migrate-import-cache.php

<?php
/**
 * Filters wp_remote_get() to:
 * 1. Return a value from the cache when it's available.
 * 2. Write a value to the cache when it's been fetched.
 *
 * Requires the WP_IMPORT_CACHE constant to be set to a writable directory.
 */

if ( defined( 'WP_CLI' ) && WP_CLI ) {

	add_filter(
		'pre_http_request',
		function( $retval, $r, $url ) {

			// Only run when importing.
			if ( ! defined( 'WP_IMPORTING' ) || ! WP_IMPORTING
				|| ! defined( 'WP_IMPORT_CACHE' ) ) {
				return $retval;
			}

			$key        = md5( $url );
			$cache_path = trailingslashit( WP_IMPORT_CACHE ) . $key;
			if ( file_exists( $cache_path ) ) {
				WP_CLI::log( " - Importing {$url} from cache..." );
				copy( $cache_path, $r['filename'] );
				return array(
					'headers'  => array(),
					'response' => array(
						'code'    => 200,
						'message' => 'OK',
					),
					'cookies'  => array(),
					'filename' => $r['filename'],
				);
			}
			return $retval;
		},
		10,
		3
	);

	add_filter(
		'http_response',
		function( $response, $args, $url ) {
			// Only run when importing.
			if ( ! defined( 'WP_IMPORTING' ) || ! WP_IMPORTING
				|| ! defined( 'WP_IMPORT_CACHE' ) ) {
				return $response;
			}

			if ( 200 !== wp_remote_retrieve_response_code( $response )
				|| empty( $response['filename'] ) ) {
				return $response;
			}
			if ( ! is_dir( WP_IMPORT_CACHE ) ) {
				@mkdir( WP_IMPORT_CACHE );
			}
			WP_CLI::log( " - Saving {$url} to cache..." );
			$key        = md5( $url );
			$cache_path = trailingslashit( WP_IMPORT_CACHE ) . $key;
			file_put_contents( $cache_path, file_get_contents( $response['filename'] ) );
			return $response;
		},
		10,
		3
	);

}