ApiMain.php

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<?php
use MediaWiki\Logger\LoggerFactory;

class ApiMain extends ApiBase {
    const API_DEFAULT_FORMAT = 'jsonfm';

    private static $Modules = [
        'login' => 'ApiLogin',
        'clientlogin' => 'ApiClientLogin',
        'logout' => 'ApiLogout',
        'createaccount' => 'ApiAMCreateAccount',
        'linkaccount' => 'ApiLinkAccount',
        'unlinkaccount' => 'ApiRemoveAuthenticationData',
        'changeauthenticationdata' => 'ApiChangeAuthenticationData',
        'removeauthenticationdata' => 'ApiRemoveAuthenticationData',
        'resetpassword' => 'ApiResetPassword',
        'query' => 'ApiQuery',
        'expandtemplates' => 'ApiExpandTemplates',
        'parse' => 'ApiParse',
        'stashedit' => 'ApiStashEdit',
        'opensearch' => 'ApiOpenSearch',
        'feedcontributions' => 'ApiFeedContributions',
        'feedrecentchanges' => 'ApiFeedRecentChanges',
        'feedwatchlist' => 'ApiFeedWatchlist',
        'help' => 'ApiHelp',
        'paraminfo' => 'ApiParamInfo',
        'rsd' => 'ApiRsd',
        'compare' => 'ApiComparePages',
        'tokens' => 'ApiTokens',
        'checktoken' => 'ApiCheckToken',
        'cspreport' => 'ApiCSPReport',

        // Write modules
        'purge' => 'ApiPurge',
        'setnotificationtimestamp' => 'ApiSetNotificationTimestamp',
        'rollback' => 'ApiRollback',
        'delete' => 'ApiDelete',
        'undelete' => 'ApiUndelete',
        'protect' => 'ApiProtect',
        'block' => 'ApiBlock',
        'unblock' => 'ApiUnblock',
        'move' => 'ApiMove',
        'edit' => 'ApiEditPage',
        'upload' => 'ApiUpload',
        'filerevert' => 'ApiFileRevert',
        'emailuser' => 'ApiEmailUser',
        'watch' => 'ApiWatch',
        'patrol' => 'ApiPatrol',
        'import' => 'ApiImport',
        'clearhasmsg' => 'ApiClearHasMsg',
        'userrights' => 'ApiUserrights',
        'options' => 'ApiOptions',
        'imagerotate' => 'ApiImageRotate',
        'revisiondelete' => 'ApiRevisionDelete',
        'managetags' => 'ApiManageTags',
        'tag' => 'ApiTag',
        'mergehistory' => 'ApiMergeHistory',
    ];

    private static $Formats = [
        'json' => 'ApiFormatJson',
        'jsonfm' => 'ApiFormatJson',
        'php' => 'ApiFormatPhp',
        'phpfm' => 'ApiFormatPhp',
        'xml' => 'ApiFormatXml',
        'xmlfm' => 'ApiFormatXml',
        'rawfm' => 'ApiFormatJson',
        'none' => 'ApiFormatNone',
    ];

    // @codingStandardsIgnoreStart String contenation on "msg" not allowed to break long line
    private static $mRights = [
        'writeapi' => [
            'msg' => 'right-writeapi',
            'params' => []
        ],
        'apihighlimits' => [
            'msg' => 'api-help-right-apihighlimits',
            'params' => [ ApiBase::LIMIT_SML2, ApiBase::LIMIT_BIG2 ]
        ]
    ];
    // @codingStandardsIgnoreEnd

    private $mPrinter;

    private $mModuleMgr, $mResult, $mErrorFormatter;
    private $mContinuationManager;
    private $mAction;
    private $mEnableWrite;
    private $mInternalMode, $mSquidMaxage;
    private $mModule;

    private $mCacheMode = 'private';
    private $mCacheControl = [];
    private $mParamsUsed = [];
    private $mParamsSensitive = [];

    private $lacksSameOriginSecurity = null;

    public function __construct( $context = null, $enableWrite = false ) {
        if ( $context === null ) {
            $context = RequestContext::getMain();
        } elseif ( $context instanceof WebRequest ) {
            // BC for pre-1.19
            $request = $context;
            $context = RequestContext::getMain();
        }
        // We set a derivative context so we can change stuff later
        $this->setContext( new DerivativeContext( $context ) );

        if ( isset( $request ) ) {
            $this->getContext()->setRequest( $request );
        } else {
            $request = $this->getRequest();
        }

        $this->mInternalMode = ( $request instanceof FauxRequest );

        // Special handling for the main module: $parent === $this
        parent::__construct( $this, $this->mInternalMode ? 'main_int' : 'main' );

        $config = $this->getConfig();

        if ( !$this->mInternalMode ) {
            // Log if a request with a non-whitelisted Origin header is seen
            // with session cookies.
            $originHeader = $request->getHeader( 'Origin' );
            if ( $originHeader === false ) {
                $origins = [];
            } else {
                $originHeader = trim( $originHeader );
                $origins = preg_split( '/\s+/', $originHeader );
            }
            $sessionCookies = array_intersect(
                array_keys( $_COOKIE ),
                MediaWiki\Session\SessionManager::singleton()->getVaryCookies()
            );
            if ( $origins && $sessionCookies && (
                count( $origins ) !== 1 || !self::matchOrigin(
                    $origins[0],
                    $config->get( 'CrossSiteAJAXdomains' ),
                    $config->get( 'CrossSiteAJAXdomainExceptions' )
                )
            ) ) {
                LoggerFactory::getInstance( 'cors' )->warning(
                    'Non-whitelisted CORS request with session cookies', [
                        'origin' => $originHeader,
                        'cookies' => $sessionCookies,
                        'ip' => $request->getIP(),
                        'userAgent' => $this->getUserAgent(),
                        'wiki' => wfWikiID(),
                    ]
                );
            }

            // If we're in a mode that breaks the same-origin policy, strip
            // user credentials for security.
            if ( $this->lacksSameOriginSecurity() ) {
                global $wgUser;
                wfDebug( "API: stripping user credentials when the same-origin policy is not applied\n" );
                $wgUser = new User();
                $this->getContext()->setUser( $wgUser );
            }
        }

        $uselang = $this->getParameter( 'uselang' );
        if ( $uselang === 'user' ) {
            // Assume the parent context is going to return the user language
            // for uselang=user (see T85635).
        } else {
            if ( $uselang === 'content' ) {
                global $wgContLang;
                $uselang = $wgContLang->getCode();
            }
            $code = RequestContext::sanitizeLangCode( $uselang );
            $this->getContext()->setLanguage( $code );
            if ( !$this->mInternalMode ) {
                global $wgLang;
                $wgLang = $this->getContext()->getLanguage();
                RequestContext::getMain()->setLanguage( $wgLang );
            }
        }

