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<?php

class JS_Custom_Post_Type
{
    public $post_type_name;
    public $post_type_args;
    public $post_type_labels;

    /* Class constructor */
    public function __construct($name, $args = array(), $labels = array())
    {
        // Set some important variables
        $this->post_type_name = strtolower(str_replace(' ', '_', $name));
        $this->post_type_args = $args;
        $this->post_type_labels = $labels;

        // Add action to register the post type, if the post type does not already exist
        if (!post_type_exists($this->post_type_name)) {
            add_action('init', array(&$this, 'register_post_type'));
        }

        // Listen for the save post hook
        $this->save();
    }

    /* Method which registers the post type */
    public function register_post_type()
    {
        //Capitilize the words and make it plural
        $name = ucwords(str_replace('_', ' ', $this->post_type_name));
        $plural = $name . 's';

        // We set the default labels based on the post type name and plural. We overwrite them with the given labels.
        $labels = array_merge(

        // Default
            array(
                'name' => _x($plural, 'post type general name'),
                'singular_name' => _x($name, 'post type singular name'),
                'add_new' => _x('Add New', strtolower($name)),
                'add_new_item' => __('Add New ' . $name),
                'edit_item' => __('Edit ' . $name),
                'new_item' => __('New ' . $name),
                'all_items' => __('All ' . $plural),
                'view_item' => __('View ' . $name),
                'search_items' => __('Search ' . $plural),
                'not_found' => __('No ' . strtolower($plural) . ' found'),
                'not_found_in_trash' => __('No ' . strtolower($plural) . ' found in Trash'),
                'parent_item_colon' => '',
                'menu_name' => $plural
            ),

            // Given labels
            $this->post_type_labels

        );

        // Same principle as the labels. We set some defaults and overwrite them with the given arguments.
        $args = array_merge(

        // Default
            array(
                'label' => $plural,
                'labels' => $labels,
                'public' => true,
                'show_ui' => true,
                'supports' => array('title', 'editor', 'thumbnail'),
                'show_in_nav_menus' => true,
                'menu_icon' => 'dashicons-category',
                '_builtin' => false,
                'publicly_queryable' => true,
                'exclude_from_search' => false,
                'has_archive' => true,
                'query_var' => true,
                'can_export' => true,
                'capability_type' => 'post',
                'show_in_rest' => true,
                'rewrite' => true
            ),

            // Given args
            $this->post_type_args

        );

        // Register the post type
        register_post_type($this->post_type_name, $args);
    }

    /* Method to attach the taxonomy to the post type */
    public function add_taxonomy($name, $args = array(), $labels = array())
    {
        if (!empty($name)) {
            // We need to know the post type name, so the new taxonomy can be attached to it.
            $post_type_name = $this->post_type_name;

            // Taxonomy properties
            $taxonomy_name = strtolower(str_replace(' ', '_', $name));
            $taxonomy_labels = $labels;
            $taxonomy_args = $args;

            /* More code coming */
            if (!taxonomy_exists($taxonomy_name)) {
                /* Create taxonomy and attach it to the object type (post type) */

                //Capitilize the words and make it plural
                $name = ucwords(str_replace('_', ' ', $name));
                $plural = $name . 's';

                // Default labels, overwrite them with the given labels.
                $labels = array_merge(

                // Default
                    array(
                        'name' => _x($plural, 'taxonomy general name'),
                        'singular_name' => _x($name, 'taxonomy singular name'),
                        'search_items' => __('Search ' . $plural),
                        'all_items' => __('All ' . $plural),
                        'parent_item' => __('Parent ' . $name),
                        'parent_item_colon' => __('Parent ' . $name . ':'),
                        'edit_item' => __('Edit ' . $name),
                        'update_item' => __('Update ' . $name),
                        'add_new_item' => __('Add New ' . $name),
                        'new_item_name' => __('New ' . $name . ' Name'),
                        'menu_name' => __($name),
                    ),

                    // Given labels
                    $taxonomy_labels

                );

