Merge "Special:Upload should not crash on failing previews"

[mediawiki.git] / includes / htmlform / HTMLForm.php

<?php

/**
 * HTML form generation and submission handling.
 *
 * 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
 */

/**
 * Object handling generic submission, CSRF protection, layout and
 * other logic for UI forms. in a reusable manner.
 *
 * In order to generate the form, the HTMLForm object takes an array
 * structure detailing the form fields available. Each element of the
 * array is a basic property-list, including the type of field, the
 * label it is to be given in the form, callbacks for validation and
 * 'filtering', and other pertinent information.
 *
 * Field types are implemented as subclasses of the generic HTMLFormField
 * object, and typically implement at least getInputHTML, which generates
 * the HTML for the input field to be placed in the table.
 *
 * You can find extensive documentation on the www.mediawiki.org wiki:
 *  - https://www.mediawiki.org/wiki/HTMLForm
 *  - https://www.mediawiki.org/wiki/HTMLForm/tutorial
 *
 * The constructor input is an associative array of $fieldname => $info,
 * where $info is an Associative Array with any of the following:
 *
 *    'class'               -- the subclass of HTMLFormField that will be used
 *                             to create the object.  *NOT* the CSS class!
 *    'type'                -- roughly translates into the <select> type attribute.
 *                             if 'class' is not specified, this is used as a map
 *                             through HTMLForm::$typeMappings to get the class name.
 *    'default'             -- default value when the form is displayed
 *    'id'                  -- HTML id attribute
 *    'cssclass'            -- CSS class
 *    'csshelpclass'        -- CSS class used to style help text
 *    'dir'                 -- Direction of the element.
 *    'options'             -- associative array mapping labels to values.
 *                             Some field types support multi-level arrays.
 *    'options-messages'    -- associative array mapping message keys to values.
 *                             Some field types support multi-level arrays.
 *    'options-message'     -- message key or object to be parsed to extract the list of
 *                             options (like 'ipbreason-dropdown').
 *    'label-message'       -- message key or object for a message to use as the label.
 *                             can be an array of msg key and then parameters to
 *                             the message.
 *    'label'               -- alternatively, a raw text message. Overridden by
 *                             label-message
 *    'help'                -- message text for a message to use as a help text.
 *    'help-message'        -- message key or object for a message to use as a help text.
 *                             can be an array of msg key and then parameters to
 *                             the message.
 *                             Overwrites 'help-messages' and 'help'.
 *    'help-messages'       -- array of message keys/objects. As above, each item can
 *                             be an array of msg key and then parameters.
 *                             Overwrites 'help'.
 *    'notice'              -- message text for a message to use as a notice in the field.
 *                             Currently used by OOUI form fields only.
 *    'notice-messages'     -- array of message keys/objects to use for notice.
 *                             Overrides 'notice'.
 *    'notice-message'      -- message key or object to use as a notice.
 *    'required'            -- passed through to the object, indicating that it
 *                             is a required field.
 *    'size'                -- the length of text fields
 *    'filter-callback'     -- a function name to give you the chance to
 *                             massage the inputted value before it's processed.
 *                             @see HTMLFormField::filter()
 *    'validation-callback' -- a function name to give you the chance
 *                             to impose extra validation on the field input.
 *                             @see HTMLFormField::validate()
 *    'name'                -- By default, the 'name' attribute of the input field
 *                             is "wp{$fieldname}".  If you want a different name
 *                             (eg one without the "wp" prefix), specify it here and
 *                             it will be used without modification.
 *    'hide-if'             -- expression given as an array stating when the field
 *                             should be hidden. The first array value has to be the
 *                             expression's logic operator. Supported expressions:
 *                               'NOT'
 *                                 [ 'NOT', array $expression ]
 *                                 To hide a field if a given expression is not true.
 *                               '==='
 *                                 [ '===', string $fieldName, string $value ]
 *                                 To hide a field if another field identified by
 *                                 $field has the value $value.
 *                               '!=='
 *                                 [ '!==', string $fieldName, string $value ]
 *                                 Same as [ 'NOT', [ '===', $fieldName, $value ]
 *                               'OR', 'AND', 'NOR', 'NAND'
 *                                 [ 'XXX', array $expression1, ..., array $expressionN ]
 *                                 To hide a field if one or more (OR), all (AND),
 *                                 neither (NOR) or not all (NAND) given expressions
 *                                 are evaluated as true.
 *                             The expressions will be given to a JavaScript frontend
 *                             module which will continually update the field's
 *                             visibility.
 *
 * Since 1.20, you can chain mutators to ease the form generation:
 * @par Example:
 * @code
 * $form = new HTMLForm( $someFields );
 * $form->setMethod( 'get' )
 *      ->setWrapperLegendMsg( 'message-key' )
 *      ->prepareForm()
 *      ->displayForm( '' );
 * @endcode
 * Note that you will have prepareForm and displayForm at the end. Other
 * methods call done after that would simply not be part of the form :(
 *
 * @todo Document 'section' / 'subsection' stuff
 */
class HTMLForm extends ContextSource {
        // A mapping of 'type' inputs onto standard HTMLFormField subclasses
        public static $typeMappings = [
                'api' => 'HTMLApiField',
                'text' => 'HTMLTextField',
                'textwithbutton' => 'HTMLTextFieldWithButton',
                'textarea' => 'HTMLTextAreaField',
                'select' => 'HTMLSelectField',
                'combobox' => 'HTMLComboboxField',
                'radio' => 'HTMLRadioField',
                'multiselect' => 'HTMLMultiSelectField',
                'limitselect' => 'HTMLSelectLimitField',
                'check' => 'HTMLCheckField',
                'toggle' => 'HTMLCheckField',
                'int' => 'HTMLIntField',
                'float' => 'HTMLFloatField',
                'info' => 'HTMLInfoField',
                'selectorother' => 'HTMLSelectOrOtherField',
                'selectandother' => 'HTMLSelectAndOtherField',
                'namespaceselect' => 'HTMLSelectNamespace',
                'namespaceselectwithbutton' => 'HTMLSelectNamespaceWithButton',
                'tagfilter' => 'HTMLTagFilter',
                'sizefilter' => 'HTMLSizeFilterField',
                'submit' => 'HTMLSubmitField',
                'hidden' => 'HTMLHiddenField',
                'edittools' => 'HTMLEditTools',
                'checkmatrix' => 'HTMLCheckMatrix',
                'cloner' => 'HTMLFormFieldCloner',
                'autocompleteselect' => 'HTMLAutoCompleteSelectField',
                'date' => 'HTMLDateTimeField',
                'time' => 'HTMLDateTimeField',
                'datetime' => 'HTMLDateTimeField',
                // HTMLTextField will output the correct type="" attribute automagically.
                // There are about four zillion other HTML5 input types, like range, but
                // we don't use those at the moment, so no point in adding all of them.
                'email' => 'HTMLTextField',
                'password' => 'HTMLTextField',
                'url' => 'HTMLTextField',
                'title' => 'HTMLTitleTextField',
                'user' => 'HTMLUserTextField',
        ];

        public $mFieldData;

        protected $mMessagePrefix;

