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[mediawiki.git] / includes / libs / virtualrest / VirtualRESTServiceClient.php

<?php
/**
 * Virtual HTTP service client
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */

/**
 * Virtual HTTP service client loosely styled after a Virtual File System
 *
 * Services can be mounted on path prefixes so that virtual HTTP operations
 * against sub-paths will map to those services. Operations can actually be
 * done using HTTP messages over the wire or may simple be emulated locally.
 *
 * Virtual HTTP request maps are arrays that use the following format:
 *   - method   : GET/HEAD/PUT/POST/DELETE
 *   - url      : HTTP/HTTPS URL or virtual service path with a registered prefix
 *   - query    : <query parameter field/value associative array> (uses RFC 3986)
 *   - headers  : <header name/value associative array>
 *   - body     : source to get the HTTP request body from;
 *                this can simply be a string (always), a resource for
 *                PUT requests, and a field/value array for POST request;
 *                array bodies are encoded as multipart/form-data and strings
 *                use application/x-www-form-urlencoded (headers sent automatically)
 *   - stream   : resource to stream the HTTP response body to
 * Request maps can use integer index 0 instead of 'method' and 1 instead of 'url'.
 *
 * @author Aaron Schulz
 * @since 1.23
 */
class VirtualRESTServiceClient {
        /** @var MultiHttpClient */
        protected $http;
        /** @var Array Map of (prefix => VirtualRESTService) */
        protected $instances = array();

        const VALID_MOUNT_REGEX = '#^/[0-9a-z]+/([0-9a-z]+/)*$#';

        /**
         * @param MultiHttpClient $http
         */
        public function __construct( MultiHttpClient $http ) {
                $this->http = $http;
        }

        /**
         * Map a prefix to service handler
         *
         * @param string $prefix Virtual path
         * @param VirtualRESTService $instance
         */
        public function mount( $prefix, VirtualRESTService $instance ) {
                if ( !preg_match( self::VALID_MOUNT_REGEX, $prefix ) ) {
                        throw new UnexpectedValueException( "Invalid service mount point '$prefix'." );
                } elseif ( isset( $this->instances[$prefix] ) ) {
                        throw new UnexpectedValueException( "A service is already mounted on '$prefix'." );
                }
                $this->instances[$prefix] = $instance;
        }

        /**
         * Unmap a prefix to service handler
         *
         * @param string $prefix Virtual path
         */
        public function unmount( $prefix ) {
                if ( !preg_match( self::VALID_MOUNT_REGEX, $prefix ) ) {
                        throw new UnexpectedValueException( "Invalid service mount point '$prefix'." );
                } elseif ( !isset( $this->instances[$prefix] ) ) {
                        throw new UnexpectedValueException( "No service is mounted on '$prefix'." );
                }
                unset( $this->instances[$prefix] );
        }

        /**
         * Get the prefix and service that a virtual path is serviced by
         *
         * @param string $path
         * @return array (prefix,VirtualRESTService) or (null,null) if none found
         */
        public function getMountAndService( $path ) {
                $cmpFunc = function( $a, $b ) {
                        $al = substr_count( $a, '/' );
                        $bl = substr_count( $b, '/' );
                        if ( $al === $bl ) {
                                return 0; // should not actually happen
                        }
                        return ( $al < $bl ) ? 1 : -1; // largest prefix first
                };

                $matches = array(); // matching prefixes (mount points)
                foreach ( $this->instances as $prefix => $service ) {
                        if ( strpos( $path, $prefix ) === 0 ) {
                                $matches[] = $prefix;
                        }
                }
                usort( $matches, $cmpFunc );

                // Return the most specific prefix and corresponding service
                return isset( $matches[0] )
                        ? array( $matches[0], $this->instances[$matches[0]] )
                        : array( null, null );
        }

        /**
         * Execute a virtual HTTP(S) request
         *
         * This method returns a response map of:
         *   - code    : HTTP response code or 0 if there was a serious cURL error
         *   - reason  : HTTP response reason (empty if there was a serious cURL error)
         *   - headers : <header name/value associative array>
         *   - body    : HTTP response body or resource (if "stream" was set)
         *   - error   : Any cURL error string
         * The map also stores integer-indexed copies of these values. This lets callers do:
         *      <code>
         *              list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $client->run( $req );
         *  </code>
         * @param array $req Virtual HTTP request maps
         * @return array Response array for request
         */
        public function run( array $req ) {
                $responses = $this->runMulti( array( $req ) );
                return $responses[0];
        }

        /**
         * Execute a set of virtual HTTP(S) requests concurrently
         *
         * A map of requests keys to response maps is returned. Each response map has:
         *   - code    : HTTP response code or 0 if there was a serious cURL error
         *   - reason  : HTTP response reason (empty if there was a serious cURL error)
         *   - headers : <header name/value associative array>
         *   - body    : HTTP response body or resource (if "stream" was set)
         *   - error   : Any cURL error string
         * The map also stores integer-indexed copies of these values. This lets callers do:
         *    <code>
         *        list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $responses[0];
         *  </code>
         *
         * @param array $reqs Map of Virtual HTTP request maps
         * @return array $reqs Map of corresponding response values with the same keys/order
         * @throws Exception
         */
        public function runMulti( array $reqs ) {
                foreach ( $reqs as $index => &$req ) {
                        if ( isset( $req[0] ) ) {
                                $req['method'] = $req[0]; // short-form
                                unset( $req[0] );
                        }
                        if ( isset( $req[1] ) ) {
                                $req['url'] = $req[1]; // short-form
                                unset( $req[1] );
                        }
                        $req['chain'] = array(); // chain or list of replaced requests
                }
                unset( $req ); // don't assign over this by accident

