using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace InheritanceAndPolymorphism
{
    abstract class Course
    {
        private string courseName;
        public string TeacherName { get; set; }
        private IList<string> students;

        public string CourseName
        {
            get
            {
                return this.courseName;
            }
            set
            {
                if (string.IsNullOrWhiteSpace(value))
                {
                    throw new ArgumentException("There is not any name of course entered.");
                }

                this.courseName = value;
            }
        }

        public IList<string> Students
        {
            get
            {
                return this.students;
            }
            set
            {
                if (value != null)
                {
                    this.students = new List<string>();

                    foreach (string student in value)
                    {
                        this.students.Add(student);
                    }
                }
                else
                {
                    this.students = null;
                }

            }
        }

        protected Course(string courseName, string teacherName, IList<string> students)
        {
            this.CourseName = courseName;
            this.TeacherName = teacherName;
            this.Students = students;
        }

        private string GetStudentsAsString()
        {
            if (this.Students == null || this.Students.Count == 0)
            {
                return "{ }";
            }
            else
            {
                return "{ " + string.Join(", ", this.Students) + " }";
            }
        }

        public override string ToString()
        {
            StringBuilder result = new StringBuilder();

            result.Append("LocalCourse { Name = ");
            result.Append(this.CourseName);

            if (this.TeacherName != null)
            {
                result.Append("; Teacher = ");
                result.Append(this.TeacherName);
            }

            result.Append("; Students = ");
            result.Append(this.GetStudentsAsString());

            return result.ToString();
        }
    }
}