Introduce a CaptchaStore abstract class that CaptchaSessionStore and CaptchaCacheStore can extend. Some tidying, documentation and type hinting.

Captcha.php

@@ -1,9 +1,19 @@
 <?php
 
 class SimpleCaptcha {
+
+	/**
+	 * @var CaptchaStore
+	 */
+	protected $storage;
+
 	function __construct() {
 		global $wgCaptchaStorageClass;
-		$this->storage = new $wgCaptchaStorageClass;
+		if( in_array( 'CaptchaStore', class_implements( $wgCaptchaStorageClass ) ) ) {
+			$this->storage = new $wgCaptchaStorageClass;
+		} else {
+			throw new MWException( "Invalid CaptchaStore class $wgCaptchaStorageClass" );
+		}
 	}
 
 	function getCaptcha() {
@@ -81,7 +91,7 @@ class SimpleCaptcha {
 	/**
 	 * Inject whazawhoo
 	 * @fixme if multiple thingies insert a header, could break
-	 * @param HTMLForm
+	 * @param $form HTMLForm
 	 * @return bool true to keep running callbacks
 	 */
 	function injectEmailUser( &$form ) {
@@ -103,7 +113,7 @@ class SimpleCaptcha {
 	/**
 	 * Inject whazawhoo
 	 * @fixme if multiple thingies insert a header, could break
-	 * @param SimpleTemplate $template
+	 * @param QuickTemplate $template
 	 * @return bool true to keep running callbacks
 	 */
 	function injectUserCreate( &$template ) {
@@ -126,7 +136,7 @@ class SimpleCaptcha {
 	 * Inject a captcha into the user login form after a failed
 	 * password attempt as a speedbump for mass attacks.
 	 * @fixme if multiple thingies insert a header, could break
-	 * @param SimpleTemplate $template
+	 * @param $template QuickTemplate
 	 * @return bool true to keep running callbacks
 	 */
 	function injectUserLogin( &$template ) {
@@ -410,6 +420,8 @@ class SimpleCaptcha {
 
 	/**
 	 * Load external links from the externallinks table
+	 * @param $title Title
+	 * @return Array
 	 */
 	function getLinksFromTracker( $title ) {
 		$dbr = wfGetDB( DB_SLAVE );

CaptchaStore.php

@@ -1,5 +1,63 @@
 <?php
-class CaptchaSessionStore {
+
+abstract class CaptchaStore {
+	/**
+	 * Store the correct answer for a given captcha
+	 * @param  $index String
+	 * @param  $info String the captcha result
+	 */
+	public abstract function store( $index, $info );
+
+	/**
+	 * Retrieve the answer for a given captcha
+	 * @param  $index String
+	 * @return String
+	 */
+	public abstract function retrieve( $index );
+
+	/**
+	 * Delete a result once the captcha has been used, so it cannot be reused
+	 * @param  $index
+	 */
+	public abstract function clear( $index );
+
+	/**
+	 * Whether this type of CaptchaStore needs cookies
+	 * @return Bool
+	 */
+	public abstract function cookiesNeeded();
+
+	/**
+	 * The singleton instance
+	 * @var CaptchaStore
+	 */
+	private static $instance;
+
+	/**
+	 * Get somewhere to store captcha data that will persist between requests
+	 *
+	 * @throws MWException
+	 * @return CaptchaStore
+	 */
+	public final static function get() {
+		if( !self::$instance instanceof self ){
+			global $wgCaptchaStorageClass;
+			if( in_array( 'CaptchaStore', class_implements( $wgCaptchaStorageClass ) ) ) {
+				self::$instance = new $wgCaptchaStorageClass;
+			} else {
+				throw new MWException( "Invalid CaptchaStore class $wgCaptchaStorageClass" );
+			}
+		}
+		return self::$instance;
+	}
+
+	/**
+	 * Protected constructor: no creating instances except through the factory method above
+	 */
+	protected function __construct(){}
+}
+
+class CaptchaSessionStore extends CaptchaStore {
 
 	function store( $index, $info ) {
 		$_SESSION['captcha' . $info['index']] = $info;
@@ -22,7 +80,7 @@ class CaptchaSessionStore {
 	}
 }
 
-class CaptchaCacheStore {
+class CaptchaCacheStore extends CaptchaStore {
 
 	function store( $index, $info ) {
 		global $wgMemc, $wgCaptchaSessionExpiration;

ConfirmEdit.php

@@ -202,6 +202,7 @@ $wgHooks['APIEditBeforeSave'][] = 'ConfirmEditHooks::confirmEditAPI';
 
 $wgAutoloadClasses['ConfirmEditHooks'] = "$wgConfirmEditIP/ConfirmEditHooks.php";
 $wgAutoloadClasses['SimpleCaptcha']= "$wgConfirmEditIP/Captcha.php";
+$wgAutoloadClasses['CaptchaStore']= "$wgConfirmEditIP/CaptchaStore.php";
 $wgAutoloadClasses['CaptchaSessionStore']= "$wgConfirmEditIP/CaptchaStore.php";
 $wgAutoloadClasses['CaptchaCacheStore']= "$wgConfirmEditIP/CaptchaStore.php";
 $wgAutoloadClasses['CaptchaSpecialPage'] = "$wgConfirmEditIP/ConfirmEditHooks.php";

ConfirmEditHooks.php

@@ -1,6 +1,12 @@
 <?php
 
 class ConfirmEditHooks {
+
+	/**
+	 * Get the global Captcha instance
+	 *
+	 * @return Captcha
+	 */
 	static function getInstance() {
 		global $wgCaptcha, $wgCaptchaClass;
 		static $done = false;

FancyCaptcha.class.php

@@ -44,7 +44,7 @@ class FancyCaptcha extends SimpleCaptcha {
 	function getForm() {
 		$info = $this->pickImage();
 		if ( !$info ) {
-			die( "out of captcha images; this shouldn't happen" );
+			throw new MWException( "Ran out of captcha images" );
 		}
 
 		// Generate a random key for use of this captcha image in this session.