        $this->mModuleMgr = new ApiModuleManager( $this );
        $this->mModuleMgr->addModules( self::$Modules, 'action' );
        $this->mModuleMgr->addModules( $config->get( 'APIModules' ), 'action' );
        $this->mModuleMgr->addModules( self::$Formats, 'format' );
        $this->mModuleMgr->addModules( $config->get( 'APIFormatModules' ), 'format' );

        Hooks::run( 'ApiMain::moduleManager', [ $this->mModuleMgr ] );

        $this->mResult = new ApiResult( $this->getConfig()->get( 'APIMaxResultSize' ) );
        $this->mErrorFormatter = new ApiErrorFormatter_BackCompat( $this->mResult );
        $this->mResult->setErrorFormatter( $this->mErrorFormatter );
        $this->mContinuationManager = null;
        $this->mEnableWrite = $enableWrite;

        $this->mSquidMaxage = -1; // flag for executeActionWithErrorHandling()
        $this->mCommit = false;
    }

    public function isInternalMode() {
        return $this->mInternalMode;
    }

    public function getResult() {
        return $this->mResult;
    }

    public function lacksSameOriginSecurity() {
        if ( $this->lacksSameOriginSecurity !== null ) {
            return $this->lacksSameOriginSecurity;
        }

        $request = $this->getRequest();

        // JSONP mode
        if ( $request->getVal( 'callback' ) !== null ) {
            $this->lacksSameOriginSecurity = true;
            return true;
        }

        // Anonymous CORS
        if ( $request->getVal( 'origin' ) === '*' ) {
            $this->lacksSameOriginSecurity = true;
            return true;
        }

        // Header to be used from XMLHTTPRequest when the request might
        // otherwise be used for XSS.
        if ( $request->getHeader( 'Treat-as-Untrusted' ) !== false ) {
            $this->lacksSameOriginSecurity = true;
            return true;
        }

        // Allow extensions to override.
        $this->lacksSameOriginSecurity = !Hooks::run( 'RequestHasSameOriginSecurity', [ $request ] );
        return $this->lacksSameOriginSecurity;
    }

    public function getErrorFormatter() {
        return $this->mErrorFormatter;
    }

    public function getContinuationManager() {
        return $this->mContinuationManager;
    }

    public function setContinuationManager( $manager ) {
        if ( $manager !== null ) {
            if ( !$manager instanceof ApiContinuationManager ) {
                throw new InvalidArgumentException( __METHOD__ . ': Was passed ' .
                    is_object( $manager ) ? get_class( $manager ) : gettype( $manager )
                );
            }
            if ( $this->mContinuationManager !== null ) {
                throw new UnexpectedValueException(
                    __METHOD__ . ': tried to set manager from ' . $manager->getSource() .
                    ' when a manager is already set from ' . $this->mContinuationManager->getSource()
                );
            }
        }
        $this->mContinuationManager = $manager;
    }

    public function getModule() {
        return $this->mModule;
    }

    public function getPrinter() {
        return $this->mPrinter;
    }

    public function setCacheMaxAge( $maxage ) {
        $this->setCacheControl( [
            'max-age' => $maxage,
            's-maxage' => $maxage
        ] );
    }

    public function setCacheMode( $mode ) {
        if ( !in_array( $mode, [ 'private', 'public', 'anon-public-user-private' ] ) ) {
            wfDebug( __METHOD__ . ": unrecognised cache mode \"$mode\"\n" );

            // Ignore for forwards-compatibility
            return;
        }

        if ( !User::isEveryoneAllowed( 'read' ) ) {
            // Private wiki, only private headers
            if ( $mode !== 'private' ) {
                wfDebug( __METHOD__ . ": ignoring request for $mode cache mode, private wiki\n" );

                return;
            }
        }

        if ( $mode === 'public' && $this->getParameter( 'uselang' ) === 'user' ) {
            // User language is used for i18n, so we don't want to publicly
            // cache. Anons are ok, because if they have non-default language
            // then there's an appropriate Vary header set by whatever set
            // their non-default language.
            wfDebug( __METHOD__ . ": downgrading cache mode 'public' to " .
                "'anon-public-user-private' due to uselang=user\n" );
            $mode = 'anon-public-user-private';
        }

        wfDebug( __METHOD__ . ": setting cache mode $mode\n" );
        $this->mCacheMode = $mode;
    }

    public function setCacheControl( $directives ) {
        $this->mCacheControl = $directives + $this->mCacheControl;
    }

    public function createPrinterByName( $format ) {
        $printer = $this->mModuleMgr->getModule( $format, 'format' );
        if ( $printer === null ) {
            $this->dieUsage( "Unrecognized format: {$format}", 'unknown_format' );
        }

        return $printer;
    }

    public function execute() {
        if ( $this->mInternalMode ) {
            $this->executeAction();
        } else {
            $this->executeActionWithErrorHandling();
        }
    }

    protected function executeActionWithErrorHandling() {
        // Verify the CORS header before executing the action
        if ( !$this->handleCORS() ) {
            // handleCORS() has sent a 403, abort
            return;
        }

        // Exit here if the request method was OPTIONS
        // (assume there will be a followup GET or POST)
        if ( $this->getRequest()->getMethod() === 'OPTIONS' ) {
            return;
        }

        // In case an error occurs during data output,
        // clear the output buffer and print just the error information
        $obLevel = ob_get_level();
        ob_start();

        $t = microtime( true );
        $isError = false;
        try {
            $this->executeAction();
            $runTime = microtime( true ) - $t;
            $this->logRequest( $runTime );
            if ( $this->mModule->isWriteMode() && $this->getRequest()->wasPosted() ) {
                $this->getStats()->timing(
                    'api.' . $this->mModule->getModuleName() . '.executeTiming', 1000 * $runTime
                );
            }
        } catch ( Exception $e ) {
            $this->handleException( $e );
            $this->logRequest( microtime( true ) - $t, $e );
            $isError = true;
        }

        // Commit DBs and send any related cookies and headers
        MediaWiki::preOutputCommit( $this->getContext() );

        // Send cache headers after any code which might generate an error, to
        // avoid sending public cache headers for errors.
        $this->sendCacheHeaders( $isError );

