Clean up spacing of doc comments

[lhc/web/wiklou.git] / includes / api / ApiBase.php

<?php
/**
 * Copyright © 2006, 2010 Yuri Astrakhan "<Firstname><Lastname>@gmail.com"
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */

use MediaWiki\Block\AbstractBlock;
use MediaWiki\Block\DatabaseBlock;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\MediaWikiServices;
use MediaWiki\Permissions\PermissionManager;
use Wikimedia\Rdbms\IDatabase;

/**
 * This abstract class implements many basic API functions, and is the base of
 * all API classes.
 * The class functions are divided into several areas of functionality:
 *
 * Module parameters: Derived classes can define getAllowedParams() to specify
 *    which parameters to expect, how to parse and validate them.
 *
 * Self-documentation: code to allow the API to document its own state
 *
 * @ingroup API
 */
abstract class ApiBase extends ContextSource {

        use ApiBlockInfoTrait;

        /**
         * @name Constants for ::getAllowedParams() arrays
         * These constants are keys in the arrays returned by ::getAllowedParams()
         * and accepted by ::getParameterFromSettings() that define how the
         * parameters coming in from the request are to be interpreted.
         * @{
         */

        /** (null|boolean|integer|string) Default value of the parameter. */
        const PARAM_DFLT = 0;

        /** (boolean) Accept multiple pipe-separated values for this parameter (e.g. titles)? */
        const PARAM_ISMULTI = 1;

        /**
         * (string|string[]) Either an array of allowed value strings, or a string
         * type as described below. If not specified, will be determined from the
         * type of PARAM_DFLT.
         *
         * Supported string types are:
         * - boolean: A boolean parameter, returned as false if the parameter is
         *   omitted and true if present (even with a falsey value, i.e. it works
         *   like HTML checkboxes). PARAM_DFLT must be boolean false, if specified.
         *   Cannot be used with PARAM_ISMULTI.
         * - integer: An integer value. See also PARAM_MIN, PARAM_MAX, and
         *   PARAM_RANGE_ENFORCE.
         * - limit: An integer or the string 'max'. Default lower limit is 0 (but
         *   see PARAM_MIN), and requires that PARAM_MAX and PARAM_MAX2 be
         *   specified. Cannot be used with PARAM_ISMULTI.
         * - namespace: An integer representing a MediaWiki namespace. Forces PARAM_ALL = true to
         *   support easily specifying all namespaces.
         * - NULL: Any string.
         * - password: Any non-empty string. Input value is private or sensitive.
         *   <input type="password"> would be an appropriate HTML form field.
         * - string: Any non-empty string, not expected to be very long or contain newlines.
         *   <input type="text"> would be an appropriate HTML form field.
         * - submodule: The name of a submodule of this module, see PARAM_SUBMODULE_MAP.
         * - tags: A string naming an existing, explicitly-defined tag. Should usually be
         *   used with PARAM_ISMULTI.
         * - text: Any non-empty string, expected to be very long or contain newlines.
         *   <textarea> would be an appropriate HTML form field.
         * - timestamp: A timestamp in any format recognized by MWTimestamp, or the
         *   string 'now' representing the current timestamp. Will be returned in
         *   TS_MW format.
         * - user: A MediaWiki username or IP. Will be returned normalized but not canonicalized.
         * - upload: An uploaded file. Will be returned as a WebRequestUpload object.
         *   Cannot be used with PARAM_ISMULTI.
         */
        const PARAM_TYPE = 2;

        /** (integer) Max value allowed for the parameter, for PARAM_TYPE 'integer' and 'limit'. */
        const PARAM_MAX = 3;

        /**
         * (integer) Max value allowed for the parameter for users with the
         * apihighlimits right, for PARAM_TYPE 'limit'.
         */
        const PARAM_MAX2 = 4;

        /** (integer) Lowest value allowed for the parameter, for PARAM_TYPE 'integer' and 'limit'. */
        const PARAM_MIN = 5;

        /** (boolean) Allow the same value to be set more than once when PARAM_ISMULTI is true? */
        const PARAM_ALLOW_DUPLICATES = 6;

        /** (boolean) Is the parameter deprecated (will show a warning)? */
        const PARAM_DEPRECATED = 7;

        /**
         * (boolean) Is the parameter required?
         * @since 1.17
         */
        const PARAM_REQUIRED = 8;

        /**
         * (boolean) For PARAM_TYPE 'integer', enforce PARAM_MIN and PARAM_MAX?
         * @since 1.17
         */
        const PARAM_RANGE_ENFORCE = 9;

        /**
         * (string|array|Message) Specify an alternative i18n documentation message
         * for this parameter. Default is apihelp-{$path}-param-{$param}.
         * @since 1.25
         */
        const PARAM_HELP_MSG = 10;

        /**
         * ((string|array|Message)[]) Specify additional i18n messages to append to
         * the normal message for this parameter.
         * @since 1.25
         */
        const PARAM_HELP_MSG_APPEND = 11;

        /**
         * (array) Specify additional information tags for the parameter. Value is
         * an array of arrays, with the first member being the 'tag' for the info
         * and the remaining members being the values. In the help, this is
         * formatted using apihelp-{$path}-paraminfo-{$tag}, which is passed
         * $1 = count, $2 = comma-joined list of values, $3 = module prefix.
         * @since 1.25
         */
        const PARAM_HELP_MSG_INFO = 12;

        /**
         * (string[]) When PARAM_TYPE is an array, this may be an array mapping
         * those values to page titles which will be linked in the help.
         * @since 1.25
         */
        const PARAM_VALUE_LINKS = 13;

        /**
         * ((string|array|Message)[]) When PARAM_TYPE is an array, this is an array
         * mapping those values to $msg for ApiBase::makeMessage(). Any value not
         * having a mapping will use apihelp-{$path}-paramvalue-{$param}-{$value}.
         * Specify an empty array to use the default message key for all values.
         * @since 1.25
         */
        const PARAM_HELP_MSG_PER_VALUE = 14;

        /**
         * (string[]) When PARAM_TYPE is 'submodule', map parameter values to
         * submodule paths. Default is to use all modules in
         * $this->getModuleManager() in the group matching the parameter name.
         * @since 1.26
         */
        const PARAM_SUBMODULE_MAP = 15;

        /**
         * (string) When PARAM_TYPE is 'submodule', used to indicate the 'g' prefix
         * added by ApiQueryGeneratorBase (and similar if anything else ever does that).
         * @since 1.26
         */
        const PARAM_SUBMODULE_PARAM_PREFIX = 16;

        /**
         * (boolean|string) When PARAM_TYPE has a defined set of values and PARAM_ISMULTI is true,
         * this allows for an asterisk ('*') to be passed in place of a pipe-separated list of
         * every possible value. If a string is set, it will be used in place of the asterisk.
         * @since 1.29
         */
        const PARAM_ALL = 17;

        /**
         * (int[]) When PARAM_TYPE is 'namespace', include these as additional possible values.
         * @since 1.29
         */
        const PARAM_EXTRA_NAMESPACES = 18;

        /**
         * (boolean) Is the parameter sensitive? Note 'password'-type fields are
         * always sensitive regardless of the value of this field.
         * @since 1.29
         */
        const PARAM_SENSITIVE = 19;

        /**
         * (array) When PARAM_TYPE is an array, this indicates which of the values are deprecated.
         * Keys are the deprecated parameter values, values define the warning
         * message to emit: either boolean true (to use a default message) or a
         * $msg for ApiBase::makeMessage().
         * @since 1.30
         */
        const PARAM_DEPRECATED_VALUES = 20;

        /**
         * (integer) Maximum number of values, for normal users. Must be used with PARAM_ISMULTI.
         * @since 1.30
         */
        const PARAM_ISMULTI_LIMIT1 = 21;

        /**
         * (integer) Maximum number of values, for users with the apihighimits right.
         * Must be used with PARAM_ISMULTI.
         * @since 1.30
         */
        const PARAM_ISMULTI_LIMIT2 = 22;

        /**
         * (integer) Maximum length of a string in bytes (in UTF-8 encoding).
         * @since 1.31
         */
        const PARAM_MAX_BYTES = 23;

        /**
         * (integer) Maximum length of a string in characters (unicode codepoints).
         * @since 1.31
         */
        const PARAM_MAX_CHARS = 24;

        /**
         * (array) Indicate that this is a templated parameter, and specify replacements. Keys are the
         * placeholders in the parameter name and values are the names of (unprefixed) parameters from
         * which the replacement values are taken.
         *
         * For example, a parameter "foo-{ns}-{title}" could be defined with
         * PARAM_TEMPLATE_VARS => [ 'ns' => 'namespaces', 'title' => 'titles' ]. Then a query for
         * namespaces=0|1&titles=X|Y would support parameters foo-0-X, foo-0-Y, foo-1-X, and foo-1-Y.
         *
         * All placeholders must be present in the parameter's name. Each target parameter must have
         * PARAM_ISMULTI true. If a target is itself a templated parameter, its PARAM_TEMPLATE_VARS must
         * be a subset of the referring parameter's, mapping the same placeholders to the same targets.
         * A parameter cannot target itself.
         *
         * @since 1.32
         */
        const PARAM_TEMPLATE_VARS = 25;

        /** @} */

        const ALL_DEFAULT_STRING = '*';

        /** Fast query, standard limit. */
        const LIMIT_BIG1 = 500;
        /** Fast query, apihighlimits limit. */
        const LIMIT_BIG2 = 5000;
        /** Slow query, standard limit. */
        const LIMIT_SML1 = 50;
        /** Slow query, apihighlimits limit. */
        const LIMIT_SML2 = 500;

        /**
         * getAllowedParams() flag: When set, the result could take longer to generate,
         * but should be more thorough. E.g. get the list of generators for ApiSandBox extension
         * @since 1.21
         */
        const GET_VALUES_FOR_HELP = 1;

        /** @var array Maps extension paths to info arrays */
        private static $extensionInfo = null;

        /** @var int[][][] Cache for self::filterIDs() */
        private static $filterIDsCache = [];

        /** $var array Map of web UI block messages to corresponding API messages and codes */
        private static $blockMsgMap = [
                'blockedtext' => [ 'apierror-blocked', 'blocked' ],
                'blockedtext-partial' => [ 'apierror-blocked-partial', 'blocked' ],
                'autoblockedtext' => [ 'apierror-autoblocked', 'autoblocked' ],
                'systemblockedtext' => [ 'apierror-systemblocked', 'blocked' ],
                'blockedtext-composite' => [ 'apierror-blocked', 'blocked' ],
        ];

        /** @var ApiMain */
        private $mMainModule;
        /** @var string */
        private $mModuleName, $mModulePrefix;
        private $mReplicaDB = null;
        private $mParamCache = [];
        /** @var array|null|bool */
        private $mModuleSource = false;

        /**
         * @param ApiMain $mainModule
         * @param string $moduleName Name of this module
         * @param string $modulePrefix Prefix to use for parameter names
         */
        public function __construct( ApiMain $mainModule, $moduleName, $modulePrefix = '' ) {
                $this->mMainModule = $mainModule;
                $this->mModuleName = $moduleName;
                $this->mModulePrefix = $modulePrefix;

                if ( !$this->isMain() ) {
                        $this->setContext( $mainModule->getContext() );
                }
        }

