<?php

class ConfirmEditHooks {
	static function getInstance() {
		global $wgCaptcha, $wgCaptchaClass, $wgExtensionMessagesFiles;
		static $done = false;
		if ( !$done ) {
			$done = true;
			wfLoadExtensionMessages( 'ConfirmEdit' );
			if ( isset( $wgExtensionMessagesFiles[$wgCaptchaClass] ) ) {
				wfLoadExtensionMessages( $wgCaptchaClass );
			}
			$wgCaptcha = new $wgCaptchaClass;
		}
		return $wgCaptcha;
	}

	static function confirmEdit( &$editPage, $newtext, $section ) {
		return self::getInstance()->confirmEdit( $editPage, $newtext, $section );
	}

	static function confirmEditMerged( &$editPage, $newtext ) {
		return self::getInstance()->confirmEditMerged( $editPage, $newtext );
	}

	static function injectUserCreate( &$template ) {
		return self::getInstance()->injectUserCreate( $template );
	}

	static function confirmUserCreate( $u, &$message ) {
		return self::getInstance()->confirmUserCreate( $u, $message );
	}

	static function triggerUserLogin( $user, $password, $retval ) {
		return self::getInstance()->triggerUserLogin( $user, $password, $retval );
	}

	static function injectUserLogin( &$template ) {
		return self::getInstance()->injectUserLogin( $template );
	}

	static function confirmUserLogin( $u, $pass, &$retval ) {
		return self::getInstance()->confirmUserLogin( $u, $pass, $retval );
	}
}

class CaptchaSpecialPage extends UnlistedSpecialPage {
	function execute( $par ) {
		$this->setHeaders();
		$instance = ConfirmEditHooks::getInstance();
		switch( $par ) {
		case "image":
			return $instance->showImage();
		case "help":
		default:
			return $instance->showHelp();
		}
	}
}


class SimpleCaptcha {
	function SimpleCaptcha() {
		global $wgCaptchaStorageClass;
		$this->storage = new $wgCaptchaStorageClass;
	}
	
	/**
	 * Insert a captcha prompt into the edit form.
	 * This sample implementation generates a simple arithmetic operation;
	 * it would be easy to defeat by machine.
	 *
	 * Override this!
	 *
	 * @return string HTML
	 */
	function getForm() {
		$a = mt_rand(0, 100);
		$b = mt_rand(0, 10);
		$op = mt_rand(0, 1) ? '+' : '-';

		$test = "$a $op $b";
		$answer = ($op == '+') ? ($a + $b) : ($a - $b);

		$index = $this->storeCaptcha( array( 'answer' => $answer ) );

		return "<p><label for=\"wpCaptchaWord\">$test</label> = " .
			wfElement( 'input', array(
				'name' => 'wpCaptchaWord',
				'id'   => 'wpCaptchaWord',
				'tabindex' => 1 ) ) . // tab in before the edit textarea
			"</p>\n" .
			wfElement( 'input', array(
				'type'  => 'hidden',
				'name'  => 'wpCaptchaId',
				'id'    => 'wpCaptchaId',
				'value' => $index ) );
	}

	/**
	 * Insert the captcha prompt into an edit form.
	 * @param OutputPage $out
	 */
	function editCallback( &$out ) {
		$out->addWikiText( $this->getMessage( $this->action ) );
		$out->addHTML( $this->getForm() );
	}

	/**
	 * Show a message asking the user to enter a captcha on edit
	 * The result will be treated as wiki text
	 *
	 * @param $action Action being performed
	 * @return string
	 */
	function getMessage( $action ) {
		$name = 'captcha-' . $action;
		$text = wfMsg( $name );
		# Obtain a more tailored message, if possible, otherwise, fall back to
		# the default for edits
		return wfEmptyMsg( $name, $text ) ? wfMsg( 'captcha-edit' ) : $text;
	}

	/**
	 * Inject whazawhoo
	 * @fixme if multiple thingies insert a header, could break
	 * @param SimpleTemplate $template
	 * @return bool true to keep running callbacks
	 */
	function injectUserCreate( &$template ) {
		global $wgCaptchaTriggers, $wgOut;
		if( $wgCaptchaTriggers['createaccount'] ) {
			$template->set( 'header',
				"<div class='captcha'>" .
				$wgOut->parse( $this->getMessage( 'createaccount' ) ) .
				$this->getForm() .
				"</div>\n" );
		}
		return true;
	}

