API: Remove deprecated response values from action=login

[mediawiki.git] / includes / specialpage / AuthManagerSpecialPage.php

<?php

use MediaWiki\Auth\AuthenticationRequest;
use MediaWiki\Auth\AuthenticationResponse;
use MediaWiki\Auth\AuthManager;
use MediaWiki\Logger\LoggerFactory;
use MediaWiki\Session\Token;

/**
 * A special page subclass for authentication-related special pages. It generates a form from
 * a set of AuthenticationRequest objects, submits the result to AuthManager and
 * partially handles the response.
 */
abstract class AuthManagerSpecialPage extends SpecialPage {
        /** @var string[] The list of actions this special page deals with. Subclasses should override
         * this. */
        protected static $allowedActions = [
                AuthManager::ACTION_LOGIN, AuthManager::ACTION_LOGIN_CONTINUE,
                AuthManager::ACTION_CREATE, AuthManager::ACTION_CREATE_CONTINUE,
                AuthManager::ACTION_LINK, AuthManager::ACTION_LINK_CONTINUE,
                AuthManager::ACTION_CHANGE, AuthManager::ACTION_REMOVE, AuthManager::ACTION_UNLINK,
        ];

        /** @var array Customized messages */
        protected static $messages = [];

        /** @var string one of the AuthManager::ACTION_* constants. */
        protected $authAction;

        /** @var AuthenticationRequest[] */
        protected $authRequests;

        /** @var string Subpage of the special page. */
        protected $subPage;

        /** @var bool True if the current request is a result of returning from a redirect flow. */
        protected $isReturn;

        /** @var WebRequest|null If set, will be used instead of the real request. Used for redirection. */
        protected $savedRequest;

        /**
         * Change the form descriptor that determines how a field will look in the authentication form.
         * Called from fieldInfoToFormDescriptor().
         * @param AuthenticationRequest[] $requests
         * @param string $fieldInfo Field information array (union of all
         *    AuthenticationRequest::getFieldInfo() responses).
         * @param array $formDescriptor HTMLForm descriptor. The special key 'weight' can be set to
         *    change the order of the fields.
         * @param string $action Authentication type (one of the AuthManager::ACTION_* constants)
         * @return bool
         */
        public function onAuthChangeFormFields(
                array $requests, array $fieldInfo, array &$formDescriptor, $action
        ) {
                return true;
        }

        protected function getLoginSecurityLevel() {
                return $this->getName();
        }

        public function getRequest() {
                return $this->savedRequest ?: $this->getContext()->getRequest();
        }

        /**
         * Override the POST data, GET data from the real request is preserved.
         *
         * Used to preserve POST data over a HTTP redirect.
         *
         * @param array $data
         * @param bool $wasPosted
         */
        protected function setRequest( array $data, $wasPosted = null ) {
                $request = $this->getContext()->getRequest();
                if ( $wasPosted === null ) {
                        $wasPosted = $request->wasPosted();
                }
                $this->savedRequest = new DerivativeRequest( $request, $data + $request->getQueryValues(),
                        $wasPosted );
        }

        protected function beforeExecute( $subPage ) {
                $this->getOutput()->disallowUserJs();

                return $this->handleReturnBeforeExecute( $subPage )
                        && $this->handleReauthBeforeExecute( $subPage );
        }

        /**
         * Handle redirection from the /return subpage.
         *
         * This is used in the redirect flow where we need
         * to be able to process data that was sent via a GET request. We set the /return subpage as
         * the reentry point so we know we need to treat GET as POST, but we don't want to handle all
         * future GETs as POSTs so we need to normalize the URL. (Also we don't want to show any
         * received parameters around in the URL; they are ugly and might be sensitive.)
         *
         * Thus when on the /return subpage, we stash the request data in the session, redirect, then
         * use the session to detect that we have been redirected, recover the data and replace the
         * real WebRequest with a fake one that contains the saved data.
         *
         * @param string $subPage
         * @return bool False if execution should be stopped.
         */
        protected function handleReturnBeforeExecute( $subPage ) {
                $authManager = AuthManager::singleton();
                $key = 'AuthManagerSpecialPage:return:' . $this->getName();

                if ( $subPage === 'return' ) {
                        $this->loadAuth( $subPage );
                        $preservedParams = $this->getPreservedParams( false );

