From f3ba47eb30f270ec82569619282ec19e7a5505a8 Mon Sep 17 00:00:00 2001
From: Gerald Schmittinger <gerald.schmittinger@ugent.be>
Date: Wed, 14 May 2025 08:45:44 +0200
Subject: [PATCH] fix(backend): Vooruitgang wordt nu enkel op basis van
 effectief bereikbare leerobjecten berekend.

---
 .../database-learning-path-provider.ts        | 32 +++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/backend/src/services/learning-paths/database-learning-path-provider.ts b/backend/src/services/learning-paths/database-learning-path-provider.ts
index fe05dda1..7dbc3168 100644
--- a/backend/src/services/learning-paths/database-learning-path-provider.ts
+++ b/backend/src/services/learning-paths/database-learning-path-provider.ts
@@ -62,6 +62,8 @@ async function convertLearningPath(learningPath: LearningPathEntity, order: numb
     // Convert the learning object notes as retrieved from the database into the expected response format-
     const convertedNodes = await convertNodes(nodesToLearningObjects, personalizedFor);
 
+    const nodesActuallyOnPath = traverseLearningPath(convertedNodes);
+
     return {
         _id: `${learningPath.hruid}/${learningPath.language}`, // For backwards compatibility with the original Dwengo API.
         __order: order,
@@ -71,8 +73,8 @@ async function convertLearningPath(learningPath: LearningPathEntity, order: numb
         image: image,
         title: learningPath.title,
         nodes: convertedNodes,
-        num_nodes: learningPath.nodes.length,
-        num_nodes_left: convertedNodes.filter((it) => !it.done).length,
+        num_nodes: nodesActuallyOnPath.length,
+        num_nodes_left: nodesActuallyOnPath.filter((it) => !it.done).length,
         keywords: keywords.join(' '),
         target_ages: targetAges,
         max_age: Math.max(...targetAges),
@@ -103,6 +105,7 @@ async function convertNode(
                 isTransitionPossible(trans, optionalJsonStringToObject(lastSubmission?.content)) // Otherwise remove all transitions that aren't possible.
         )
         .map((trans, i) => convertTransition(trans, i, nodesToLearningObjects));
+
     return {
         _id: learningObject.uuid,
         language: learningObject.language,
@@ -174,6 +177,31 @@ function convertTransition(
     }
 }
 
+/**
+ * Start from the start node and then always take the first transition until there are no transitions anymore.
+ * Returns the traversed nodes as an array. (This effectively filters outs nodes that cannot be reached.)
+ */
+function traverseLearningPath(nodes: LearningObjectNode[]): LearningObjectNode[] {
+    const traversedNodes: LearningObjectNode[] = [];
+    let currentNode = nodes.find(it => it.start_node);
+
+    while (currentNode) {
+        traversedNodes.push(currentNode);
+
+        const next = currentNode.transitions[0]?.next;
+
+        if (next) {
+            currentNode = nodes.find(it =>
+                it.learningobject_hruid === next.hruid && it.language === next.language && it.version === next.version
+            );
+        } else {
+            currentNode = undefined;
+        }
+    }
+
+    return traversedNodes;
+}
+
 /**
  * Service providing access to data about learning paths from the database.
  */