	/**
	 * 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 $template
	 * @return bool true to keep running callbacks
	 */
	function injectUserLogin( &$template ) {
		if( $this->isBadLoginTriggered() ) {
			global $wgOut;
			$template->set( 'header',
				"<div class='captcha'>" .
				$wgOut->parse( $this->getMessage( 'badlogin' ) ) .
				$this->getForm() .
				"</div>\n" );
		}
		return true;
	}
	
	/**
	 * When a bad login attempt is made, increment an expiring counter
	 * in the memcache cloud. Later checks for this may trigger a
	 * captcha display to prevent too many hits from the same place.
	 * @param User $user
	 * @param string $password
	 * @param int $retval authentication return value
	 * @return bool true to keep running callbacks
	 */
	function triggerUserLogin( $user, $password, $retval ) {
		global $wgCaptchaTriggers, $wgCaptchaBadLoginExpiration, $wgMemc;
		if( $retval == LoginForm::WRONG_PASS && $wgCaptchaTriggers['badlogin'] ) {
			$key = $this->badLoginKey();
			$count = $wgMemc->get( $key );
			if( !$count ) {
				$wgMemc->add( $key, 0, $wgCaptchaBadLoginExpiration );
			}
			$count = $wgMemc->incr( $key );
		}
		return true;
	}
	
	/**
	 * Check if a bad login has already been registered for this
	 * IP address. If so, require a captcha.
	 * @return bool
	 * @access private
	 */
	function isBadLoginTriggered() {
		global $wgMemc;
		return intval( $wgMemc->get( $this->badLoginKey() ) ) > 0;
	}
	
	/**
	 * Internal cache key for badlogin checks.
	 * @return string
	 * @access private
	 */
	function badLoginKey() {
		return wfMemcKey( 'captcha', 'badlogin', 'ip', wfGetIP() );
	}
	
	/**
	 * Check if the submitted form matches the captcha session data provided
	 * by the plugin when the form was generated.
	 *
	 * Override this!
	 *
	 * @param WebRequest $request
	 * @param array $info
	 * @return bool
	 */
	function keyMatch( $request, $info ) {
		return $request->getVal( 'wpCaptchaWord' ) == $info['answer'];
	}

	// ----------------------------------

	/**
	 * @param EditPage $editPage
	 * @param string $action (edit/create/addurl...)
	 * @return bool true if action triggers captcha on editPage's namespace
	 */
	function captchaTriggers( &$editPage, $action) {
		global $wgCaptchaTriggers, $wgCaptchaTriggersOnNamespace;	
		//Special config for this NS?
		if (isset( $wgCaptchaTriggersOnNamespace[$editPage->mTitle->getNamespace()][$action] ) )
			return $wgCaptchaTriggersOnNamespace[$editPage->mTitle->getNamespace()][$action];

		return ( !empty( $wgCaptchaTriggers[$action] ) ); //Default
	}


	/**
	 * @param EditPage $editPage
	 * @param string $newtext
	 * @param string $section
	 * @return bool true if the captcha should run
	 */
	function shouldCheck( &$editPage, $newtext, $section, $merged = false ) {
		$this->trigger = '';
		$title = $editPage->mArticle->getTitle();

		global $wgUser;
		if( $wgUser->isAllowed( 'skipcaptcha' ) ) {
			wfDebug( "ConfirmEdit: user group allows skipping captcha\n" );
			return false;
		}
		global $wgCaptchaWhitelistIP;
		if( !empty( $wgCaptchaWhitelistIP ) ) {
			$ip = wfGetIp();
			foreach ( $wgCaptchaWhitelistIP as $range ) {
				if ( IP::isInRange( $ip, $range ) ) {
					return false;
				}
			}
		}


		global $wgEmailAuthentication, $ceAllowConfirmedEmail;
		if( $wgEmailAuthentication && $ceAllowConfirmedEmail &&
			$wgUser->isEmailConfirmed() ) {
			wfDebug( "ConfirmEdit: user has confirmed mail, skipping captcha\n" );
			return false;
		}