        // Executing the action might have already messed with the output
        // buffers.
        while ( ob_get_level() > $obLevel ) {
            ob_end_flush();
        }
    }

    protected function handleException( Exception $e ) {
        // Bug 63145: Rollback any open database transactions
        if ( !( $e instanceof UsageException ) ) {
            // UsageExceptions are intentional, so don't rollback if that's the case
            try {
                MWExceptionHandler::rollbackMasterChangesAndLog( $e );
            } catch ( DBError $e2 ) {
                // Rollback threw an exception too. Log it, but don't interrupt
                // our regularly scheduled exception handling.
                MWExceptionHandler::logException( $e2 );
            }
        }

        // Allow extra cleanup and logging
        Hooks::run( 'ApiMain::onException', [ $this, $e ] );

        // Log it
        if ( !( $e instanceof UsageException ) ) {
            MWExceptionHandler::logException( $e );
        }

        // Handle any kind of exception by outputting properly formatted error message.
        // If this fails, an unhandled exception should be thrown so that global error
        // handler will process and log it.

        $errCode = $this->substituteResultWithError( $e );

        // Error results should not be cached
        $this->setCacheMode( 'private' );

        $response = $this->getRequest()->response();
        $headerStr = 'MediaWiki-API-Error: ' . $errCode;
        if ( $e->getCode() === 0 ) {
            $response->header( $headerStr );
        } else {
            $response->header( $headerStr, true, $e->getCode() );
        }

        // Reset and print just the error message
        ob_clean();

        // Printer may not be initialized if the extractRequestParams() fails for the main module
        $this->createErrorPrinter();

        try {
            $this->printResult( true );
        } catch ( UsageException $ex ) {
            // The error printer itself is failing. Try suppressing its request
            // parameters and redo.
            $this->setWarning(
                'Error printer failed (will retry without params): ' . $ex->getMessage()
            );
            $this->mPrinter = null;
            $this->createErrorPrinter();
            $this->mPrinter->forceDefaultParams();
            $this->printResult( true );
        }
    }

    public static function handleApiBeforeMainException( Exception $e ) {
        ob_start();

        try {
            $main = new self( RequestContext::getMain(), false );
            $main->handleException( $e );
            $main->logRequest( 0, $e );
        } catch ( Exception $e2 ) {
            // Nope, even that didn't work. Punt.
            throw $e;
        }

        // Reset cache headers
        $main->sendCacheHeaders( true );

        ob_end_flush();
    }

    protected function handleCORS() {
        $originParam = $this->getParameter( 'origin' ); // defaults to null
        if ( $originParam === null ) {
            // No origin parameter, nothing to do
            return true;
        }

        $request = $this->getRequest();
        $response = $request->response();

        $matchOrigin = false;
        $allowTiming = false;
        $varyOrigin = true;

        if ( $originParam === '*' ) {
            // Request for anonymous CORS
            $matchOrigin = true;
            $allowOrigin = '*';
            $allowCredentials = 'false';
            $varyOrigin = false; // No need to vary
        } else {
            // Non-anonymous CORS, check we allow the domain

            // Origin: header is a space-separated list of origins, check all of them
            $originHeader = $request->getHeader( 'Origin' );
            if ( $originHeader === false ) {
                $origins = [];
            } else {
                $originHeader = trim( $originHeader );
                $origins = preg_split( '/\s+/', $originHeader );
            }

            if ( !in_array( $originParam, $origins ) ) {
                // origin parameter set but incorrect
                // Send a 403 response
                $response->statusHeader( 403 );
                $response->header( 'Cache-Control: no-cache' );
                echo "'origin' parameter does not match Origin header\n";

                return false;
            }

            $config = $this->getConfig();
            $matchOrigin = count( $origins ) === 1 && self::matchOrigin(
                $originParam,
                $config->get( 'CrossSiteAJAXdomains' ),
                $config->get( 'CrossSiteAJAXdomainExceptions' )
            );

            $allowOrigin = $originHeader;
            $allowCredentials = 'true';
            $allowTiming = $originHeader;
        }

        if ( $matchOrigin ) {
            $requestedMethod = $request->getHeader( 'Access-Control-Request-Method' );
            $preflight = $request->getMethod() === 'OPTIONS' && $requestedMethod !== false;
            if ( $preflight ) {
                // This is a CORS preflight request
                if ( $requestedMethod !== 'POST' && $requestedMethod !== 'GET' ) {
                    // If method is not a case-sensitive match, do not set any additional headers and terminate.
                    return true;
                }
                // We allow the actual request to send the following headers
                $requestedHeaders = $request->getHeader( 'Access-Control-Request-Headers' );
                if ( $requestedHeaders !== false ) {
                    if ( !self::matchRequestedHeaders( $requestedHeaders ) ) {
                        return true;
                    }
                    $response->header( 'Access-Control-Allow-Headers: ' . $requestedHeaders );
                }

                // We only allow the actual request to be GET or POST
                $response->header( 'Access-Control-Allow-Methods: POST, GET' );
            }

            $response->header( "Access-Control-Allow-Origin: $allowOrigin" );
            $response->header( "Access-Control-Allow-Credentials: $allowCredentials" );
            // http://www.w3.org/TR/resource-timing/#timing-allow-origin
            if ( $allowTiming !== false ) {
                $response->header( "Timing-Allow-Origin: $allowTiming" );
            }

            if ( !$preflight ) {
                $response->header(
                    'Access-Control-Expose-Headers: MediaWiki-API-Error, Retry-After, X-Database-Lag'
                );
            }
        }

        if ( $varyOrigin ) {
            $this->getOutput()->addVaryHeader( 'Origin' );
        }

        return true;
    }

    protected static function matchOrigin( $value, $rules, $exceptions ) {
        foreach ( $rules as $rule ) {
            if ( preg_match( self::wildcardToRegex( $rule ), $value ) ) {
                // Rule matches, check exceptions
                foreach ( $exceptions as $exc ) {
                    if ( preg_match( self::wildcardToRegex( $exc ), $value ) ) {
                        return false;
                    }
                }

                return true;
            }
        }

        return false;
    }

    protected static function matchRequestedHeaders( $requestedHeaders ) {
        if ( trim( $requestedHeaders ) === '' ) {
            return true;
        }
        $requestedHeaders = explode( ',', $requestedHeaders );
        $allowedAuthorHeaders = array_flip( [
            /* simple headers (see spec) */
            'accept',
            'accept-language',
            'content-language',
            'content-type',
            /* non-authorable headers in XHR, which are however requested by some UAs */
            'accept-encoding',
            'dnt',
            'origin',
            /* MediaWiki whitelist */
            'api-user-agent',
        ] );
        foreach ( $requestedHeaders as $rHeader ) {
            $rHeader = strtolower( trim( $rHeader ) );
            if ( !isset( $allowedAuthorHeaders[$rHeader] ) ) {
                wfDebugLog( 'api', 'CORS preflight failed on requested header: ' . $rHeader );
                return false;
            }
        }
        return true;
    }

    protected static function wildcardToRegex( $wildcard ) {
        $wildcard = preg_quote( $wildcard, '/' );
        $wildcard = str_replace(
            [ '\*', '\?' ],
            [ '.*?', '.' ],
            $wildcard
        );

        return "/^https?:\/\/$wildcard$/";
    }

    protected function sendCacheHeaders( $isError ) {
        $response = $this->getRequest()->response();
        $out = $this->getOutput();

