Remorhaz\UniLex\Parser\LL1\Lookup\FirstBuilder

Complexity

Total Complexity

8

Size/Duplication

Total Lines	47
Duplicated Lines	0 %

Importance

Changes

0

4 Methods

Rating	Name	Duplication	Size	Complexity
A	addTokensFromTerminalMap()	0	5	2
A	getFirst()	0	12	3
A	mergeProductionsFromNonTerminalMap()	0	5	2
A	__construct()	0	3	1

<?php

declare(strict_types=1);

namespace Remorhaz\UniLex\Parser\LL1\Lookup;

use Remorhaz\UniLex\Grammar\ContextFree\GrammarInterface;

class FirstBuilder
{
    private $grammar;

    private $first;

    public function __construct(GrammarInterface $grammar)
    {
        $this->grammar = $grammar;
    }

    /**
     * @return FirstInterface
     */
    public function getFirst(): FirstInterface
    {
        if (!isset($this->first)) {
            $first = new First();
            $this->addTokensFromTerminalMap($first);
            do {
                $first->resetChangeCount();
                $this->mergeProductionsFromNonTerminalMap($first);
            } while ($first->getChangeCount() > 0);
            $this->first = $first;
        }
        return $this->first;
    }

    /**
     * @param First $first
     */
    private function addTokensFromTerminalMap(First $first): void
    {
        foreach ($this->grammar->getTerminalList() as $symbolId) {
            $tokenId = $this->grammar->getToken($symbolId);
            $first->addToken($symbolId, $tokenId);
        }
    }

    /**
     * @param First $first
     */
    private function mergeProductionsFromNonTerminalMap(First $first): void
    {
        foreach ($this->grammar->getFullProductionList() as $production) {
            $first->mergeProductionEpsilons($production->getHeaderId(), ...$production->getSymbolList());
            $first->mergeProductionTokens($production->getHeaderId(), ...$production->getSymbolList());
        }
    }
}