More fixes

src/databases/CourseDatabase.java

@@ -60,14 +60,22 @@ public void deleteLesson(int id) {
         for (Course c : getRecords()) {
             c.getLessons().removeIf((t) -> t.getId() == id);
         }
+        saveToFile();
     }
 
     public void deleteQuiz(int id) {
         for (Course c : getRecords()) {
             for (Lesson l : c.getLessons()) {
                 if (l.getQuiz() != null && l.getQuiz().getId() == id) l.setQuiz(null);
+
+                // Delete all student attempts
+                for (Map.Entry<Integer, Progress> entry : l.getStudentProgress().entrySet()) {
+                    entry.getValue().removeAttempts(id);
+                }
             }
         }
+
+        saveToFile();
     }
 
     public Course getCourseById(int id) {return getRecordById(id);}

src/models/Progress.java

@@ -20,6 +20,10 @@ public void addAttempt(QuizAttempt attempt) {
         if (attempt.isPassed()) this.lessonComplete = true;
     }
 
+    public void removeAttempts(int quizId) {
+        this.attempts.removeIf((attempt -> attempt.getQuizId() == quizId));
+    }
+
     /* Getters & Setters */
     public int getUserId() {return userId;}
     public void setUserId(int userId) {this.userId = userId;}

src/models/User.java

@@ -11,15 +11,12 @@ public class User implements Model {
     private String email;
     private String name;
     private String role;
-    private List<Certificate> certificates;
+    private List<Certificate> certificates = new ArrayList<>();
 
     /* This constructor is necessary for JSON parsing */
     public User() {}
 
     public void addCertificate(Certificate certificate) {
-        if (this.certificates == null) {
-            this.certificates = new ArrayList<>();
-        }
         this.certificates.add(certificate);
     }