        $out->addVaryHeader( 'Treat-as-Untrusted' );

        $config = $this->getConfig();

        if ( $config->get( 'VaryOnXFP' ) ) {
            $out->addVaryHeader( 'X-Forwarded-Proto' );
        }

        if ( !$isError && $this->mModule &&
            ( $this->getRequest()->getMethod() === 'GET' || $this->getRequest()->getMethod() === 'HEAD' )
        ) {
            $etag = $this->mModule->getConditionalRequestData( 'etag' );
            if ( $etag !== null ) {
                $response->header( "ETag: $etag" );
            }
            $lastMod = $this->mModule->getConditionalRequestData( 'last-modified' );
            if ( $lastMod !== null ) {
                $response->header( 'Last-Modified: ' . wfTimestamp( TS_RFC2822, $lastMod ) );
            }
        }

        // The logic should be:
        // $this->mCacheControl['max-age'] is set?
        //    Use it, the module knows better than our guess.
        // !$this->mModule || $this->mModule->isWriteMode(), and mCacheMode is private?
        //    Use 0 because we can guess caching is probably the wrong thing to do.
        // Use $this->getParameter( 'maxage' ), which already defaults to 0.
        $maxage = 0;
        if ( isset( $this->mCacheControl['max-age'] ) ) {
            $maxage = $this->mCacheControl['max-age'];
        } elseif ( ( $this->mModule && !$this->mModule->isWriteMode() ) ||
            $this->mCacheMode !== 'private'
        ) {
            $maxage = $this->getParameter( 'maxage' );
        }
        $privateCache = 'private, must-revalidate, max-age=' . $maxage;

        if ( $this->mCacheMode == 'private' ) {
            $response->header( "Cache-Control: $privateCache" );
            return;
        }

        $useKeyHeader = $config->get( 'UseKeyHeader' );
        if ( $this->mCacheMode == 'anon-public-user-private' ) {
            $out->addVaryHeader( 'Cookie' );
            $response->header( $out->getVaryHeader() );
            if ( $useKeyHeader ) {
                $response->header( $out->getKeyHeader() );
                if ( $out->haveCacheVaryCookies() ) {
                    // Logged in, mark this request private
                    $response->header( "Cache-Control: $privateCache" );
                    return;
                }
                // Logged out, send normal public headers below
            } elseif ( MediaWiki\Session\SessionManager::getGlobalSession()->isPersistent() ) {
                // Logged in or otherwise has session (e.g. anonymous users who have edited)
                // Mark request private
                $response->header( "Cache-Control: $privateCache" );

                return;
            } // else no Key and anonymous, send public headers below
        }

        // Send public headers
        $response->header( $out->getVaryHeader() );
        if ( $useKeyHeader ) {
            $response->header( $out->getKeyHeader() );
        }

        // If nobody called setCacheMaxAge(), use the (s)maxage parameters
        if ( !isset( $this->mCacheControl['s-maxage'] ) ) {
            $this->mCacheControl['s-maxage'] = $this->getParameter( 'smaxage' );
        }
        if ( !isset( $this->mCacheControl['max-age'] ) ) {
            $this->mCacheControl['max-age'] = $this->getParameter( 'maxage' );
        }

        if ( !$this->mCacheControl['s-maxage'] && !$this->mCacheControl['max-age'] ) {
            // Public cache not requested
            // Sending a Vary header in this case is harmless, and protects us
            // against conditional calls of setCacheMaxAge().
            $response->header( "Cache-Control: $privateCache" );

            return;
        }

        $this->mCacheControl['public'] = true;

        // Send an Expires header
        $maxAge = min( $this->mCacheControl['s-maxage'], $this->mCacheControl['max-age'] );
        $expiryUnixTime = ( $maxAge == 0 ? 1 : time() + $maxAge );
        $response->header( 'Expires: ' . wfTimestamp( TS_RFC2822, $expiryUnixTime ) );

        // Construct the Cache-Control header
        $ccHeader = '';
        $separator = '';
        foreach ( $this->mCacheControl as $name => $value ) {
            if ( is_bool( $value ) ) {
                if ( $value ) {
                    $ccHeader .= $separator . $name;
                    $separator = ', ';
                }
            } else {
                $ccHeader .= $separator . "$name=$value";
                $separator = ', ';
            }
        }

        $response->header( "Cache-Control: $ccHeader" );
    }

    private function createErrorPrinter() {
        if ( !isset( $this->mPrinter ) ) {
            $value = $this->getRequest()->getVal( 'format', self::API_DEFAULT_FORMAT );
            if ( !$this->mModuleMgr->isDefined( $value, 'format' ) ) {
                $value = self::API_DEFAULT_FORMAT;
            }
            $this->mPrinter = $this->createPrinterByName( $value );
        }

        // Printer may not be able to handle errors. This is particularly
        // likely if the module returns something for getCustomPrinter().
        if ( !$this->mPrinter->canPrintErrors() ) {
            $this->mPrinter = $this->createPrinterByName( self::API_DEFAULT_FORMAT );
        }
    }

    protected function errorMessageFromException( $e ) {
        if ( $e instanceof UsageException ) {
            // User entered incorrect parameters - generate error response
            $errMessage = $e->getMessageArray();
        } else {
            $config = $this->getConfig();
            // Something is seriously wrong
            if ( ( $e instanceof DBQueryError ) && !$config->get( 'ShowSQLErrors' ) ) {
                $info = 'Database query error';
            } else {
                $info = "Exception Caught: {$e->getMessage()}";
            }

