Function to resolve assets url with attached content hash

functions.php

<?php

/**
 * Function to resolve assets url with attached content hash.
 * 
 * Browser cache mechanism is used to store locally once downloaded assets. This
 * improves website performance and saves network bandwidth. It may be also creating
 * a problem when a user visits your website and do not see the newest changes in assets
 * because the browser is serving an old file from cache.
 * 
 * This function aims to resolve this issue by adding a content hash to each asset.
 * If you want to load e.g. "/css/style.css" file function will find this file
 * add a content hash to a filename and copy file to new path "/css/style.am51n9x...css".
 * 
 * @author    Motivast motivast.com
 * @copyright 2019 - present, Motivast
 *
 * @license   https://www.gnu.org/licenses/old-licenses/gpl-2.0.txt GPL-2.0-or-later
 *
 * @link      https://gist.github.com/kierzniak/b8fc18518837d61e3c9850c2b43736da
 */
if ( ! function_exists( 'motivast_assets' ) ) {

	/**
	 * Resolve assets url with attached content hash.
	 *
	 * @param string $path Relative path to asset
	 *
	 * @return string Full url to the assets with checksum attached
	 */
	function motivast_assets( $path ) {

		$theme_path = ( ! motivast_is_child_theme_scope() ) ? get_template_directory() : get_stylesheet_directory();
		$theme_url  = ( ! motivast_is_child_theme_scope() ) ? get_template_directory_uri() : get_stylesheet_directory_uri();

		$full_path = sprintf('%s%s', $theme_path, $path);

		if( !file_exists( $full_path ) ) {
			throw new \Exception( sprintf( 'Provided assest do not exist in given path "%s"', $full_path ));
		}

		$checksum  = sha1_file( $full_path );
		$dir       = pathinfo( $full_path, PATHINFO_DIRNAME );
		$file      = pathinfo( $full_path, PATHINFO_FILENAME );
		$ext       = pathinfo( $full_path, PATHINFO_EXTENSION);

		$checksum_path = sprintf( '%s/%s.%s.%s', $dir, $file, $checksum, $ext );
		$checksum_url  = str_replace( $theme_path, $theme_url, $checksum_path );

		if( !file_exists( $checksum_path ) ) {
			$copy_results = copy($full_path, $checksum_path);

			if( !$copy_results ) {
				throw new \Exception( sprintf( 'Failed to copy asset from path "%s" to "%s"', $full_path, $checksum_path ));
			}
		}

		return $checksum_url;
	}
}

if ( ! function_exists( 'motivast_is_child_theme_scope' ) ) {
	
	/**
	 * Detect if executed code is inside parrent or child theme scope
	 * 
	 * @return bool
	 */
	function motivast_is_child_theme_scope() {
		
		// If there is no child theme we can not execute code from it.
		if( !is_child_theme() ){
			return false;
		}

		$trace      = current( debug_backtrace() );
		$trace_file = $trace['file'];

		$parrent_theme = get_template_directory();
		$child_theme = get_stylesheet_directory();

		if( strpos( $trace_file, $parrent_theme ) !== false ) {
			return false;
		}

		if( strpos( $trace_file, $child_theme ) !== false ) {
			return true;
		}

		throw new \Exception( 'Current scope is not executed from parent or child theme.' );

	}
}