        /************************************************************************//**
         * @name   Methods to implement
         * @{
         */

        /**
         * Evaluates the parameters, performs the requested query, and sets up
         * the result. Concrete implementations of ApiBase must override this
         * method to provide whatever functionality their module offers.
         * Implementations must not produce any output on their own and are not
         * expected to handle any errors.
         *
         * The execute() method will be invoked directly by ApiMain immediately
         * before the result of the module is output. Aside from the
         * constructor, implementations should assume that no other methods
         * will be called externally on the module before the result is
         * processed.
         *
         * The result data should be stored in the ApiResult object available
         * through getResult().
         */
        abstract public function execute();

        /**
         * Get the module manager, or null if this module has no sub-modules
         * @since 1.21
         * @return ApiModuleManager
         */
        public function getModuleManager() {
                return null;
        }

        /**
         * If the module may only be used with a certain format module,
         * it should override this method to return an instance of that formatter.
         * A value of null means the default format will be used.
         * @note Do not use this just because you don't want to support non-json
         * formats. This should be used only when there is a fundamental
         * requirement for a specific format.
         * @return mixed Instance of a derived class of ApiFormatBase, or null
         */
        public function getCustomPrinter() {
                return null;
        }

        /**
         * Returns usage examples for this module.
         *
         * Return value has query strings as keys, with values being either strings
         * (message key), arrays (message key + parameter), or Message objects.
         *
         * Do not call this base class implementation when overriding this method.
         *
         * @since 1.25
         * @return array
         */
        protected function getExamplesMessages() {
                return [];
        }

        /**
         * Return links to more detailed help pages about the module.
         * @since 1.25, returning boolean false is deprecated
         * @return string|array
         */
        public function getHelpUrls() {
                return [];
        }

        /**
         * Returns an array of allowed parameters (parameter name) => (default
         * value) or (parameter name) => (array with PARAM_* constants as keys)
         * Don't call this function directly: use getFinalParams() to allow
         * hooks to modify parameters as needed.
         *
         * Some derived classes may choose to handle an integer $flags parameter
         * in the overriding methods. Callers of this method can pass zero or
         * more OR-ed flags like GET_VALUES_FOR_HELP.
         *
         * @return array
         */
        protected function getAllowedParams( /* $flags = 0 */ ) {
                // int $flags is not declared because it causes "Strict standards"
                // warning. Most derived classes do not implement it.
                return [];
        }

        /**
         * Indicates if this module needs maxlag to be checked
         * @return bool
         */
        public function shouldCheckMaxlag() {
                return true;
        }

        /**
         * Indicates whether this module requires read rights
         * @return bool
         */
        public function isReadMode() {
                return true;
        }

        /**
         * Indicates whether this module requires write mode
         *
         * This should return true for modules that may require synchronous database writes.
         * Modules that do not need such writes should also not rely on master database access,
         * since only read queries are needed and each master DB is a single point of failure.
         * Additionally, requests that only need replica DBs can be efficiently routed to any
         * datacenter via the Promise-Non-Write-API-Action header.
         *
         * @return bool
         */
        public function isWriteMode() {
                return false;
        }

        /**
         * Indicates whether this module must be called with a POST request
         * @return bool
         */
        public function mustBePosted() {
                return $this->needsToken() !== false;
        }

        /**
         * Indicates whether this module is deprecated
         * @since 1.25
         * @return bool
         */
        public function isDeprecated() {
                return false;
        }

        /**
         * Indicates whether this module is "internal"
         * Internal API modules are not (yet) intended for 3rd party use and may be unstable.
         * @since 1.25
         * @return bool
         */
        public function isInternal() {
                return false;
        }

        /**
         * Returns the token type this module requires in order to execute.
         *
         * Modules are strongly encouraged to use the core 'csrf' type unless they
         * have specialized security needs. If the token type is not one of the
         * core types, you must use the ApiQueryTokensRegisterTypes hook to
         * register it.
         *
         * Returning a non-falsey value here will force the addition of an
         * appropriate 'token' parameter in self::getFinalParams(). Also,
         * self::mustBePosted() must return true when tokens are used.
         *
         * In previous versions of MediaWiki, true was a valid return value.
         * Returning true will generate errors indicating that the API module needs
         * updating.
         *
         * @return string|false
         */
        public function needsToken() {
                return false;
        }

        /**
         * Fetch the salt used in the Web UI corresponding to this module.
         *
         * Only override this if the Web UI uses a token with a non-constant salt.
         *
         * @since 1.24
         * @param array $params All supplied parameters for the module
         * @return string|array|null
         */
        protected function getWebUITokenSalt( array $params ) {
                return null;
        }

        /**
         * Returns data for HTTP conditional request mechanisms.
         *
         * @since 1.26
         * @param string $condition Condition being queried:
         *  - last-modified: Return a timestamp representing the maximum of the
         *    last-modified dates for all resources involved in the request. See
         *    RFC 7232 § 2.2 for semantics.
         *  - etag: Return an entity-tag representing the state of all resources involved
         *    in the request. Quotes must be included. See RFC 7232 § 2.3 for semantics.
         * @return string|bool|null As described above, or null if no value is available.
         */
        public function getConditionalRequestData( $condition ) {
                return null;
        }

        /** @} */

        /************************************************************************//**
         * @name   Data access methods
         * @{
         */

        /**
         * Get the name of the module being executed by this instance
         * @return string
         */
        public function getModuleName() {
                return $this->mModuleName;
        }

        /**
         * Get parameter prefix (usually two letters or an empty string).
         * @return string
         */
        public function getModulePrefix() {
                return $this->mModulePrefix;
        }

        /**
         * Get the main module
         * @return ApiMain
         */
        public function getMain() {
                return $this->mMainModule;
        }

        /**
         * Returns true if this module is the main module ($this === $this->mMainModule),
         * false otherwise.
         * @return bool
         */
        public function isMain() {
                return $this === $this->mMainModule;
        }

        /**
         * Get the parent of this module
         * @since 1.25
         * @return ApiBase|null
         */
        public function getParent() {
                return $this->isMain() ? null : $this->getMain();
        }

        /**
         * Returns true if the current request breaks the same-origin policy.
         *
         * For example, json with callbacks.
         *
         * https://en.wikipedia.org/wiki/Same-origin_policy
         *
         * @since 1.25
         * @return bool
         */
        public function lacksSameOriginSecurity() {
                // Main module has this method overridden
                // Safety - avoid infinite loop:
                if ( $this->isMain() ) {
                        self::dieDebug( __METHOD__, 'base method was called on main module.' );
                }

                return $this->getMain()->lacksSameOriginSecurity();
        }

        /**
         * Get the path to this module
         *
         * @since 1.25
         * @return string
         */
        public function getModulePath() {
                if ( $this->isMain() ) {
                        return 'main';
                } elseif ( $this->getParent()->isMain() ) {
                        return $this->getModuleName();
                } else {
                        return $this->getParent()->getModulePath() . '+' . $this->getModuleName();
                }
        }

        /**
         * Get a module from its module path
         *
         * @since 1.25
         * @param string $path
         * @return ApiBase|null
         * @throws ApiUsageException
         */
        public function getModuleFromPath( $path ) {
                $module = $this->getMain();
                if ( $path === 'main' ) {
                        return $module;
                }

                $parts = explode( '+', $path );
                if ( count( $parts ) === 1 ) {
                        // In case the '+' was typed into URL, it resolves as a space
                        $parts = explode( ' ', $path );
                }

                $count = count( $parts );
                for ( $i = 0; $i < $count; $i++ ) {
                        $parent = $module;
                        $manager = $parent->getModuleManager();
                        if ( $manager === null ) {
                                $errorPath = implode( '+', array_slice( $parts, 0, $i ) );
                                $this->dieWithError( [ 'apierror-badmodule-nosubmodules', $errorPath ], 'badmodule' );
                        }
                        $module = $manager->getModule( $parts[$i] );

                        if ( $module === null ) {
                                $errorPath = $i ? implode( '+', array_slice( $parts, 0, $i ) ) : $parent->getModuleName();
                                $this->dieWithError(
                                        [ 'apierror-badmodule-badsubmodule', $errorPath, wfEscapeWikiText( $parts[$i] ) ],
                                        'badmodule'
                                );
                        }
                }

                return $module;
        }

        /**
         * Get the result object
         * @return ApiResult
         */
        public function getResult() {
                // Main module has getResult() method overridden
                // Safety - avoid infinite loop:
                if ( $this->isMain() ) {
                        self::dieDebug( __METHOD__, 'base method was called on main module. ' );
                }

                return $this->getMain()->getResult();
        }

        /**
         * Get the error formatter
         * @return ApiErrorFormatter
         */
        public function getErrorFormatter() {
                // Main module has getErrorFormatter() method overridden
                // Safety - avoid infinite loop:
                if ( $this->isMain() ) {
                        self::dieDebug( __METHOD__, 'base method was called on main module. ' );
                }

                return $this->getMain()->getErrorFormatter();
        }

        /**
         * Gets a default replica DB connection object
         * @return IDatabase
         */
        protected function getDB() {
                if ( !isset( $this->mReplicaDB ) ) {
                        $this->mReplicaDB = wfGetDB( DB_REPLICA, 'api' );
                }

                return $this->mReplicaDB;
        }

        /**
         * Get the continuation manager
         * @return ApiContinuationManager|null
         */
        public function getContinuationManager() {
                // Main module has getContinuationManager() method overridden
                // Safety - avoid infinite loop:
                if ( $this->isMain() ) {
                        self::dieDebug( __METHOD__, 'base method was called on main module. ' );
                }

                return $this->getMain()->getContinuationManager();
        }

        /**
         * Set the continuation manager
         * @param ApiContinuationManager|null $manager
         */
        public function setContinuationManager( ApiContinuationManager $manager = null ) {
                // Main module has setContinuationManager() method overridden
                // Safety - avoid infinite loop:
                if ( $this->isMain() ) {
                        self::dieDebug( __METHOD__, 'base method was called on main module. ' );
                }

                $this->getMain()->setContinuationManager( $manager );
        }

        /**
         * Obtain a PermissionManager instance that subclasses may use in their authorization checks.
         *
         * @since 1.34
         * @return PermissionManager
         */
        protected function getPermissionManager(): PermissionManager {
                return MediaWikiServices::getInstance()->getPermissionManager();
        }

        /** @} */

        /************************************************************************//**
         * @name   Parameter handling
         * @{
         */

        /**
         * Indicate if the module supports dynamically-determined parameters that
         * cannot be included in self::getAllowedParams().
         * @return string|array|Message|null Return null if the module does not
         *  support additional dynamic parameters, otherwise return a message
         *  describing them.
         */
        public function dynamicParameterDocumentation() {
                return null;
        }

        /**
         * This method mangles parameter name based on the prefix supplied to the constructor.
         * Override this method to change parameter name during runtime
         * @param string|string[] $paramName Parameter name
         * @return string|string[] Prefixed parameter name
         * @since 1.29 accepts an array of strings
         */
        public function encodeParamName( $paramName ) {
                if ( is_array( $paramName ) ) {
                        return array_map( function ( $name ) {
                                return $this->mModulePrefix . $name;
                        }, $paramName );
                } else {
                        return $this->mModulePrefix . $paramName;
                }
        }

