokens));

                                $value = $this->formatScientific($value);

                                $parsed .= $value;
                        } else {
                                // Token is a string, either a field placeholder [[Field name]] or a string starting with "
                                if (strpos($token, '"') === 0) {
                                        $parsed .= strip_tags(trim($token, '"'));
                                } elseif (strpos($token, '[[') === 0) {
                                        $parsed .= trim(strip_tags($this->substituteFieldValue($token)));
                                } else {
                                        throw new ilException("Unrecognized string token: '$token'");
                                }
                        }
                }

                return $parsed;
        }


        protected function formatScientific($value) {
                if (abs($value) >= self::SCIENTIFIC_NOTATION_UPPER) {
                        return sprintf("%e", $value);
                }
                if (abs($value) <= self::SCIENTIFIC_NOTATION_LOWER && $value != 0 ) {
                        return sprintf("%e", $value);
                }
                if (is_float($value)) {
                        return $value;
                }

                return $value;
        }


        public static function getOperators() {
                return self::$operators;
        }


        public static function getFunctions() {
                return self::$functions;
        }


        protected function isMathToken($token) {
                if (isset(self::$cache_math_tokens[$this->field->getId()][$token])) {
                        return self::$cache_math_tokens[$this->field->getId()][$token];
                } else {
                        if (strpos($token, '"') === 0) {
                                return false;
                        }
                        $operators = array_keys(self::getOperators());
                        $functions = self::getFunctions();
                        $result = (bool)preg_match('#(\\' . implode("|\\", $operators) . '|' . implode('|', $functions) . ')#', $token);
                        self::$cache_math_tokens[$this->field->getId()][$token] = $result;

                        return $result;
                }
        }


        protected function calculateFunctions($token) {
                if (isset(self::$cache_math_function_tokens[$this->field->getId()][$token])) {
                        $result = self::$cache_math_function_tokens[$this->field->getId()][$token];
                        if ($result === false) {
                                return $token;
                        }
                } else {
                        $pattern = '#';
                        foreach (self::getFunctions() as $function) {
                                $pattern .= "($function)\\(([^)]*)\\)|";
                        }
                        if (!preg_match_all(rtrim($pattern, '|') . '#', $token, $result)) {
                                // No functions found inside token, just return token again
                                self::$cache_math_function_tokens[$this->field->getId()][$token] = false;

                                return $token;
                        }
                }
                // Function found inside token, calculate!
                foreach ($result[0] as $k => $to_replace) {
                        $function_args = $this->getFunctionArgs($k, $result);
                        $function = $function_args['function'];
                        $args = $this->substituteFieldValues($function_args['args']);
                        $token = str_replace($to_replace, $this->calculateFunction($function, $args), $token);
                }

                return $token;
        }


        protected function getFunctionArgs($index, array $data) {
                $return = array(
                        'function' => '',
                        'args' => array(),
                );
                for ($i = 1; $i < count($data); $i ++) {
                        $_data = $data[$i];
                        if ($_data[$index]) {
                                $function = $_data[$index];
                                $args = explode(';', $data[$i + 1][$index]);
                                $return['function'] = $function;
                                $return['args'] = $args;
                                break;
                        }
                }

                return $return;
        }


        protected function substituteFieldValues(array $tokens) {
                $replaced = array();
                foreach ($tokens as $token) {
                        if (strpos($token, '[[') === 0) {
                                $replaced[] = $this->substituteFieldValue($token);
                        } else {
                                $replaced[] = $token;
                        }
                }

                return $replaced;
        }


        protected function substituteFieldValue($placeholder) {
                if (isset(self::$cache_fields[$placeholder])) {
                        $field = self::$cache_fields[$placeholder];
                } else {
                        $table = ilDataCollectionCache::getTableCache($this->record->getTableId()); // TODO May need caching per table in future
                        $field_title = preg_replace('#^\[\[(.*)\]\]#', "$1", $placeholder);
                        $field = $table->getFieldByTitle($field_title);
                        if ($field === NULL) {
                                // Workaround for standardfields - title my be ID
                                $field = $table->getField($field_title);
                                if ($field === NULL) {
                                        global $lng;
                                        $lng->loadLanguageModule('dcl');
//                                      throw new ilException("Field with title '$field_title' not found");
                                        throw new ilException(sprintf($lng->txt('dcl_err_formula_field_not_found'), $field_title));
                                }
                        }
                        self::$cache_fields[$placeholder] = $field;
                }

