<?php

declare(strict_types=1);

namespace MeshVault\Catalog;

use InvalidArgumentException;

final class ModelMetadata
{
    public static function validateTitle(string $title): void
    {
        $length = preg_match_all('/./us', $title);
        if (
            $length === false || $length < 1 || $length > 255 || preg_match('/^\s*$/u', $title)
            || str_contains($title, "\0")
        ) {
            throw new InvalidArgumentException('Model name must contain 1 to 255 characters and not be blank or NUL.');
        }
    }

    public static function validateShape(array $metadata): void
    {
        if (count($metadata) !== 3 || !isset($metadata['title']) || !is_string($metadata['title'])) {
            throw new InvalidArgumentException('Metadata requires exactly title, notes and sourceURL.');
        }
        foreach (['notes', 'sourceURL'] as $field) {
            if (
                !array_key_exists($field, $metadata)
                || ($metadata[$field] !== null && !is_string($metadata[$field]))
            ) {
                throw new InvalidArgumentException('Metadata requires nullable string notes and sourceURL.');
            }
        }
    }

    /** Validate/normalize changed fields only; expected is always a raw snapshot. */
    public static function replacement(array $expected, array $replacement): array
    {
        self::validateShape($expected);
        self::validateShape($replacement);
        $result = [];
        foreach (['title', 'notes', 'sourceURL'] as $field) {
            $value = $replacement[$field];
            if ($value !== $expected[$field]) {
                if ($field === 'title') {
                    self::validateTitle($value);
                } elseif ($value === '' || $value === null) {
                    $value = null;
                } elseif ($field === 'notes') {
                    if (preg_match('//u', $value) !== 1 || str_contains($value, "\0")) {
                        throw new InvalidArgumentException('Notes must be valid UTF-8 without NUL.');
                    }
                } else {
                    self::validateUrl($value);
                }
            }
            $result[$field] = $value;
        }
        return $result;
    }

    private static function validateUrl(string $url): void
    {
        $parts = parse_url($url);
        if (
            strlen($url) > 2048 || preg_match('/[^\x21-\x7e]|\\\\|%(?![0-9a-fA-F]{2})/', $url)
            || $parts === false || !in_array(strtolower($parts['scheme'] ?? ''), ['http', 'https'], true)
            || empty($parts['host']) || isset($parts['user']) || isset($parts['pass'])
            || filter_var($url, FILTER_VALIDATE_URL) === false
        ) {
            throw new InvalidArgumentException('Source URL must be an absolute ASCII HTTP(S) URL without userinfo.');
        }
    }
}