        /**
         * Using getAllowedParams(), this function makes an array of the values
         * provided by the user, with key being the name of the variable, and
         * value - validated value from user or default. limits will not be
         * parsed if $parseLimit is set to false; use this when the max
         * limit is not definitive yet, e.g. when getting revisions.
         * @param bool|array $options If a boolean, uses that as the value for 'parseLimit'
         *  - parseLimit: (bool, default true) Whether to parse the 'max' value for limit types
         *  - safeMode: (bool, default false) If true, avoid throwing for parameter validation errors.
         *    Returned parameter values might be ApiUsageException instances.
         * @return array
         */
        public function extractRequestParams( $options = [] ) {
                if ( is_bool( $options ) ) {
                        $options = [ 'parseLimit' => $options ];
                }
                $options += [
                        'parseLimit' => true,
                        'safeMode' => false,
                ];

                $parseLimit = (bool)$options['parseLimit'];

                // Cache parameters, for performance and to avoid T26564.
                if ( !isset( $this->mParamCache[$parseLimit] ) ) {
                        $params = $this->getFinalParams() ?: [];
                        $results = [];
                        $warned = [];

                        // Process all non-templates and save templates for secondary
                        // processing.
                        $toProcess = [];
                        foreach ( $params as $paramName => $paramSettings ) {
                                if ( isset( $paramSettings[self::PARAM_TEMPLATE_VARS] ) ) {
                                        $toProcess[] = [ $paramName, $paramSettings[self::PARAM_TEMPLATE_VARS], $paramSettings ];
                                } else {
                                        try {
                                                $results[$paramName] = $this->getParameterFromSettings(
                                                        $paramName, $paramSettings, $parseLimit
                                                );
                                        } catch ( ApiUsageException $ex ) {
                                                $results[$paramName] = $ex;
                                        }
                                }
                        }

                        // Now process all the templates by successively replacing the
                        // placeholders with all client-supplied values.
                        // This bit duplicates JavaScript logic in
                        // ApiSandbox.PageLayout.prototype.updateTemplatedParams().
                        // If you update this, see if that needs updating too.
                        while ( $toProcess ) {
                                list( $name, $targets, $settings ) = array_shift( $toProcess );

                                foreach ( $targets as $placeholder => $target ) {
                                        if ( !array_key_exists( $target, $results ) ) {
                                                // The target wasn't processed yet, try the next one.
                                                // If all hit this case, the parameter has no expansions.
                                                continue;
                                        }
                                        if ( !is_array( $results[$target] ) || !$results[$target] ) {
                                                // The target was processed but has no (valid) values.
                                                // That means it has no expansions.
                                                break;
                                        }

                                        // Expand this target in the name and all other targets,
                                        // then requeue if there are more targets left or put in
                                        // $results if all are done.
                                        unset( $targets[$placeholder] );
                                        $placeholder = '{' . $placeholder . '}';
                                        // @phan-suppress-next-line PhanTypeNoAccessiblePropertiesForeach
                                        foreach ( $results[$target] as $value ) {
                                                if ( !preg_match( '/^[^{}]*$/', $value ) ) {
                                                        // Skip values that make invalid parameter names.
                                                        $encTargetName = $this->encodeParamName( $target );
                                                        if ( !isset( $warned[$encTargetName][$value] ) ) {
                                                                $warned[$encTargetName][$value] = true;
                                                                $this->addWarning( [
                                                                        'apiwarn-ignoring-invalid-templated-value',
                                                                        wfEscapeWikiText( $encTargetName ),
                                                                        wfEscapeWikiText( $value ),
                                                                ] );
                                                        }
                                                        continue;
                                                }

                                                $newName = str_replace( $placeholder, $value, $name );
                                                if ( !$targets ) {
                                                        try {
                                                                $results[$newName] = $this->getParameterFromSettings( $newName, $settings, $parseLimit );
                                                        } catch ( ApiUsageException $ex ) {
                                                                $results[$newName] = $ex;
                                                        }
                                                } else {
                                                        $newTargets = [];
                                                        foreach ( $targets as $k => $v ) {
                                                                $newTargets[$k] = str_replace( $placeholder, $value, $v );
                                                        }
                                                        $toProcess[] = [ $newName, $newTargets, $settings ];
                                                }
                                        }
                                        break;
                                }
                        }

                        $this->mParamCache[$parseLimit] = $results;
                }

                $ret = $this->mParamCache[$parseLimit];
                if ( !$options['safeMode'] ) {
                        foreach ( $ret as $v ) {
                                if ( $v instanceof ApiUsageException ) {
                                        throw $v;
                                }
                        }
                }

                return $this->mParamCache[$parseLimit];
        }

        /**
         * Get a value for the given parameter
         * @param string $paramName Parameter name
         * @param bool $parseLimit See extractRequestParams()
         * @return mixed Parameter value
         */
        protected function getParameter( $paramName, $parseLimit = true ) {
                $ret = $this->extractRequestParams( [
                        'parseLimit' => $parseLimit,
                        'safeMode' => true,
                ] )[$paramName];
                if ( $ret instanceof ApiUsageException ) {
                        throw $ret;
                }
                return $ret;
        }

        /**
         * Die if none or more than one of a certain set of parameters is set and not false.
         *
         * @param array $params User provided set of parameters, as from $this->extractRequestParams()
         * @param string $required,... Names of parameters of which exactly one must be set
         */
        public function requireOnlyOneParameter( $params, $required /*...*/ ) {
                $required = func_get_args();
                array_shift( $required );

                $intersection = array_intersect( array_keys( array_filter( $params,
                        [ $this, 'parameterNotEmpty' ] ) ), $required );

                if ( count( $intersection ) > 1 ) {
                        $this->dieWithError( [
                                'apierror-invalidparammix',
                                Message::listParam( array_map(
                                        function ( $p ) {
                                                return '<var>' . $this->encodeParamName( $p ) . '</var>';
                                        },
                                        array_values( $intersection )
                                ) ),
                                count( $intersection ),
                        ] );
                } elseif ( count( $intersection ) == 0 ) {
                        $this->dieWithError( [
                                'apierror-missingparam-one-of',
                                Message::listParam( array_map(
                                        function ( $p ) {
                                                return '<var>' . $this->encodeParamName( $p ) . '</var>';
                                        },
                                        array_values( $required )
                                ) ),
                                count( $required ),
                        ], 'missingparam' );
                }
        }

        /**
         * Die if more than one of a certain set of parameters is set and not false.
         *
         * @param array $params User provided set of parameters, as from $this->extractRequestParams()
         * @param string $required,... Names of parameters of which at most one must be set
         */
        public function requireMaxOneParameter( $params, $required /*...*/ ) {
                $required = func_get_args();
                array_shift( $required );

                $intersection = array_intersect( array_keys( array_filter( $params,
                        [ $this, 'parameterNotEmpty' ] ) ), $required );

                if ( count( $intersection ) > 1 ) {
                        $this->dieWithError( [
                                'apierror-invalidparammix',
                                Message::listParam( array_map(
                                        function ( $p ) {
                                                return '<var>' . $this->encodeParamName( $p ) . '</var>';
                                        },
                                        array_values( $intersection )
                                ) ),
                                count( $intersection ),
                        ] );
                }
        }

        /**
         * Die if none of a certain set of parameters is set and not false.
         *
         * @since 1.23
         * @param array $params User provided set of parameters, as from $this->extractRequestParams()
         * @param string $required,... Names of parameters of which at least one must be set
         */
        public function requireAtLeastOneParameter( $params, $required /*...*/ ) {
                $required = func_get_args();
                array_shift( $required );

                $intersection = array_intersect(
                        array_keys( array_filter( $params, [ $this, 'parameterNotEmpty' ] ) ),
                        $required
                );

                if ( count( $intersection ) == 0 ) {
                        $this->dieWithError( [
                                'apierror-missingparam-at-least-one-of',
                                Message::listParam( array_map(
                                        function ( $p ) {
                                                return '<var>' . $this->encodeParamName( $p ) . '</var>';
                                        },
                                        array_values( $required )
                                ) ),
                                count( $required ),
                        ], 'missingparam' );
                }
        }

        /**
         * Die if any of the specified parameters were found in the query part of
         * the URL rather than the post body.
         * @since 1.28
         * @param string[] $params Parameters to check
         * @param string $prefix Set to 'noprefix' to skip calling $this->encodeParamName()
         */
        public function requirePostedParameters( $params, $prefix = 'prefix' ) {
                // Skip if $wgDebugAPI is set or we're in internal mode
                if ( $this->getConfig()->get( 'DebugAPI' ) || $this->getMain()->isInternalMode() ) {
                        return;
                }

                $queryValues = $this->getRequest()->getQueryValues();
                $badParams = [];
                foreach ( $params as $param ) {
                        if ( $prefix !== 'noprefix' ) {
                                $param = $this->encodeParamName( $param );
                        }
                        if ( array_key_exists( $param, $queryValues ) ) {
                                $badParams[] = $param;
                        }
                }

                if ( $badParams ) {
                        $this->dieWithError(
                                [ 'apierror-mustpostparams', implode( ', ', $badParams ), count( $badParams ) ]
                        );
                }
        }

        /**
         * Callback function used in requireOnlyOneParameter to check whether required parameters are set
         *
         * @param object $x Parameter to check is not null/false
         * @return bool
         */
        private function parameterNotEmpty( $x ) {
                return !is_null( $x ) && $x !== false;
        }

        /**
         * Get a WikiPage object from a title or pageid param, if possible.
         * Can die, if no param is set or if the title or page id is not valid.
         *
         * @param array $params User provided set of parameters, as from $this->extractRequestParams()
         * @param bool|string $load Whether load the object's state from the database:
         *        - false: don't load (if the pageid is given, it will still be loaded)
         *        - 'fromdb': load from a replica DB
         *        - 'fromdbmaster': load from the master database
         * @return WikiPage
         */
        public function getTitleOrPageId( $params, $load = false ) {
                $this->requireOnlyOneParameter( $params, 'title', 'pageid' );

                $pageObj = null;
                if ( isset( $params['title'] ) ) {
                        $titleObj = Title::newFromText( $params['title'] );
                        if ( !$titleObj || $titleObj->isExternal() ) {
                                $this->dieWithError( [ 'apierror-invalidtitle', wfEscapeWikiText( $params['title'] ) ] );
                        }
                        if ( !$titleObj->canExist() ) {
                                $this->dieWithError( 'apierror-pagecannotexist' );
                        }
                        $pageObj = WikiPage::factory( $titleObj );
                        if ( $load !== false ) {
                                $pageObj->loadPageData( $load );
                        }
                } elseif ( isset( $params['pageid'] ) ) {
                        if ( $load === false ) {
                                $load = 'fromdb';
                        }
                        $pageObj = WikiPage::newFromID( $params['pageid'], $load );
                        if ( !$pageObj ) {
                                $this->dieWithError( [ 'apierror-nosuchpageid', $params['pageid'] ] );
                        }
                }

                return $pageObj;
        }

        /**
         * Get a Title object from a title or pageid param, if possible.
         * Can die, if no param is set or if the title or page id is not valid.
         *
         * @since 1.29
         * @param array $params User provided set of parameters, as from $this->extractRequestParams()
         * @return Title
         */
        public function getTitleFromTitleOrPageId( $params ) {
                $this->requireOnlyOneParameter( $params, 'title', 'pageid' );