        /** @var HTMLFormField[] */
        protected $mFlatFields;

        protected $mFieldTree;
        protected $mShowReset = false;
        protected $mShowSubmit = true;
        protected $mSubmitFlags = [ 'primary', 'progressive' ];
        protected $mShowCancel = false;
        protected $mCancelTarget;

        protected $mSubmitCallback;
        protected $mValidationErrorMessage;

        protected $mPre = '';
        protected $mHeader = '';
        protected $mFooter = '';
        protected $mSectionHeaders = [];
        protected $mSectionFooters = [];
        protected $mPost = '';
        protected $mId;
        protected $mName;
        protected $mTableId = '';

        protected $mSubmitID;
        protected $mSubmitName;
        protected $mSubmitText;
        protected $mSubmitTooltip;

        protected $mFormIdentifier;
        protected $mTitle;
        protected $mMethod = 'post';
        protected $mWasSubmitted = false;

        /**
         * Form action URL. false means we will use the URL to set Title
         * @since 1.19
         * @var bool|string
         */
        protected $mAction = false;

        /**
         * Form attribute autocomplete. false does not set the attribute
         * @since 1.27
         * @var bool|string
         */
        protected $mAutocomplete = false;

        protected $mUseMultipart = false;
        protected $mHiddenFields = [];
        protected $mButtons = [];

        protected $mWrapperLegend = false;

        /**
         * Salt for the edit token.
         * @var string|array
         */
        protected $mTokenSalt = '';

        /**
         * If true, sections that contain both fields and subsections will
         * render their subsections before their fields.
         *
         * Subclasses may set this to false to render subsections after fields
         * instead.
         */
        protected $mSubSectionBeforeFields = true;

        /**
         * Format in which to display form. For viable options,
         * @see $availableDisplayFormats
         * @var string
         */
        protected $displayFormat = 'table';

        /**
         * Available formats in which to display the form
         * @var array
         */
        protected $availableDisplayFormats = [
                'table',
                'div',
                'raw',
                'inline',
        ];

        /**
         * Available formats in which to display the form
         * @var array
         */
        protected $availableSubclassDisplayFormats = [
                'vform',
                'ooui',
        ];

        /**
         * Construct a HTMLForm object for given display type. May return a HTMLForm subclass.
         *
         * @param string $displayFormat
         * @param mixed $arguments... Additional arguments to pass to the constructor.
         * @return HTMLForm
         */
        public static function factory( $displayFormat/*, $arguments...*/ ) {
                $arguments = func_get_args();
                array_shift( $arguments );

                switch ( $displayFormat ) {
                        case 'vform':
                                return ObjectFactory::constructClassInstance( VFormHTMLForm::class, $arguments );
                        case 'ooui':
                                return ObjectFactory::constructClassInstance( OOUIHTMLForm::class, $arguments );
                        default:
                                /** @var HTMLForm $form */
                                $form = ObjectFactory::constructClassInstance( HTMLForm::class, $arguments );
                                $form->setDisplayFormat( $displayFormat );
                                return $form;
                }
        }

        /**
         * Build a new HTMLForm from an array of field attributes
         *
         * @param array $descriptor Array of Field constructs, as described above
         * @param IContextSource $context Available since 1.18, will become compulsory in 1.18.
         *     Obviates the need to call $form->setTitle()
         * @param string $messagePrefix A prefix to go in front of default messages
         */
        public function __construct( $descriptor, /*IContextSource*/ $context = null,
                $messagePrefix = ''
        ) {
                if ( $context instanceof IContextSource ) {
                        $this->setContext( $context );
                        $this->mTitle = false; // We don't need them to set a title
                        $this->mMessagePrefix = $messagePrefix;
                } elseif ( $context === null && $messagePrefix !== '' ) {
                        $this->mMessagePrefix = $messagePrefix;
                } elseif ( is_string( $context ) && $messagePrefix === '' ) {
                        // B/C since 1.18
                        // it's actually $messagePrefix
                        $this->mMessagePrefix = $context;
                }

                // Evil hack for mobile :(
                if (
                        !$this->getConfig()->get( 'HTMLFormAllowTableFormat' )
                        && $this->displayFormat === 'table'
                ) {
                        $this->displayFormat = 'div';
                }

                // Expand out into a tree.
                $loadedDescriptor = [];
                $this->mFlatFields = [];

                foreach ( $descriptor as $fieldname => $info ) {
                        $section = isset( $info['section'] )
                                ? $info['section']
                                : '';

                        if ( isset( $info['type'] ) && $info['type'] === 'file' ) {
                                $this->mUseMultipart = true;
                        }

                        $field = static::loadInputFromParameters( $fieldname, $info, $this );

                        $setSection =& $loadedDescriptor;
                        if ( $section ) {
                                $sectionParts = explode( '/', $section );

                                while ( count( $sectionParts ) ) {
                                        $newName = array_shift( $sectionParts );

                                        if ( !isset( $setSection[$newName] ) ) {
                                                $setSection[$newName] = [];
                                        }

                                        $setSection =& $setSection[$newName];
                                }
                        }

                        $setSection[$fieldname] = $field;
                        $this->mFlatFields[$fieldname] = $field;
                }

                $this->mFieldTree = $loadedDescriptor;
        }

        /**
         * @param string $fieldname
         * @return bool
         */
        public function hasField( $fieldname ) {
                return isset( $this->mFlatFields[$fieldname] );
        }

        /**
         * @param string $fieldname
         * @return HTMLFormField
         * @throws DomainException on invalid field name
         */
        public function getField( $fieldname ) {
                if ( !$this->hasField( $fieldname ) ) {
                        throw new DomainException( __METHOD__ . ': no field named ' . $fieldname );
                }
                return $this->mFlatFields[$fieldname];
        }

        /**
         * Set format in which to display the form
         *
         * @param string $format The name of the format to use, must be one of
         *   $this->availableDisplayFormats
         *
         * @throws MWException
         * @since 1.20
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setDisplayFormat( $format ) {
                if (
                        in_array( $format, $this->availableSubclassDisplayFormats, true ) ||
                        in_array( $this->displayFormat, $this->availableSubclassDisplayFormats, true )
                ) {
                        throw new MWException( 'Cannot change display format after creation, ' .
                                'use HTMLForm::factory() instead' );
                }

                if ( !in_array( $format, $this->availableDisplayFormats, true ) ) {
                        throw new MWException( 'Display format must be one of ' .
                                print_r( $this->availableDisplayFormats, true ) );
                }