		if( $this->captchaTriggers( $editPage, 'edit' ) ) {
			// Check on all edits
			global $wgUser;
			$this->trigger = sprintf( "edit trigger by '%s' at [[%s]]",
				$wgUser->getName(),
				$title->getPrefixedText() );
			$this->action = 'edit';
			wfDebug( "ConfirmEdit: checking all edits...\n" );
			return true;
		}

		if( $this->captchaTriggers( $editPage, 'create' )  && !$editPage->mTitle->exists() ) {
			//Check if creating a page
			global $wgUser;
			$this->trigger = sprintf( "Create trigger by '%s' at [[%s]]",
				$wgUser->getName(),
				$title->getPrefixedText() );
			$this->action = 'create';
			wfDebug( "ConfirmEdit: checking on page creation...\n" );
			return true;
		}

		if( $this->captchaTriggers( $editPage, 'addurl' ) ) {
			// Only check edits that add URLs
			if ( $merged ) {
				// Get links from the database
				$oldLinks = $this->getLinksFromTracker( $title );
				// Share a parse operation with Article::doEdit()
				$editInfo = $editPage->mArticle->prepareTextForEdit( $newtext );
				$newLinks = array_keys( $editInfo->output->getExternalLinks() );
			} else {
				// Get link changes in the slowest way known to man
				$oldtext = $this->loadText( $editPage, $section );
				$oldLinks = $this->findLinks( $oldtext );
				$newLinks = $this->findLinks( $newtext );
			}

			$unknownLinks = array_filter( $newLinks, array( &$this, 'filterLink' ) );
			$addedLinks = array_diff( $unknownLinks, $oldLinks );
			$numLinks = count( $addedLinks );

			if( $numLinks > 0 ) {
				global $wgUser;
				$this->trigger = sprintf( "%dx url trigger by '%s' at [[%s]]: %s",
					$numLinks,
					$wgUser->getName(),
					$title->getPrefixedText(),
					implode( ", ", $addedLinks ) );
				$this->action = 'addurl';
				return true;
			}
		}

		global $wgCaptchaRegexes;
		if( !empty( $wgCaptchaRegexes ) ) {
			// Custom regex checks
			$oldtext = $this->loadText( $editPage, $section );

			foreach( $wgCaptchaRegexes as $regex ) {
				$newMatches = array();
				if( preg_match_all( $regex, $newtext, $newMatches ) ) {
					$oldMatches = array();
					preg_match_all( $regex, $oldtext, $oldMatches );

					$addedMatches = array_diff( $newMatches[0], $oldMatches[0] );

					$numHits = count( $addedMatches );
					if( $numHits > 0 ) {
						global $wgUser;
						$this->trigger = sprintf( "%dx %s at [[%s]]: %s",
							$numHits,
							$regex,
							$wgUser->getName(),
							$title->getPrefixedText(),
							implode( ", ", $addedMatches ) );
						$this->action = 'edit';
						return true;
					}
				}
			}
		}

		return false;
	}

	/**
	 * Filter callback function for URL whitelisting
	 * @param string url to check
	 * @return bool true if unknown, false if whitelisted
	 * @access private
	 */
	function filterLink( $url ) {
		global $wgCaptchaWhitelist;
		$source = wfMsgForContent( 'captcha-addurl-whitelist' );

		$whitelist = wfEmptyMsg( 'captcha-addurl-whitelist', $source ) 
			? false
			: $this->buildRegexes( explode( "\n", $source ) );

		$cwl = $wgCaptchaWhitelist !== false ? preg_match( $wgCaptchaWhitelist, $url ) : false;
		$wl  = $whitelist          !== false ? preg_match( $whitelist, $url )          : false;

		return !( $cwl || $wl );
	}

	/**
	 * Build regex from whitelist
	 * @param string lines from [[MediaWiki:Captcha-addurl-whitelist]]
	 * @return string Regex or bool false if whitelist is empty
	 * @access private
	 */
	function buildRegexes( $lines ) {
		# Code duplicated from the SpamBlacklist extension (r19197)

		# Strip comments and whitespace, then remove blanks
		$lines = array_filter( array_map( 'trim', preg_replace( '/#.*$/', '', $lines ) ) );