                $titleObj = null;
                if ( isset( $params['title'] ) ) {
                        $titleObj = Title::newFromText( $params['title'] );
                        if ( !$titleObj || $titleObj->isExternal() ) {
                                $this->dieWithError( [ 'apierror-invalidtitle', wfEscapeWikiText( $params['title'] ) ] );
                        }
                        return $titleObj;
                } elseif ( isset( $params['pageid'] ) ) {
                        $titleObj = Title::newFromID( $params['pageid'] );
                        if ( !$titleObj ) {
                                $this->dieWithError( [ 'apierror-nosuchpageid', $params['pageid'] ] );
                        }
                }

                return $titleObj;
        }

        /**
         * Return true if we're to watch the page, false if not, null if no change.
         * @param string $watchlist Valid values: 'watch', 'unwatch', 'preferences', 'nochange'
         * @param Title $titleObj The page under consideration
         * @param string|null $userOption The user option to consider when $watchlist=preferences.
         *    If not set will use watchdefault always and watchcreations if $titleObj doesn't exist.
         * @return bool
         */
        protected function getWatchlistValue( $watchlist, $titleObj, $userOption = null ) {
                $userWatching = $this->getUser()->isWatched( $titleObj, User::IGNORE_USER_RIGHTS );

                switch ( $watchlist ) {
                        case 'watch':
                                return true;

                        case 'unwatch':
                                return false;

                        case 'preferences':
                                # If the user is already watching, don't bother checking
                                if ( $userWatching ) {
                                        return true;
                                }
                                # If no user option was passed, use watchdefault and watchcreations
                                if ( is_null( $userOption ) ) {
                                        return $this->getUser()->getBoolOption( 'watchdefault' ) ||
                                                $this->getUser()->getBoolOption( 'watchcreations' ) && !$titleObj->exists();
                                }

                                # Watch the article based on the user preference
                                return $this->getUser()->getBoolOption( $userOption );

                        case 'nochange':
                                return $userWatching;

                        default:
                                return $userWatching;
                }
        }

        /**
         * Using the settings determine the value for the given parameter
         *
         * @param string $paramName Parameter name
         * @param array|mixed $paramSettings Default value or an array of settings
         *  using PARAM_* constants.
         * @param bool $parseLimit Whether to parse and validate 'limit' parameters
         * @return mixed Parameter value
         */
        protected function getParameterFromSettings( $paramName, $paramSettings, $parseLimit ) {
                // Some classes may decide to change parameter names
                $encParamName = $this->encodeParamName( $paramName );

                // Shorthand
                if ( !is_array( $paramSettings ) ) {
                        $paramSettings = [
                                self::PARAM_DFLT => $paramSettings,
                        ];
                }

                $default = $paramSettings[self::PARAM_DFLT] ?? null;
                $multi = $paramSettings[self::PARAM_ISMULTI] ?? false;
                $multiLimit1 = $paramSettings[self::PARAM_ISMULTI_LIMIT1] ?? null;
                $multiLimit2 = $paramSettings[self::PARAM_ISMULTI_LIMIT2] ?? null;
                $type = $paramSettings[self::PARAM_TYPE] ?? null;
                $dupes = $paramSettings[self::PARAM_ALLOW_DUPLICATES] ?? false;
                $deprecated = $paramSettings[self::PARAM_DEPRECATED] ?? false;
                $deprecatedValues = $paramSettings[self::PARAM_DEPRECATED_VALUES] ?? [];
                $required = $paramSettings[self::PARAM_REQUIRED] ?? false;
                $allowAll = $paramSettings[self::PARAM_ALL] ?? false;

                // When type is not given, and no choices, the type is the same as $default
                if ( !isset( $type ) ) {
                        if ( isset( $default ) ) {
                                $type = gettype( $default );
                        } else {
                                $type = 'NULL'; // allow everything
                        }
                }

                if ( $type == 'password' || !empty( $paramSettings[self::PARAM_SENSITIVE] ) ) {
                        $this->getMain()->markParamsSensitive( $encParamName );
                }

                if ( $type == 'boolean' ) {
                        if ( isset( $default ) && $default !== false ) {
                                // Having a default value of anything other than 'false' is not allowed
                                self::dieDebug(
                                        __METHOD__,
                                        "Boolean param $encParamName's default is set to '$default'. " .
                                                'Boolean parameters must default to false.'
                                );
                        }

                        $value = $this->getMain()->getCheck( $encParamName );
                        $provided = $value;
                } elseif ( $type == 'upload' ) {
                        if ( isset( $default ) ) {
                                // Having a default value is not allowed
                                self::dieDebug(
                                        __METHOD__,
                                        "File upload param $encParamName's default is set to " .
                                                "'$default'. File upload parameters may not have a default." );
                        }
                        if ( $multi ) {
                                self::dieDebug( __METHOD__, "Multi-values not supported for $encParamName" );
                        }
                        $value = $this->getMain()->getUpload( $encParamName );
                        $provided = $value->exists();
                        if ( !$value->exists() ) {
                                // This will get the value without trying to normalize it
                                // (because trying to normalize a large binary file
                                // accidentally uploaded as a field fails spectacularly)
                                $value = $this->getMain()->getRequest()->unsetVal( $encParamName );
                                if ( $value !== null ) {
                                        $this->dieWithError(
                                                [ 'apierror-badupload', $encParamName ],
                                                "badupload_{$encParamName}"
                                        );
                                }
                        }
                } else {
                        $value = $this->getMain()->getVal( $encParamName, $default );
                        $provided = $this->getMain()->getCheck( $encParamName );

                        if ( isset( $value ) && $type == 'namespace' ) {
                                $type = MediaWikiServices::getInstance()->getNamespaceInfo()->
                                        getValidNamespaces();
                                if ( isset( $paramSettings[self::PARAM_EXTRA_NAMESPACES] ) &&
                                        is_array( $paramSettings[self::PARAM_EXTRA_NAMESPACES] )
                                ) {
                                        $type = array_merge( $type, $paramSettings[self::PARAM_EXTRA_NAMESPACES] );
                                }
                                // Namespace parameters allow ALL_DEFAULT_STRING to be used to
                                // specify all namespaces irrespective of PARAM_ALL.
                                $allowAll = true;
                        }
                        if ( isset( $value ) && $type == 'submodule' ) {
                                if ( isset( $paramSettings[self::PARAM_SUBMODULE_MAP] ) ) {
                                        $type = array_keys( $paramSettings[self::PARAM_SUBMODULE_MAP] );
                                } else {
                                        $type = $this->getModuleManager()->getNames( $paramName );
                                }
                        }

                        $request = $this->getMain()->getRequest();
                        $rawValue = $request->getRawVal( $encParamName );
                        if ( $rawValue === null ) {
                                $rawValue = $default;
                        }

                        // Preserve U+001F for self::parseMultiValue(), or error out if that won't be called
                        if ( isset( $value ) && substr( $rawValue, 0, 1 ) === "\x1f" ) {
                                if ( $multi ) {
                                        // This loses the potential checkTitleEncoding() transformation done by
                                        // WebRequest for $_GET. Let's call that a feature.
                                        $value = implode( "\x1f", $request->normalizeUnicode( explode( "\x1f", $rawValue ) ) );
                                } else {
                                        $this->dieWithError( 'apierror-badvalue-notmultivalue', 'badvalue_notmultivalue' );
                                }
                        }

                        // Check for NFC normalization, and warn
                        if ( $rawValue !== $value ) {
                                $this->handleParamNormalization( $paramName, $value, $rawValue );
                        }
                }

                $allSpecifier = ( is_string( $allowAll ) ? $allowAll : self::ALL_DEFAULT_STRING );
                if ( $allowAll && $multi && is_array( $type ) && in_array( $allSpecifier, $type, true ) ) {
                        self::dieDebug(
                                __METHOD__,
                                "For param $encParamName, PARAM_ALL collides with a possible value" );
                }
                if ( isset( $value ) && ( $multi || is_array( $type ) ) ) {
                        $value = $this->parseMultiValue(
                                $encParamName,
                                $value,
                                $multi,
                                is_array( $type ) ? $type : null,
                                $allowAll ? $allSpecifier : null,
                                $multiLimit1,
                                $multiLimit2
                        );
                }

                if ( isset( $value ) ) {
                        // More validation only when choices were not given
                        // choices were validated in parseMultiValue()
                        if ( !is_array( $type ) ) {
                                switch ( $type ) {
                                        case 'NULL': // nothing to do
                                                break;
                                        case 'string':
                                        case 'text':
                                        case 'password':
                                                if ( $required && $value === '' ) {
                                                        $this->dieWithError( [ 'apierror-missingparam', $encParamName ] );
                                                }
                                                break;
                                        case 'integer': // Force everything using intval() and optionally validate limits
                                                $min = $paramSettings[self::PARAM_MIN] ?? null;
                                                $max = $paramSettings[self::PARAM_MAX] ?? null;
                                                $enforceLimits = $paramSettings[self::PARAM_RANGE_ENFORCE] ?? false;

                                                if ( is_array( $value ) ) {
                                                        $value = array_map( 'intval', $value );
                                                        if ( !is_null( $min ) || !is_null( $max ) ) {
                                                                foreach ( $value as &$v ) {
                                                                        $this->validateLimit( $paramName, $v, $min, $max, null, $enforceLimits );
                                                                }
                                                        }
                                                } else {
                                                        $value = (int)$value;
                                                        if ( !is_null( $min ) || !is_null( $max ) ) {
                                                                $this->validateLimit( $paramName, $value, $min, $max, null, $enforceLimits );
                                                        }
                                                }
                                                break;
                                        case 'limit':
                                                if ( !$parseLimit ) {
                                                        // Don't do any validation whatsoever
                                                        break;
                                                }
                                                if ( !isset( $paramSettings[self::PARAM_MAX] )
                                                        || !isset( $paramSettings[self::PARAM_MAX2] )
                                                ) {
                                                        self::dieDebug(
                                                                __METHOD__,
                                                                "MAX1 or MAX2 are not defined for the limit $encParamName"
                                                        );
                                                }
                                                if ( $multi ) {
                                                        self::dieDebug( __METHOD__, "Multi-values not supported for $encParamName" );
                                                }
                                                $min = $paramSettings[self::PARAM_MIN] ?? 0;
                                                if ( $value == 'max' ) {
                                                        $value = $this->getMain()->canApiHighLimits()
                                                                ? $paramSettings[self::PARAM_MAX2]
                                                                : $paramSettings[self::PARAM_MAX];
                                                        $this->getResult()->addParsedLimit( $this->getModuleName(), $value );
                                                } else {
                                                        $value = (int)$value;
                                                        $this->validateLimit(
                                                                $paramName,
                                                                $value,
                                                                $min,
                                                                $paramSettings[self::PARAM_MAX],
                                                                $paramSettings[self::PARAM_MAX2]
                                                        );
                                                }
                                                break;
                                        case 'boolean':
                                                if ( $multi ) {
                                                        self::dieDebug( __METHOD__, "Multi-values not supported for $encParamName" );
                                                }
                                                break;
                                        case 'timestamp':
                                                if ( is_array( $value ) ) {
                                                        foreach ( $value as $key => $val ) {
                                                                $value[$key] = $this->validateTimestamp( $val, $encParamName );
                                                        }
                                                } else {
                                                        $value = $this->validateTimestamp( $value, $encParamName );
                                                }
                                                break;
                                        case 'user':
                                                if ( is_array( $value ) ) {
                                                        foreach ( $value as $key => $val ) {
                                                                $value[$key] = $this->validateUser( $val, $encParamName );
                                                        }
                                                } else {
                                                        $value = $this->validateUser( $value, $encParamName );
                                                }
                                                break;
                                        case 'upload': // nothing to do
                                                break;
                                        case 'tags':
                                                // If change tagging was requested, check that the tags are valid.
                                                if ( !is_array( $value ) && !$multi ) {
                                                        $value = [ $value ];
                                                }
                                                $tagsStatus = ChangeTags::canAddTagsAccompanyingChange( $value );
                                                if ( !$tagsStatus->isGood() ) {
                                                        $this->dieStatus( $tagsStatus );
                                                }
                                                break;
                                        default:
                                                self::dieDebug( __METHOD__, "Param $encParamName's type is unknown - $type" );
                                }
                        }

