code: protected static function prepare_files( $type ) {
  
  		$params['type']   = $type;
  		$params['routes'] = self::get_routes_to_folder( $type );
  
  		self::get_processed_files();
  
  		foreach ( self::$data[ $type ] as $id => $file ) {
  
  			$path = self::get_path_from_url( $file['url'] );
  
  			$params['files'][ $id ] = basename( $file['url'] );
  			$params['urls'][ $id ]  = $file['url'];
  			$params['paths'][ $id ] = $path;
  
  			if ( is_file( $path ) && self::is_modified_file( $path ) ) {
  				unset( $params['urls'][ $id ] );
  				continue;
  			}
  
  			$path = $params['routes']['path'] . $params['files'][ $id ];
  
  			if ( is_file( $path ) ) {
  				if ( self::is_modified_hash( $file['url'], $path ) ) {
  					continue;
  				}
  				$params['paths'][ $id ] = $path;
  
  			} elseif ( self::is_external_url( $file['url'] ) ) {
  				continue;
  			}
  
  			unset( $params['urls'][ $id ] );
  		}
  
  		return $params;
  	}
docs: Check files and prepare paths and urls.
  
  @since 1.0.4
  
  @param string $type → script|style.
  
  @return array|false → paths, urls and outdated files.