                        // FIXME save POST values only from request
                        $authData = array_diff_key( $this->getRequest()->getValues(),
                                $preservedParams, [ 'title' => 1 ] );
                        $authManager->setAuthenticationSessionData( $key, $authData );

                        $url = $this->getPageTitle()->getFullURL( $preservedParams, false, PROTO_HTTPS );
                        $this->getOutput()->redirect( $url );
                        return false;
                }

                $authData = $authManager->getAuthenticationSessionData( $key );
                if ( $authData ) {
                        $authManager->removeAuthenticationSessionData( $key );
                        $this->isReturn = true;
                        $this->setRequest( $authData, true );
                }

                return true;
        }

        /**
         * Handle redirection when the user needs to (re)authenticate.
         *
         * Send the user to the login form if needed; in case the request was a POST, stash in the
         * session and simulate it once the user gets back.
         *
         * @param string $subPage
         * @return bool False if execution should be stopped.
         * @throws ErrorPageError When the user is not allowed to use this page.
         */
        protected function handleReauthBeforeExecute( $subPage ) {
                $authManager = AuthManager::singleton();
                $request = $this->getRequest();
                $key = 'AuthManagerSpecialPage:reauth:' . $this->getName();

                $securityLevel = $this->getLoginSecurityLevel();
                if ( $securityLevel ) {
                        $securityStatus = AuthManager::singleton()
                                ->securitySensitiveOperationStatus( $securityLevel );
                        if ( $securityStatus === AuthManager::SEC_REAUTH ) {
                                $queryParams = array_diff_key( $request->getQueryValues(), [ 'title' => true ] );

                                if ( $request->wasPosted() ) {
                                        // unique ID in case the same special page is open in multiple browser tabs
                                        $uniqueId = MWCryptRand::generateHex( 6 );
                                        $key = $key . ':' . $uniqueId;

                                        $queryParams = [ 'authUniqueId' => $uniqueId ] + $queryParams;
                                        $authData = array_diff_key( $request->getValues(),
                                                        $this->getPreservedParams( false ), [ 'title' => 1 ] );
                                        $authManager->setAuthenticationSessionData( $key, $authData );
                                }

                                $title = SpecialPage::getTitleFor( 'Userlogin' );
                                $url = $title->getFullURL( [
                                        'returnto' => $this->getFullTitle()->getPrefixedDBkey(),
                                        'returntoquery' => wfArrayToCgi( $queryParams ),
                                        'force' => $securityLevel,
                                ], false, PROTO_HTTPS );

                                $this->getOutput()->redirect( $url );
                                return false;
                        } elseif ( $securityStatus !== AuthManager::SEC_OK ) {
                                throw new ErrorPageError( 'cannotauth-not-allowed-title', 'cannotauth-not-allowed' );
                        }
                }

                $uniqueId = $request->getVal( 'authUniqueId' );
                if ( $uniqueId ) {
                        $key = $key . ':' . $uniqueId;
                        $authData = $authManager->getAuthenticationSessionData( $key );
                        if ( $authData ) {
                                $authManager->removeAuthenticationSessionData( $key );
                                $this->setRequest( $authData, true );
                        }
                }

                return true;
        }

        /**
         * Get the default action for this special page, if none is given via URL/POST data.
         * Subclasses should override this (or override loadAuth() so this is never called).
         * @param string $subPage Subpage of the special page.
         * @return string an AuthManager::ACTION_* constant.
         */
        protected function getDefaultAction( $subPage ) {
                throw new BadMethodCallException( 'Subclass did not implement getDefaultAction' );
        }

        /**
         * Return custom message key.
         * Allows subclasses to customize messages.
         * @return string
         */
        protected function messageKey( $defaultKey ) {
                return array_key_exists( $defaultKey, static::$messages )
                        ? static::$messages[$defaultKey] : $defaultKey;
        }

        /**
         * Allows blacklisting certain request types.
         * @return array A list of AuthenticationRequest subclass names
         */
        protected function getRequestBlacklist() {
                return [];
        }