                        // Throw out duplicates if requested
                        if ( !$dupes && is_array( $value ) ) {
                                $value = array_unique( $value );
                        }

                        if ( in_array( $type, [ 'NULL', 'string', 'text', 'password' ], true ) ) {
                                foreach ( (array)$value as $val ) {
                                        if ( isset( $paramSettings[self::PARAM_MAX_BYTES] )
                                                && strlen( $val ) > $paramSettings[self::PARAM_MAX_BYTES]
                                        ) {
                                                $this->dieWithError( [ 'apierror-maxbytes', $encParamName,
                                                        $paramSettings[self::PARAM_MAX_BYTES] ] );
                                        }
                                        if ( isset( $paramSettings[self::PARAM_MAX_CHARS] )
                                                && mb_strlen( $val, 'UTF-8' ) > $paramSettings[self::PARAM_MAX_CHARS]
                                        ) {
                                                $this->dieWithError( [ 'apierror-maxchars', $encParamName,
                                                        $paramSettings[self::PARAM_MAX_CHARS] ] );
                                        }
                                }
                        }

                        // Set a warning if a deprecated parameter has been passed
                        if ( $deprecated && $provided ) {
                                $feature = $encParamName;
                                $m = $this;
                                while ( !$m->isMain() ) {
                                        $p = $m->getParent();
                                        $name = $m->getModuleName();
                                        $param = $p->encodeParamName( $p->getModuleManager()->getModuleGroup( $name ) );
                                        $feature = "{$param}={$name}&{$feature}";
                                        $m = $p;
                                }
                                $this->addDeprecation( [ 'apiwarn-deprecation-parameter', $encParamName ], $feature );
                        }

                        // Set a warning if a deprecated parameter value has been passed
                        $usedDeprecatedValues = $deprecatedValues && $provided
                                ? array_intersect( array_keys( $deprecatedValues ), (array)$value )
                                : [];
                        if ( $usedDeprecatedValues ) {
                                $feature = "$encParamName=";
                                $m = $this;
                                while ( !$m->isMain() ) {
                                        $p = $m->getParent();
                                        $name = $m->getModuleName();
                                        $param = $p->encodeParamName( $p->getModuleManager()->getModuleGroup( $name ) );
                                        $feature = "{$param}={$name}&{$feature}";
                                        $m = $p;
                                }
                                foreach ( $usedDeprecatedValues as $v ) {
                                        $msg = $deprecatedValues[$v];
                                        if ( $msg === true ) {
                                                $msg = [ 'apiwarn-deprecation-parameter', "$encParamName=$v" ];
                                        }
                                        $this->addDeprecation( $msg, "$feature$v" );
                                }
                        }
                } elseif ( $required ) {
                        $this->dieWithError( [ 'apierror-missingparam', $encParamName ] );
                }

                return $value;
        }

        /**
         * Handle when a parameter was Unicode-normalized
         * @since 1.28
         * @param string $paramName Unprefixed parameter name
         * @param string $value Input that will be used.
         * @param string $rawValue Input before normalization.
         */
        protected function handleParamNormalization( $paramName, $value, $rawValue ) {
                $encParamName = $this->encodeParamName( $paramName );
                $this->addWarning( [ 'apiwarn-badutf8', $encParamName ] );
        }

        /**
         * Split a multi-valued parameter string, like explode()
         * @since 1.28
         * @param string $value
         * @param int $limit
         * @return string[]
         */
        protected function explodeMultiValue( $value, $limit ) {
                if ( substr( $value, 0, 1 ) === "\x1f" ) {
                        $sep = "\x1f";
                        $value = substr( $value, 1 );
                } else {
                        $sep = '|';
                }

                return explode( $sep, $value, $limit );
        }

        /**
         * Return an array of values that were given in a 'a|b|c' notation,
         * after it optionally validates them against the list allowed values.
         *
         * @param string $valueName The name of the parameter (for error
         *  reporting)
         * @param mixed $value The value being parsed
         * @param bool $allowMultiple Can $value contain more than one value
         *  separated by '|'?
         * @param string[]|null $allowedValues An array of values to check against. If
         *  null, all values are accepted.
         * @param string|null $allSpecifier String to use to specify all allowed values, or null
         *  if this behavior should not be allowed
         * @param int|null $limit1 Maximum number of values, for normal users.
         * @param int|null $limit2 Maximum number of values, for users with the apihighlimits right.
         * @return string|string[] (allowMultiple ? an_array_of_values : a_single_value)
         */
        protected function parseMultiValue( $valueName, $value, $allowMultiple, $allowedValues,
                $allSpecifier = null, $limit1 = null, $limit2 = null
        ) {
                if ( ( $value === '' || $value === "\x1f" ) && $allowMultiple ) {
                        return [];
                }
                $limit1 = $limit1 ?: self::LIMIT_SML1;
                $limit2 = $limit2 ?: self::LIMIT_SML2;

                // This is a bit awkward, but we want to avoid calling canApiHighLimits()
                // because it unstubs $wgUser
                $valuesList = $this->explodeMultiValue( $value, $limit2 + 1 );
                $sizeLimit = count( $valuesList ) > $limit1 && $this->mMainModule->canApiHighLimits()
                        ? $limit2
                        : $limit1;

                if ( $allowMultiple && is_array( $allowedValues ) && $allSpecifier &&
                        count( $valuesList ) === 1 && $valuesList[0] === $allSpecifier
                ) {
                        return $allowedValues;
                }

                if ( count( $valuesList ) > $sizeLimit ) {
                        $this->dieWithError(
                                [ 'apierror-toomanyvalues', $valueName, $sizeLimit ],
                                "too-many-$valueName"
                        );
                }

                if ( !$allowMultiple && count( $valuesList ) != 1 ) {
                        // T35482 - Allow entries with | in them for non-multiple values
                        if ( in_array( $value, $allowedValues, true ) ) {
                                return $value;
                        }

                        $values = array_map( function ( $v ) {
                                return '<kbd>' . wfEscapeWikiText( $v ) . '</kbd>';
                        }, $allowedValues );
                        $this->dieWithError( [
                                'apierror-multival-only-one-of',
                                $valueName,
                                Message::listParam( $values ),
                                count( $values ),
                        ], "multival_$valueName" );
                }

                if ( is_array( $allowedValues ) ) {
                        // Check for unknown values
                        $unknown = array_map( 'wfEscapeWikiText', array_diff( $valuesList, $allowedValues ) );
                        if ( count( $unknown ) ) {
                                if ( $allowMultiple ) {
                                        $this->addWarning( [
                                                'apiwarn-unrecognizedvalues',
                                                $valueName,
                                                Message::listParam( $unknown, 'comma' ),
                                                count( $unknown ),
                                        ] );
                                } else {
                                        $this->dieWithError(
                                                [ 'apierror-unrecognizedvalue', $valueName, wfEscapeWikiText( $valuesList[0] ) ],
                                                "unknown_$valueName"
                                        );
                                }
                        }
                        // Now throw them out
                        $valuesList = array_intersect( $valuesList, $allowedValues );
                }

                return $allowMultiple ? $valuesList : $valuesList[0];
        }

        /**
         * Validate the value against the minimum and user/bot maximum limits.
         * Prints usage info on failure.
         * @param string $paramName Parameter name
         * @param int &$value Parameter value
         * @param int|null $min Minimum value
         * @param int|null $max Maximum value for users
         * @param int|null $botMax Maximum value for sysops/bots
         * @param bool $enforceLimits Whether to enforce (die) if value is outside limits
         */
        protected function validateLimit( $paramName, &$value, $min, $max, $botMax = null,
                $enforceLimits = false
        ) {
                if ( !is_null( $min ) && $value < $min ) {
                        $msg = ApiMessage::create(
                                [ 'apierror-integeroutofrange-belowminimum',
                                        $this->encodeParamName( $paramName ), $min, $value ],
                                'integeroutofrange',
                                [ 'min' => $min, 'max' => $max, 'botMax' => $botMax ?: $max ]
                        );
                        $this->warnOrDie( $msg, $enforceLimits );
                        $value = $min;
                }

                // Minimum is always validated, whereas maximum is checked only if not
                // running in internal call mode
                if ( $this->getMain()->isInternalMode() ) {
                        return;
                }

                // Optimization: do not check user's bot status unless really needed -- skips db query
                // assumes $botMax >= $max
                if ( !is_null( $max ) && $value > $max ) {
                        if ( !is_null( $botMax ) && $this->getMain()->canApiHighLimits() ) {
                                if ( $value > $botMax ) {
                                        $msg = ApiMessage::create(
                                                [ 'apierror-integeroutofrange-abovebotmax',
                                                        $this->encodeParamName( $paramName ), $botMax, $value ],
                                                'integeroutofrange',
                                                [ 'min' => $min, 'max' => $max, 'botMax' => $botMax ?: $max ]
                                        );
                                        $this->warnOrDie( $msg, $enforceLimits );
                                        $value = $botMax;
                                }
                        } else {
                                $msg = ApiMessage::create(
                                        [ 'apierror-integeroutofrange-abovemax',
                                                $this->encodeParamName( $paramName ), $max, $value ],
                                        'integeroutofrange',
                                        [ 'min' => $min, 'max' => $max, 'botMax' => $botMax ?: $max ]
                                );
                                $this->warnOrDie( $msg, $enforceLimits );
                                $value = $max;
                        }
                }
        }