                // Evil hack for mobile :(
                if ( !$this->getConfig()->get( 'HTMLFormAllowTableFormat' ) && $format === 'table' ) {
                        $format = 'div';
                }

                $this->displayFormat = $format;

                return $this;
        }

        /**
         * Getter for displayFormat
         * @since 1.20
         * @return string
         */
        public function getDisplayFormat() {
                return $this->displayFormat;
        }

        /**
         * Test if displayFormat is 'vform'
         * @since 1.22
         * @deprecated since 1.25
         * @return bool
         */
        public function isVForm() {
                wfDeprecated( __METHOD__, '1.25' );
                return false;
        }

        /**
         * Get the HTMLFormField subclass for this descriptor.
         *
         * The descriptor can be passed either 'class' which is the name of
         * a HTMLFormField subclass, or a shorter 'type' which is an alias.
         * This makes sure the 'class' is always set, and also is returned by
         * this function for ease.
         *
         * @since 1.23
         *
         * @param string $fieldname Name of the field
         * @param array $descriptor Input Descriptor, as described above
         *
         * @throws MWException
         * @return string Name of a HTMLFormField subclass
         */
        public static function getClassFromDescriptor( $fieldname, &$descriptor ) {
                if ( isset( $descriptor['class'] ) ) {
                        $class = $descriptor['class'];
                } elseif ( isset( $descriptor['type'] ) ) {
                        $class = static::$typeMappings[$descriptor['type']];
                        $descriptor['class'] = $class;
                } else {
                        $class = null;
                }

                if ( !$class ) {
                        throw new MWException( "Descriptor with no class for $fieldname: "
                                . print_r( $descriptor, true ) );
                }

                return $class;
        }

        /**
         * Initialise a new Object for the field
         *
         * @param string $fieldname Name of the field
         * @param array $descriptor Input Descriptor, as described above
         * @param HTMLForm|null $parent Parent instance of HTMLForm
         *
         * @throws MWException
         * @return HTMLFormField Instance of a subclass of HTMLFormField
         */
        public static function loadInputFromParameters( $fieldname, $descriptor,
                HTMLForm $parent = null
        ) {
                $class = static::getClassFromDescriptor( $fieldname, $descriptor );

                $descriptor['fieldname'] = $fieldname;
                if ( $parent ) {
                        $descriptor['parent'] = $parent;
                }

                # @todo This will throw a fatal error whenever someone try to use
                # 'class' to feed a CSS class instead of 'cssclass'. Would be
                # great to avoid the fatal error and show a nice error.
                return new $class( $descriptor );
        }

        /**
         * Prepare form for submission.
         *
         * @attention When doing method chaining, that should be the very last
         * method call before displayForm().
         *
         * @throws MWException
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function prepareForm() {
                # Check if we have the info we need
                if ( !$this->mTitle instanceof Title && $this->mTitle !== false ) {
                        throw new MWException( 'You must call setTitle() on an HTMLForm' );
                }

                # Load data from the request.
                if (
                        $this->mFormIdentifier === null ||
                        $this->getRequest()->getVal( 'wpFormIdentifier' ) === $this->mFormIdentifier
                ) {
                        $this->loadData();
                } else {
                        $this->mFieldData = [];
                }

                return $this;
        }

        /**
         * Try submitting, with edit token check first
         * @return Status|bool
         */
        public function tryAuthorizedSubmit() {
                $result = false;

                $identOkay = false;
                if ( $this->mFormIdentifier === null ) {
                        $identOkay = true;
                } else {
                        $identOkay = $this->getRequest()->getVal( 'wpFormIdentifier' ) === $this->mFormIdentifier;
                }

                $tokenOkay = false;
                if ( $this->getMethod() !== 'post' ) {
                        $tokenOkay = true; // no session check needed
                } elseif ( $this->getRequest()->wasPosted() ) {
                        $editToken = $this->getRequest()->getVal( 'wpEditToken' );
                        if ( $this->getUser()->isLoggedIn() || $editToken !== null ) {
                                // Session tokens for logged-out users have no security value.
                                // However, if the user gave one, check it in order to give a nice
                                // "session expired" error instead of "permission denied" or such.
                                $tokenOkay = $this->getUser()->matchEditToken( $editToken, $this->mTokenSalt );
                        } else {
                                $tokenOkay = true;
                        }
                }

                if ( $tokenOkay && $identOkay ) {
                        $this->mWasSubmitted = true;
                        $result = $this->trySubmit();
                }

                return $result;
        }

        /**
         * The here's-one-I-made-earlier option: do the submission if
         * posted, or display the form with or without funky validation
         * errors
         * @return bool|Status Whether submission was successful.
         */
        public function show() {
                $this->prepareForm();

                $result = $this->tryAuthorizedSubmit();
                if ( $result === true || ( $result instanceof Status && $result->isGood() ) ) {
                        return $result;
                }

                $this->displayForm( $result );

                return false;
        }

        /**
         * Same as self::show with the difference, that the form will be
         * added to the output, no matter, if the validation was good or not.
         * @return bool|Status Whether submission was successful.
         */
        public function showAlways() {
                $this->prepareForm();

                $result = $this->tryAuthorizedSubmit();

                $this->displayForm( $result );

                return $result;
        }

        /**
         * Validate all the fields, and call the submission callback
         * function if everything is kosher.
         * @throws MWException
         * @return bool|string|array|Status
         *     - Bool true or a good Status object indicates success,
         *     - Bool false indicates no submission was attempted,
         *     - Anything else indicates failure. The value may be a fatal Status
         *       object, an HTML string, or an array of arrays (message keys and
         *       params) or strings (message keys)
         */
        public function trySubmit() {
                $valid = true;
                $hoistedErrors = Status::newGood();
                if ( $this->mValidationErrorMessage ) {
                        foreach ( (array)$this->mValidationErrorMessage as $error ) {
                                call_user_func_array( [ $hoistedErrors, 'fatal' ], $error );
                        }
                } else {
                        $hoistedErrors->fatal( 'htmlform-invalid-input' );
                }

                $this->mWasSubmitted = true;

                # Check for cancelled submission
                foreach ( $this->mFlatFields as $fieldname => $field ) {
                        if ( !array_key_exists( $fieldname, $this->mFieldData ) ) {
                                continue;
                        }
                        if ( $field->cancelSubmit( $this->mFieldData[$fieldname], $this->mFieldData ) ) {
                                $this->mWasSubmitted = false;
                                return false;
                        }
                }