        /**
         * Load or initialize $authAction, $authRequests and $subPage.
         * Subclasses should call this from execute() or otherwise ensure the variables are initialized.
         * @param string $subPage Subpage of the special page.
         * @param string $authAction Override auth action specified in request (this is useful
         *    when the form needs to be changed from <action> to <action>_CONTINUE after a successful
         *    authentication step)
         * @param bool $reset Regenerate the requests even if a cached version is available
         */
        protected function loadAuth( $subPage, $authAction = null, $reset = false ) {
                // Do not load if already loaded, to cut down on the number of getAuthenticationRequests
                // calls. This is important for requests which have hidden information so any
                // getAuthenticationRequests call would mean putting data into some cache.
                if (
                        !$reset && $this->subPage === $subPage && $this->authAction
                        && ( !$authAction || $authAction === $this->authAction )
                ) {
                        return;
                }

                $request = $this->getRequest();
                $this->subPage = $subPage;
                $this->authAction = $authAction ?: $request->getText( 'authAction' );
                if ( !in_array( $this->authAction, static::$allowedActions, true ) ) {
                        $this->authAction = $this->getDefaultAction( $subPage );
                        if ( $request->wasPosted() ) {
                                $continueAction = $this->getContinueAction( $this->authAction );
                                if ( in_array( $continueAction, static::$allowedActions, true ) ) {
                                        $this->authAction = $continueAction;
                                }
                        }
                }

                $allReqs = AuthManager::singleton()->getAuthenticationRequests(
                        $this->authAction, $this->getUser() );
                $this->authRequests = array_filter( $allReqs, function ( $req ) use ( $subPage ) {
                        return !in_array( get_class( $req ), $this->getRequestBlacklist(), true );
                } );
        }

        /**
         * Returns true if this is not the first step of the authentication.
         * @return bool
         */
        protected function isContinued() {
                return in_array( $this->authAction, [
                        AuthManager::ACTION_LOGIN_CONTINUE,
                        AuthManager::ACTION_CREATE_CONTINUE,
                        AuthManager::ACTION_LINK_CONTINUE,
                ], true );
        }

        /**
         * Gets the _CONTINUE version of an action.
         * @param string $action An AuthManager::ACTION_* constant.
         * @return string An AuthManager::ACTION_*_CONTINUE constant.
         */
        protected function getContinueAction( $action ) {
                switch ( $action ) {
                        case AuthManager::ACTION_LOGIN:
                                $action = AuthManager::ACTION_LOGIN_CONTINUE;
                                break;
                        case AuthManager::ACTION_CREATE:
                                $action = AuthManager::ACTION_CREATE_CONTINUE;
                                break;
                        case AuthManager::ACTION_LINK:
                                $action = AuthManager::ACTION_LINK_CONTINUE;
                                break;
                }
                return $action;
        }

        /**
         * Checks whether AuthManager is ready to perform the action.
         * ACTION_CHANGE needs special verification (AuthManager::allowsAuthenticationData*) which is
         * the caller's responsibility.
         * @param string $action One of the AuthManager::ACTION_* constants in static::$allowedActions
         * @return bool
         * @throws LogicException if $action is invalid
         */
        protected function isActionAllowed( $action ) {
                $authManager = AuthManager::singleton();
                if ( !in_array( $action, static::$allowedActions, true ) ) {
                        throw new InvalidArgumentException( 'invalid action: ' . $action );
                }

                // calling getAuthenticationRequests can be expensive, avoid if possible
                $requests = ( $action === $this->authAction ) ? $this->authRequests
                        : $authManager->getAuthenticationRequests( $action );
                if ( !$requests ) {
                        // no provider supports this action in the current state
                        return false;
                }

                switch ( $action ) {
                        case AuthManager::ACTION_LOGIN:
                        case AuthManager::ACTION_LOGIN_CONTINUE:
                                return $authManager->canAuthenticateNow();
                        case AuthManager::ACTION_CREATE:
                        case AuthManager::ACTION_CREATE_CONTINUE:
                                return $authManager->canCreateAccounts();
                        case AuthManager::ACTION_LINK:
                        case AuthManager::ACTION_LINK_CONTINUE:
                                return $authManager->canLinkAccounts();
                        case AuthManager::ACTION_CHANGE:
                        case AuthManager::ACTION_REMOVE:
                        case AuthManager::ACTION_UNLINK:
                                return true;
                        default:
                                // should never reach here but makes static code analyzers happy
                                throw new InvalidArgumentException( 'invalid action: ' . $action );
                }
        }

