[Add] Implementation of StudentDAO class

LangLang/Core/Model/DAO/StudentDAO.cs

@@ -0,0 +1,62 @@
+using System.Collections.Generic;
+using System.Linq;
+using LangLang.Core.Repository;
+using LangLang.Core.Observer;
+
+namespace LangLang.Core.Model.DAO
+{
+    /**
+     * This class encapsulates a list of Student objects and provides methods
+     * for adding, updating, deleting, and retrieving Student objects.
+     * Additionally, this class uses Repository<Student> for loading and saving objects.
+    **/
+    public class StudentDAO : Subject
+    {
+        private readonly List<Student> _students;
+        private readonly Repository<Student> _repository;
+
+
+        public StudentDAO()
+        {
+            _repository = new Repository<Student>("student.csv");
+            _students = _repository.Load();
+        }
+
+        private int GenerateId()
+        {
+            if (_students.Count == 0) return 0;
+            return _students.Last().Profile.Id + 1;
+        }
+
+        public Student AddStudent(Student student)
+        {
+            student.Profile.Id = GenerateId();
+            _students.Add(student);
+            _repository.Save(_students);
+            NotifyObservers();
+            return student;
+        }
+
+        public Student? UpdateStudent(Student student)
+        {
+            Student oldStudent = GetStudentById(student.Profile.Id);
+            if (oldStudent == null) return null;
+
+            oldStudent.Profile = student.Profile;
+            oldStudent.CanModifyInfo = student.CanModifyInfo;
+            oldStudent.ProfessionalQualification = student.ProfessionalQualification;
+
+            _repository.Save(_students);
+            NotifyObservers();
+            return oldStudent;
+        }
+
+        public Student GetStudentById(int id)
+        {
+            return _students.Find(s => s.Profile.Id == id);
+        }
+
+        // TODO: implement RemoveStudent(int id), GetAllStudent()
+    }
+
+}