WP-LIT-MCP/src/Integrations/Divi/Compose/HtmlTokens.php

<?php

declare(strict_types=1);

namespace LIT\MCP\Integrations\Divi\Compose;

defined('ABSPATH') || exit;

/**
 * Ruling S45 tokenizer of lit/divi-replace-text (spec §5.7, rulings S8/S45): splits a string into
 * tags (quote-aware – a ">" inside a quoted attribute value does not end the tag), comments,
 * entities and $variable(…)$ references ("token"), the bodies of raw-text elements such as
 * <script> ("raw") and the rest ("text"). A string with an unterminated tag, quote, comment or
 * reference has no tokens (null) – nobody can say where its text is. TextReplacer searches text
 * tokens only and compares the non-text structure before and after; HtmlContext is the second,
 * independently written scan. Linear time, pure PHP.
 */
final class HtmlTokens
{
    /**
     * Rulings S8/S45: comments, tags (quote-aware: a ">" inside a quoted attribute value does not
     * end the tag; an unquoted "<" does, so an unterminated tag cannot make PCRE rescan the
     * rest from every "<"), entities and references are tokens, the rest is text. Possessive
     * quantifiers keep it linear.
     */
    public const SPLIT = '/((?s:<!--.*?-->)|<(?:[^<>"\']++|"[^"]*+"|\'[^\']*+\')*+>|&[#A-Za-z0-9]++;'
        . '|\$variable\(.+?\)\$)/';

    /**
     * Raw-text elements: their body is code, never text. Must equal HtmlContext::RAW (the second,
     * independent scan) – HtmlTokensTest asserts it, and that RAW_OPEN opens exactly these.
     */
    public const RAW_ELEMENTS = ['script', 'style', 'xmp', 'iframe', 'noembed', 'noframes', 'noscript', 'plaintext'];

    /** Opening tag of a RAW_ELEMENTS element. */
    private const RAW_OPEN = '/^<(script|style|xmp|iframe|noembed|noframes|noscript|plaintext)\b/i';

    /**
     * Ruling S45 tokenizer: [type, bytes, offset] with type "token" (tag – quote-aware, ">" in a
     * quoted value does not end it –, comment, entity, reference), "raw" (body of script, style
     * and the other raw-text elements) or "text". Null when the value has an unterminated tag,
     * quote, comment or reference – then nobody can say where its text is.
     *
     * @return list<array{string, string, int}>|null
     */
    public static function tokenize(string $value): ?array
    {
        if (self::unterminated($value)) {
            return null;
        }

        $parts = preg_split(self::SPLIT, $value, -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_OFFSET_CAPTURE);
        if (! is_array($parts)) {
            return null;
        }

        $tokens = [];
        $raw = null;
        foreach ($parts as $i => [$text, $offset]) {
            $text = (string) $text;
            if ($i % 2 === 1) {
                if ($raw === null && preg_match(self::RAW_OPEN, $text, $match) === 1) {
                    $raw = strtolower($match[1]);
                } elseif ($raw !== null && self::closes($raw, $text)) {
                    $raw = null;
                }
                $tokens[] = ['token', $text, (int) $offset];
                continue;
            }

            if ($text === '') {
                continue;
            }

            // A "<" that starts markup but matched no token: an unterminated tag or quote.
            if ($raw === null && preg_match('#<[A-Za-z/!?]#', $text) === 1) {
                return null;
            }
            $tokens[] = [$raw === null ? 'text' : 'raw', $text, (int) $offset];
        }

        return $tokens;
    }

    /** Whether token $text closes raw-text element $raw ("</script-x>" does not; plaintext never ends). */
    private static function closes(string $raw, string $text): bool
    {
        return $raw !== 'plaintext' && preg_match('#^</' . $raw . '[\s/>]#i', $text) === 1;
    }

    /**
     * Cheap checks that keep the tokenizer linear: a comment opened after the last "-->", or a
     * reference marker after the last ")$" of its line, can never be closed – PCRE would retry
     * it from every later opener.
     */
    private static function unterminated(string $value): bool
    {
        $open = strrpos($value, '<!--');
        if ($open !== false) {
            $close = strrpos($value, '-->');
            if ($close === false || $close < $open + 2) {
                return true;
            }
        }

        if (! str_contains($value, VariableRef::MARKER)) {
            return false;
        }

        foreach (explode("\n", $value) as $line) {
            $marker = strrpos($line, VariableRef::MARKER);
            $end = $marker === false ? false : strrpos($line, VariableRef::END);
            if ($marker !== false && ($end === false || $end < $marker)) {
                return true;
            }
        }

        return false;
    }

    /**
     * @param list<array{string, string, int}> $tokens
     * @return list<array{string, string}> The non-text tokens (type and bytes), in order.
     */
    public static function structure(array $tokens): array
    {
        $structure = [];
        foreach ($tokens as [$type, $text]) {
            if ($type !== 'text') {
                $structure[] = [$type, $text];
            }
        }

        return $structure;
    }
}