using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace TinyPosEntity
{
    public class EntityController
    {
        public static string ConnectionString { get; set; }

        private static EntityController instance;

        private EntityController(string connectionString)
        {
            EntityContext.ConnectionString = connectionString;
        }

        public static EntityController GetInstance()
        {
            if (string.IsNullOrEmpty(ConnectionString))
                throw new Exception("ConnectionString 값이 필요합니다.");

            if (instance == null)
                instance = new EntityController(ConnectionString);

            return instance;
        }

        public void Initialize()
        {
            Database.SetInitializer<EntityContext>(new EntityInitializer());

            using (EntityContext context = new EntityContext())
            {
                context.Database.CreateIfNotExists();
            }
        }

        public void AddStudent(Student student)
        {
            using (EntityContext context = new EntityContext())
            {
                context.Students.Add(student);
                context.SaveChanges();
            }
        }

        public List<Student> FindStudent(string name)
        {
            List<Student> result = null;
            using (EntityContext context = new EntityContext())
            {
                var student = from s in context.Students
                                  where s.StudentName.Equals(name)
                                  select s;

                if (student.Count() > 0)
                    result = student.ToList();
            }

            return result;
        }

        public void RemoveStudent(Student student)
        {
            using (EntityContext context = new EntityContext())
            {
                context.Database.ExecuteSqlCommand("DELETE FROM dbo.Students WHERE StudentName = {0}", student.StudentName);
            }
        }
    }
}