WordPress class for downloading missing assets from production to dev on the fly

wp-file-proxy.php

<?php

if ( ! class_exists( 'WP_File_Proxy' ) ) :

	class WP_File_Proxy {

		/**
		 * @var string
		 */
		protected $proxy_domain;

		/**
		 * WP_File_Proxy constructor.
		 *
		 * @param string $proxy_domain
		 */
		function __construct( string $proxy_domain ) {
			$this->proxy_domain = trailingslashit( $proxy_domain );
			add_action( 'template_redirect', [ $this, 'maybe_fetch_asset' ] );
		}

		/**
		 * Maybe fetch missing asset.
		 */
		function maybe_fetch_asset() {
			global $wp;
			if ( is_404() && 0 === strpos( $wp->request, 'wp-content/uploads/' ) ) {
				$this->fetch_asset( $wp->request );
			}
		}

		/**
		 * Fetch the given asset from the remote host.
		 *
		 * @param string $filepath
		 */
		protected function fetch_asset( string $filepath ) {
			$filename  = basename( $filepath );
			$proxy_url = $this->proxy_domain . $filepath;
			$response  = wp_remote_get( $proxy_url, [ 'stream' => true, 'sslverify' => false ] );

			if ( ! is_wp_error( $response ) && ! empty( $response['filename'] ) ) {
				$time = null;
				if ( 1 === preg_match( '~([0-9]{4}/[0-9]{2})~', $filepath, $matches ) ) {
					$time = $matches[1];
				}

				$upload_file = wp_upload_bits( $filename, null, file_get_contents( $response['filename'] ), $time );
				if ( ! $upload_file['error'] ) {
					$filetype = wp_check_filetype( $filename, null );
					if ( ! empty( $filetype['type'] ) ) {
						status_header( 200 );
						header( 'Content-type: ' . $filetype['type'] );
						header( 'Pragma: no-cache' );
						header( 'Expires: 0' );
						echo file_get_contents( $response['filename'] );
						exit;
					}
				}
			}
		}
	}

endif;