            $errMessage = [
                'code' => 'internal_api_error_' . get_class( $e ),
                'info' => '[' . WebRequest::getRequestId() . '] ' . $info,
            ];
        }
        return $errMessage;
    }

    protected function substituteResultWithError( $e ) {
        $result = $this->getResult();
        $config = $this->getConfig();

        $errMessage = $this->errorMessageFromException( $e );
        if ( $e instanceof UsageException ) {
            // User entered incorrect parameters - generate error response
            $link = wfExpandUrl( wfScript( 'api' ) );
            ApiResult::setContentValue( $errMessage, 'docref', "See $link for API usage" );
        } else {
            // Something is seriously wrong
            if ( $config->get( 'ShowExceptionDetails' ) ) {
                ApiResult::setContentValue(
                    $errMessage,
                    'trace',
                    MWExceptionHandler::getRedactedTraceAsString( $e )
                );
            }
        }

        // Remember all the warnings to re-add them later
        $warnings = $result->getResultData( [ 'warnings' ] );

        $result->reset();
        // Re-add the id
        $requestid = $this->getParameter( 'requestid' );
        if ( !is_null( $requestid ) ) {
            $result->addValue( null, 'requestid', $requestid, ApiResult::NO_SIZE_CHECK );
        }
        if ( $config->get( 'ShowHostnames' ) ) {
            // servedby is especially useful when debugging errors
            $result->addValue( null, 'servedby', wfHostname(), ApiResult::NO_SIZE_CHECK );
        }
        if ( $warnings !== null ) {
            $result->addValue( null, 'warnings', $warnings, ApiResult::NO_SIZE_CHECK );
        }

        $result->addValue( null, 'error', $errMessage, ApiResult::NO_SIZE_CHECK );

        return $errMessage['code'];
    }

    protected function setupExecuteAction() {
        // First add the id to the top element
        $result = $this->getResult();
        $requestid = $this->getParameter( 'requestid' );
        if ( !is_null( $requestid ) ) {
            $result->addValue( null, 'requestid', $requestid );
        }

        if ( $this->getConfig()->get( 'ShowHostnames' ) ) {
            $servedby = $this->getParameter( 'servedby' );
            if ( $servedby ) {
                $result->addValue( null, 'servedby', wfHostname() );
            }
        }

        if ( $this->getParameter( 'curtimestamp' ) ) {
            $result->addValue( null, 'curtimestamp', wfTimestamp( TS_ISO_8601, time() ),
                ApiResult::NO_SIZE_CHECK );
        }

        $params = $this->extractRequestParams();

        $this->mAction = $params['action'];

        if ( !is_string( $this->mAction ) ) {
            $this->dieUsage( 'The API requires a valid action parameter', 'unknown_action' );
        }

        return $params;
    }

    protected function setupModule() {
        // Instantiate the module requested by the user
        $module = $this->mModuleMgr->getModule( $this->mAction, 'action' );
        if ( $module === null ) {
            $this->dieUsage( 'The API requires a valid action parameter', 'unknown_action' );
        }
        $moduleParams = $module->extractRequestParams();

        // Check token, if necessary
        if ( $module->needsToken() === true ) {
            throw new MWException(
                "Module '{$module->getModuleName()}' must be updated for the new token handling. " .
                'See documentation for ApiBase::needsToken for details.'
            );
        }
        if ( $module->needsToken() ) {
            if ( !$module->mustBePosted() ) {
                throw new MWException(
                    "Module '{$module->getModuleName()}' must require POST to use tokens."
                );
            }

            if ( !isset( $moduleParams['token'] ) ) {
                $this->dieUsageMsg( [ 'missingparam', 'token' ] );
            }

            $module->requirePostedParameters( [ 'token' ] );

            if ( !$module->validateToken( $moduleParams['token'], $moduleParams ) ) {
                $this->dieUsageMsg( 'sessionfailure' );
            }
        }

        return $module;
    }

    protected function checkMaxLag( $module, $params ) {
        if ( $module->shouldCheckMaxlag() && isset( $params['maxlag'] ) ) {
            $maxLag = $params['maxlag'];
            list( $host, $lag ) = wfGetLB()->getMaxLag();
            if ( $lag > $maxLag ) {
                $response = $this->getRequest()->response();

                $response->header( 'Retry-After: ' . max( intval( $maxLag ), 5 ) );
                $response->header( 'X-Database-Lag: ' . intval( $lag ) );

                if ( $this->getConfig()->get( 'ShowHostnames' ) ) {
                    $this->dieUsage( "Waiting for $host: $lag seconds lagged", 'maxlag' );
                }

                $this->dieUsage( "Waiting for a database server: $lag seconds lagged", 'maxlag' );
            }
        }

        return true;
    }

    protected function checkConditionalRequestHeaders( $module ) {
        if ( $this->mInternalMode ) {
            // No headers to check in internal mode
            return true;
        }

        if ( $this->getRequest()->getMethod() !== 'GET' && $this->getRequest()->getMethod() !== 'HEAD' ) {
            // Don't check POSTs
            return true;
        }

        $return304 = false;

        $ifNoneMatch = array_diff(
            $this->getRequest()->getHeader( 'If-None-Match', WebRequest::GETHEADER_LIST ) ?: [],
            [ '' ]
        );
        if ( $ifNoneMatch ) {
            if ( $ifNoneMatch === [ '*' ] ) {
                // API responses always "exist"
                $etag = '*';
            } else {
                $etag = $module->getConditionalRequestData( 'etag' );
            }
        }
        if ( $ifNoneMatch && $etag !== null ) {
            $test = substr( $etag, 0, 2 ) === 'W/' ? substr( $etag, 2 ) : $etag;
            $match = array_map( function ( $s ) {
                return substr( $s, 0, 2 ) === 'W/' ? substr( $s, 2 ) : $s;
            }, $ifNoneMatch );
            $return304 = in_array( $test, $match, true );
        } else {
            $value = trim( $this->getRequest()->getHeader( 'If-Modified-Since' ) );