        /**
         * @param string $action One of the AuthManager::ACTION_* constants
         * @param AuthenticationRequest[] $requests
         * @return AuthenticationResponse
         * @throws LogicException if $action is invalid
         */
        protected function performAuthenticationStep( $action, array $requests ) {
                if ( !in_array( $action, static::$allowedActions, true ) ) {
                        throw new InvalidArgumentException( 'invalid action: ' . $action );
                }

                $authManager = AuthManager::singleton();
                $returnToUrl = $this->getPageTitle( 'return' )
                        ->getFullURL( $this->getPreservedParams( true ), false, PROTO_HTTPS );

                switch ( $action ) {
                        case AuthManager::ACTION_LOGIN:
                                return $authManager->beginAuthentication( $requests, $returnToUrl );
                        case AuthManager::ACTION_LOGIN_CONTINUE:
                                return $authManager->continueAuthentication( $requests );
                        case AuthManager::ACTION_CREATE:
                                return $authManager->beginAccountCreation( $this->getUser(), $requests,
                                        $returnToUrl );
                        case AuthManager::ACTION_CREATE_CONTINUE:
                                return $authManager->continueAccountCreation( $requests );
                        case AuthManager::ACTION_LINK:
                                return $authManager->beginAccountLink( $this->getUser(), $requests, $returnToUrl );
                        case AuthManager::ACTION_LINK_CONTINUE:
                                return $authManager->continueAccountLink( $requests );
                        case AuthManager::ACTION_CHANGE:
                        case AuthManager::ACTION_REMOVE:
                        case AuthManager::ACTION_UNLINK:
                                if ( count( $requests ) > 1 ) {
                                        throw new InvalidArgumentException( 'only one auth request can be changed at a time' );
                                } elseif ( !$requests ) {
                                        throw new InvalidArgumentException( 'no auth request' );
                                }
                                $req = reset( $requests );
                                $status = $authManager->allowsAuthenticationDataChange( $req );
                                Hooks::run( 'ChangeAuthenticationDataAudit', [ $req, $status ] );
                                if ( !$status->isGood() ) {
                                        return AuthenticationResponse::newFail( $status->getMessage() );
                                }
                                $authManager->changeAuthenticationData( $req );
                                return AuthenticationResponse::newPass();
                        default:
                                // should never reach here but makes static code analyzers happy
                                throw new InvalidArgumentException( 'invalid action: ' . $action );
                }
        }

        /**
         * Attempts to do an authentication step with the submitted data.
         * Subclasses should probably call this from execute().
         * @return false|Status
         *    - false if there was no submit at all
         *    - a good Status wrapping an AuthenticationResponse if the form submit was successful.
         *      This does not necessarily mean that the authentication itself was successful; see the
         *      response for that.
         *    - a bad Status for form errors.
         */
        protected function trySubmit() {
                $status = false;

                $form = $this->getAuthForm( $this->authRequests, $this->authAction );
                $form->setSubmitCallback( [ $this, 'handleFormSubmit' ] );

                if ( $this->getRequest()->wasPosted() ) {
                        // handle tokens manually; $form->tryAuthorizedSubmit only works for logged-in users
                        $requestTokenValue = $this->getRequest()->getVal( $this->getTokenName() );
                        $sessionToken = $this->getToken();
                        if ( $sessionToken->wasNew() ) {
                                return Status::newFatal( $this->messageKey( 'authform-newtoken' ) );
                        } elseif ( !$requestTokenValue ) {
                                return Status::newFatal( $this->messageKey( 'authform-notoken' ) );
                        } elseif ( !$sessionToken->match( $requestTokenValue ) ) {
                                return Status::newFatal( $this->messageKey( 'authform-wrongtoken' ) );
                        }

                        $form->prepareForm();
                        $status = $form->trySubmit();

