using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace IEnumerable_vs_IEnumerator

{

    class Program

    {

        static void Main(string[] args)

        {

            List<string> WeekDays = new List<string>();

            WeekDays.Add("Sunday");

            WeekDays.Add("Monday");

            WeekDays.Add("Tuesday");

            WeekDays.Add("Wednesday");

            WeekDays.Add("Thursday");

            WeekDays.Add("Friday");

            WeekDays.Add("Saturday");

            Console.WriteLine("********** Print Collection with IEnumerable **********");

            IEnumerable<string> iEnum = (IEnumerable<string>)WeekDays;

            foreach (string str in iEnum)

            {

                Console.WriteLine(str);

            }

            Console.WriteLine("********** Print Collection with IEnumerator **********");

            IEnumerator<string> iEnumerat = WeekDays.GetEnumerator(); // to convert list into IEnumerator we can invoke the GetEnumerator method

            while(iEnumerat.MoveNext())

            {

                Console.WriteLine(iEnumerat.Current.ToString());

            }

            Console.ReadLine();

            List<int> myYears = new List<int>();

            myYears.Add(2001);

            myYears.Add(2002);

            myYears.Add(2003);

            myYears.Add(2004);

            myYears.Add(2005);

            myYears.Add(2006);

            myYears.Add(2007);

            IEnumerable<int> iEnum2 = (IEnumerable<int>)myYears;

            PrintFirstThreeValues(iEnum2);

            Console.ReadLine();

            IEnumerator<int> iEnumerat2 = myYears.GetEnumerator();

            PrintFirstThreeValues(iEnumerat2);

            Console.ReadLine();

        }

        static void PrintFirstThreeValues(IEnumerable<int> Obj)

        {

            foreach (int temp in Obj)

            {

                Console.WriteLine(temp.ToString());

                if(temp>2002)

                {

                    PrintLastFourValues(Obj);

                }

            }

        }

        static void PrintLastFourValues(IEnumerable<int> Obj)

        {

            foreach (int temp in Obj)

            {

                Console.WriteLine(temp.ToString());

            }

        }

        static void PrintFirstThreeValues(IEnumerator<int> Obj)

        {

            while(Obj.MoveNext())

            {

                Console.WriteLine(Obj.Current.ToString());

                if ((int)Obj.Current > 2002)

                {

                    PrintLastFourValues(Obj);

                }

            }

        }

        static void PrintLastFourValues(IEnumerator<int> Obj)

        {

            while(Obj.MoveNext())

            {

                Console.WriteLine(Obj.Current.ToString());

            }

        }

        public IEnumerator GetEnumerator()

        {

            // return IEnumerator of our Custom Type

            return (IEnumerator)this;

        }

        // IEnumerator interface contains the below three methods Reset, MoveNext, Current

        //public void Reset()

        //{

        //    //Get total number of element in a collection

        //    length = slist.Count;

        //    //Setting the pointer to just before the beginning of collection

        //    current = -1;

        //}

        //public bool MoveNext()

        //{

        //    //this will increment the counter variable

        //    //and will check whether it is exceeding the actual length of our collection

        //    return (++current < length);

        //}

        //public object Current

        //{

        //    get

        //    { //Here "slist" is the collection and "current" is the location pointer

        //        return (slist[current]);

        //    }

        //}

    }

}