            // Some old browsers sends sizes after the date, like this:
            //  Wed, 20 Aug 2003 06:51:19 GMT; length=5202
            // Ignore that.
            $i = strpos( $value, ';' );
            if ( $i !== false ) {
                $value = trim( substr( $value, 0, $i ) );
            }

            if ( $value !== '' ) {
                try {
                    $ts = new MWTimestamp( $value );
                    if (
                        // RFC 7231 IMF-fixdate
                        $ts->getTimestamp( TS_RFC2822 ) === $value ||
                        // RFC 850
                        $ts->format( 'l, d-M-y H:i:s' ) . ' GMT' === $value ||
                        // asctime (with and without space-padded day)
                        $ts->format( 'D M j H:i:s Y' ) === $value ||
                        $ts->format( 'D M  j H:i:s Y' ) === $value
                    ) {
                        $lastMod = $module->getConditionalRequestData( 'last-modified' );
                        if ( $lastMod !== null ) {
                            // Mix in some MediaWiki modification times
                            $modifiedTimes = [
                                'page' => $lastMod,
                                'user' => $this->getUser()->getTouched(),
                                'epoch' => $this->getConfig()->get( 'CacheEpoch' ),
                            ];
                            if ( $this->getConfig()->get( 'UseSquid' ) ) {
                                // T46570: the core page itself may not change, but resources might
                                $modifiedTimes['sepoch'] = wfTimestamp(
                                    TS_MW, time() - $this->getConfig()->get( 'SquidMaxage' )
                                );
                            }
                            Hooks::run( 'OutputPageCheckLastModified', [ &$modifiedTimes, $this->getOutput() ] );
                            $lastMod = max( $modifiedTimes );
                            $return304 = wfTimestamp( TS_MW, $lastMod ) <= $ts->getTimestamp( TS_MW );
                        }
                    }
                } catch ( TimestampException $e ) {
                    // Invalid timestamp, ignore it
                }
            }
        }

        if ( $return304 ) {
            $this->getRequest()->response()->statusHeader( 304 );

            // Avoid outputting the compressed representation of a zero-length body
            MediaWiki\suppressWarnings();
            ini_set( 'zlib.output_compression', 0 );
            MediaWiki\restoreWarnings();
            wfClearOutputBuffers();

            return false;
        }

        return true;
    }

    protected function checkExecutePermissions( $module ) {
        $user = $this->getUser();
        if ( $module->isReadMode() && !User::isEveryoneAllowed( 'read' ) &&
            !$user->isAllowed( 'read' )
        ) {
            $this->dieUsageMsg( 'readrequired' );
        }

        if ( $module->isWriteMode() ) {
            if ( !$this->mEnableWrite ) {
                $this->dieUsageMsg( 'writedisabled' );
            } elseif ( !$user->isAllowed( 'writeapi' ) ) {
                $this->dieUsageMsg( 'writerequired' );
            } elseif ( $this->getRequest()->getHeader( 'Promise-Non-Write-API-Action' ) ) {
                $this->dieUsage(
                    'Promise-Non-Write-API-Action HTTP header cannot be sent to write API modules',
                    'promised-nonwrite-api'
                );
            }

            $this->checkReadOnly( $module );
        }

        // Allow extensions to stop execution for arbitrary reasons.
        $message = false;
        if ( !Hooks::run( 'ApiCheckCanExecute', [ $module, $user, &$message ] ) ) {
            $this->dieUsageMsg( $message );
        }
    }

    protected function checkReadOnly( $module ) {
        if ( wfReadOnly() ) {
            $this->dieReadOnly();
        }

        if ( $module->isWriteMode()
            && $this->getUser()->isBot()
            && wfGetLB()->getServerCount() > 1
        ) {
            $this->checkBotReadOnly();
        }
    }

    private function checkBotReadOnly() {
        // Figure out how many servers have passed the lag threshold
        $numLagged = 0;
        $lagLimit = $this->getConfig()->get( 'APIMaxLagThreshold' );
        $laggedServers = [];
        $loadBalancer = wfGetLB();
        foreach ( $loadBalancer->getLagTimes() as $serverIndex => $lag ) {
            if ( $lag > $lagLimit ) {
                ++$numLagged;
                $laggedServers[] = $loadBalancer->getServerName( $serverIndex ) . " ({$lag}s)";
            }
        }

        // If a majority of replica DBs are too lagged then disallow writes
        $replicaCount = wfGetLB()->getServerCount() - 1;
        if ( $numLagged >= ceil( $replicaCount / 2 ) ) {
            $laggedServers = implode( ', ', $laggedServers );
            wfDebugLog(
                'api-readonly',
                "Api request failed as read only because the following DBs are lagged: $laggedServers"
            );

            $parsed = $this->parseMsg( [ 'readonlytext' ] );
            $this->dieUsage(
                $parsed['info'],
                $parsed['code'],
                /* http error */
                0,
                [ 'readonlyreason' => "Waiting for $numLagged lagged database(s)" ]
            );
        }
    }

    protected function checkAsserts( $params ) {
        if ( isset( $params['assert'] ) ) {
            $user = $this->getUser();
            switch ( $params['assert'] ) {
                case 'user':
                    if ( $user->isAnon() ) {
                        $this->dieUsage( 'Assertion that the user is logged in failed', 'assertuserfailed' );
                    }
                    break;
                case 'bot':
                    if ( !$user->isAllowed( 'bot' ) ) {
                        $this->dieUsage( 'Assertion that the user has the bot right failed', 'assertbotfailed' );
                    }
                    break;
            }
        }
        if ( isset( $params['assertuser'] ) ) {
            $assertUser = User::newFromName( $params['assertuser'], false );
            if ( !$assertUser || !$this->getUser()->equals( $assertUser ) ) {
                $this->dieUsage(
                    'Assertion that the user is "' . $params['assertuser'] . '" failed',
                    'assertnameduserfailed'
                );
            }
        }
    }

    protected function setupExternalResponse( $module, $params ) {
        $request = $this->getRequest();
        if ( !$request->wasPosted() && $module->mustBePosted() ) {
            // Module requires POST. GET request might still be allowed
            // if $wgDebugApi is true, otherwise fail.
            $this->dieUsageMsgOrDebug( [ 'mustbeposted', $this->mAction ] );
        }

        // See if custom printer is used
        $this->mPrinter = $module->getCustomPrinter();
        if ( is_null( $this->mPrinter ) ) {
            // Create an appropriate printer
            $this->mPrinter = $this->createPrinterByName( $params['format'] );
        }

        if ( $request->getProtocol() === 'http' && (
            $request->getSession()->shouldForceHTTPS() ||
            ( $this->getUser()->isLoggedIn() &&
                $this->getUser()->requiresHTTPS() )
        ) ) {
            $this->logFeatureUsage( 'https-expected' );
            $this->setWarning( 'HTTP used when HTTPS was expected' );
        }
    }

    protected function executeAction() {
        $params = $this->setupExecuteAction();
        $module = $this->setupModule();
        $this->mModule = $module;

        if ( !$this->mInternalMode ) {
            $this->setRequestExpectations( $module );
        }

