MathCaptcha.php

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<?php
 
use MediaWiki\Auth\AuthenticationRequest;
 
class MathCaptcha extends SimpleCaptcha {
 
    protected function keyMatch( $answer, $info ) {
        return (int)$answer == (int)$info['answer'];
    }
 
    protected function addCaptchaAPI( &$resultArr ) {
        list( $sum, $answer ) = $this->pickSum();
        $html = $this->fetchMath( $sum );
        $index = $this->storeCaptcha( [ 'answer' => $answer ] );
        $resultArr['captcha'] = $this->describeCaptchaType();
        $resultArr['captcha']['id'] = $index;
        $resultArr['captcha']['question'] = $html;
    }
 
    public function describeCaptchaType() {
        return [
            'type' => 'math',
            'mime' => 'text/html',
        ];
    }
 
    public function getFormInformation( $tabIndex = 1 ) {
        list( $sum, $answer ) = $this->pickSum();
        $index = $this->storeCaptcha( [ 'answer' => $answer ] );
 
        $form = '<table><tr><td>' . $this->fetchMath( $sum ) . '</td>';
        $form .= '<td>' . Html::input( 'wpCaptchaWord', false, false, [
            'tabindex' => $tabIndex,
            'autocomplete' => 'off',
            'required'
        ] ) . '</td></tr></table>';
        $form .= Html::hidden( 'wpCaptchaId', $index );
        return [ 'html' => $form ];
    }
 
    private function pickSum() {
        $a = mt_rand( 0, 100 );
        $b = mt_rand( 0, 10 );
        $op = mt_rand( 0, 1 ) ? '+' : '-';
        $sum = "{$a} {$op} {$b} = ";
        $ans = $op == '+' ? ( $a + $b ) : ( $a - $b );
        return [ $sum, $ans ];
    }
 
    private function fetchMath( $sum ) {
        $math = MathRenderer::getRenderer( $sum, [], 'png' );
        $math->render();
        $html = $math->getHtmlOutput();
        return preg_replace( '/alt=".*?"/', '', $html );
    }
 
    public function getCaptcha() {
        list( $sum, $answer ) = $this->pickSum();
        return [ 'question' => $sum, 'answer' => $answer ];
    }
 
    public function getCaptchaInfo( $captchaData, $id ) {
        $sum = $captchaData['question'];
        return $this->fetchMath( $sum );
    }
 
    public function onAuthChangeFormFields( array $requests, array $fieldInfo,
        array &$formDescriptor, $action ) {
        $req = AuthenticationRequest::getRequestByClass(
            $requests,
            CaptchaAuthenticationRequest::class,
                true
        );
        if ( !$req ) {
            return;
        }
 
        $formDescriptor['captchaInfo']['raw'] = true;
        $formDescriptor['captchaWord']['label-message'] = null;
    }
}