                        // HTMLForm submit return values are a mess; let's ensure it is false or a Status
                        // FIXME this probably should be in HTMLForm
                        if ( $status === true ) {
                                // not supposed to happen since our submit handler should always return a Status
                                throw new UnexpectedValueException( 'HTMLForm::trySubmit() returned true' );
                        } elseif ( $status === false ) {
                                // form was not submitted; nothing to do
                        } elseif ( $status instanceof Status ) {
                                // already handled by the form; nothing to do
                        } elseif ( $status instanceof StatusValue ) {
                                // in theory not an allowed return type but nothing stops the submit handler from
                                // accidentally returning it so best check and fix
                                $status = Status::wrap( $status );
                        } elseif ( is_string( $status ) ) {
                                $status = Status::newFatal( new RawMessage( '$1', $status ) );
                        } elseif ( is_array( $status ) ) {
                                if ( is_string( reset( $status ) ) ) {
                                        $status = call_user_func_array( 'Status::newFatal', $status );
                                } elseif ( is_array( reset( $status ) ) ) {
                                        $status = Status::newGood();
                                        foreach ( $status as $message ) {
                                                call_user_func_array( [ $status, 'fatal' ], $message );
                                        }
                                } else {
                                        throw new UnexpectedValueException( 'invalid HTMLForm::trySubmit() return value: '
                                                . 'first element of array is ' . gettype( reset( $status ) ) );
                                }
                        } else {
                                // not supposed to happen but HTMLForm does not actually verify the return type
                                // from the submit callback; better safe then sorry
                                throw new UnexpectedValueException( 'invalid HTMLForm::trySubmit() return type: '
                                        . gettype( $status ) );
                        }

                        if ( ( !$status || !$status->isOK() ) && $this->isReturn ) {
                                // This is awkward. There was a form validation error, which means the data was not
                                // passed to AuthManager. Normally we would display the form with an error message,
                                // but for the data we received via the redirect flow that would not be helpful at all.
                                // Let's just submit the data to AuthManager directly instead.
                                LoggerFactory::getInstance( 'authmanager' )
                                        ->warning( 'Validation error on return', [ 'data' => $form->mFieldData,
                                                'status' => $status->getWikiText() ] );
                                $status = $this->handleFormSubmit( $form->mFieldData );
                        }
                }

                $changeActions = [
                        AuthManager::ACTION_CHANGE, AuthManager::ACTION_REMOVE, AuthManager::ACTION_UNLINK
                ];
                if ( in_array( $this->authAction, $changeActions, true ) && $status && !$status->isOK() ) {
                        Hooks::run( 'ChangeAuthenticationDataAudit', [ reset( $this->authRequests ), $status ] );
                }

                return $status;
        }

        /**
         * Submit handler callback for HTMLForm
         * @private
         * @param $data array Submitted data
         * @return Status
         */
        public function handleFormSubmit( $data ) {
                $requests = AuthenticationRequest::loadRequestsFromSubmission( $this->authRequests, $data );
                $response = $this->performAuthenticationStep( $this->authAction, $requests );

                // we can't handle FAIL or similar as failure here since it might require changing the form
                return Status::newGood( $response );
        }

        /**
         * Returns URL query parameters which can be used to reload the page (or leave and return) while
         * preserving all information that is necessary for authentication to continue. These parameters
         * will be preserved in the action URL of the form and in the return URL for redirect flow.
         * @param bool $withToken Include CSRF token
         * @return array
         */
        protected function getPreservedParams( $withToken = false ) {
                $params = [];
                if ( $this->authAction !== $this->getDefaultAction( $this->subPage ) ) {
                        $params['authAction'] = $this->getContinueAction( $this->authAction );
                }
                if ( $withToken ) {
                        $params[$this->getTokenName()] = $this->getToken()->toString();
                }
                return $params;
        }

        /**
         * Generates a HTMLForm descriptor array from a set of authentication requests.
         * @param AuthenticationRequest[] $requests
         * @param string $action AuthManager action name (one of the AuthManager::ACTION_* constants)
         * @return array
         */
        protected function getAuthFormDescriptor( $requests, $action ) {
                $fieldInfo = AuthenticationRequest::mergeFieldInfo( $requests );
                $formDescriptor = $this->fieldInfoToFormDescriptor( $requests, $fieldInfo, $action );

