feat: implement Learning Tracer (heartbeat duration tracking) for LPK Audit

app/Http/Controllers/CoursePlayerController.php

@@ -45,9 +45,16 @@ class CoursePlayerController extends Controller
         // Get user progress for this course
         $completedLessonsIds = UserProgress::where('user_id', $user->id)
             ->whereIn('lesson_id', $allLessons->pluck('id'))
+            ->whereNotNull('completed_at')
             ->pluck('lesson_id')
             ->toArray();
 
+        // Initialize started_at if first time viewing
+        UserProgress::firstOrCreate(
+            ['user_id' => $user->id, 'lesson_id' => $currentLesson->id],
+            ['started_at' => now(), 'last_heartbeat_at' => now()]
+        );
+
         return Inertia::render('Courses/Player', [
             'course' => [
                 'id' => $course->id,
@@ -109,4 +116,33 @@ class CoursePlayerController extends Controller
 
         return back()->with('success', 'Materi selesai! +50 XP');
     }
+
+    /**
+     * Update learning duration via heartbeat.
+     */
+    public function heartbeat(Request $request, Lesson $lesson)
+    {
+        $user = $request->user();
+        $now = now();
+
+        $progress = UserProgress::firstOrCreate(
+            ['user_id' => $user->id, 'lesson_id' => $lesson->id],
+            ['started_at' => $now, 'last_heartbeat_at' => $now]
+        );
+
+        $lastHeartbeat = $progress->last_heartbeat_at ?? $progress->created_at;
+        $diffSeconds = $now->diffInSeconds($lastHeartbeat);
+
+        // Limit diff to prevent massive jumps (e.g. if user leaves tab open and comes back hours later)
+        // Max 90 seconds per heartbeat (assuming heartbeat is every 60s)
+        $increment = min($diffSeconds, 90);
+
+        $progress->increment('time_spent_seconds', $increment);
+        $progress->update(['last_heartbeat_at' => $now]);
+
+        return response()->json([
+            'status' => 'success',
+            'time_spent' => $progress->time_spent_seconds,
+        ]);
+    }
 }

app/Models/UserProgress.php

@@ -15,7 +15,9 @@ class UserProgress extends Model
     protected $guarded = [];
 
     protected $casts = [
+        'started_at' => 'datetime',
         'completed_at' => 'datetime',
+        'last_heartbeat_at' => 'datetime',
         'metadata' => 'array',
     ];