		# No lines, don't make a regex which will match everything
		if ( count( $lines ) == 0 ) {
			wfDebug( "No lines\n" );
			return false;
		} else {
			# Make regex
			# It's faster using the S modifier even though it will usually only be run once
			//$regex = 'http://+[a-z0-9_\-.]*(' . implode( '|', $lines ) . ')';
			//return '/' . str_replace( '/', '\/', preg_replace('|\\\*/|', '/', $regex) ) . '/Si';
			$regexes = '';
			$regexStart = '/http:\/\/+[a-z0-9_\-.]*(';
			$regexEnd = ')/Si';
			$regexMax = 4096;
			$build = false;
			foreach( $lines as $line ) {
				// FIXME: not very robust size check, but should work. :)
				if( $build === false ) {
					$build = $line;
				} elseif( strlen( $build ) + strlen( $line ) > $regexMax ) {
					$regexes .= $regexStart .
						str_replace( '/', '\/', preg_replace('|\\\*/|', '/', $build) ) .
						$regexEnd;
					$build = $line;
				} else {
					$build .= '|' . $line;
				}
			}
			if( $build !== false ) {
				$regexes .= $regexStart .
					str_replace( '/', '\/', preg_replace('|\\\*/|', '/', $build) ) .
					$regexEnd;
			}
			return $regexes;
		}
	}

	/**
	 * Load external links from the externallinks table
	 */
	function getLinksFromTracker( $title ) {
		$dbr =& wfGetDB( DB_SLAVE );
		$id = $title->getArticleId(); // should be zero queries
		$res = $dbr->select( 'externallinks', array( 'el_to' ), 
			array( 'el_from' => $id ), __METHOD__ );
		$links = array();
		while ( $row = $dbr->fetchObject( $res ) ) {
			$links[] = $row->el_to;
		}
		return $links;
	}		

	/**
	 * The main callback run on edit attempts.
	 * @param EditPage $editPage
	 * @param string $newtext
	 * @param string $section
	 * @param bool true to continue saving, false to abort and show a captcha form
	 */
	function confirmEdit( &$editPage, $newtext, $section, $merged = false ) {
		if( $this->shouldCheck( $editPage, $newtext, $section, $merged ) ) {
			if( $this->passCaptcha() ) {
				return true;
			} else {
				$editPage->showEditForm( array( &$this, 'editCallback' ) );
				return false;
			}
		} else {
			wfDebug( "ConfirmEdit: no need to show captcha.\n" );
			return true;
		}
	}

	/**
	 * A more efficient edit filter callback based on the text after section merging
	 * @param EditPage $editPage
	 * @param string $newtext
	 */
	function confirmEditMerged( &$editPage, $newtext ) {
		return $this->confirmEdit( $editPage, $newtext, false, true );
	}

	/**
	 * Hook for user creation form submissions.
	 * @param User $u
	 * @param string $message
	 * @return bool true to continue, false to abort user creation
	 */
	function confirmUserCreate( $u, &$message ) {
		global $wgCaptchaTriggers;
		if( $wgCaptchaTriggers['createaccount'] ) {
			$this->trigger = "new account '" . $u->getName() . "'";
			if( !$this->passCaptcha() ) {
				$message = wfMsg( 'captcha-createaccount-fail' );
				return false;
			}
		}
		return true;
	}
	
	/**
	 * Hook for user login form submissions.
	 * @param User $u
	 * @param string $message
	 * @return bool true to continue, false to abort user creation
	 */
	function confirmUserLogin( $u, $pass, &$retval ) {
		if( $this->isBadLoginTriggered() ) {
			$this->trigger = "post-badlogin login '" . $u->getName() . "'";
			if( !$this->passCaptcha() ) {
				$message = wfMsg( 'captcha-badlogin-fail' );
				// Emulate a bad-password return to confuse the shit out of attackers
				$retval = LoginForm::WRONG_PASS;
				return false;
			}
		}
		return true;
	}

	/**
	 * Given a required captcha run, test form input for correct
	 * input on the open session.
	 * @return bool if passed, false if failed or new session
	 */
	function passCaptcha() {
		$info = $this->retrieveCaptcha();
		if( $info ) {
			global $wgRequest;
			if( $this->keyMatch( $wgRequest, $info ) ) {
				$this->log( "passed" );
				$this->clearCaptcha( $info );
				return true;
			} else {
				$this->clearCaptcha( $info );
				$this->log( "bad form input" );
				return false;
			}
		} else {
			$this->log( "new captcha session" );
			return false;
		}
	}