                $this->addTabIndex( $formDescriptor );

                return $formDescriptor;
        }

        /**
         * @param AuthenticationRequest[] $requests
         * @param string $action AuthManager action name (one of the AuthManager::ACTION_* constants)
         * @return HTMLForm
         */
        protected function getAuthForm( array $requests, $action ) {
                $formDescriptor = $this->getAuthFormDescriptor( $requests, $action );
                $context = $this->getContext();
                if ( $context->getRequest() !== $this->getRequest() ) {
                        // We have overridden the request, need to make sure the form uses that too.
                        $context = new DerivativeContext( $this->getContext() );
                        $context->setRequest( $this->getRequest() );
                }
                $form = HTMLForm::factory( 'ooui', $formDescriptor, $context );
                $form->setAction( $this->getFullTitle()->getFullURL( $this->getPreservedParams() ) );
                $form->addHiddenField( $this->getTokenName(), $this->getToken()->toString() );
                $form->addHiddenField( 'authAction', $this->authAction );
                $form->suppressDefaultSubmit( !$this->needsSubmitButton( $formDescriptor ) );

                return $form;
        }

        /**
         * Display the form.
         * @param false|Status|StatusValue $status A form submit status, as in HTMLForm::trySubmit()
         */
        protected function displayForm( $status ) {
                if ( $status instanceof StatusValue ) {
                        $status = Status::wrap( $status );
                }
                $form = $this->getAuthForm( $this->authRequests, $this->authAction );
                $form->prepareForm()->displayForm( $status );
        }

        /**
         * Returns true if the form has fields which take values. If all available providers use the
         * redirect flow, the form might contain nothing but submit buttons, in which case we should
         * not add an extra submit button which does nothing.
         *
         * @param array $formDescriptor A HTMLForm descriptor
         * @return bool
         */
        protected function needsSubmitButton( $formDescriptor ) {
                return (bool)array_filter( $formDescriptor, function ( $item ) {
                        $class = false;
                        if ( array_key_exists( 'class', $item ) ) {
                                $class = $item['class'];
                        } elseif ( array_key_exists( 'type', $item ) ) {
                                $class = HTMLForm::$typeMappings[$item['type']];
                        }
                        return !is_a( $class, \HTMLInfoField::class, true ) &&
                                !is_a( $class, \HTMLSubmitField::class, true );
                } );
        }

        /**
         * Adds a sequential tabindex starting from 1 to all form elements. This way the user can
         * use the tab key to traverse the form without having to step through all links and such.
         * @param $formDescriptor
         */
        protected function addTabIndex( &$formDescriptor ) {
                $i = 1;
                foreach ( $formDescriptor as $field => &$definition ) {
                        $class = false;
                        if ( array_key_exists( 'class', $definition ) ) {
                                $class = $definition['class'];
                        } elseif ( array_key_exists( 'type', $definition ) ) {
                                $class = HTMLForm::$typeMappings[$definition['type']];
                        }
                        if ( $class !== 'HTMLInfoField' ) {
                                $definition['tabindex'] = $i;
                                $i++;
                        }
                }
        }

        /**
         * Returns the CSRF token.
         * @return Token
         */
        protected function getToken() {
                return $this->getRequest()->getSession()->getToken( 'AuthManagerSpecialPage:'
                        . $this->getName() );
        }

        /**
         * Returns the name of the CSRF token (under which it should be found in the POST or GET data).
         * @return string
         */
        protected function getTokenName() {
                return 'wpAuthToken';
        }

        /**
         * Turns a field info array into a form descriptor. Behavior can be modified by the
         * AuthChangeFormFields hook.
         * @param AuthenticationRequest[] $requests
         * @param array $fieldInfo Field information, in the format used by
         *   AuthenticationRequest::getFieldInfo()
         * @param string $action One of the AuthManager::ACTION_* constants
         * @return array A form descriptor that can be passed to HTMLForm
         */
        protected function fieldInfoToFormDescriptor( array $requests, array $fieldInfo, $action ) {
                $formDescriptor = [];
                foreach ( $fieldInfo as $fieldName => $singleFieldInfo ) {
                        $formDescriptor[$fieldName] = self::mapSingleFieldInfo( $singleFieldInfo, $fieldName );
                }

