<?php
/**
Plugin Name: Custom Post Field
Plugin URI:
Description:
Author: ABC
Version: 1.0
Author URI: 24h.com.vn
*/

//exit if acessed directly
if(!defined('ABSPATH')){
    exit();
}

//Add new Metabox to all post type
function add_my_custom_metabox(){
    $types = get_post_types(); //apply for all post_types;
    foreach( $types as $type ) {
        add_meta_box('featured-meta', 'Custom_Post_Field', 'custom_meta_featured', $type, 'side','high');
        //side là bên trái, đổi thành normal để ở dưới, còn high là priority, xuất hiện ở đầu
    }
}

add_action('add_meta_boxes','add_my_custom_metabox');

function custom_meta_featured($post){
    $custom_field_name = get_post_meta($post->ID,'custom_field_name', true);
    //$post là biến toàn cục có sẵn, tham số thứ 2 là key, tham số thứ 3 nếu true là 1 giá trị, false là mảng giá trị
    ?>
    <label for="custom-id">My Custom Field Name</label>
    <input type = "text" name="custom-field-name" id="custom-name" value=" <?php echo esc_attr($custom_field_name); ?>"/>
    <?php
}

function save_custom_field_value($post_id){ //$post_id là ID của post hiện tại
    $field_name = sanitize_text_field($_POST['custom-field-name']);
    //apply_filters( 'wp_insert_post_data', 'filter_handler' );
    update_post_meta($post_id,'custom_field_name', $field_name);
}
add_action('save_post','save_custom_field_value',10,1);



///Start Validate Custom Field Whose Post Type Is Post
add_action('admin_enqueue_scripts-post.php', 'ep_load_jquery_js');
add_action('admin_enqueue_scripts-post-new.php', 'ep_load_jquery_js');
function ep_load_jquery_js(){
    global $post;
    if ( $post->post_type == 'post' ) {
        wp_enqueue_script('jquery');
    }
}

add_action('admin_head-post.php','ep_publish_admin_hook');
add_action('admin_head-post-new.php','ep_publish_admin_hook');

function ep_publish_admin_hook(){
    global $post;
    if ( is_admin() && $post->post_type == 'post' ){
        ?>
        <script language="javascript" type="text/javascript">
            jQuery(document).ready(function(){

                jQuery('#publish').click(function() {
                    if(jQuery(this).data("valid")) {
                        return true;
                    }
                    var form_data = jQuery('#post').serializeArray();
                    form_data = jQuery.param(form_data);

                    var data = {
                        action: 'ep_pre_product_submit',
                        security: '<?php echo wp_create_nonce('pre_publish_validation'); ?>',
                        form_data: form_data
                    };

                    jQuery.post(ajaxurl, data, function(response) {
                        if (response.indexOf('true') > -1 || response == true){
                            jQuery("#post").data("valid", true).submit();
                        } else {
                            alert("please correct the following errors: " + response);
                            jQuery("#post").data("valid", false);
                        }

                        //hide loading icon, return Publish button to normal
                        jQuery('#ajax-loading').hide();
                        jQuery('#publish').removeClass('button-primary-disabled');
                        jQuery('#save-post').removeClass('button-disabled');
                    });
                    return false;
                });
            });
        </script>
        <?php
    }
}

add_action('wp_ajax_ep_pre_product_submit', 'ep_pre_product_submit_func');
function ep_pre_product_submit_func() {
    //simple Security check
    check_ajax_referer( 'pre_publish_validation', 'security' );
    parse_str( $_POST['form_data'], $vars);

    $value = trim($vars['custom-field-name']);

    if(empty($value)){
        echo 'Custom Field Can Not Empty';
        die();
    }

    echo 'true';
}
///End Validate Custom Field Whose Post Type Is Post