ilAssLacConditionParser.php

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<?php

class ilAssLacConditionParser
{
    protected $condition;

    protected $expressions;

    protected $operators;

    protected $index;

    protected $spaces;

    public function parse($condition): ilAssLacAbstractComposite
    {
        $this->condition = $condition;
        $this->index = 0;
        $this->checkBrackets();
        $this->fetchExpressions();
        $this->fetchOperators();
        $this->cannonicalizeCondition();
        $nodes = $this->createNodeArray();
        $compositeBuilder = new ilAssLacCompositeBuilder();
        return $compositeBuilder->create($nodes);
    }

    protected function fetchExpressions(): void
    {
        $manufacturer = ilAssLacExpressionManufacturer::_getInstance();
        $this->expressions = $manufacturer->match($this->condition);
    }

    protected function fetchOperators(): void
    {
        $manufacturer = ilAssLacOperationManufacturer::_getInstance();
        $this->operators = $manufacturer->match($this->condition);
    }

    protected function cannonicalizeCondition(): void
    {
        $manufacturer = ilAssLacExpressionManufacturer::_getInstance();
        $this->condition = preg_replace($manufacturer->getPattern(), 'n', $this->condition);
        $manufacturer = ilAssLacOperationManufacturer::_getInstance();
        $this->condition = preg_replace($manufacturer->getPattern(), 'o', $this->condition);
        $this->condition = preg_replace("/no/", "n o", $this->condition);
        $this->condition = preg_replace("/on/", "o n", $this->condition);

        for ($i = 0; $i < strlen($this->condition); $i++) {
            if ($this->condition[$i] == "!" && !$this->isNegationSurroundedByBrackets($i)) {
                $this->surroundNegationExpression($i);
            }
        }
    }

    protected function checkBrackets(): void
    {
        $num_brackets_open = substr_count($this->condition, "(");
        $num_brackets_close = substr_count($this->condition, ")");

        if ($num_brackets_open > $num_brackets_close) {
            throw new ilAssLacMissingBracket(")");
        }
        if ($num_brackets_open < $num_brackets_close) {
            throw new ilAssLacMissingBracket("(");
        }
    }

    protected function createNodeArray(): array
    {
        $expected = ["n", "(", "!"];
        $group = [];
        $negation = false;

        while ($this->index < strlen($this->condition)) {
            $a = $this->condition[$this->index];
            if (trim($this->condition[$this->index]) != "" && in_array($this->condition[$this->index], $expected)) {
                if ($this->condition[$this->index] == ')') {
                    return $group;
                } elseif ($this->condition[$this->index] == 'n') {
                    $group[] = ['type' => 'expression', 'value' => array_shift($this->expressions)];
                    $expected = ["o", ")"];
                } elseif ($this->condition[$this->index] == 'o') {
                    $group[] = ['type' => 'operator', 'value' => array_shift($this->operators)];
                    $expected = ["n", "(", "!"];
                } elseif ($this->condition[$this->index] == '(') {
                    $this->index++;
                    $elements = $this->createNodeArray();
                    $group[] = ['type' => "group", "negated" => $negation, 'nodes' => $elements];
                    $negation = false;
                    $expected = ["o",")"];
                } elseif ($this->condition[$this->index] == "!") {
                    $negation = true;
                }
            } elseif (trim($this->condition[$this->index]) != "") {
                throw new ilAssLacConditionParserException($this->index - $this->spaces + 1);
            } else {
                $this->spaces++;
            }

            $this->index++;
        }
        return ['type' => 'group', "negated" => $negation, 'nodes' => $group];
    }

    public function getExpressions(): array
    {
        return $this->expressions;
    }

    protected function surroundNegationExpression($index): void
    {
        $start = strpos($this->condition, "n", $index + 1);
        $end = false;

        if ($start !== false) {
            $end = strpos($this->condition, "n", $start + 1);
        }

        if ($start !== false && $end !== false) {
            $this->condition = substr_replace($this->condition, "(n o n)", $start, $end - $start + 1);
        }
    }

    protected function isNegationSurroundedByBrackets($index)
    {
        $next_bracket = strpos($this->condition, "(", $index + 1);
        $next_expression = strpos($this->condition, "n", $index + 1);

        return $next_bracket !== false && $next_bracket < $next_expression;
    }
}