smuuf/primi

<?php

declare(strict_types=1);

namespace Smuuf\Primi\Parser;

use \Smuuf\StrictObject;
use \Smuuf\Primi\EnvInfo;

use \hafriedlander\Peg\Compiler;

abstract class ParserFactory {

    use StrictObject;

    private const PARSER_CLASS = __NAMESPACE__ . '\\Compiled\\PrimiParser';
    private const GRAMMAR_FILE = __DIR__ . '/Grammar/Primi.peg';
    private const TARGET_PARSER_FILE = __DIR__ . '/Compiled/PrimiParser.php';
    private const VERSION_FILE = __DIR__ . '/Compiled/version';

    /**
     * Recompile only once per runtime to avoid expensive checks on each use.
     * If the grammar changes, the client just needs to restart the process.
     */
    private static bool $recompiled = \false;

    public static function getParserClass(): string {

        // If we're running inside Phar, we assume the parser already is
        // compiled in the newest version (also, compiling it again - within the
        // Phar - would be nonsense).
        if (self::$recompiled === \true || EnvInfo::isRunningInPhar()) {
            return self::PARSER_CLASS;
        }

        $grammarVersion = \md5((string) \filemtime(self::GRAMMAR_FILE));
        $parserVersion = \file_exists(self::VERSION_FILE)
            ? \file_get_contents(self::VERSION_FILE)
            : \false;

        if ($grammarVersion !== $parserVersion) {
            self::recompileParser($grammarVersion);
        }

        self::$recompiled = \true;
        return self::PARSER_CLASS;

    }

    private static function recompileParser(string $newVersion): void {

        $grammar = \file_get_contents(self::GRAMMAR_FILE);
        $code = Compiler::compile($grammar);

        \file_put_contents(self::TARGET_PARSER_FILE, $code, \LOCK_EX);
        \file_put_contents(self::VERSION_FILE, $newVersion, \LOCK_EX);

    }

}