                $curUniqueId = 0;
                $armoredIndexMap = array(); // (original index => new index)

                $doneReqs = array(); // (index => request)
                $executeReqs = array(); // (index => request)
                $replaceReqsByService = array(); // (prefix => index => request)
                $origPending = array(); // (index => 1) for original requests

                foreach ( $reqs as $origIndex => $req ) {
                        // Re-index keys to consecutive integers (they will be swapped back later)
                        $index = $curUniqueId++;
                        $armoredIndexMap[$origIndex] = $index;
                        $origPending[$index] = 1;
                        if ( preg_match( '#^(http|ftp)s?://#', $req['url'] ) ) {
                                // Absolute FTP/HTTP(S) URL, run it as normal
                                $executeReqs[$index] = $req;
                        } else {
                                // Must be a virtual HTTP URL; resolve it
                                list( $prefix, $service ) = $this->getMountAndService( $req['url'] );
                                if ( !$service ) {
                                        throw new UnexpectedValueException( "Path '{$req['url']}' has no service." );
                                }
                                // Set the URL to the mount-relative portion
                                $req['url'] = substr( $req['url'], strlen( $prefix ) );
                                $replaceReqsByService[$prefix][$index] = $req;
                        }
                }

                // Function to get IDs that won't collide with keys in $armoredIndexMap
                $idFunc = function() use ( &$curUniqueId ) {
                        return $curUniqueId++;
                };

                $rounds = 0;
                do {
                        if ( ++$rounds > 5 ) { // sanity
                                throw new Exception( "Too many replacement rounds detected. Aborting." );
                        }
                        // Track requests executed this round that have a prefix/service.
                        // Note that this also includes requests where 'response' was forced.
                        $checkReqIndexesByPrefix = array();
                        // Resolve the virtual URLs valid and qualified HTTP(S) URLs
                        // and add any required authentication headers for the backend.
                        // Services can also replace requests with new ones, either to
                        // defer the original or to set a proxy response to the original.
                        $newReplaceReqsByService = array();
                        foreach ( $replaceReqsByService as $prefix => $servReqs ) {
                                $service = $this->instances[$prefix];
                                foreach ( $service->onRequests( $servReqs, $idFunc ) as $index => $req ) {
                                        // Services use unique IDs for replacement requests
                                        if ( isset( $servReqs[$index] ) || isset( $origPending[$index] ) ) {
                                                // A current or original request which was not modified
                                        } else {
                                                // Replacement request that will convert to original requests
                                                $newReplaceReqsByService[$prefix][$index] = $req;
                                        }
                                        if ( isset( $req['response'] ) ) {
                                                // Replacement requests with pre-set responses should not execute
                                                unset( $executeReqs[$index] );
                                                unset( $origPending[$index] );
                                                $doneReqs[$index] = $req;
                                        } else {
                                                // Original or mangled request included
                                                $executeReqs[$index] = $req;
                                        }
                                        $checkReqIndexesByPrefix[$prefix][$index] = 1;
                                }
                        }
                        // Update index of requests to inspect for replacement
                        $replaceReqsByService = $newReplaceReqsByService;
                        // Run the actual work HTTP requests
                        foreach ( $this->http->runMulti( $executeReqs ) as $index => $ranReq ) {
                                $doneReqs[$index] = $ranReq;
                                unset( $origPending[$index] );
                        }
                        $executeReqs = array();
                        // Services can also replace requests with new ones, either to
                        // defer the original or to set a proxy response to the original.
                        // Any replacement requests executed above will need to be replaced
                        // with new requests (eventually the original). The responses can be
                        // forced by setting 'response' rather than actually be sent over the wire.
                        $newReplaceReqsByService = array();
                        foreach ( $checkReqIndexesByPrefix as $prefix => $servReqIndexes ) {
                                $service = $this->instances[$prefix];
                                // $doneReqs actually has the requests (with 'response' set)
                                $servReqs = array_intersect_key( $doneReqs, $servReqIndexes );
                                foreach ( $service->onResponses( $servReqs, $idFunc ) as $index => $req ) {
                                        // Services use unique IDs for replacement requests
                                        if ( isset( $servReqs[$index] ) || isset( $origPending[$index] ) ) {
                                                // A current or original request which was not modified
                                        } else {
                                                // Replacement requests with pre-set responses should not execute
                                                $newReplaceReqsByService[$prefix][$index] = $req;
                                        }
                                        if ( isset( $req['response'] ) ) {
                                                // Replacement requests with pre-set responses should not execute
                                                unset( $origPending[$index] );
                                                $doneReqs[$index] = $req;
                                        } else {
                                                // Update the request in case it was mangled
                                                $executeReqs[$index] = $req;
                                        }
                                }
                        }
                        // Update index of requests to inspect for replacement
                        $replaceReqsByService = $newReplaceReqsByService;
                } while ( count( $origPending ) );

                $responses = array();
                // Update $reqs to include 'response' and normalized request 'headers'.
                // This maintains the original order of $reqs.
                foreach ( $reqs as $origIndex => $req ) {
                        $index = $armoredIndexMap[$origIndex];
                        if ( !isset( $doneReqs[$index] ) ) {
                                throw new UnexpectedValueException( "Response for request '$index' is NULL." );
                        }
                        $responses[$origIndex] = $doneReqs[$index]['response'];
                }

                return $responses;
        }
}