        $this->checkExecutePermissions( $module );

        if ( !$this->checkMaxLag( $module, $params ) ) {
            return;
        }

        if ( !$this->checkConditionalRequestHeaders( $module ) ) {
            return;
        }

        if ( !$this->mInternalMode ) {
            $this->setupExternalResponse( $module, $params );
        }

        $this->checkAsserts( $params );

        // Execute
        $module->execute();
        Hooks::run( 'APIAfterExecute', [ &$module ] );

        $this->reportUnusedParams();

        if ( !$this->mInternalMode ) {
            // append Debug information
            MWDebug::appendDebugInfoToApiResult( $this->getContext(), $this->getResult() );

            // Print result data
            $this->printResult( false );
        }
    }

    protected function setRequestExpectations( ApiBase $module ) {
        $limits = $this->getConfig()->get( 'TrxProfilerLimits' );
        $trxProfiler = Profiler::instance()->getTransactionProfiler();
        $trxProfiler->setLogger( LoggerFactory::getInstance( 'DBPerformance' ) );
        if ( $this->getRequest()->hasSafeMethod() ) {
            $trxProfiler->setExpectations( $limits['GET'], __METHOD__ );
        } elseif ( $this->getRequest()->wasPosted() && !$module->isWriteMode() ) {
            $trxProfiler->setExpectations( $limits['POST-nonwrite'], __METHOD__ );
            $this->getRequest()->markAsSafeRequest();
        } else {
            $trxProfiler->setExpectations( $limits['POST'], __METHOD__ );
        }
    }

    protected function logRequest( $time, $e = null ) {
        $request = $this->getRequest();
        $logCtx = [
            'ts' => time(),
            'ip' => $request->getIP(),
            'userAgent' => $this->getUserAgent(),
            'wiki' => wfWikiID(),
            'timeSpentBackend' => (int) round( $time * 1000 ),
            'hadError' => $e !== null,
            'errorCodes' => [],
            'params' => [],
        ];

        if ( $e ) {
            $logCtx['errorCodes'][] = $this->errorMessageFromException( $e )['code'];
        }

        // Construct space separated message for 'api' log channel
        $msg = "API {$request->getMethod()} " .
            wfUrlencode( str_replace( ' ', '_', $this->getUser()->getName() ) ) .
            " {$logCtx['ip']} " .
            "T={$logCtx['timeSpentBackend']}ms";

        $sensitive = array_flip( $this->getSensitiveParams() );
        foreach ( $this->getParamsUsed() as $name ) {
            $value = $request->getVal( $name );
            if ( $value === null ) {
                continue;
            }

            if ( isset( $sensitive[$name] ) ) {
                $value = '[redacted]';
                $encValue = '[redacted]';
            } elseif ( strlen( $value ) > 256 ) {
                $value = substr( $value, 0, 256 );
                $encValue = $this->encodeRequestLogValue( $value ) . '[...]';
            } else {
                $encValue = $this->encodeRequestLogValue( $value );
            }

            $logCtx['params'][$name] = $value;
            $msg .= " {$name}={$encValue}";
        }

        wfDebugLog( 'api', $msg, 'private' );
        // ApiAction channel is for structured data consumers
        wfDebugLog( 'ApiAction', '', 'private', $logCtx );
    }

    protected function encodeRequestLogValue( $s ) {
        static $table;
        if ( !$table ) {
            $chars = ';@$!*(),/:';
            $numChars = strlen( $chars );
            for ( $i = 0; $i < $numChars; $i++ ) {
                $table[rawurlencode( $chars[$i] )] = $chars[$i];
            }
        }

        return strtr( rawurlencode( $s ), $table );
    }

    protected function getParamsUsed() {
        return array_keys( $this->mParamsUsed );
    }

    public function markParamsUsed( $params ) {
        $this->mParamsUsed += array_fill_keys( (array)$params, true );
    }

    protected function getSensitiveParams() {
        return array_keys( $this->mParamsSensitive );
    }

    public function markParamsSensitive( $params ) {
        $this->mParamsSensitive += array_fill_keys( (array)$params, true );
    }

    public function getVal( $name, $default = null ) {
        $this->mParamsUsed[$name] = true;

        $ret = $this->getRequest()->getVal( $name );
        if ( $ret === null ) {
            if ( $this->getRequest()->getArray( $name ) !== null ) {
                // See bug 10262 for why we don't just implode( '|', ... ) the
                // array.
                $this->setWarning(
                    "Parameter '$name' uses unsupported PHP array syntax"
                );
            }
            $ret = $default;
        }
        return $ret;
    }

    public function getCheck( $name ) {
        return $this->getVal( $name, null ) !== null;
    }

    public function getUpload( $name ) {
        $this->mParamsUsed[$name] = true;

        return $this->getRequest()->getUpload( $name );
    }

    protected function reportUnusedParams() {
        $paramsUsed = $this->getParamsUsed();
        $allParams = $this->getRequest()->getValueNames();

        if ( !$this->mInternalMode ) {
            // Printer has not yet executed; don't warn that its parameters are unused
            $printerParams = array_map(
                [ $this->mPrinter, 'encodeParamName' ],
                array_keys( $this->mPrinter->getFinalParams() ?: [] )
            );
            $unusedParams = array_diff( $allParams, $paramsUsed, $printerParams );
        } else {
            $unusedParams = array_diff( $allParams, $paramsUsed );
        }

        if ( count( $unusedParams ) ) {
            $s = count( $unusedParams ) > 1 ? 's' : '';
            $this->setWarning( "Unrecognized parameter$s: '" . implode( $unusedParams, "', '" ) . "'" );
        }
    }

    protected function printResult( $isError ) {
        if ( $this->getConfig()->get( 'DebugAPI' ) !== false ) {
            $this->setWarning( 'SECURITY WARNING: $wgDebugAPI is enabled' );
        }

