1 files changed, 74 insertions, 3 deletions

diff --git a/src/main/java/design/model/course_search/CurrentSearchQuery.java b/src/main/java/design/model/course_search/CurrentSearchQuery.java
index c00eb86..e1f52ce 100644
--- a/src/main/java/design/model/course_search/CurrentSearchQuery.java
+++ b/src/main/java/design/model/course_search/CurrentSearchQuery.java
@@ -17,12 +17,10 @@ public class CurrentSearchQuery {
     private CourseList query = db.getCourseList();
     private final List<CourseSorter> filters = new ArrayList<CourseSorter>();
 
-
     // reset the query
     public void reset()
     {
         query = db.getCourseList();
-        clearFilters();
     }
 
     // add a new filter
@@ -79,6 +77,79 @@ public class CurrentSearchQuery {
             .filter(s -> s.toString().toLowerCase().contains(searchQuery.toLowerCase()))
             .collect(Collectors.toList());
 
-        query.setCourses(courses);
+        // and now, we filter it!
+        CourseList filtered = applyFilters(filters, courses);
+        query.setCourses(filtered.getCourses());
+    }
+
+    // to apply our filters we need to traverse the tree and make new grouping as we go. 
+    public CourseList applyFilters(List<CourseSorter> filters, List<ICourse> coursesToFilter) 
+    {
+        CourseList root = new CourseList();
+        root.setCourses(applyFiltersRecursive(coursesToFilter, filters, 0));
+        return root;
+    }
+
+    // the actual recursive part. Level is how many filters deep we are.
+    private List<ICourse> applyFiltersRecursive(List<ICourse> courses, List<CourseSorter> filters, int level) 
+    {
+       // base case. we have gone past all filters or theres only one course in this list. already sorted!
+        if (level >= filters.size() || courses.size() <= 1) 
+        {
+            return courses;
+        }
+
+        // grab out current sorting strategy for this level, and sort the courselist.
+        CourseSorter sorter = filters.get(level);
+        sorter.sortCourses(courses);
+
+        // the resulting sorted list, with new groupings
+        List<ICourse> result = new ArrayList<>();
+
+        // courses with an equal value.
+        List<ICourse> currentGroup = new ArrayList<>();
+
+        ICourse prev = null;
+
+        // run through the courses, if
+        for (ICourse c : courses) 
+        {
+            /* always add the first course to a new group. when iterating through courses, if we have to values that are equal, we need to add them into a group together.
+            * think about it this way. If we have [ 1, 2, 2, 2, 3, 4 ]. 1 is first, so its in it's own group. 2 /= 1, so 2 gets its own group.
+            * now do 2 again. we add it to the existing group 2. Same with the next 2. Now 3. 3 /= 2, so we put it in it's own group.
+            */
+            if (prev == null || !sorter.isEqual(prev, c)) 
+            {
+                // already a course in that group? we now have two equal values and so 
+                if (!currentGroup.isEmpty()) 
+                {
+                    result.add(makeGroup(currentGroup, filters, level));
+                    currentGroup = new ArrayList<>();
+                }
+            }
+
+            currentGroup.add(c);
+            prev = c;
+        }
+
+        // handle the last group.
+        if (!currentGroup.isEmpty()) 
+        {
+            result.add(makeGroup(currentGroup, filters, level));
+        }
+
+        return result;
     }
+
+    // make a CourseList group, a sublist of a group, and filter it. 
+    private ICourse makeGroup(List<ICourse> group, List<CourseSorter> filters, int level) 
+    {
+        // base case, group only has one course in it (already sorted)
+        if (group.size() == 1) return group.get(0);
+
+        // group has more than 1 course in it, it needs to be sorted more if possible.
+        CourseList subList = new CourseList();
+        subList.setCourses(applyFiltersRecursive(group, filters, level + 1));
+        return subList;
+    }  
 }