                // Default arguments, overwritten with the given arguments
                $args = array_merge(

                // Default
                    array(
                        'label' => $plural,
                        'labels' => $labels,
                        'public' => true,
                        'show_ui' => true,
                        'show_in_nav_menus' => true,
                        '_builtin' => false,
                    ),

                    // Given
                    $taxonomy_args

                );

                // Add the taxonomy to the post type
                add_action('init',
                    function () use ($taxonomy_name, $post_type_name, $args) {
                        register_taxonomy($taxonomy_name, $post_type_name, $args);
                    }
                );
            } else {
                /* The taxonomy already exists. We are going to attach the existing taxonomy to the object type (post type) */
                add_action('init',
                    function () use ($taxonomy_name, $post_type_name) {
                        register_taxonomy_for_object_type($taxonomy_name, $post_type_name);
                    }
                );
            }
        }

    }


    /* Attaches meta boxes to the post type */
    public function add_meta_box($title, $fields = array(), $context = 'normal', $priority = 'default')
    {
        if (!empty($title)) {
            // We need to know the Post Type name again
            $post_type_name = $this->post_type_name;

            // Meta variables
            $box_id = strtolower(str_replace(' ', '_', $title));
            $box_title = ucwords(str_replace('_', ' ', $title));
            $box_context = $context;
            $box_priority = $priority;

            // Make the fields global
            global $custom_fields;
            $custom_fields[$title] = $fields;

            /* More code coming */

            add_action('admin_init',
                function () use ($box_id, $box_title, $post_type_name, $box_context, $box_priority, $fields) {
                    add_meta_box(
                        $box_id,
                        $box_title,
                        function ($post, $data) {
                            global $post;

                            // Nonce field for some validation
                            wp_nonce_field(plugin_basename(__FILE__), 'custom_post_type');

                            // Get all inputs from $data
                            $custom_fields = $data['args'][0];

                            // Get the saved values
                            $meta = get_post_custom($post->ID);

                            // Check the array and loop through it
                            if (!empty($custom_fields)) {
                                /* Loop through $custom_fields */
                                foreach ($custom_fields as $label => $type) {
                                    $field_id_name = strtolower(str_replace(' ', '_', $data['id'])) . '_' . strtolower(str_replace(' ', '_', $label));

                                    echo '<label for="' . $field_id_name . '">' . $label . '</label><input type="text" name="custom_meta[' . $field_id_name . ']" id="' . $field_id_name . '" value="' . $meta[$field_id_name][0] . '" />';
                                }
                            }

                        },
                        $post_type_name,
                        $box_context,
                        $box_priority,
                        array($fields)
                    );
                }
            );
        }

    }

    /* Listens for when the post type being saved */
    public function save()
    {
        // Need the post type name again
        $post_type_name = $this->post_type_name;

        add_action('save_post',
            function () use ($post_type_name) {
                // Deny the WordPress autosave function
                if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) return;

                if (!wp_verify_nonce($_POST['custom_post_type'], plugin_basename(__FILE__))) return;

                global $post;

                if (isset($_POST) && isset($post->ID) && get_post_type($post->ID) == $post_type_name) {
                    global $custom_fields;

                    // Loop through each meta box
                    foreach ($custom_fields as $title => $fields) {
                        // Loop through all fields
                        foreach ($fields as $label => $type) {
                            $field_id_name = strtolower(str_replace(' ', '_', $title)) . '_' . strtolower(str_replace(' ', '_', $label));

                            update_post_meta($post->ID, $field_id_name, $_POST['custom_meta'][$field_id_name]);
                        }

                    }
                }
            }
        );

    }
}

$book = new JS_Custom_Post_Type( 'JobQS' );
$book->add_taxonomy( 'jobqs category' );
$book->add_meta_box( 
    'Book Info', 
    array(
        'Year' => 'text',
        'Genre' => 'text'
    )
);
 
$book->add_meta_box( 
    'Author Info', 
    array(
        'Name' => 'text',
        'Nationality' => 'text',
        'Birthday' => 'text'
    )
);