<?php

declare(strict_types=1);

namespace LIT\MCP\Integrations\Media;

/**
 * The pure part of MediaUsageFinder: whether a piece of stored content (post content or a
 * block widget) references an attachment – by ID (wp-image-<id>, [gallery ids], Divi 4
 * gallery_ids, core media blocks, Divi 5 "id"/"galleryIds") or only by its file URL. A regex
 * that fails (PCRE limit) is undecided and counts as a possible usage. No database access.
 */
final class ContentMediaReferences
{
    private const CORE_MEDIA_BLOCKS = ['image', 'gallery', 'cover', 'media-text', 'file', 'video', 'audio'];

    /** Block delimiter pattern of WordPress' block parser (WP_Block_Parser::next_token()). */
    private const BLOCK_PATTERN = '/<!--\s+wp:(?P<namespace>[a-z][a-z0-9_-]*\/)?(?P<name>[a-z][a-z0-9_-]*)\s+'
        . '(?P<attrs>{(?:(?:[^}]+|}+(?=})|(?!}\s+\/?-->).)*+)?}\s+)?\/?-->/s';

    /** [gallery ids="…"] and Divi 4 gallery_ids="…" – quotes also JSON-escaped inside Divi 5 blocks. */
    private const ID_LIST_PATTERN = '/(?:\[gallery\b[^\]]*?\bids|\bgallery_ids)=(?:"|\'|\\\\u0022)?([\d,\s]+)/i';

    /** Content a regex could not check (PCRE limit) counts as a possible usage. */
    public static function certainty(string $content, int $attachmentId, ?string $fileRegex): ?string
    {
        $references = self::referencesId($content, $attachmentId);
        if ($references !== false) {
            return $references === true ? MediaUsageFinder::CERTAIN : MediaUsageFinder::POSSIBLE;
        }

        return self::matches($fileRegex, $content) === false ? null : MediaUsageFinder::POSSIBLE;
    }

    /** @return bool|null Null when a regex failed (e.g. backtrack limit) – undecided. */
    private static function referencesId(string $content, int $attachmentId): ?bool
    {
        $wpImage = self::matches('/\bwp-image-' . $attachmentId . '\b/', $content);
        if ($wpImage !== false) {
            return $wpImage;
        }

        $listCount = preg_match_all(self::ID_LIST_PATTERN, $content, $lists);
        if ($listCount === false) {
            return null;
        }
        if ($listCount > 0 && self::inList($lists[1], $attachmentId)) {
            return true;
        }

        if (preg_match_all(self::BLOCK_PATTERN, $content, $blocks, PREG_SET_ORDER) === false) {
            return null;
        }
        foreach ($blocks as $block) {
            $attrs = json_decode(trim((string) ($block['attrs'] ?? '')), true);
            if (! is_array($attrs)) {
                continue;
            }

            $namespace = rtrim((string) $block['namespace'], '/');
            $isCoreMedia = in_array($namespace, ['', 'core'], true)
                && in_array($block['name'], self::CORE_MEDIA_BLOCKS, true);
            if (
                ($isCoreMedia && self::coreBlockReferences($attrs, $attachmentId))
                || ($namespace === 'divi' && self::diviAttrsReference($attrs, $attachmentId))
            ) {
                return true;
            }
        }

        return false;
    }

    /**
     * preg_match() as ?bool: null when the regex failed (backtrack/recursion limit), false
     * without a pattern.
     */
    public static function matches(?string $pattern, string $subject): ?bool
    {
        if ($pattern === null) {
            return false;
        }

        $result = preg_match($pattern, $subject);

        return $result === false ? null : $result === 1;
    }

    /** @param array<mixed> $attrs */
    private static function coreBlockReferences(array $attrs, int $attachmentId): bool
    {
        foreach (['id', 'mediaId'] as $key) {
            if (isset($attrs[$key]) && is_numeric($attrs[$key]) && (int) $attrs[$key] === $attachmentId) {
                return true;
            }
        }

        $ids = is_array($attrs['ids'] ?? null) ? array_filter($attrs['ids'], 'is_numeric') : [];

        return in_array($attachmentId, array_map('intval', $ids), true);
    }

    /**
     * Divi 5 image modules store {"src": url, "id": "<ID>"}, galleries "galleryIds" as "1,2,3"
     * or as an array of IDs.
     *
     * @param array<mixed> $attrs
     */
    private static function diviAttrsReference(array $attrs, int $attachmentId): bool
    {
        foreach ($attrs as $key => $value) {
            if ($key === 'id' && (is_int($value) || is_string($value)) && (string) $value === (string) $attachmentId) {
                return true;
            }

            if ($key === 'galleryIds' && self::inList(self::stringLeaves($value), $attachmentId)) {
                return true;
            }

            if (is_array($value) && self::diviAttrsReference($value, $attachmentId)) {
                return true;
            }
        }

        return false;
    }

    /** @return list<string> String and integer leaves, integers as strings. */
    public static function stringLeaves(mixed $value): array
    {
        if (is_string($value) || is_int($value)) {
            return [(string) $value];
        }

        $leaves = [];
        if (is_array($value)) {
            array_walk_recursive($value, static function ($leaf) use (&$leaves): void {
                if (is_string($leaf) || is_int($leaf)) {
                    $leaves[] = (string) $leaf;
                }
            });
        }

        return $leaves;
    }

    /** @param list<string> $lists Comma-separated ID lists. */
    public static function inList(array $lists, int $attachmentId): bool
    {
        foreach ($lists as $list) {
            foreach (explode(',', $list) as $item) {
                $item = trim($item);
                if ($item !== '' && ctype_digit($item) && (int) $item === $attachmentId) {
                    return true;
                }
            }
        }

        return false;
    }

    /** Original or a generated size of the file, with plain or JSON-escaped slashes. */
    public static function fileRegex(string $stem): string
    {
        $separator = '(?:/|\\\\/)';
        $parts = array_map(static fn (string $part): string => preg_quote($part, '~'), explode('/', $stem));

        return '~' . $separator . implode($separator, $parts)
            . '(?:-\d+x\d+|-scaled|-rotated|-e\d{10,})*\.[a-z0-9]{2,5}(?![a-z0-9])~i';
    }
}