<?php
/**
 * Create the image attachment and return the new media upload id.
 *
 * @author Joshua David Nelson, josh@joshuadnelson.com
 *
 * @since 03.29.2017 updated to a class, utilizing code from Takuro Hishikawa's gist linked below.
 *
 * @see https://gist.github.com/hissy/7352933
 *
 * @see http://codex.wordpress.org/Function_Reference/wp_insert_attachment#Example
 *
 * @link https://joshuadnelson.com/programmatically-add-images-to-media-library/
 */
class JDN_Create_Media_File
{
    public $post_id;
    public $image_url;
    public $wp_upload_url;
    public $attachment_id;
 
    /**
     * Setup the class variables
     */
    public function __construct($image_url, $post_id = 0)
    {
        // Setup class variables
        $this->image_url = esc_url($image_url);
        $this->post_id = absint($post_id);
        $this->wp_upload_url = $this->get_wp_upload_url();
        $this->attachment_id = $this->attachment_id ?: false;

        return $this->create_image_id();
    }

    /**
     * Set the upload directory
     */
    private function get_wp_upload_url()
    {
        $wp_upload_dir = wp_upload_dir();
        return isset($wp_upload_dir['url']) ? $wp_upload_dir['url'] : false;
    }

    /**
     * Create the image and return the new media upload id.
     *
     * @see https://gist.github.com/hissy/7352933
     *
     * @see http://codex.wordpress.org/Function_Reference/wp_insert_attachment#Example
     */
    public function create_image_id()
    {
        if ($this->attachment_id) {
            return $this->attachment_id;
        }
        if (empty($this->image_url) || empty($this->wp_upload_url)) {
            return false;
        }
        $filename = basename($this->image_url);
        $upload_file = wp_upload_bits($filename, null, file_get_contents($this->image_url));
        if (!$upload_file['error']) {
            $wp_filetype = wp_check_filetype($filename, null);
            $attachment = [
                'post_mime_type' => $wp_filetype['type'],
                'post_parent' => $this->post_id,
                'post_title' => preg_replace('/\.[^.]+$/', '', $filename),
                'post_content' => '',
                'post_status' => 'inherit',
            ];
            $attachment_id = wp_insert_attachment($attachment, $upload_file['file'], $this->post_id);
            if (!is_wp_error($attachment_id)) {
                require_once(ABSPATH . "wp-admin" . '/includes/image.php');
                require_once(ABSPATH . 'wp-admin/includes/media.php');
                $attachment_data = wp_generate_attachment_metadata($attachment_id, $upload_file['file']);
                wp_update_attachment_metadata($attachment_id, $attachment_data);
                $this->attachment_id = $attachment_id;
                return $attachment_id;
            }
        }
        return false;
    }
}