        /**
         * Validate and normalize parameters of type 'timestamp'
         * @param string $value Parameter value
         * @param string $encParamName Parameter name
         * @return string Validated and normalized parameter
         */
        protected function validateTimestamp( $value, $encParamName ) {
                // Confusing synonyms for the current time accepted by wfTimestamp()
                // (wfTimestamp() also accepts various non-strings and the string of 14
                // ASCII NUL bytes, but those can't get here)
                if ( !$value ) {
                        $this->addDeprecation(
                                [ 'apiwarn-unclearnowtimestamp', $encParamName, wfEscapeWikiText( $value ) ],
                                'unclear-"now"-timestamp'
                        );
                        return wfTimestamp( TS_MW );
                }

                // Explicit synonym for the current time
                if ( $value === 'now' ) {
                        return wfTimestamp( TS_MW );
                }

                $timestamp = wfTimestamp( TS_MW, $value );
                if ( $timestamp === false ) {
                        $this->dieWithError(
                                [ 'apierror-badtimestamp', $encParamName, wfEscapeWikiText( $value ) ],
                                "badtimestamp_{$encParamName}"
                        );
                }

                return $timestamp;
        }

        /**
         * Validate the supplied token.
         *
         * @since 1.24
         * @param string $token Supplied token
         * @param array $params All supplied parameters for the module
         * @return bool
         * @throws MWException
         */
        final public function validateToken( $token, array $params ) {
                $tokenType = $this->needsToken();
                $salts = ApiQueryTokens::getTokenTypeSalts();
                if ( !isset( $salts[$tokenType] ) ) {
                        throw new MWException(
                                "Module '{$this->getModuleName()}' tried to use token type '$tokenType' " .
                                        'without registering it'
                        );
                }

                $tokenObj = ApiQueryTokens::getToken(
                        $this->getUser(), $this->getRequest()->getSession(), $salts[$tokenType]
                );
                if ( $tokenObj->match( $token ) ) {
                        return true;
                }

                $webUiSalt = $this->getWebUITokenSalt( $params );
                if ( $webUiSalt !== null && $this->getUser()->matchEditToken(
                        $token,
                        $webUiSalt,
                        $this->getRequest()
                ) ) {
                        return true;
                }

                return false;
        }

        /**
         * Validate and normalize parameters of type 'user'
         * @param string $value Parameter value
         * @param string $encParamName Parameter name
         * @return string Validated and normalized parameter
         */
        private function validateUser( $value, $encParamName ) {
                if ( ExternalUserNames::isExternal( $value ) && User::newFromName( $value, false ) ) {
                        return $value;
                }

                $name = User::getCanonicalName( $value, 'valid' );
                if ( $name !== false ) {
                        return $name;
                }

                if (
                        // We allow ranges as well, for blocks.
                        IP::isIPAddress( $value ) ||
                        // See comment for User::isIP.  We don't just call that function
                        // here because it also returns true for things like
                        // 300.300.300.300 that are neither valid usernames nor valid IP
                        // addresses.
                        preg_match(
                                '/^' . RE_IP_BYTE . '\.' . RE_IP_BYTE . '\.' . RE_IP_BYTE . '\.xxx$/',
                                $value
                        )
                ) {
                        return IP::sanitizeIP( $value );
                }

                $this->dieWithError(
                        [ 'apierror-baduser', $encParamName, wfEscapeWikiText( $value ) ],
                        "baduser_{$encParamName}"
                );
        }

        /** @} */

        /************************************************************************//**
         * @name   Utility methods
         * @{
         */

        /**
         * Set a watch (or unwatch) based the based on a watchlist parameter.
         * @param string $watch Valid values: 'watch', 'unwatch', 'preferences', 'nochange'
         * @param Title $titleObj The article's title to change
         * @param string|null $userOption The user option to consider when $watch=preferences
         */
        protected function setWatch( $watch, $titleObj, $userOption = null ) {
                $value = $this->getWatchlistValue( $watch, $titleObj, $userOption );
                if ( $value === null ) {
                        return;
                }

                WatchAction::doWatchOrUnwatch( $value, $titleObj, $this->getUser() );
        }

        /**
         * Gets the user for whom to get the watchlist
         *
         * @param array $params
         * @return User
         */
        public function getWatchlistUser( $params ) {
                if ( !is_null( $params['owner'] ) && !is_null( $params['token'] ) ) {
                        $user = User::newFromName( $params['owner'], false );
                        if ( !( $user && $user->getId() ) ) {
                                $this->dieWithError(
                                        [ 'nosuchusershort', wfEscapeWikiText( $params['owner'] ) ], 'bad_wlowner'
                                );
                        }
                        $token = $user->getOption( 'watchlisttoken' );
                        if ( $token == '' || !hash_equals( $token, $params['token'] ) ) {
                                $this->dieWithError( 'apierror-bad-watchlist-token', 'bad_wltoken' );
                        }
                } else {
                        if ( !$this->getUser()->isLoggedIn() ) {
                                $this->dieWithError( 'watchlistanontext', 'notloggedin' );
                        }
                        $this->checkUserRightsAny( 'viewmywatchlist' );
                        $user = $this->getUser();
                }

                return $user;
        }

        /**
         * Create a Message from a string or array
         *
         * A string is used as a message key. An array has the message key as the
         * first value and message parameters as subsequent values.
         *
         * @since 1.25
         * @param string|array|Message $msg
         * @param IContextSource $context
         * @param array|null $params
         * @return Message|null
         */
        public static function makeMessage( $msg, IContextSource $context, array $params = null ) {
                if ( is_string( $msg ) ) {
                        $msg = wfMessage( $msg );
                } elseif ( is_array( $msg ) ) {
                        $msg = wfMessage( ...$msg );
                }
                if ( !$msg instanceof Message ) {
                        return null;
                }

                $msg->setContext( $context );
                if ( $params ) {
                        $msg->params( $params );
                }

                return $msg;
        }

        /**
         * Turn an array of message keys or key+param arrays into a Status
         * @since 1.29
         * @param array $errors
         * @param User|null $user
         * @return Status
         */
        public function errorArrayToStatus( array $errors, User $user = null ) {
                if ( $user === null ) {
                        $user = $this->getUser();
                }

                $status = Status::newGood();
                foreach ( $errors as $error ) {
                        if ( !is_array( $error ) ) {
                                $error = [ $error ];
                        }
                        if ( is_string( $error[0] ) && isset( self::$blockMsgMap[$error[0]] ) && $user->getBlock() ) {
                                list( $msg, $code ) = self::$blockMsgMap[$error[0]];
                                $status->fatal( ApiMessage::create( $msg, $code,
                                        [ 'blockinfo' => $this->getBlockDetails( $user->getBlock() ) ]
                                ) );
                        } else {
                                $status->fatal( ...$error );
                        }
                }
                return $status;
        }

        /**
         * Add block info to block messages in a Status
         * @since 1.33
         * @param StatusValue $status
         * @param User|null $user
         */
        public function addBlockInfoToStatus( StatusValue $status, User $user = null ) {
                if ( $user === null ) {
                        $user = $this->getUser();
                }

                foreach ( self::$blockMsgMap as $msg => list( $apiMsg, $code ) ) {
                        if ( $status->hasMessage( $msg ) && $user->getBlock() ) {
                                $status->replaceMessage( $msg, ApiMessage::create( $apiMsg, $code,
                                        [ 'blockinfo' => $this->getBlockDetails( $user->getBlock() ) ]
                                ) );
                        }
                }
        }

        /**
         * Call wfTransactionalTimeLimit() if this request was POSTed
         * @since 1.26
         */
        protected function useTransactionalTimeLimit() {
                if ( $this->getRequest()->wasPosted() ) {
                        wfTransactionalTimeLimit();
                }
        }

        /**
         * Filter out-of-range values from a list of positive integer IDs
         * @since 1.33
         * @param array $fields Array of pairs of table and field to check
         * @param (string|int)[] $ids IDs to filter. Strings in the array are
         *  expected to be stringified ints.
         * @return (string|int)[] Filtered IDs.
         */
        protected function filterIDs( $fields, array $ids ) {
                $min = INF;
                $max = 0;
                foreach ( $fields as list( $table, $field ) ) {
                        if ( isset( self::$filterIDsCache[$table][$field] ) ) {
                                $row = self::$filterIDsCache[$table][$field];
                        } else {
                                $row = $this->getDB()->selectRow(
                                        $table,
                                        [
                                                'min_id' => "MIN($field)",
                                                'max_id' => "MAX($field)",
                                        ],
                                        '',
                                        __METHOD__
                                );
                                self::$filterIDsCache[$table][$field] = $row;
                        }
                        $min = min( $min, $row->min_id );
                        $max = max( $max, $row->max_id );
                }
                return array_filter( $ids, function ( $id ) use ( $min, $max ) {
                        return ( is_int( $id ) && $id >= 0 || ctype_digit( $id ) )
                                && $id >= $min && $id <= $max;
                } );
        }

        /** @} */

        /************************************************************************//**
         * @name   Warning and error reporting
         * @{
         */

        /**
         * Add a warning for this module.
         *
         * Users should monitor this section to notice any changes in API. Multiple
         * calls to this function will result in multiple warning messages.
         *
         * If $msg is not an ApiMessage, the message code will be derived from the
         * message key by stripping any "apiwarn-" or "apierror-" prefix.
         *
         * @since 1.29
         * @param string|array|Message $msg See ApiErrorFormatter::addWarning()
         * @param string|null $code See ApiErrorFormatter::addWarning()
         * @param array|null $data See ApiErrorFormatter::addWarning()
         */
        public function addWarning( $msg, $code = null, $data = null ) {
                $this->getErrorFormatter()->addWarning( $this->getModulePath(), $msg, $code, $data );
        }

        /**
         * Add a deprecation warning for this module.
         *
         * A combination of $this->addWarning() and $this->logFeatureUsage()
         *
         * @since 1.29
         * @param string|array|Message $msg See ApiErrorFormatter::addWarning()
         * @param string|null $feature See ApiBase::logFeatureUsage()
         * @param array|null $data See ApiErrorFormatter::addWarning()
         */
        public function addDeprecation( $msg, $feature, $data = [] ) {
                $data = (array)$data;
                if ( $feature !== null ) {
                        $data['feature'] = $feature;
                        $this->logFeatureUsage( $feature );
                }
                $this->addWarning( $msg, 'deprecation', $data );

                // No real need to deduplicate here, ApiErrorFormatter does that for
                // us (assuming the hook is deterministic).
                $msgs = [ $this->msg( 'api-usage-mailinglist-ref' ) ];
                Hooks::run( 'ApiDeprecationHelp', [ &$msgs ] );
                if ( count( $msgs ) > 1 ) {
                        $key = '$' . implode( ' $', range( 1, count( $msgs ) ) );
                        $msg = ( new RawMessage( $key ) )->params( $msgs );
                } else {
                        $msg = reset( $msgs );
                }
                $this->getMain()->addWarning( $msg, 'deprecation-help' );
        }

        /**
         * Add an error for this module without aborting
         *
         * If $msg is not an ApiMessage, the message code will be derived from the
         * message key by stripping any "apiwarn-" or "apierror-" prefix.
         *
         * @note If you want to abort processing, use self::dieWithError() instead.
         * @since 1.29
         * @param string|array|Message $msg See ApiErrorFormatter::addError()
         * @param string|null $code See ApiErrorFormatter::addError()
         * @param array|null $data See ApiErrorFormatter::addError()
         */
        public function addError( $msg, $code = null, $data = null ) {
                $this->getErrorFormatter()->addError( $this->getModulePath(), $msg, $code, $data );
        }