                $requestSnapshot = serialize( $requests );
                $this->onAuthChangeFormFields( $requests, $fieldInfo, $formDescriptor, $action );
                \Hooks::run( 'AuthChangeFormFields', [ $requests, $fieldInfo, &$formDescriptor, $action ] );
                if ( $requestSnapshot !== serialize( $requests ) ) {
                        LoggerFactory::getInstance( 'authentication' )->warning(
                                'AuthChangeFormFields hook changed auth requests' );
                }

                // Process the special 'weight' property, which is a way for AuthChangeFormFields hook
                // subscribers (who only see one field at a time) to influence ordering.
                self::sortFormDescriptorFields( $formDescriptor );

                return $formDescriptor;
        }

        /**
         * Maps an authentication field configuration for a single field (as returned by
         * AuthenticationRequest::getFieldInfo()) to a HTMLForm field descriptor.
         * @param array $singleFieldInfo
         * @return array
         */
        protected static function mapSingleFieldInfo( $singleFieldInfo, $fieldName ) {
                $type = self::mapFieldInfoTypeToFormDescriptorType( $singleFieldInfo['type'] );
                $descriptor = [
                        'type' => $type,
                        // Do not prefix input name with 'wp'. This is important for the redirect flow.
                        'name' => $fieldName,
                ];

                if ( $type === 'submit' && isset( $singleFieldInfo['label'] ) ) {
                        $descriptor['default'] = wfMessage( $singleFieldInfo['label'] )->plain();
                } elseif ( $type !== 'submit' ) {
                        $descriptor += array_filter( [
                                // help-message is omitted as it is usually not really useful for a web interface
                                'label-message' => self::getField( $singleFieldInfo, 'label' ),
                        ] );

                        if ( isset( $singleFieldInfo['options'] ) ) {
                                $descriptor['options'] = array_flip( array_map( function ( $message ) {
                                        /** @var $message Message */
                                        return $message->parse();
                                }, $singleFieldInfo['options'] ) );
                        }

                        if ( isset( $singleFieldInfo['value'] ) ) {
                                $descriptor['default'] = $singleFieldInfo['value'];
                        }

                        if ( empty( $singleFieldInfo['optional'] ) ) {
                                $descriptor['required'] = true;
                        }
                }

                return $descriptor;
        }

        /**
         * Sort the fields of a form descriptor by their 'weight' property. (Fields with higher weight
         * are shown closer to the bottom; weight defaults to 0. Negative weight is allowed.)
         * Keep order if weights are equal.
         * @param array $formDescriptor
         * @return array
         */
        protected static function sortFormDescriptorFields( array &$formDescriptor ) {
                $i = 0;
                foreach ( $formDescriptor as &$field ) {
                        $field['__index'] = $i++;
                }
                uasort( $formDescriptor, function ( $first, $second ) {
                        return self::getField( $first, 'weight', 0 ) - self::getField( $second, 'weight', 0 )
                                ?: $first['__index'] - $second['__index'];
                } );
                foreach ( $formDescriptor as &$field ) {
                        unset( $field['__index'] );
                }
        }

        /**
         * Get an array value, or a default if it does not exist.
         * @param array $array
         * @param string $fieldName
         * @param mixed $default
         * @return mixed
         */
        protected static function getField( array $array, $fieldName, $default = null ) {
                if ( array_key_exists( $fieldName, $array ) ) {
                        return $array[$fieldName];
                } else {
                        return $default;
                }
        }

        /**
         * Maps AuthenticationRequest::getFieldInfo() types to HTMLForm types
         * @param string $type
         * @return string
         * @throws \LogicException
         */
        protected static function mapFieldInfoTypeToFormDescriptorType( $type ) {
                $map = [
                        'string' => 'text',
                        'password' => 'password',
                        'select' => 'select',
                        'checkbox' => 'check',
                        'multiselect' => 'multiselect',
                        'button' => 'submit',
                        'hidden' => 'hidden',
                        'null' => 'info',
                ];
                if ( !array_key_exists( $type, $map ) ) {
                        throw new \LogicException( 'invalid field type: ' . $type );
                }
                return $map[$type];
        }
}