	/**
	 * Log the status and any triggering info for debugging or statistics
	 * @param string $message
	 */
	function log( $message ) {
		wfDebugLog( 'captcha', 'ConfirmEdit: ' . $message . '; ' .  $this->trigger );
	}

	/**
	 * Generate a captcha session ID and save the info in PHP's session storage.
	 * (Requires the user to have cookies enabled to get through the captcha.)
	 *
	 * A random ID is used so legit users can make edits in multiple tabs or
	 * windows without being unnecessarily hobbled by a serial order requirement.
	 * Pass the returned id value into the edit form as wpCaptchaId.
	 *
	 * @param array $info data to store
	 * @return string captcha ID key
	 */
	function storeCaptcha( $info ) {
		if( !isset( $info['index'] ) ) {
			// Assign random index if we're not udpating
			$info['index'] = strval( mt_rand() );
		}
		$this->storage->store( $info['index'], $info );
		return $info['index'];
	}

	/**
	 * Fetch this session's captcha info.
	 * @return mixed array of info, or false if missing
	 */
	function retrieveCaptcha() {
		global $wgRequest;
		$index = $wgRequest->getVal( 'wpCaptchaId' );
		return $this->storage->retrieve( $index );
	}

	/**
	 * Clear out existing captcha info from the session, to ensure
	 * it can't be reused.
	 */
	function clearCaptcha( $info ) {
		$this->storage->clear( $info['index'] );
	}

	/**
	 * Retrieve the current version of the page or section being edited...
	 * @param EditPage $editPage
	 * @param string $section
	 * @return string
	 * @access private
	 */
	function loadText( $editPage, $section ) {
		$rev = Revision::newFromTitle( $editPage->mTitle );
		if( is_null( $rev ) ) {
			return "";
		} else {
			$text = $rev->getText();
			if( $section != '' ) {
				return Article::getSection( $text, $section );
			} else {
				return $text;
			}
		}
	}

	/**
	 * Extract a list of all recognized HTTP links in the text.
	 * @param string $text
	 * @return array of strings
	 */
	function findLinks( $text ) {
		global $wgParser, $wgTitle, $wgUser;

		$options = new ParserOptions();
		$text = $wgParser->preSaveTransform( $text, $wgTitle, $wgUser, $options );
		$out = $wgParser->parse( $text, $wgTitle, $options );

		return array_keys( $out->getExternalLinks() );
	}

	/**
	 * Show a page explaining what this wacky thing is.
	 */
	function showHelp() {
		global $wgOut, $ceAllowConfirmedEmail;
		$wgOut->setPageTitle( wfMsg( 'captchahelp-title' ) );
		$wgOut->addWikiText( wfMsg( 'captchahelp-text' ) );
		if ( $this->storage->cookiesNeeded() ) {
			$wgOut->addWikiText( wfMsg( 'captchahelp-cookies-needed' ) );
		}
	}

}

class CaptchaSessionStore {
	function store( $index, $info ) {
		$_SESSION['captcha' . $info['index']] = $info;
	}
	
	function retrieve( $index ) {
		if( isset( $_SESSION['captcha' . $index] ) ) {
			return $_SESSION['captcha' . $index];
		} else {
			return false;
		}
	}
	
	function clear( $index ) {
		unset( $_SESSION['captcha' . $index] );
	}

	function cookiesNeeded() {
		return true;
	}
}

class CaptchaCacheStore {
	function store( $index, $info ) {
		global $wgMemc, $wgCaptchaSessionExpiration;
		$wgMemc->set( wfMemcKey( 'captcha', $index ), $info,
			$wgCaptchaSessionExpiration );
	}

	function retrieve( $index ) {
		global $wgMemc;
		$info = $wgMemc->get( wfMemcKey( 'captcha', $index ) );
		if( $info ) {
			return $info;
		} else {
			return false;
		}
	}
	
	function clear( $index ) {
		global $wgMemc;
		$wgMemc->delete( wfMemcKey( 'captcha', $index ) );
	}

	function cookiesNeeded() {
		return false;
	}
}