        $printer = $this->mPrinter;
        $printer->initPrinter( false );
        $printer->execute();
        $printer->closePrinter();
    }

    public function isReadMode() {
        return false;
    }

    public function getAllowedParams() {
        return [
            'action' => [
                ApiBase::PARAM_DFLT => 'help',
                ApiBase::PARAM_TYPE => 'submodule',
            ],
            'format' => [
                ApiBase::PARAM_DFLT => ApiMain::API_DEFAULT_FORMAT,
                ApiBase::PARAM_TYPE => 'submodule',
            ],
            'maxlag' => [
                ApiBase::PARAM_TYPE => 'integer'
            ],
            'smaxage' => [
                ApiBase::PARAM_TYPE => 'integer',
                ApiBase::PARAM_DFLT => 0
            ],
            'maxage' => [
                ApiBase::PARAM_TYPE => 'integer',
                ApiBase::PARAM_DFLT => 0
            ],
            'assert' => [
                ApiBase::PARAM_TYPE => [ 'user', 'bot' ]
            ],
            'assertuser' => [
                ApiBase::PARAM_TYPE => 'user',
            ],
            'requestid' => null,
            'servedby' => false,
            'curtimestamp' => false,
            'origin' => null,
            'uselang' => [
                ApiBase::PARAM_DFLT => 'user',
            ],
        ];
    }

    protected function getExamplesMessages() {
        return [
            'action=help'
                => 'apihelp-help-example-main',
            'action=help&recursivesubmodules=1'
                => 'apihelp-help-example-recursive',
        ];
    }

    public function modifyHelp( array &$help, array $options, array &$tocData ) {
        // Wish PHP had an "array_insert_before". Instead, we have to manually
        // reindex the array to get 'permissions' in the right place.
        $oldHelp = $help;
        $help = [];
        foreach ( $oldHelp as $k => $v ) {
            if ( $k === 'submodules' ) {
                $help['permissions'] = '';
            }
            $help[$k] = $v;
        }
        $help['datatypes'] = '';
        $help['credits'] = '';

        // Fill 'permissions'
        $help['permissions'] .= Html::openElement( 'div',
            [ 'class' => 'apihelp-block apihelp-permissions' ] );
        $m = $this->msg( 'api-help-permissions' );
        if ( !$m->isDisabled() ) {
            $help['permissions'] .= Html::rawElement( 'div', [ 'class' => 'apihelp-block-head' ],
                $m->numParams( count( self::$mRights ) )->parse()
            );
        }
        $help['permissions'] .= Html::openElement( 'dl' );
        foreach ( self::$mRights as $right => $rightMsg ) {
            $help['permissions'] .= Html::element( 'dt', null, $right );

            $rightMsg = $this->msg( $rightMsg['msg'], $rightMsg['params'] )->parse();
            $help['permissions'] .= Html::rawElement( 'dd', null, $rightMsg );

            $groups = array_map( function ( $group ) {
                return $group == '*' ? 'all' : $group;
            }, User::getGroupsWithPermission( $right ) );

            $help['permissions'] .= Html::rawElement( 'dd', null,
                $this->msg( 'api-help-permissions-granted-to' )
                    ->numParams( count( $groups ) )
                    ->params( $this->getLanguage()->commaList( $groups ) )
                    ->parse()
            );
        }
        $help['permissions'] .= Html::closeElement( 'dl' );
        $help['permissions'] .= Html::closeElement( 'div' );

        // Fill 'datatypes' and 'credits', if applicable
        if ( empty( $options['nolead'] ) ) {
            $level = $options['headerlevel'];
            $tocnumber = &$options['tocnumber'];

            $header = $this->msg( 'api-help-datatypes-header' )->parse();

            // Add an additional span with sanitized ID
            if ( !$this->getConfig()->get( 'ExperimentalHtmlIds' ) ) {
                $header = Html::element( 'span', [ 'id' => Sanitizer::escapeId( 'main/datatypes' ) ] ) .
                    $header;
            }
            $help['datatypes'] .= Html::rawElement( 'h' . min( 6, $level ),
                [ 'id' => 'main/datatypes', 'class' => 'apihelp-header' ],
                $header
            );
            $help['datatypes'] .= $this->msg( 'api-help-datatypes' )->parseAsBlock();
            if ( !isset( $tocData['main/datatypes'] ) ) {
                $tocnumber[$level]++;
                $tocData['main/datatypes'] = [
                    'toclevel' => count( $tocnumber ),
                    'level' => $level,
                    'anchor' => 'main/datatypes',
                    'line' => $header,
                    'number' => implode( '.', $tocnumber ),
                    'index' => false,
                ];
            }

            // Add an additional span with sanitized ID
            if ( !$this->getConfig()->get( 'ExperimentalHtmlIds' ) ) {
                $header = Html::element( 'span', [ 'id' => Sanitizer::escapeId( 'main/credits' ) ] ) .
                    $header;
            }
            $header = $this->msg( 'api-credits-header' )->parse();
            $help['credits'] .= Html::rawElement( 'h' . min( 6, $level ),
                [ 'id' => 'main/credits', 'class' => 'apihelp-header' ],
                $header
            );
            $help['credits'] .= $this->msg( 'api-credits' )->useDatabase( false )->parseAsBlock();
            if ( !isset( $tocData['main/credits'] ) ) {
                $tocnumber[$level]++;
                $tocData['main/credits'] = [
                    'toclevel' => count( $tocnumber ),
                    'level' => $level,
                    'anchor' => 'main/credits',
                    'line' => $header,
                    'number' => implode( '.', $tocnumber ),
                    'index' => false,
                ];
            }
        }
    }

    private $mCanApiHighLimits = null;

    public function canApiHighLimits() {
        if ( !isset( $this->mCanApiHighLimits ) ) {
            $this->mCanApiHighLimits = $this->getUser()->isAllowed( 'apihighlimits' );
        }

        return $this->mCanApiHighLimits;
    }

    public function getModuleManager() {
        return $this->mModuleMgr;
    }

    public function getUserAgent() {
        return trim(
            $this->getRequest()->getHeader( 'Api-user-agent' ) . ' ' .
            $this->getRequest()->getHeader( 'User-agent' )
        );
    }
}

class UsageException extends MWException {

    private $mCodestr;

    private $mExtraData;

    public function __construct( $message, $codestr, $code = 0, $extradata = null ) {
        parent::__construct( $message, $code );
        $this->mCodestr = $codestr;
        $this->mExtraData = $extradata;

        // This should never happen, so throw an exception about it that will
        // hopefully get logged with a backtrace (T138585)
        if ( !is_string( $codestr ) || $codestr === '' ) {
            throw new InvalidArgumentException( 'Invalid $codestr, was ' .
                ( $codestr === '' ? 'empty string' : gettype( $codestr ) )
            );
        }
    }

    public function getCodeString() {
        return $this->mCodestr;
    }

    public function getMessageArray() {
        $result = [
            'code' => $this->mCodestr,
            'info' => $this->getMessage()
        ];
        if ( is_array( $this->mExtraData ) ) {
            $result = array_merge( $result, $this->mExtraData );
        }

        return $result;
    }

    public function __toString() {
        return "{$this->getCodeString()}: {$this->getMessage()}";
    }
}