BP_Document::bp_document_pdf_previews( $ids,  $check_mime_type = false,  $document_id )

	static function bp_document_pdf_previews( $ids, $check_mime_type = false, $document_id ) {

		$cnt                    = $num_updates = $num_fails = $time = 0;
		$preview_attachment_id  = bp_document_get_meta( $document_id, 'preview_attachment_id', true );
		if ( $ids && ! $preview_attachment_id ) {
			$time = microtime( true );
			$cnt = count( $ids );
			self::bp_document_set_time_limit( max( $cnt * self::$per_pdf_secs, self::$min_time_limit ) );

			foreach ( $ids as $idx => $id ) {
				if ( $check_mime_type && 'application/pdf' !== get_post_mime_type( $id ) ) {
					continue;
				}
				$file = get_attached_file( $id );
				if ( false === $file || '' === $file ) {
					$num_fails++;
				} else {
					// Get current metadata if any.
					$old_value = get_metadata( 'post', $id, '_wp_attachment_metadata' );
					if ( $old_value && ( ! is_array( $old_value ) || 1 !== count( $old_value ) ) ) {
						$old_value = null;
					}
					// Remove old intermediate thumbnails if any.
					if ( $old_value && ! empty( $old_value[0]['sizes'] ) && is_array( $old_value[0]['sizes'] ) ) {
						$dirname = dirname( $file ) . '/';
						foreach ( $old_value[0]['sizes'] as $sizeinfo ) {
							// Check whether pre WP 4.7.3 lacking PDF marker and if so don't delete so as not to break links to thumbnails in content.
							if ( false !== strpos( $sizeinfo['file'], '-pdf' ) ) {
								@ unlink( $dirname . $sizeinfo['file'] );
							}
						}
					}
					if ( ! function_exists( 'wp_generate_attachment_metadata' ) ) {
						require_once ABSPATH . 'wp-admin' . '/includes/image.php';
						require_once ABSPATH . 'wp-admin' . '/includes/file.php';
						require_once ABSPATH . 'wp-admin' . '/includes/media.php';
					}
					// Generate new intermediate thumbnails.
					$meta = wp_generate_attachment_metadata( $id, $file );
					if ( ! $meta ) {
						$num_fails++;
					} else {
						// wp_update_attachment_metadata() returns false if nothing to update so check first.
						if ( ( $old_value && $old_value[0] === $meta ) || false !== wp_update_attachment_metadata( $id, $meta ) ) {
							$num_updates++;
						} else {
							$num_fails++;
						}
					}
					if ( $meta ) {
						$upload_dir     = wp_upload_dir();
						$preview_folder = '';
						$output_file     = wp_get_attachment_image_url( $id, 'full' );
						$output_file_src = bp_document_scaled_image_path( $id );

						if ( '' !== $output_file && '' !== basename( $output_file ) && strstr( $output_file, 'bb_documents/' ) ) {
							add_filter( 'upload_dir', 'bp_document_upload_dir_script' );
							$upload_dir = $upload_dir['basedir'];

							// Create temp folder.
							$upload_dir = $upload_dir . '/preview-image-folder-' . time();

							// If folder not exists then create.
							if ( ! is_dir( $upload_dir ) ) {

								// Create temp folder.
								wp_mkdir_p( $upload_dir );
								chmod( $upload_dir, 0777 );

								// Create given main parent folder.
								$preview_folder = $upload_dir;
								wp_mkdir_p( $preview_folder );

								$file_name = basename( $output_file );
								$extension_pos = strrpos($file_name, '.'); // find position of the last dot, so where the extension starts
								$thumb = substr($file_name, 0, $extension_pos) . '_thumb' . substr($file_name, $extension_pos);
								copy( $output_file_src, $preview_folder . '/' . $thumb );

							}

							$files = scandir( $preview_folder );
							$firstFile = $preview_folder . '/' . $files[2];
							bp_document_chmod_r( $preview_folder );

							$image_data = file_get_contents( $firstFile );

							$filename = basename( $output_file );
							$upload_dir = wp_upload_dir();

							if ( wp_mkdir_p( $upload_dir['path'] ) ) {
								$file = $upload_dir['path'] . '/' . $filename;
							} else {
								$file = $upload_dir['basedir'] . '/' . $filename;
							}

							file_put_contents( $file, $image_data );

							$wp_filetype = wp_check_filetype( $filename, null );

							$attachment = array(
								'post_mime_type' => $wp_filetype['type'],
								'post_title'     => sanitize_file_name( $filename ),
								'post_content'   => '',
								'post_status'    => 'inherit',
							);

							$preview_attachment_id = wp_insert_attachment( $attachment, $file );
							if ( ! function_exists( 'wp_generate_attachment_metadata' ) ) {
								require_once ABSPATH . 'wp-admin' . '/includes/image.php';
								require_once ABSPATH . 'wp-admin' . '/includes/file.php';
								require_once ABSPATH . 'wp-admin' . '/includes/media.php';
							}
							$attach_data = wp_generate_attachment_metadata( $preview_attachment_id, $file );
							wp_update_attachment_metadata( $preview_attachment_id, $attach_data );
							update_post_meta( $id, 'document_preview_generated', 'yes' );
							update_post_meta( $id, 'document_preview_attachment_id', $preview_attachment_id );
							bp_document_update_meta( $document_id, 'preview_attachment_id', $preview_attachment_id );
							BP_Document::bp_document_remove_temp_directory( $preview_folder );
							remove_filter( 'upload_dir', 'bp_document_upload_dir_script' );
						}
					}
				}
			}
			$time = round( microtime( true ) - $time, self::$timing_dec_places );
		}
		return array( $cnt, $num_updates, $num_fails, $time );
	}