                # Check for validation
                foreach ( $this->mFlatFields as $fieldname => $field ) {
                        if ( !array_key_exists( $fieldname, $this->mFieldData ) ) {
                                continue;
                        }
                        if ( $field->isHidden( $this->mFieldData ) ) {
                                continue;
                        }
                        $res = $field->validate( $this->mFieldData[$fieldname], $this->mFieldData );
                        if ( $res !== true ) {
                                $valid = false;
                                if ( $res !== false && !$field->canDisplayErrors() ) {
                                        if ( is_string( $res ) ) {
                                                $hoistedErrors->fatal( 'rawmessage', $res );
                                        } else {
                                                $hoistedErrors->fatal( $res );
                                        }
                                }
                        }
                }

                if ( !$valid ) {
                        return $hoistedErrors;
                }

                $callback = $this->mSubmitCallback;
                if ( !is_callable( $callback ) ) {
                        throw new MWException( 'HTMLForm: no submit callback provided. Use ' .
                                'setSubmitCallback() to set one.' );
                }

                $data = $this->filterDataForSubmit( $this->mFieldData );

                $res = call_user_func( $callback, $data, $this );
                if ( $res === false ) {
                        $this->mWasSubmitted = false;
                }

                return $res;
        }

        /**
         * Test whether the form was considered to have been submitted or not, i.e.
         * whether the last call to tryAuthorizedSubmit or trySubmit returned
         * non-false.
         *
         * This will return false until HTMLForm::tryAuthorizedSubmit or
         * HTMLForm::trySubmit is called.
         *
         * @since 1.23
         * @return bool
         */
        public function wasSubmitted() {
                return $this->mWasSubmitted;
        }

        /**
         * Set a callback to a function to do something with the form
         * once it's been successfully validated.
         *
         * @param callable $cb The function will be passed the output from
         *   HTMLForm::filterDataForSubmit and this HTMLForm object, and must
         *   return as documented for HTMLForm::trySubmit
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setSubmitCallback( $cb ) {
                $this->mSubmitCallback = $cb;

                return $this;
        }

        /**
         * Set a message to display on a validation error.
         *
         * @param string|array $msg String or Array of valid inputs to wfMessage()
         *     (so each entry can be either a String or Array)
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setValidationErrorMessage( $msg ) {
                $this->mValidationErrorMessage = $msg;

                return $this;
        }

        /**
         * Set the introductory message, overwriting any existing message.
         *
         * @param string $msg Complete text of message to display
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setIntro( $msg ) {
                $this->setPreText( $msg );

                return $this;
        }

        /**
         * Set the introductory message HTML, overwriting any existing message.
         * @since 1.19
         *
         * @param string $msg Complete HTML of message to display
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setPreText( $msg ) {
                $this->mPre = $msg;

                return $this;
        }

        /**
         * Add HTML to introductory message.
         *
         * @param string $msg Complete HTML of message to display
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function addPreText( $msg ) {
                $this->mPre .= $msg;

                return $this;
        }

        /**
         * Add HTML to the header, inside the form.
         *
         * @param string $msg Additional HTML to display in header
         * @param string|null $section The section to add the header to
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function addHeaderText( $msg, $section = null ) {
                if ( $section === null ) {
                        $this->mHeader .= $msg;
                } else {
                        if ( !isset( $this->mSectionHeaders[$section] ) ) {
                                $this->mSectionHeaders[$section] = '';
                        }
                        $this->mSectionHeaders[$section] .= $msg;
                }

                return $this;
        }

        /**
         * Set header text, inside the form.
         * @since 1.19
         *
         * @param string $msg Complete HTML of header to display
         * @param string|null $section The section to add the header to
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setHeaderText( $msg, $section = null ) {
                if ( $section === null ) {
                        $this->mHeader = $msg;
                } else {
                        $this->mSectionHeaders[$section] = $msg;
                }

                return $this;
        }

        /**
         * Get header text.
         *
         * @param string|null $section The section to get the header text for
         * @since 1.26
         * @return string HTML
         */
        public function getHeaderText( $section = null ) {
                if ( $section === null ) {
                        return $this->mHeader;
                } else {
                        return isset( $this->mSectionHeaders[$section] ) ? $this->mSectionHeaders[$section] : '';
                }
        }

        /**
         * Add footer text, inside the form.
         *
         * @param string $msg Complete text of message to display
         * @param string|null $section The section to add the footer text to
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function addFooterText( $msg, $section = null ) {
                if ( $section === null ) {
                        $this->mFooter .= $msg;
                } else {
                        if ( !isset( $this->mSectionFooters[$section] ) ) {
                                $this->mSectionFooters[$section] = '';
                        }
                        $this->mSectionFooters[$section] .= $msg;
                }

                return $this;
        }

        /**
         * Set footer text, inside the form.
         * @since 1.19
         *
         * @param string $msg Complete text of message to display
         * @param string|null $section The section to add the footer text to
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setFooterText( $msg, $section = null ) {
                if ( $section === null ) {
                        $this->mFooter = $msg;
                } else {
                        $this->mSectionFooters[$section] = $msg;
                }

                return $this;
        }

        /**
         * Get footer text.
         *
         * @param string|null $section The section to get the footer text for
         * @since 1.26
         * @return string
         */
        public function getFooterText( $section = null ) {
                if ( $section === null ) {
                        return $this->mFooter;
                } else {
                        return isset( $this->mSectionFooters[$section] ) ? $this->mSectionFooters[$section] : '';
                }
        }

        /**
         * Add text to the end of the display.
         *
         * @param string $msg Complete text of message to display
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function addPostText( $msg ) {
                $this->mPost .= $msg;

                return $this;
        }

        /**
         * Set text at the end of the display.
         *
         * @param string $msg Complete text of message to display
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setPostText( $msg ) {
                $this->mPost = $msg;

                return $this;
        }

        /**
         * Add a hidden field to the output
         *
         * @param string $name Field name.  This will be used exactly as entered
         * @param string $value Field value
         * @param array $attribs
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function addHiddenField( $name, $value, array $attribs = [] ) {
                $attribs += [ 'name' => $name ];
                $this->mHiddenFields[] = [ $value, $attribs ];

                return $this;
        }

        /**
         * Add an array of hidden fields to the output
         *
         * @since 1.22
         *
         * @param array $fields Associative array of fields to add;
         *        mapping names to their values
         *
         * @return HTMLForm $this for chaining calls
         */
        public function addHiddenFields( array $fields ) {
                foreach ( $fields as $name => $value ) {
                        $this->mHiddenFields[] = [ $value, [ 'name' => $name ] ];
                }

