<?php

namespace AOP\App\ImportExport;

use AOP\App\Database\PageRepository;
use AOP\App\Plugin;

/**
 * Builds the export file: the selected menus with their pages and the values of their options.
 * The format is described in `includes/schema/export.v1.json`.
 */
final class Exporter
{
    public const VERSION = 1;

    /**
     * @param string[] $menuIds The `menu_id` of the menus to export.
     *
     * @return array The file, ready for json_encode().
     */
    public static function build(array $menuIds): array
    {
        $menuIds = array_map('strval', $menuIds);
        $menus = [];
        $names = [];

        foreach (PageRepository::rows() as $row) {
            // A row of a newer format is not ours to read: leave it out rather than export a hollow page.
            if (! PageRepository::isSupported($row->page_value)) {
                continue;
            }

            $value = PageRepository::decode($row->page_value);

            if (! isset($value['menu_id']) || ! in_array((string) $value['menu_id'], $menuIds, true)) {
                continue;
            }

            $menus[] = ['menu_slug' => (string) $row->menu_slug, 'page_value' => $value];

            foreach (self::optionNames($value) as $name) {
                $names[$name] = true;
            }
        }

        $missing = '__aop_missing__';
        $options = [];

        foreach (array_keys($names) as $name) {
            $current = get_option($name, $missing);

            // An option that does not exist is not exported as false.
            if ($current !== $missing) {
                $options[$name] = $current;
            }
        }

        return [
            'aop_export_version' => self::VERSION,
            'plugin_version' => Plugin::releaseVersion(),
            'generated' => gmdate('Y-m-d\TH:i:s\Z'),
            'menus_and_pages' => $menus,
            'options' => (object) $options,
        ];
    }

    /**
     * @return string[] The option names of the fields of a page value.
     */
    public static function optionNames(array $pageValue): array
    {
        $names = [];

        foreach ($pageValue['pages'] ?? [] as $page) {
            foreach ($page['fields'] ?? [] as $field) {
                if (! empty($field['field_name'])) {
                    $names[] = (string) $field['field_name'];
                }
            }
        }

        return $names;
    }
}