                return $this->record->getRecordFieldHTML($field->getId());
        }


        protected function parseMath(array $tokens) {
                $operators = self::$operators;
                $precedence = 0;
                $stack = new ilDclStack();
                $precedences = new ilDclStack();
                $in_bracket = false;
                foreach ($tokens as $token) {
                        if (empty($token) OR is_null($token)) {
                                $token = 0;
                        }
                        if (is_numeric($token) OR $token === '(') {
                                $stack->push($token);
                                if ($token === '(') {
                                        $in_bracket = true;
                                }
                        } elseif (in_array($token, array_keys($operators))) {
                                $new_precedence = $operators[$token]['precedence'];
                                if ($new_precedence > $precedence || $in_bracket) {
                                        // Precedence of operator is higher, push operator on stack
                                        $stack->push($token);
                                        $precedences->push($new_precedence);
                                        $precedence = $new_precedence;
                                } else {
                                        // Precedence is equal or lower, calculate result on stack
                                        while ($new_precedence <= $precedence && $stack->count() > 1) {
                                                $right = (float)$stack->pop();
                                                $operator = $stack->pop();
                                                $left = (float)$stack->pop();
                                                $result = $this->calculate($operator, $left, $right);
                                                $stack->push($result);
                                                $precedence = $precedences->pop();
                                        }
                                        $stack->push($token);
                                        $precedence = $new_precedence;
                                        $precedences->push($new_precedence);
                                }
                        } elseif ($token === ')') {
                                // Need to calculate stack back to opening bracket
                                $_tokens = array();
                                $elem = $stack->pop();
                                while ($elem !== '(' && !$stack->isEmpty()) {
                                        $_tokens[] = $elem;
                                        $elem = $stack->pop();
                                }
                                // Get result within brackets recursive and push to stack
                                $stack->push($this->parseMath(array_reverse($_tokens)));
                                $in_bracket = false;
                        } else {
                                throw new ilException("Unrecognized token '$token'");
                        }
                        // $stack->debug();
                }
                // If one element is left on stack, we are done. Otherwise calculate
                if ($stack->count() == 1) {
                        $result = $stack->pop();

                        return (ctype_digit((string)$result)) ? $result : number_format($result, self::N_DECIMALS, '.', "'");
                } else {

                        while ($stack->count() >= 2) {
                                $right = $stack->pop();
                                $operator = $stack->pop();
                                $left = $stack->count() ? $stack->pop() : 0;
                                $stack->push($this->calculate($operator, $left, $right));
                        }
                        $result = $stack->pop();

                        return $result;
                }
        }


        protected function calculateFunction($function, array $args = array()) {
                switch ($function) {
                        case 'AVERAGE':
                                $count = count($args);

                                return ($count) ? array_sum($args) / $count : 0;
                        case 'SUM':
                                return array_sum($args);
                        case 'MIN':
                                return min($args);
                        case 'MAX':
                                return max($args);
                        default:
                                throw new ilException("Unrecognized function '$function'");
                }
        }


        protected function calculate($operator, $left, $right) {
                switch ($operator) {
                        case '+':
                                $result = $left + $right;
                                break;
                        case '-':
                                $result = $left - $right;
                                break;
                        case '*':
                                $result = $left * $right;
                                break;
                        case '/':
                                $result = ($right == 0) ? 0 : $left / $right;
                                break;
                        case '^':
                                $result = pow($left, $right);
                                break;
                        default:
                                throw new ilException("Unrecognized operator '$operator'");
                }

                return $result;
        }
}


?>