                return $this;
        }

        /**
         * Add a button to the form
         *
         * @since 1.27 takes an array as shown. Earlier versions accepted
         *  'name', 'value', 'id', and 'attribs' as separate parameters in that
         *  order.
         * @note Custom labels ('label', 'label-message', 'label-raw') are not
         *  supported for IE6 and IE7 due to bugs in those browsers. If detected,
         *  they will be served buttons using 'value' as the button label.
         * @param array $data Data to define the button:
         *  - name: (string) Button name.
         *  - value: (string) Button value.
         *  - label-message: (string, optional) Button label message key to use
         *    instead of 'value'. Overrides 'label' and 'label-raw'.
         *  - label: (string, optional) Button label text to use instead of
         *    'value'. Overrides 'label-raw'.
         *  - label-raw: (string, optional) Button label HTML to use instead of
         *    'value'.
         *  - id: (string, optional) DOM id for the button.
         *  - attribs: (array, optional) Additional HTML attributes.
         *  - flags: (string|string[], optional) OOUI flags.
         *  - framed: (boolean=true, optional) OOUI framed attribute.
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function addButton( $data ) {
                if ( !is_array( $data ) ) {
                        $args = func_get_args();
                        if ( count( $args ) < 2 || count( $args ) > 4 ) {
                                throw new InvalidArgumentException(
                                        'Incorrect number of arguments for deprecated calling style'
                                );
                        }
                        $data = [
                                'name' => $args[0],
                                'value' => $args[1],
                                'id' => isset( $args[2] ) ? $args[2] : null,
                                'attribs' => isset( $args[3] ) ? $args[3] : null,
                        ];
                } else {
                        if ( !isset( $data['name'] ) ) {
                                throw new InvalidArgumentException( 'A name is required' );
                        }
                        if ( !isset( $data['value'] ) ) {
                                throw new InvalidArgumentException( 'A value is required' );
                        }
                }
                $this->mButtons[] = $data + [
                        'id' => null,
                        'attribs' => null,
                        'flags' => null,
                        'framed' => true,
                ];

                return $this;
        }

        /**
         * Set the salt for the edit token.
         *
         * Only useful when the method is "post".
         *
         * @since 1.24
         * @param string|array $salt Salt to use
         * @return HTMLForm $this For chaining calls
         */
        public function setTokenSalt( $salt ) {
                $this->mTokenSalt = $salt;

                return $this;
        }

        /**
         * Display the form (sending to the context's OutputPage object), with an
         * appropriate error message or stack of messages, and any validation errors, etc.
         *
         * @attention You should call prepareForm() before calling this function.
         * Moreover, when doing method chaining this should be the very last method
         * call just after prepareForm().
         *
         * @param bool|string|array|Status $submitResult Output from HTMLForm::trySubmit()
         *
         * @return void Nothing, should be last call
         */
        public function displayForm( $submitResult ) {
                $this->getOutput()->addHTML( $this->getHTML( $submitResult ) );
        }

        /**
         * Returns the raw HTML generated by the form
         *
         * @param bool|string|array|Status $submitResult Output from HTMLForm::trySubmit()
         *
         * @return string HTML
         */
        public function getHTML( $submitResult ) {
                # For good measure (it is the default)
                $this->getOutput()->preventClickjacking();
                $this->getOutput()->addModules( 'mediawiki.htmlform' );
                $this->getOutput()->addModuleStyles( 'mediawiki.htmlform.styles' );

                $html = ''
                        . $this->getErrorsOrWarnings( $submitResult, 'error' )
                        . $this->getErrorsOrWarnings( $submitResult, 'warning' )
                        . $this->getHeaderText()
                        . $this->getBody()
                        . $this->getHiddenFields()
                        . $this->getButtons()
                        . $this->getFooterText();

                $html = $this->wrapForm( $html );

                return '' . $this->mPre . $html . $this->mPost;
        }

        /**
         * Get HTML attributes for the `<form>` tag.
         * @return array
         */
        protected function getFormAttributes() {
                # Use multipart/form-data
                $encType = $this->mUseMultipart
                        ? 'multipart/form-data'
                        : 'application/x-www-form-urlencoded';
                # Attributes
                $attribs = [
                        'class' => 'mw-htmlform',
                        'action' => $this->getAction(),
                        'method' => $this->getMethod(),
                        'enctype' => $encType,
                ];
                if ( $this->mId ) {
                        $attribs['id'] = $this->mId;
                }
                if ( $this->mAutocomplete ) {
                        $attribs['autocomplete'] = $this->mAutocomplete;
                }
                if ( $this->mName ) {
                        $attribs['name'] = $this->mName;
                }
                if ( $this->needsJSForHtml5FormValidation() ) {
                        $attribs['novalidate'] = true;
                }
                return $attribs;
        }

        /**
         * Wrap the form innards in an actual "<form>" element
         *
         * @param string $html HTML contents to wrap.
         *
         * @return string Wrapped HTML.
         */
        public function wrapForm( $html ) {
                # Include a <fieldset> wrapper for style, if requested.
                if ( $this->mWrapperLegend !== false ) {
                        $legend = is_string( $this->mWrapperLegend ) ? $this->mWrapperLegend : false;
                        $html = Xml::fieldset( $legend, $html );
                }

                return Html::rawElement(
                        'form',
                        $this->getFormAttributes(),
                        $html
                );
        }

        /**
         * Get the hidden fields that should go inside the form.
         * @return string HTML.
         */
        public function getHiddenFields() {
                $html = '';
                if ( $this->mFormIdentifier !== null ) {
                        $html .= Html::hidden(
                                'wpFormIdentifier',
                                $this->mFormIdentifier
                        ) . "\n";
                }
                if ( $this->getMethod() === 'post' ) {
                        $html .= Html::hidden(
                                'wpEditToken',
                                $this->getUser()->getEditToken( $this->mTokenSalt ),
                                [ 'id' => 'wpEditToken' ]
                        ) . "\n";
                        $html .= Html::hidden( 'title', $this->getTitle()->getPrefixedText() ) . "\n";
                }

                $articlePath = $this->getConfig()->get( 'ArticlePath' );
                if ( strpos( $articlePath, '?' ) !== false && $this->getMethod() === 'get' ) {
                        $html .= Html::hidden( 'title', $this->getTitle()->getPrefixedText() ) . "\n";
                }

                foreach ( $this->mHiddenFields as $data ) {
                        list( $value, $attribs ) = $data;
                        $html .= Html::hidden( $attribs['name'], $value, $attribs ) . "\n";
                }

                return $html;
        }

        /**
         * Get the submit and (potentially) reset buttons.
         * @return string HTML.
         */
        public function getButtons() {
                $buttons = '';
                $useMediaWikiUIEverywhere = $this->getConfig()->get( 'UseMediaWikiUIEverywhere' );

                if ( $this->mShowSubmit ) {
                        $attribs = [];

                        if ( isset( $this->mSubmitID ) ) {
                                $attribs['id'] = $this->mSubmitID;
                        }

                        if ( isset( $this->mSubmitName ) ) {
                                $attribs['name'] = $this->mSubmitName;
                        }

                        if ( isset( $this->mSubmitTooltip ) ) {
                                $attribs += Linker::tooltipAndAccesskeyAttribs( $this->mSubmitTooltip );
                        }

                        $attribs['class'] = [ 'mw-htmlform-submit' ];

