natascha-rieter-nl/user/plugins/draft-preview/draft-preview.php

<?php
namespace Grav\Plugin;

use Composer\Autoload\ClassLoader;
use Grav\Common\Plugin;
use Grav\Common\Uri;
use Grav\Common\Page\Page;

/**
 * Class DraftPreviewPlugin
 * @package Grav\Plugin
 */
class DraftPreviewPlugin extends Plugin
{

    const SLUG = 'draft-preview';

    /**
     * @return array
     *
     * The getSubscribedEvents() gives the core a list of events
     *     that the plugin wants to listen to. The key of each
     *     array section is the event that the plugin listens to
     *     and the value (in the form of an array) contains the
     *     callable (or function) as well as the priority. The
     *     higher the number the higher the priority.
     */
    public static function getSubscribedEvents(): array
    {
        return [
            'onPluginsInitialized' => [
                // Uncomment following line when plugin requires Grav < 1.7
                // ['autoload', 100000],
                ['onPluginsInitialized', 0]
            ],
            'onTwigTemplatePaths'   => [ 'onTwigTemplatePaths', 0 ],
            'onPagesInitialized'    => ['onPagesInitialized', 0],
        ];
    }

    /**
     * Composer autoload
     *
     * @return ClassLoader
     */
    public function autoload(): ClassLoader
    {
        return require __DIR__ . '/vendor/autoload.php';
    }

    /**
     * Initialize the plugin
     */
    public function onPluginsInitialized(): void
    {
        // Don't proceed if we are in the admin plugin
        if ($this->isAdmin()) {
            /** @var UserInterface|null $user */
            $user = $this->grav['user'] ?? null;

            if (null === $user || !$user->authorize('login', 'admin')) {
                return;
            }

            $this->enable([
                // Put your main events here
                'onAssetsInitialized' => ['onAssetsInitialized', 0],
            ]);
        }

        // Enable the main events we are interested in
        $this->enable([
            // Put your main events here
        ]);

    }

    /**
     * [onTwigTemplatePaths]
     *
     * @return void
     */
    public function onTwigTemplatePaths()
    {
        $this->grav['twig']->twig_paths[] = __DIR__ . '/templates';
    }

    /**
     * Programmatically add a custom page.
     *
     * @param $url
     * @param $filename
     * @param null $object
     * @throws \Exception
     */
    public function addPage($url, $filename)
    {
        /** @var Pages $pages */
        $pages = $this->grav['pages'];
        $page = $pages->dispatch($url);

        if (!$page) {
            $page = new Page;
            $page->init(new \SplFileInfo(__DIR__ . '/pages/' . $filename));
            $page->slug(basename($url));
            $page->id($page->modified() . md5($url));
            $page->folder(basename($url));
            $page->route($url);
            $page->rawRoute($url);
            $pages->addPage($page, $url);
        }
    }

    /**
     * [onPagesInitialized]
     *
     * @return void
     */
    public function onPagesInitialized(): void
    {
        /** @var Uri $uri */
        $uri = $this->grav['uri'];
        $route = Uri::getCurrentRoute()->getRoute();
        $trigger = $this->config->get('plugins.' . self::SLUG . '.route');
        if ($route === '/' . $trigger ) {
            $this->addPage($route, 'preview.md');
        }
    }

    /**
     * [getLanguageRoute]
     *
     * @return string
     */
    public function getLanguageRoute(): string
    {
        $page = $this->grav['admin']->page();
        $config = $this->grav['config']['system']['languages'];
        $current_lang = $page->language();
        $lang = '/' . $current_lang;

        if ( ! $config['include_default_lang'] && $current_lang == $config['default_lang'] )
        {
            $lang = '';
        }

        return $lang;
    }

    /**
     * [onAssetsInitialized]
     *
     * @return void
     */
    public function onAssetsInitialized()
    {
        $page = $this->grav['admin']->page();
        // $this->grav['debugger']->addMessage( $page->published() );
        if ( $page->published() == false )
        {
            $trigger = $this->config->get( 'plugins.' . self::SLUG . '.route' );
            $route = $this->grav['base_url'] . '/' . ltrim( $trigger, '/' );
            $lang = $this->getLanguageRoute();
            $lang = ( $lang == '/' ) ? '' : $lang;
            $assets = $this->grav['assets'];
            $assets->addInlineJs( 'const draft_preview_route = "' . $route . '";' );
            $assets->addInlineJs( 'const draft_preview_language = "' . $lang . '";' );
            $assets->addJs( 'plugin://' . self::SLUG . '/assets/preview.js', [ 'group' => 'bottom' ] );
        }
    }
}