From deee57aa0152b1c82e62dc8da770e5b99f85e61b Mon Sep 17 00:00:00 2001
From: Fabien Benetou <fabien@benetou.fr>
Date: Fri, 12 Aug 2011 23:40:25 +0200
Subject: [PATCH] partly managing difficulty

---
 pmwiki_recipes/exercises.php | 36 +++++++++++++++++++++++-------------
 1 file changed, 23 insertions(+), 13 deletions(-)

diff --git a/pmwiki_recipes/exercises.php b/pmwiki_recipes/exercises.php
index 9851144..63f4144 100644
--- a/pmwiki_recipes/exercises.php
+++ b/pmwiki_recipes/exercises.php
@@ -23,14 +23,16 @@ SDV($HandleAuth['Exercises'],'read');
 
 function Exercises($pagename, $auth){
 	$type = $_GET["type"];
+	$counter = (int) $_GET["counter"];
+	$difficulty = (int) $_GET["difficulty"];
+	list($group,$page) = explode(".",$pagename);
 
-	$availableexercisetypes = array("pagelink", "expressioninpage");
+	$availableexercisetypes = array("pagelink", "expressioninpage", "pagehasexpression");
 	if ($type=="random")
 		$type= $availableexercisetypes[rand(0,count($availableexercisetypes)-1)];
 
 	switch ($type){
 		case "pagelink":
-			list($group,$page) = explode(".",$pagename);
 			// the pattern should be improve, e.g. remove PmWiki. , RecentChanges, GroupFooter, GroupHeader, Template, ...
 			if ($group == "AllPages"){
 				// equivalent to getting ALL pages
@@ -53,27 +55,31 @@ function Exercises($pagename, $auth){
 			//consider pilling up potential in $answers[]
 
 			//randomly pick a page amongst the linked pages
-			$pageA = $links_array[rand(0,count($links_array)-1)];
+			$answers[] = $links_array[rand(0,count($links_array)-1)];
 
-			unset($pages[array_search($pageA,$links_array)]);
-			unset($pages[array_search($pageA,$pages)]);
-			//randomly pick 2 others pages which are not amongst the list of linked page
-			$pageB = $pages[rand(0,count($pages)-1)];
-			unset($pages[array_search($pageB,$pages)]);
-			$pageC = $pages[rand(0,count($pages)-1)];
-			unset($pages[array_search($pageC,$pages)]);
+			unset($pages[array_search($answers[0],$links_array)]);
+			unset($pages[array_search($answers[0],$pages)]);
+
+			//randomly pick n-1 others pages which may not be amongst the list of linked page
+			// n should be based on $difficulty, e.g. n=2+$difficulty or n=2^$difficulty
+			$n=3;
+			for ($i=1;$i<$n;$i++) {
+				$answers[] = $pages[rand(0,count($pages)-1)];
+				unset($pages[array_search($answers[$i],$pages)]);
+			}
 
 			//display
 			$result .="Is page [[$sourcepage]] linked to ";
-			$counter = (int) $_GET["counter"];
 
 			$counterparam = "";
 			if ( $counter > 0) {
 				$counterparam = "counter=$counter&";
 			}
 
-			$answers = array ($pageA,$pageB,$pageC);
+			// there should now be at least 1 needle in the haystack, the first one
+			// note that there might be more but this is not a problem as long as the question is stated clearly.
 			shuffle($answers);
+
 			for ($i=0;$i<count($answers);$i++) {
 				if ($answers[$i] != "") {
 					if ( $i == count($answers) -1 )
@@ -92,9 +98,13 @@ function Exercises($pagename, $auth){
 			$result .="? ";
 			$result .="\n\nClick on the answer.";
 			break;
+		case "pagehasexpression":
+			// explode content by line "%0a" or word " "
+			$result .= "Does the page 'PAGE' has expression 'EXPRESSIONA', 'EXPRESSIONB' or 'EXPRESSIONC?";
+			break;
 		case "expressioninpage":
 			// explode content by line "%0a" or word " "
-			$result .= "Does the expression 'EXPRESSION' come from PAGEA PAGEB or PAGEC?";
+			$result .= "Does the expression 'EXPRESSION' come from PAGEA, PAGEB or PAGEC?";
 			break;
 		default:
 			$result .= "Exercise type unknown.";