1 files changed, 57 insertions, 0 deletions
diff --git a/extensions/ConfirmEdit/MathCaptcha.class.php b/extensions/ConfirmEdit/MathCaptcha.class.php
new file mode 100644
index 00000000..220df31d
--- /dev/null
+++ b/extensions/ConfirmEdit/MathCaptcha.class.php
@@ -0,0 +1,57 @@
+<?php
+
+class MathCaptcha extends SimpleCaptcha {
+
+	/** Validate a captcha response */
+	function keyMatch( $answer, $info ) {
+		return (int)$answer == (int)$info['answer'];
+	}
+
+	function addCaptchaAPI( &$resultArr ) {
+		list( $sum, $answer ) = $this->pickSum();
+		$index = $this->storeCaptcha( array( 'answer' => $answer ) );
+		$resultArr['captcha']['type'] = 'math';
+		$resultArr['captcha']['mime'] = 'text/tex';
+		$resultArr['captcha']['id'] = $index;
+		$resultArr['captcha']['question'] = $sum;
+	}
+
+	/** Produce a nice little form */
+	function getForm() {
+		list( $sum, $answer ) = $this->pickSum();
+		$index = $this->storeCaptcha( array( 'answer' => $answer ) );
+
+		$form = '<table><tr><td>' . $this->fetchMath( $sum ) . '</td>';
+		$form .= '<td>' . Xml::input( 'wpCaptchaWord', false, false, array( 'tabindex' => '1' ) ) . '</td></tr></table>';
+		$form .= Html::hidden( 'wpCaptchaId', $index );
+		return $form;
+	}
+
+	/** Pick a random sum */
+	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 array( $sum, $ans );
+	}
+
+	/** Fetch the math */
+	function fetchMath( $sum ) {
+		// class_exists() unfortunately doesn't work with HipHop, and
+		// its replacement, MWInit::classExists(), wasn't added until
+		// MW 1.18, and is thus unusable here - so instead, we'll
+		// just duplicate the code of MWInit::classExists().
+		try {
+			$r = new ReflectionClass( 'MathRenderer' );
+		} catch( ReflectionException $r ) {
+			throw new MWException( 'MathCaptcha requires the Math extension for MediaWiki versions 1.18 and above.' );
+		}
+
+		$math = new MathRenderer( $sum );
+		$math->setOutputMode( MW_MATH_PNG );
+		$html = $math->render();
+		return preg_replace( '/alt=".*?"/', '', $html );
+	}
+}