                        if ( $useMediaWikiUIEverywhere ) {
                                foreach ( $this->mSubmitFlags as $flag ) {
                                        $attribs['class'][] = 'mw-ui-' . $flag;
                                }
                                $attribs['class'][] = 'mw-ui-button';
                        }

                        $buttons .= Xml::submitButton( $this->getSubmitText(), $attribs ) . "\n";
                }

                if ( $this->mShowReset ) {
                        $buttons .= Html::element(
                                'input',
                                [
                                        'type' => 'reset',
                                        'value' => $this->msg( 'htmlform-reset' )->text(),
                                        'class' => $useMediaWikiUIEverywhere ? 'mw-ui-button' : null,
                                ]
                        ) . "\n";
                }

                if ( $this->mShowCancel ) {
                        $target = $this->mCancelTarget ?: Title::newMainPage();
                        if ( $target instanceof Title ) {
                                $target = $target->getLocalURL();
                        }
                        $buttons .= Html::element(
                                        'a',
                                        [
                                                'class' => $useMediaWikiUIEverywhere ? 'mw-ui-button' : null,
                                                'href' => $target,
                                        ],
                                        $this->msg( 'cancel' )->text()
                                ) . "\n";
                }

                // IE<8 has bugs with <button>, so we'll need to avoid them.
                $isBadIE = preg_match( '/MSIE [1-7]\./i', $this->getRequest()->getHeader( 'User-Agent' ) );

                foreach ( $this->mButtons as $button ) {
                        $attrs = [
                                'type' => 'submit',
                                'name' => $button['name'],
                                'value' => $button['value']
                        ];

                        if ( isset( $button['label-message'] ) ) {
                                $label = $this->getMessage( $button['label-message'] )->parse();
                        } elseif ( isset( $button['label'] ) ) {
                                $label = htmlspecialchars( $button['label'] );
                        } elseif ( isset( $button['label-raw'] ) ) {
                                $label = $button['label-raw'];
                        } else {
                                $label = htmlspecialchars( $button['value'] );
                        }

                        if ( $button['attribs'] ) {
                                $attrs += $button['attribs'];
                        }

                        if ( isset( $button['id'] ) ) {
                                $attrs['id'] = $button['id'];
                        }

                        if ( $useMediaWikiUIEverywhere ) {
                                $attrs['class'] = isset( $attrs['class'] ) ? (array)$attrs['class'] : [];
                                $attrs['class'][] = 'mw-ui-button';
                        }

                        if ( $isBadIE ) {
                                $buttons .= Html::element( 'input', $attrs ) . "\n";
                        } else {
                                $buttons .= Html::rawElement( 'button', $attrs, $label ) . "\n";
                        }
                }

                if ( !$buttons ) {
                        return '';
                }

                return Html::rawElement( 'span',
                        [ 'class' => 'mw-htmlform-submit-buttons' ], "\n$buttons" ) . "\n";
        }

        /**
         * Get the whole body of the form.
         * @return string
         */
        public function getBody() {
                return $this->displaySection( $this->mFieldTree, $this->mTableId );
        }

        /**
         * Format and display an error message stack.
         *
         * @param string|array|Status $errors
         *
         * @deprecated since 1.28, use getErrorsOrWarnings() instead
         *
         * @return string
         */
        public function getErrors( $errors ) {
                wfDeprecated( __METHOD__ );
                return $this->getErrorsOrWarnings( $errors, 'error' );
        }

        /**
         * Returns a formatted list of errors or warnings from the given elements.
         *
         * @param string|array|Status $elements The set of errors/warnings to process.
         * @param string $elementsType Should warnings or errors be returned.  This is meant
         *      for Status objects, all other valid types are always considered as errors.
         * @return string
         */
        public function getErrorsOrWarnings( $elements, $elementsType ) {
                if ( !in_array( $elementsType, [ 'error', 'warning' ], true ) ) {
                        throw new DomainException( $elementsType . ' is not a valid type.' );
                }
                $elementstr = false;
                if ( $elements instanceof Status ) {
                        list( $errorStatus, $warningStatus ) = $elements->splitByErrorType();
                        $status = $elementsType === 'error' ? $errorStatus : $warningStatus;
                        if ( $status->isGood() ) {
                                $elementstr = '';
                        } else {
                                $elementstr = $this->getOutput()->parse(
                                        $status->getWikiText()
                                );
                        }
                } elseif ( is_array( $elements ) && $elementsType === 'error' ) {
                        $elementstr = $this->formatErrors( $elements );
                } elseif ( $elementsType === 'error' ) {
                        $elementstr = $elements;
                }

                return $elementstr
                        ? Html::rawElement( 'div', [ 'class' => $elementsType ], $elementstr )
                        : '';
        }

        /**
         * Format a stack of error messages into a single HTML string
         *
         * @param array $errors Array of message keys/values
         *
         * @return string HTML, a "<ul>" list of errors
         */
        public function formatErrors( $errors ) {
                $errorstr = '';

                foreach ( $errors as $error ) {
                        $errorstr .= Html::rawElement(
                                'li',
                                [],
                                $this->getMessage( $error )->parse()
                        );
                }

                $errorstr = Html::rawElement( 'ul', [], $errorstr );

                return $errorstr;
        }

        /**
         * Set the text for the submit button
         *
         * @param string $t Plaintext
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setSubmitText( $t ) {
                $this->mSubmitText = $t;

                return $this;
        }

        /**
         * Identify that the submit button in the form has a destructive action
         * @since 1.24
         *
         * @return HTMLForm $this for chaining calls (since 1.28)
         */
        public function setSubmitDestructive() {
                $this->mSubmitFlags = [ 'destructive', 'primary' ];

                return $this;
        }

        /**
         * Identify that the submit button in the form has a progressive action
         * @since 1.25
         *
         * @return HTMLForm $this for chaining calls (since 1.28)
         */
        public function setSubmitProgressive() {
                $this->mSubmitFlags = [ 'progressive', 'primary' ];

                return $this;
        }

        /**
         * Set the text for the submit button to a message
         * @since 1.19
         *
         * @param string|Message $msg Message key or Message object
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setSubmitTextMsg( $msg ) {
                if ( !$msg instanceof Message ) {
                        $msg = $this->msg( $msg );
                }
                $this->setSubmitText( $msg->text() );

                return $this;
        }

        /**
         * Get the text for the submit button, either customised or a default.
         * @return string
         */
        public function getSubmitText() {
                return $this->mSubmitText ?: $this->msg( 'htmlform-submit' )->text();
        }

