public void Withdraw(Course course)
{
if (null == course)
{
throw new ArgumentNullException(nameof(course));
}
var oldCourses = _courses.Where(c => c.CourseId == course.Id).ToArray();
var isEmpty = !oldCourses.Any();
var isCompleted = !isEmpty && oldCourses.OrderByDescending(c => c.CreatedAt).First().Status == StudentCourseStatus.Statuses.Completed;
if (isCompleted)
{
throw new ArgumentException($"student {this.Id} has completed course {course.Id} already");
}
var isEnrolled = !isEmpty && oldCourses.OrderByDescending(c => c.CreatedAt).First().Status == StudentCourseStatus.Statuses.Enrolled;
if (!isEnrolled)
{
throw new ArgumentException($"student {this.Id} not enrolled in course {course.Id}");
}
_courses.Add(StudentCourseStatus.Withdrawn(this, course));
this.AddEvent(new StudentWithdrawn(this, course));
}
public void Enroll(Course course)
{
if (null == course)
{
throw new ArgumentNullException(nameof(course));
}
var oldCourses = _courses.Where(c => c.CourseId == course.Id).ToArray();
var isEmpty = !oldCourses.Any();
var hasWithdrawn = !isEmpty && oldCourses.OrderByDescending(c => c.CreatedAt).First().Status == StudentCourseStatus.Statuses.Withdrawn;
if (isEmpty || hasWithdrawn)
{
_courses.Add(StudentCourseStatus.Enrolled(this, course));
this.AddEvent(new StudentEnrolled(this, course));
}
}
public void Complete(Course course)
{
if (null == course)
{
throw new ArgumentNullException(nameof(course));
}
var oldCourses = _courses.Where(c => c.CourseId == course.Id).ToArray();
if (!oldCourses.Any())
{
throw new ArgumentException($"student {this.Id} not enrolled in course {course.Id}");
}
if (oldCourses.Any(c => c.Status == StudentCourseStatus.Statuses.Withdrawn))
{
throw new ArgumentException($"student {this.Id} has withdrawn from course {course.Id}");
}
_courses.Add(StudentCourseStatus.Completed(this, course));
this.AddEvent(new CourseCompleted(this, course));
}