issuepage.php

<?php
/**
 * Plugin Name:     issuepage
 * Description:     Example block written with ESNext standard and JSX support – build step required.
 * Version:         0.1.0
 * Author:          The WordPress Contributors
 * License:         GPL-2.0-or-later
 * License URI:     https://www.gnu.org/licenses/gpl-2.0.html
 * Text Domain:     issuepage
 *
 * @package         siejmy
 */

require_once dirname(__FILE__) . '/metaboxes/issuepage_metabox_html.php';

function issuepage_register_post_fields() {
	register_post_meta( 'post', 'issuepage_issue_no', array(
			'description' => 'Numer i miesiąc wydania (tekst wyświetlany nad tytułem)',
			'show_in_rest' => true,
			'single' => true,
			'type' => 'string',
	) );

	register_post_meta( 'post', 'issuepage_download_url', array(
		'description' => 'Url pobierania numeru',
		'show_in_rest' => true,
		'single' => true,
		'type' => 'string',
	) );
}

function issuepage_save_post($post_id) {
	if ( array_key_exists( 'issuepage_issue_no', $_POST ) ) {
		update_post_meta(
				$post_id,
				'issuepage_issue_no',
				$_POST['issuepage_issue_no']
		);
	}

	if ( array_key_exists( 'issuepage_download_url', $_POST ) ) {
		update_post_meta(
				$post_id,
				'issuepage_download_url',
				$_POST['issuepage_download_url']
		);
	}
}

function issuepage_add_metaboxes() {
	add_meta_box(
			'issuepage_metabox',                 // Unique ID
			'Strona pobierania wydania',      // Box title
			'issuepage_metabox_html',  // Content callback, must be of type callable
			'post'                           // Post type
	);
}

function issuepage_plugin_init() {
	$dir = dirname( __FILE__ );

	$script_asset_path = "$dir/build/index.asset.php";
	if ( ! file_exists( $script_asset_path ) ) {
		throw new Error(
			'You need to run `npm start` or `npm run build` for the "siejmy/issuepage" block first.'
		);
	}
	$index_js     = 'build/index.js';
	$script_asset = require( $script_asset_path );
	wp_register_script(
		'siejmy-issuepage-block-editor',
		plugins_url( $index_js, __FILE__ ),
		$script_asset['dependencies'],
		$script_asset['version']
	);

	$editor_css = 'build/index.css';
	wp_register_style(
		'siejmy-issuepage-block-editor',
		plugins_url( $editor_css, __FILE__ ),
		array(),
		filemtime( "$dir/$editor_css" )
	);

	$style_css = 'build/style-index.css';
	wp_register_style(
		'siejmy-issuepage-block',
		plugins_url( $style_css, __FILE__ ),
		array(),
		filemtime( "$dir/$style_css" )
	);

	wp_enqueue_style('siejmy-issuepage-block');

	issuepage_register_post_fields();
}

add_action( 'init', 'issuepage_plugin_init' );
add_action( 'add_meta_boxes', 'issuepage_add_metaboxes' );
add_action( 'save_post', 'issuepage_save_post' );