        /**
         * @param string $name Submit button name
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setSubmitName( $name ) {
                $this->mSubmitName = $name;

                return $this;
        }

        /**
         * @param string $name Tooltip for the submit button
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setSubmitTooltip( $name ) {
                $this->mSubmitTooltip = $name;

                return $this;
        }

        /**
         * Set the id for the submit button.
         *
         * @param string $t
         *
         * @todo FIXME: Integrity of $t is *not* validated
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setSubmitID( $t ) {
                $this->mSubmitID = $t;

                return $this;
        }

        /**
         * Set an internal identifier for this form. It will be submitted as a hidden form field, allowing
         * HTMLForm to determine whether the form was submitted (or merely viewed). Setting this serves
         * two purposes:
         *
         * - If you use two or more forms on one page, it allows HTMLForm to identify which of the forms
         *   was submitted, and not attempt to validate the other ones.
         * - If you use checkbox or multiselect fields inside a form using the GET method, it allows
         *   HTMLForm to distinguish between the initial page view and a form submission with all
         *   checkboxes or select options unchecked.
         *
         * @since 1.28
         * @param string $ident
         * @return $this
         */
        public function setFormIdentifier( $ident ) {
                $this->mFormIdentifier = $ident;

                return $this;
        }

        /**
         * Stop a default submit button being shown for this form. This implies that an
         * alternate submit method must be provided manually.
         *
         * @since 1.22
         *
         * @param bool $suppressSubmit Set to false to re-enable the button again
         *
         * @return HTMLForm $this for chaining calls
         */
        public function suppressDefaultSubmit( $suppressSubmit = true ) {
                $this->mShowSubmit = !$suppressSubmit;

                return $this;
        }

        /**
         * Show a cancel button (or prevent it). The button is not shown by default.
         * @param bool $show
         * @return HTMLForm $this for chaining calls
         * @since 1.27
         */
        public function showCancel( $show = true ) {
                $this->mShowCancel = $show;
                return $this;
        }

        /**
         * Sets the target where the user is redirected to after clicking cancel.
         * @param Title|string $target Target as a Title object or an URL
         * @return HTMLForm $this for chaining calls
         * @since 1.27
         */
        public function setCancelTarget( $target ) {
                $this->mCancelTarget = $target;
                return $this;
        }

        /**
         * Set the id of the \<table\> or outermost \<div\> element.
         *
         * @since 1.22
         *
         * @param string $id New value of the id attribute, or "" to remove
         *
         * @return HTMLForm $this for chaining calls
         */
        public function setTableId( $id ) {
                $this->mTableId = $id;

                return $this;
        }

        /**
         * @param string $id DOM id for the form
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setId( $id ) {
                $this->mId = $id;

                return $this;
        }

        /**
         * @param string $name 'name' attribute for the form
         * @return HTMLForm $this for chaining calls
         */
        public function setName( $name ) {
                $this->mName = $name;

                return $this;
        }

        /**
         * Prompt the whole form to be wrapped in a "<fieldset>", with
         * this text as its "<legend>" element.
         *
         * @param string|bool $legend If false, no wrapper or legend will be displayed.
         *     If true, a wrapper will be displayed, but no legend.
         *     If a string, a wrapper will be displayed with that string as a legend.
         *     The string will be escaped before being output (this doesn't support HTML).
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setWrapperLegend( $legend ) {
                $this->mWrapperLegend = $legend;

                return $this;
        }

        /**
         * Prompt the whole form to be wrapped in a "<fieldset>", with
         * this message as its "<legend>" element.
         * @since 1.19
         *
         * @param string|Message $msg Message key or Message object
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setWrapperLegendMsg( $msg ) {
                if ( !$msg instanceof Message ) {
                        $msg = $this->msg( $msg );
                }
                $this->setWrapperLegend( $msg->text() );

                return $this;
        }

        /**
         * Set the prefix for various default messages
         * @todo Currently only used for the "<fieldset>" legend on forms
         * with multiple sections; should be used elsewhere?
         *
         * @param string $p
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setMessagePrefix( $p ) {
                $this->mMessagePrefix = $p;

                return $this;
        }

        /**
         * Set the title for form submission
         *
         * @param Title $t Title of page the form is on/should be posted to
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setTitle( $t ) {
                $this->mTitle = $t;

                return $this;
        }

        /**
         * Get the title
         * @return Title
         */
        public function getTitle() {
                return $this->mTitle === false
                        ? $this->getContext()->getTitle()
                        : $this->mTitle;
        }

        /**
         * Set the method used to submit the form
         *
         * @param string $method
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setMethod( $method = 'post' ) {
                $this->mMethod = strtolower( $method );

                return $this;
        }

        /**
         * @return string Always lowercase
         */
        public function getMethod() {
                return $this->mMethod;
        }

        /**
         * Wraps the given $section into an user-visible fieldset.
         *
         * @param string $legend Legend text for the fieldset
         * @param string $section The section content in plain Html
         * @param array $attributes Additional attributes for the fieldset
         * @return string The fieldset's Html
         */
        protected function wrapFieldSetSection( $legend, $section, $attributes ) {
                return Xml::fieldset( $legend, $section, $attributes ) . "\n";
        }

        /**
         * @todo Document
         *
         * @param array[]|HTMLFormField[] $fields Array of fields (either arrays or
         *   objects).
         * @param string $sectionName ID attribute of the "<table>" tag for this
         *   section, ignored if empty.
         * @param string $fieldsetIDPrefix ID prefix for the "<fieldset>" tag of
         *   each subsection, ignored if empty.
         * @param bool &$hasUserVisibleFields Whether the section had user-visible fields.
         * @throws LogicException When called on uninitialized field data, e.g. When
         *  HTMLForm::displayForm was called without calling HTMLForm::prepareForm
         *  first.
         *
         * @return string
         */
        public function displaySection( $fields,
                $sectionName = '',
                $fieldsetIDPrefix = '',
                &$hasUserVisibleFields = false
        ) {
                if ( $this->mFieldData === null ) {
                        throw new LogicException( 'HTMLForm::displaySection() called on uninitialized field data. '
                                . 'You probably called displayForm() without calling prepareForm() first.' );
                }

                $displayFormat = $this->getDisplayFormat();

                $html = [];
                $subsectionHtml = '';
                $hasLabel = false;

                // Conveniently, PHP method names are case-insensitive.
                // For grep: this can call getDiv, getRaw, getInline, getVForm, getOOUI
                $getFieldHtmlMethod = $displayFormat === 'table' ? 'getTableRow' : ( 'get' . $displayFormat );

                foreach ( $fields as $key => $value ) {
                        if ( $value instanceof HTMLFormField ) {
                                $v = array_key_exists( $key, $this->mFieldData )
                                        ? $this->mFieldData[$key]
                                        : $value->getDefault();

                                $retval = $value->$getFieldHtmlMethod( $v );

                                // check, if the form field should be added to
                                // the output.
                                if ( $value->hasVisibleOutput() ) {
                                        $html[] = $retval;

