<?php

declare(strict_types=1);

namespace DigitalBrew\Featherdash\Modules\Admin;

use DigitalBrew\Featherdash\Settings\Settings;

/**
 * Faster-feeling admin navigation without replacing page loads:
 *  - Speculation Rules prefetch admin pages on hover (Chromium), skipping
 *    anything that changes state when requested with GET.
 *  - Cross-document view transitions fade between pages while the toolbar and
 *    sidebar stay put (Chromium, Safari).
 * Independent of the admin theme.
 */
final class Navigation
{
    public function register(Settings $settings): void
    {
        if ($settings->get('admin.navigation.prefetch', true)) {
            add_action('admin_print_footer_scripts', [$this, 'speculationRules']);
        }

        if ($settings->get('admin.navigation.transitions', true)) {
            add_action('admin_enqueue_scripts', [$this, 'viewTransitions']);
        }
    }

    public function speculationRules(): void
    {
        $admin = (string) wp_parse_url(admin_url(), PHP_URL_PATH);
        $admin = '/' . trim($admin, '/') . '/';

        // Screens that do work on a plain GET: post locks (post.php), auto-drafts
        // (post-new.php), endpoints, updaters, downloads and the Customizer.
        $unsafePaths = [
            'post.php', 'post-new.php', 'admin-ajax.php', 'admin-post.php', 'async-upload.php',
            'customize.php', 'update.php', 'update-core.php', 'export.php', 'export-personal-data.php',
            'erase-personal-data.php', 'site-editor.php', 'plugin-install.php', 'theme-install.php',
            'press-this.php', 'upgrade.php', 'setup-config.php', 'install.php', 'network.php',
        ];

        $unsafe = array_map(static fn (string $file): string => $admin . $file . '*', $unsafePaths);

        // Any URL that carries an action or a nonce may change something. The
        // object form keeps "?" from being read as a pattern modifier.
        foreach (['*action=*', '*nonce*', '*delete*', '*trash*', '*activate*', '*logout*', '*doing_wp_cron*'] as $search) {
            $unsafe[] = ['pathname' => $admin . '*', 'search' => $search];
        }

        $rules = [
            'prefetch' => [[
                'source' => 'document',
                'where' => [
                    'and' => [
                        ['href_matches' => $admin . '*'],
                        ['not' => ['href_matches' => $unsafe]],
                        ['not' => ['href_matches' => '/wp-login.php*']],
                        ['not' => ['selector_matches' => implode(', ', [
                            'a[target]',
                            'a[download]',
                            'a[rel~="nofollow"]',
                            '.submitdelete',
                            '.row-actions .delete a',
                            '.row-actions .trash a',
                            'a.thickbox',
                            '#wp-admin-bar-logout a',
                            '[data-fd-no-prefetch]',
                            '[data-fd-no-prefetch] a',
                        ])]],
                    ],
                ],
                'eagerness' => 'moderate',
            ]],
        ];

        /**
         * Filters the Speculation Rules used to prefetch admin pages on hover.
         * Add exclusions to `prefetch[0].where.and`, or return [] to turn
         * prefetching off.
         *
         * @param array<string, mixed> $rules
         */
        $rules = (array) apply_filters('featherdash/navigation/prefetch_rules', $rules);

        if ($rules === []) {
            return;
        }

        wp_print_inline_script_tag(
            (string) wp_json_encode($rules, JSON_UNESCAPED_SLASHES | JSON_HEX_TAG),
            ['type' => 'speculationrules']
        );
    }

    public function viewTransitions(): void
    {
        wp_register_style('featherdash-view-transitions', false, [], FEATHERDASH_VERSION);
        wp_enqueue_style('featherdash-view-transitions');
        wp_add_inline_style(
            'featherdash-view-transitions',
            '@media (prefers-reduced-motion:no-preference){@view-transition{navigation:auto}}'
            // The toolbar and sidebar are captured separately, so they stay still
            // while the page content cross-fades.
            . '#wpadminbar{view-transition-name:fd-toolbar}'
            . '#adminmenuwrap{view-transition-name:fd-menu}'
            . '::view-transition-group(*),::view-transition-old(*),::view-transition-new(*){animation-duration:.16s}'
        );
    }
}