        /**
         * Add warnings and/or errors from a Status
         *
         * @note If you want to abort processing, use self::dieStatus() instead.
         * @since 1.29
         * @param StatusValue $status
         * @param string[] $types 'warning' and/or 'error'
         * @param string[] $filter Message keys to filter out (since 1.33)
         */
        public function addMessagesFromStatus(
                StatusValue $status, $types = [ 'warning', 'error' ], array $filter = []
        ) {
                $this->getErrorFormatter()->addMessagesFromStatus(
                        $this->getModulePath(), $status, $types, $filter
                );
        }

        /**
         * Abort execution with an error
         *
         * If $msg is not an ApiMessage, the message code will be derived from the
         * message key by stripping any "apiwarn-" or "apierror-" prefix.
         *
         * @since 1.29
         * @param string|array|Message $msg See ApiErrorFormatter::addError()
         * @param string|null $code See ApiErrorFormatter::addError()
         * @param array|null $data See ApiErrorFormatter::addError()
         * @param int|null $httpCode HTTP error code to use
         * @throws ApiUsageException always
         */
        public function dieWithError( $msg, $code = null, $data = null, $httpCode = null ) {
                throw ApiUsageException::newWithMessage( $this, $msg, $code, $data, $httpCode );
        }

        /**
         * Abort execution with an error derived from an exception
         *
         * @since 1.29
         * @param Exception|Throwable $exception See ApiErrorFormatter::getMessageFromException()
         * @param array $options See ApiErrorFormatter::getMessageFromException()
         * @throws ApiUsageException always
         */
        public function dieWithException( $exception, array $options = [] ) {
                $this->dieWithError(
                        $this->getErrorFormatter()->getMessageFromException( $exception, $options )
                );
        }

        /**
         * Adds a warning to the output, else dies
         *
         * @param ApiMessage $msg Message to show as a warning, or error message if dying
         * @param bool $enforceLimits Whether this is an enforce (die)
         */
        private function warnOrDie( ApiMessage $msg, $enforceLimits = false ) {
                if ( $enforceLimits ) {
                        $this->dieWithError( $msg );
                } else {
                        $this->addWarning( $msg );
                }
        }

        /**
         * Throw an ApiUsageException, which will (if uncaught) call the main module's
         * error handler and die with an error message including block info.
         *
         * @since 1.27
         * @param AbstractBlock $block The block used to generate the ApiUsageException
         * @throws ApiUsageException always
         */
        public function dieBlocked( AbstractBlock $block ) {
                // Die using the appropriate message depending on block type
                if ( $block->getType() == DatabaseBlock::TYPE_AUTO ) {
                        $this->dieWithError(
                                'apierror-autoblocked',
                                'autoblocked',
                                [ 'blockinfo' => $this->getBlockDetails( $block ) ]
                        );
                } elseif ( !$block->isSitewide() ) {
                        $this->dieWithError(
                                'apierror-blocked-partial',
                                'blocked',
                                [ 'blockinfo' => $this->getBlockDetails( $block ) ]
                        );
                } else {
                        $this->dieWithError(
                                'apierror-blocked',
                                'blocked',
                                [ 'blockinfo' => $this->getBlockDetails( $block ) ]
                        );
                }
        }

        /**
         * Throw an ApiUsageException based on the Status object.
         *
         * @since 1.22
         * @since 1.29 Accepts a StatusValue
         * @param StatusValue $status
         * @throws ApiUsageException always
         */
        public function dieStatus( StatusValue $status ) {
                if ( $status->isGood() ) {
                        throw new MWException( 'Successful status passed to ApiBase::dieStatus' );
                }

                // ApiUsageException needs a fatal status, but this method has
                // historically accepted any non-good status. Convert it if necessary.
                $status->setOK( false );
                if ( !$status->getErrorsByType( 'error' ) ) {
                        $newStatus = Status::newGood();
                        foreach ( $status->getErrorsByType( 'warning' ) as $err ) {
                                $newStatus->fatal( $err['message'], ...$err['params'] );
                        }
                        if ( !$newStatus->getErrorsByType( 'error' ) ) {
                                $newStatus->fatal( 'unknownerror-nocode' );
                        }
                        $status = $newStatus;
                }

                $this->addBlockInfoToStatus( $status );
                throw new ApiUsageException( $this, $status );
        }

        /**
         * Helper function for readonly errors
         *
         * @throws ApiUsageException always
         */
        public function dieReadOnly() {
                $this->dieWithError(
                        'apierror-readonly',
                        'readonly',
                        [ 'readonlyreason' => wfReadOnlyReason() ]
                );
        }

        /**
         * Helper function for permission-denied errors
         * @since 1.29
         * @param string|string[] $rights
         * @param User|null $user
         * @throws ApiUsageException if the user doesn't have any of the rights.
         *  The error message is based on $rights[0].
         */
        public function checkUserRightsAny( $rights, $user = null ) {
                if ( !$user ) {
                        $user = $this->getUser();
                }
                $rights = (array)$rights;
                if ( !$user->isAllowedAny( ...$rights ) ) {
                        $this->dieWithError( [ 'apierror-permissiondenied', $this->msg( "action-{$rights[0]}" ) ] );
                }
        }

        /**
         * Helper function for permission-denied errors
         *
         * @param LinkTarget $linkTarget
         * @param string|string[] $actions
         * @param array $options Additional options
         *   - user: (User) User to use rather than $this->getUser()
         *   - autoblock: (bool, default false) Whether to spread autoblocks
         *  For compatibility, passing a User object is treated as the value for the 'user' option.
         * @throws ApiUsageException if the user doesn't have all of the rights.
         *
         * @since 1.29
         * @since 1.33 Changed the third parameter from $user to $options.
         */
        public function checkTitleUserPermissions( LinkTarget $linkTarget, $actions, $options = [] ) {
                if ( !is_array( $options ) ) {
                        wfDeprecated( '$user as the third parameter to ' . __METHOD__, '1.33' );
                        $options = [ 'user' => $options ];
                }
                $user = $options['user'] ?? $this->getUser();

                $errors = [];
                foreach ( (array)$actions as $action ) {
                        $errors = array_merge(
                                $errors,
                                $this->getPermissionManager()->getPermissionErrors( $action, $user, $linkTarget )
                        );
                }

                if ( $errors ) {
                        if ( !empty( $options['autoblock'] ) ) {
                                $user->spreadAnyEditBlock();
                        }

                        $this->dieStatus( $this->errorArrayToStatus( $errors, $user ) );
                }
        }

        /**
         * Will only set a warning instead of failing if the global $wgDebugAPI
         * is set to true. Otherwise behaves exactly as self::dieWithError().
         *
         * @since 1.29
         * @param string|array|Message $msg
         * @param string|null $code
         * @param array|null $data
         * @param int|null $httpCode
         * @throws ApiUsageException
         */
        public function dieWithErrorOrDebug( $msg, $code = null, $data = null, $httpCode = null ) {
                if ( $this->getConfig()->get( 'DebugAPI' ) !== true ) {
                        $this->dieWithError( $msg, $code, $data, $httpCode );
                } else {
                        $this->addWarning( $msg, $code, $data );
                }
        }

        /**
         * Die with the 'badcontinue' error.
         *
         * This call is common enough to make it into the base method.
         *
         * @param bool $condition Will only die if this value is true
         * @throws ApiUsageException
         * @since 1.21
         */
        protected function dieContinueUsageIf( $condition ) {
                if ( $condition ) {
                        $this->dieWithError( 'apierror-badcontinue' );
                }
        }

        /**
         * Internal code errors should be reported with this method
         * @param string $method Method or function name
         * @param string $message Error message
         * @throws MWException always
         */
        protected static function dieDebug( $method, $message ) {
                throw new MWException( "Internal error in $method: $message" );
        }

        /**
         * Write logging information for API features to a debug log, for usage
         * analysis.
         * @note Consider using $this->addDeprecation() instead to both warn and log.
         * @param string $feature Feature being used.
         */
        public function logFeatureUsage( $feature ) {
                static $loggedFeatures = [];

                // Only log each feature once per request. We can get multiple calls from calls to
                // extractRequestParams() with different values for 'parseLimit', for example.
                if ( isset( $loggedFeatures[$feature] ) ) {
                        return;
                }
                $loggedFeatures[$feature] = true;

                $request = $this->getRequest();
                $ctx = [
                        'feature' => $feature,
                        // Spaces to underscores in 'username' for historical reasons.
                        'username' => str_replace( ' ', '_', $this->getUser()->getName() ),
                        'ip' => $request->getIP(),
                        'referer' => (string)$request->getHeader( 'Referer' ),
                        'agent' => $this->getMain()->getUserAgent(),
                ];

                // Text string is deprecated. Remove (or replace with just $feature) in MW 1.34.
                $s = '"' . addslashes( $ctx['feature'] ) . '"' .
                        ' "' . wfUrlencode( $ctx['username'] ) . '"' .
                        ' "' . $ctx['ip'] . '"' .
                        ' "' . addslashes( $ctx['referer'] ) . '"' .
                        ' "' . addslashes( $ctx['agent'] ) . '"';

                wfDebugLog( 'api-feature-usage', $s, 'private', $ctx );
        }

        /** @} */

        /************************************************************************//**
         * @name   Help message generation
         * @{
         */

        /**
         * Return the summary message.
         *
         * This is a one-line description of the module, suitable for display in a
         * list of modules.
         *
         * @since 1.30
         * @return string|array|Message
         */
        protected function getSummaryMessage() {
                return "apihelp-{$this->getModulePath()}-summary";
        }

        /**
         * Return the extended help text message.
         *
         * This is additional text to display at the top of the help section, below
         * the summary.
         *
         * @since 1.30
         * @return string|array|Message
         */
        protected function getExtendedDescription() {
                return [ [
                        "apihelp-{$this->getModulePath()}-extended-description",
                        'api-help-no-extended-description',
                ] ];
        }

        /**
         * Get final module summary
         *
         * @since 1.30
         * @return Message
         */
        public function getFinalSummary() {
                $msg = self::makeMessage( $this->getSummaryMessage(), $this->getContext(), [
                        $this->getModulePrefix(),
                        $this->getModuleName(),
                        $this->getModulePath(),
                ] );
                return $msg;
        }

        /**
         * Get final module description, after hooks have had a chance to tweak it as
         * needed.
         *
         * @since 1.25, returns Message[] rather than string[]
         * @return Message[]
         */
        public function getFinalDescription() {
                $summary = self::makeMessage( $this->getSummaryMessage(), $this->getContext(), [
                        $this->getModulePrefix(),
                        $this->getModuleName(),
                        $this->getModulePath(),
                ] );
                $extendedDescription = self::makeMessage(
                        $this->getExtendedDescription(), $this->getContext(), [
                                $this->getModulePrefix(),
                                $this->getModuleName(),
                                $this->getModulePath(),
                        ]
                );

                $msgs = [ $summary, $extendedDescription ];

