Rewrite quiz logic to be more robust

Fixes #470

1 files changed, 68 insertions, 31 deletions

diff --git a/lib/parse/is_quiz.js b/lib/parse/is_quiz.js
index aa6125a..4a24cfc 100644
--- a/lib/parse/is_quiz.js
+++ b/lib/parse/is_quiz.js
@@ -4,42 +4,79 @@ function isQuizNode(node) {
     return (/^[(\[][ x][)\]]/).test(node.text || node);
 }
 
-function isQuiz(nodes) {
-    if (nodes.length < 3) {
-        return false;
-    }
+function isTableQuestion(nodes) {
+    var block = questionBlock(nodes);
+    return (
+        block.length === 1 &&
+        block[0].type === 'table' &&
+        _.all(block[0].cells[0].slice(1), isQuizNode)
+    );
+}
 
-    // Support having a first paragraph block
-    // before our series of questions
-    var quizNodes = nodes.slice(nodes[0].type === 'paragraph' ? 1 : 0);
+function isListQuestion(nodes) {
+    var block = questionBlock(nodes);
+    // Counter of when we go in and out of lists
+    var inlist = 0;
+    // Number of lists we found
+    var lists = 0;
+    // Elements found outside a list
+    var outsiders = 0;
+    // Ensure that we have nothing except lists
+    _.each(block, function(node) {
+        if(node.type === 'list_start') {
+            inlist++;
+        } else if(node.type === 'list_end') {
+            inlist--;
+            lists++;
+        } else if(inlist === 0) {
+            // Found non list_start or list_end whilst outside a list
+            outsiders++;
+        }
+    });
+    return lists > 0 && outsiders === 0;
+}
 
-    // No questions
-    if (!_.some(quizNodes, { type: 'blockquote_start' })) {
-        return false;
-    }
+function isQuestion(nodes) {
+    return isListQuestion(nodes) || isTableQuestion(nodes);
+}
 
-    // Check if section has list of questions
-    // or table of questions
-    var listIdx = _.findIndex(quizNodes, { type: 'list_item_start' });
-    var tableIdx = _.findIndex(quizNodes, { type: 'table' });
-
-
-    if(
-        // List of questions
-        listIdx !== -1 && isQuizNode(quizNodes[listIdx + 1]) ||
-
-        // Table of questions
-        (
-            tableIdx !== -1 &&
-            // Last entry
-            tableIdx === nodes.length - 1 &&
-            _.every(quizNodes[tableIdx].cells[0].slice(1), isQuizNode)
-        )
-    ) {
-        return true;
+// Remove (optional) paragraph header node and blockquote
+function questionBlock(nodes) {
+    return nodes.slice(
+        nodes[0].type === 'paragraph' ? 1 : 0,
+        _.findIndex(nodes, { type: 'blockquote_start' })
+    );
+}
+
+function splitQuestions(nodes) {
+    // Represents nodes in current question
+    var buffer = [];
+    return _.reduce(nodes, function(accu, node) {
+        // Add node to buffer
+        buffer.push(node);
+
+        // Flush buffer once we hit the end of a question
+        if(node.type === 'blockquote_end') {
+            accu.push(buffer);
+            // Clear buffer
+            buffer = [];
+        }
+
+        return accu;
+    }, []);
+}
+
+function isQuiz(nodes) {
+    // Extract potential questions
+    var questions = splitQuestions(nodes);
+
+    // Nothing that looks like questions
+    if(questions.length === 0) {
+        return false;
     }
 
-    return false;
+    // Ensure all questions are correctly structured
+    return _.all(questions, isQuestion);
 }
 
 module.exports = isQuiz;