                                        $labelValue = trim( $value->getLabel() );
                                        if ( $labelValue !== '&#160;' && $labelValue !== '' ) {
                                                $hasLabel = true;
                                        }

                                        $hasUserVisibleFields = true;
                                }
                        } elseif ( is_array( $value ) ) {
                                $subsectionHasVisibleFields = false;
                                $section =
                                        $this->displaySection( $value,
                                                "mw-htmlform-$key",
                                                "$fieldsetIDPrefix$key-",
                                                $subsectionHasVisibleFields );
                                $legend = null;

                                if ( $subsectionHasVisibleFields === true ) {
                                        // Display the section with various niceties.
                                        $hasUserVisibleFields = true;

                                        $legend = $this->getLegend( $key );

                                        $section = $this->getHeaderText( $key ) .
                                                $section .
                                                $this->getFooterText( $key );

                                        $attributes = [];
                                        if ( $fieldsetIDPrefix ) {
                                                $attributes['id'] = Sanitizer::escapeId( "$fieldsetIDPrefix$key" );
                                        }
                                        $subsectionHtml .= $this->wrapFieldSetSection( $legend, $section, $attributes );
                                } else {
                                        // Just return the inputs, nothing fancy.
                                        $subsectionHtml .= $section;
                                }
                        }
                }

                $html = $this->formatSection( $html, $sectionName, $hasLabel );

                if ( $subsectionHtml ) {
                        if ( $this->mSubSectionBeforeFields ) {
                                return $subsectionHtml . "\n" . $html;
                        } else {
                                return $html . "\n" . $subsectionHtml;
                        }
                } else {
                        return $html;
                }
        }

        /**
         * Put a form section together from the individual fields' HTML, merging it and wrapping.
         * @param array $fieldsHtml
         * @param string $sectionName
         * @param bool $anyFieldHasLabel
         * @return string HTML
         */
        protected function formatSection( array $fieldsHtml, $sectionName, $anyFieldHasLabel ) {
                $displayFormat = $this->getDisplayFormat();
                $html = implode( '', $fieldsHtml );

                if ( $displayFormat === 'raw' ) {
                        return $html;
                }

                $classes = [];

                if ( !$anyFieldHasLabel ) { // Avoid strange spacing when no labels exist
                        $classes[] = 'mw-htmlform-nolabel';
                }

                $attribs = [
                        'class' => implode( ' ', $classes ),
                ];

                if ( $sectionName ) {
                        $attribs['id'] = Sanitizer::escapeId( $sectionName );
                }

                if ( $displayFormat === 'table' ) {
                        return Html::rawElement( 'table',
                                        $attribs,
                                        Html::rawElement( 'tbody', [], "\n$html\n" ) ) . "\n";
                } elseif ( $displayFormat === 'inline' ) {
                        return Html::rawElement( 'span', $attribs, "\n$html\n" );
                } else {
                        return Html::rawElement( 'div', $attribs, "\n$html\n" );
                }
        }

        /**
         * Construct the form fields from the Descriptor array
         */
        public function loadData() {
                $fieldData = [];

                foreach ( $this->mFlatFields as $fieldname => $field ) {
                        $request = $this->getRequest();
                        if ( $field->skipLoadData( $request ) ) {
                                continue;
                        } elseif ( !empty( $field->mParams['disabled'] ) ) {
                                $fieldData[$fieldname] = $field->getDefault();
                        } else {
                                $fieldData[$fieldname] = $field->loadDataFromRequest( $request );
                        }
                }

                # Filter data.
                foreach ( $fieldData as $name => &$value ) {
                        $field = $this->mFlatFields[$name];
                        $value = $field->filter( $value, $this->mFlatFields );
                }

                $this->mFieldData = $fieldData;
        }

        /**
         * Stop a reset button being shown for this form
         *
         * @param bool $suppressReset Set to false to re-enable the button again
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function suppressReset( $suppressReset = true ) {
                $this->mShowReset = !$suppressReset;

                return $this;
        }

        /**
         * Overload this if you want to apply special filtration routines
         * to the form as a whole, after it's submitted but before it's
         * processed.
         *
         * @param array $data
         *
         * @return array
         */
        public function filterDataForSubmit( $data ) {
                return $data;
        }

        /**
         * Get a string to go in the "<legend>" of a section fieldset.
         * Override this if you want something more complicated.
         *
         * @param string $key
         *
         * @return string
         */
        public function getLegend( $key ) {
                return $this->msg( "{$this->mMessagePrefix}-$key" )->text();
        }

        /**
         * Set the value for the action attribute of the form.
         * When set to false (which is the default state), the set title is used.
         *
         * @since 1.19
         *
         * @param string|bool $action
         *
         * @return HTMLForm $this for chaining calls (since 1.20)
         */
        public function setAction( $action ) {
                $this->mAction = $action;

                return $this;
        }

        /**
         * Get the value for the action attribute of the form.
         *
         * @since 1.22
         *
         * @return string
         */
        public function getAction() {
                // If an action is alredy provided, return it
                if ( $this->mAction !== false ) {
                        return $this->mAction;
                }

                $articlePath = $this->getConfig()->get( 'ArticlePath' );
                // Check whether we are in GET mode and the ArticlePath contains a "?"
                // meaning that getLocalURL() would return something like "index.php?title=...".
                // As browser remove the query string before submitting GET forms,
                // it means that the title would be lost. In such case use wfScript() instead
                // and put title in an hidden field (see getHiddenFields()).
                if ( strpos( $articlePath, '?' ) !== false && $this->getMethod() === 'get' ) {
                        return wfScript();
                }

                return $this->getTitle()->getLocalURL();
        }

        /**
         * Set the value for the autocomplete attribute of the form.
         * When set to false (which is the default state), the attribute get not set.
         *
         * @since 1.27
         *
         * @param string|bool $autocomplete
         *
         * @return HTMLForm $this for chaining calls
         */
        public function setAutocomplete( $autocomplete ) {
                $this->mAutocomplete = $autocomplete;

                return $this;
        }

        /**
         * Turns a *-message parameter (which could be a MessageSpecifier, or a message name, or a
         * name + parameters array) into a Message.
         * @param mixed $value
         * @return Message
         */
        protected function getMessage( $value ) {
                return Message::newFromSpecifier( $value )->setContext( $this );
        }

        /**
         * Whether this form, with its current fields, requires the user agent to have JavaScript enabled
         * for the client-side HTML5 form validation to work correctly. If this function returns true, a
         * 'novalidate' attribute will be added on the `<form>` element. It will be removed if the user
         * agent has JavaScript support, in htmlform.js.
         *
         * @return boolean
         * @since 1.29
         */
        public function needsJSForHtml5FormValidation() {
                foreach ( $this->mFlatFields as $fieldname => $field ) {
                        if ( $field->needsJSForHtml5FormValidation() ) {
                                return true;
                        }
                }
                return false;
        }
}