                Hooks::run( 'APIGetDescriptionMessages', [ $this, &$msgs ] );

                return $msgs;
        }

        /**
         * Get final list of parameters, after hooks have had a chance to
         * tweak it as needed.
         *
         * @param int $flags Zero or more flags like GET_VALUES_FOR_HELP
         * @return array|bool False on no parameters
         * @since 1.21 $flags param added
         */
        public function getFinalParams( $flags = 0 ) {
                $params = $this->getAllowedParams( $flags );
                if ( !$params ) {
                        $params = [];
                }

                if ( $this->needsToken() ) {
                        $params['token'] = [
                                self::PARAM_TYPE => 'string',
                                self::PARAM_REQUIRED => true,
                                self::PARAM_SENSITIVE => true,
                                self::PARAM_HELP_MSG => [
                                        'api-help-param-token',
                                        $this->needsToken(),
                                ],
                        ] + ( $params['token'] ?? [] );
                }

                // Avoid PHP 7.1 warning of passing $this by reference
                $apiModule = $this;
                Hooks::run( 'APIGetAllowedParams', [ &$apiModule, &$params, $flags ] );

                return $params;
        }

        /**
         * Get final parameter descriptions, after hooks have had a chance to tweak it as
         * needed.
         *
         * @since 1.25, returns array of Message[] rather than array of string[]
         * @return array Keys are parameter names, values are arrays of Message objects
         */
        public function getFinalParamDescription() {
                $prefix = $this->getModulePrefix();
                $name = $this->getModuleName();
                $path = $this->getModulePath();

                $params = $this->getFinalParams( self::GET_VALUES_FOR_HELP );
                $msgs = [];
                foreach ( $params as $param => $settings ) {
                        if ( !is_array( $settings ) ) {
                                $settings = [];
                        }

                        if ( isset( $settings[self::PARAM_HELP_MSG] ) ) {
                                $msg = $settings[self::PARAM_HELP_MSG];
                        } else {
                                $msg = $this->msg( "apihelp-{$path}-param-{$param}" );
                        }
                        $msg = self::makeMessage( $msg, $this->getContext(),
                                [ $prefix, $param, $name, $path ] );
                        if ( !$msg ) {
                                self::dieDebug( __METHOD__,
                                        'Value in ApiBase::PARAM_HELP_MSG is not valid' );
                        }
                        $msgs[$param] = [ $msg ];

                        if ( isset( $settings[self::PARAM_TYPE] ) &&
                                $settings[self::PARAM_TYPE] === 'submodule'
                        ) {
                                if ( isset( $settings[self::PARAM_SUBMODULE_MAP] ) ) {
                                        $map = $settings[self::PARAM_SUBMODULE_MAP];
                                } else {
                                        $prefix = $this->isMain() ? '' : ( $this->getModulePath() . '+' );
                                        $map = [];
                                        foreach ( $this->getModuleManager()->getNames( $param ) as $submoduleName ) {
                                                $map[$submoduleName] = $prefix . $submoduleName;
                                        }
                                }
                                ksort( $map );
                                $submodules = [];
                                $deprecatedSubmodules = [];
                                foreach ( $map as $v => $m ) {
                                        $arr = &$submodules;
                                        $isDeprecated = false;
                                        $summary = null;
                                        try {
                                                $submod = $this->getModuleFromPath( $m );
                                                if ( $submod ) {
                                                        $summary = $submod->getFinalSummary();
                                                        $isDeprecated = $submod->isDeprecated();
                                                        if ( $isDeprecated ) {
                                                                $arr = &$deprecatedSubmodules;
                                                        }
                                                }
                                        } catch ( ApiUsageException $ex ) {
                                                // Ignore
                                        }
                                        if ( $summary ) {
                                                $key = $summary->getKey();
                                                $params = $summary->getParams();
                                        } else {
                                                $key = 'api-help-undocumented-module';
                                                $params = [ $m ];
                                        }
                                        $m = new ApiHelpParamValueMessage( "[[Special:ApiHelp/$m|$v]]", $key, $params, $isDeprecated );
                                        $arr[] = $m->setContext( $this->getContext() );
                                }
                                $msgs[$param] = array_merge( $msgs[$param], $submodules, $deprecatedSubmodules );
                        } elseif ( isset( $settings[self::PARAM_HELP_MSG_PER_VALUE] ) ) {
                                if ( !is_array( $settings[self::PARAM_HELP_MSG_PER_VALUE] ) ) {
                                        self::dieDebug( __METHOD__,
                                                'ApiBase::PARAM_HELP_MSG_PER_VALUE is not valid' );
                                }
                                if ( !is_array( $settings[self::PARAM_TYPE] ) ) {
                                        self::dieDebug( __METHOD__,
                                                'ApiBase::PARAM_HELP_MSG_PER_VALUE may only be used when ' .
                                                'ApiBase::PARAM_TYPE is an array' );
                                }

                                $valueMsgs = $settings[self::PARAM_HELP_MSG_PER_VALUE];
                                $deprecatedValues = $settings[self::PARAM_DEPRECATED_VALUES] ?? [];

                                foreach ( $settings[self::PARAM_TYPE] as $value ) {
                                        if ( isset( $valueMsgs[$value] ) ) {
                                                $msg = $valueMsgs[$value];
                                        } else {
                                                $msg = "apihelp-{$path}-paramvalue-{$param}-{$value}";
                                        }
                                        $m = self::makeMessage( $msg, $this->getContext(),
                                                [ $prefix, $param, $name, $path, $value ] );
                                        if ( $m ) {
                                                $m = new ApiHelpParamValueMessage(
                                                        $value,
                                                        [ $m->getKey(), 'api-help-param-no-description' ],
                                                        $m->getParams(),
                                                        isset( $deprecatedValues[$value] )
                                                );
                                                $msgs[$param][] = $m->setContext( $this->getContext() );
                                        } else {
                                                self::dieDebug( __METHOD__,
                                                        "Value in ApiBase::PARAM_HELP_MSG_PER_VALUE for $value is not valid" );
                                        }
                                }
                        }

                        if ( isset( $settings[self::PARAM_HELP_MSG_APPEND] ) ) {
                                if ( !is_array( $settings[self::PARAM_HELP_MSG_APPEND] ) ) {
                                        self::dieDebug( __METHOD__,
                                                'Value for ApiBase::PARAM_HELP_MSG_APPEND is not an array' );
                                }
                                foreach ( $settings[self::PARAM_HELP_MSG_APPEND] as $m ) {
                                        $m = self::makeMessage( $m, $this->getContext(),
                                                [ $prefix, $param, $name, $path ] );
                                        if ( $m ) {
                                                $msgs[$param][] = $m;
                                        } else {
                                                self::dieDebug( __METHOD__,
                                                        'Value in ApiBase::PARAM_HELP_MSG_APPEND is not valid' );
                                        }
                                }
                        }
                }

                Hooks::run( 'APIGetParamDescriptionMessages', [ $this, &$msgs ] );

                return $msgs;
        }

        /**
         * Generates the list of flags for the help screen and for action=paraminfo
         *
         * Corresponding messages: api-help-flag-deprecated,
         * api-help-flag-internal, api-help-flag-readrights,
         * api-help-flag-writerights, api-help-flag-mustbeposted
         *
         * @return string[]
         */
        protected function getHelpFlags() {
                $flags = [];

                if ( $this->isDeprecated() ) {
                        $flags[] = 'deprecated';
                }
                if ( $this->isInternal() ) {
                        $flags[] = 'internal';
                }
                if ( $this->isReadMode() ) {
                        $flags[] = 'readrights';
                }
                if ( $this->isWriteMode() ) {
                        $flags[] = 'writerights';
                }
                if ( $this->mustBePosted() ) {
                        $flags[] = 'mustbeposted';
                }

                return $flags;
        }

        /**
         * Returns information about the source of this module, if known
         *
         * Returned array is an array with the following keys:
         * - path: Install path
         * - name: Extension name, or "MediaWiki" for core
         * - namemsg: (optional) i18n message key for a display name
         * - license-name: (optional) Name of license
         *
         * @return array|null
         */
        protected function getModuleSourceInfo() {
                global $IP;

                if ( $this->mModuleSource !== false ) {
                        return $this->mModuleSource;
                }

                // First, try to find where the module comes from...
                $rClass = new ReflectionClass( $this );
                $path = $rClass->getFileName();
                if ( !$path ) {
                        // No path known?
                        $this->mModuleSource = null;
                        return null;
                }
                $path = realpath( $path ) ?: $path;

                // Build map of extension directories to extension info
                if ( self::$extensionInfo === null ) {
                        $extDir = $this->getConfig()->get( 'ExtensionDirectory' );
                        self::$extensionInfo = [
                                realpath( __DIR__ ) ?: __DIR__ => [
                                        'path' => $IP,
                                        'name' => 'MediaWiki',
                                        'license-name' => 'GPL-2.0-or-later',
                                ],
                                realpath( "$IP/extensions" ) ?: "$IP/extensions" => null,
                                realpath( $extDir ) ?: $extDir => null,
                        ];
                        $keep = [
                                'path' => null,
                                'name' => null,
                                'namemsg' => null,
                                'license-name' => null,
                        ];
                        foreach ( $this->getConfig()->get( 'ExtensionCredits' ) as $group ) {
                                foreach ( $group as $ext ) {
                                        if ( !isset( $ext['path'] ) || !isset( $ext['name'] ) ) {
                                                // This shouldn't happen, but does anyway.
                                                continue;
                                        }

                                        $extpath = $ext['path'];
                                        if ( !is_dir( $extpath ) ) {
                                                $extpath = dirname( $extpath );
                                        }
                                        self::$extensionInfo[realpath( $extpath ) ?: $extpath] =
                                                array_intersect_key( $ext, $keep );
                                }
                        }
                        foreach ( ExtensionRegistry::getInstance()->getAllThings() as $ext ) {
                                $extpath = $ext['path'];
                                if ( !is_dir( $extpath ) ) {
                                        $extpath = dirname( $extpath );
                                }
                                self::$extensionInfo[realpath( $extpath ) ?: $extpath] =
                                        array_intersect_key( $ext, $keep );
                        }
                }

                // Now traverse parent directories until we find a match or run out of
                // parents.
                do {
                        if ( array_key_exists( $path, self::$extensionInfo ) ) {
                                // Found it!
                                $this->mModuleSource = self::$extensionInfo[$path];
                                return $this->mModuleSource;
                        }

                        $oldpath = $path;
                        $path = dirname( $path );
                } while ( $path !== $oldpath );

                // No idea what extension this might be.
                $this->mModuleSource = null;
                return null;
        }

        /**
         * Called from ApiHelp before the pieces are joined together and returned.
         *
         * This exists mainly for ApiMain to add the Permissions and Credits
         * sections. Other modules probably don't need it.
         *
         * @param string[] &$help Array of help data
         * @param array $options Options passed to ApiHelp::getHelp
         * @param array &$tocData If a TOC is being generated, this array has keys
         *   as anchors in the page and values as for Linker::generateTOC().
         */
        public function modifyHelp( array &$help, array $options, array &$tocData ) {
        }

        /** @} */
}

/**
 * For really cool vim folding this needs to be at the end:
 * vim: foldmarker=@{,@} foldmethod=marker
 */