using System;
using System.Collections;
namespace Core
{
    public class GenericList<T> : IEnumerable
    {
        private T[] _items;
        private int _count;

        public GenericList()
        {
            _items = new T[1];
            _count = 0;
        }

        public int Count
        {
            get { return _count; }
        }

        public void Add(T item)
        {
            if (_count == _items.Length)
            {
                T[] expandedArray = new T[_items.Length * 2];
                for (int i = 0; i < _items.Length; i++)
                {
                    expandedArray[i] = _items[i];
                }
                _items = expandedArray;
            }

            _items[_count] = item;
            _count++;
        }

        public T GetAt(int index)
        {
            if (index < 0 || index >= _count)
            {
                throw new ArgumentException();
            }
            return _items[index];
        }

        public void RemoveAt(int index)
        {
            int idx = 0;
            T[] newOutputArray = new T[_items.Length];

            for (int i = 0; i < _items.Length; i++)
            {
                if (i == index)
                {
                    i++;
                }
                if (i < _items.Length)
                {
                    newOutputArray[idx] = _items[i];
                    idx++;
                }
            }

            _items = newOutputArray;
            _count--;
        }

        public bool Remove(T item)
        {
            T[] tempArray = new T[_items.Length];
            int idx = 0;
            int i = 0;
            bool found = false;

            if (IsInList(_items, item))
            {
                while (i < _items.Length && !found)
                {
                    if (!object.Equals(_items[i], item))
                    {
                        tempArray[idx] = _items[i];
                        idx++;
                    }
                    else
                    {
                        found = true;
                    }
                    i++;
                }

                while (i < _items.Length)
                {
                    tempArray[idx] = _items[i];
                    idx++;
                    i++;
                }

                _items = tempArray;
                _count--;
                return true;
            }

            return false;
        }

        public void Insert(int index, T item)
        {
            int idx = 0;

            if (index == _count)
            {
                Add(item);
            }
            else if (index >= 0 && index < _count)
            {
                if (_count == _items.Length)
                {
                    T[] tempExpandedArr = new T[_items.Length * 2];

                    for (int i = 0; i < _items.Length;)
                    {
                        if (index != idx)
                        {
                            tempExpandedArr[idx] = _items[i];
                            idx++;
                            i++;
                        }
                        else
                        {
                            tempExpandedArr[idx] = item;
                            idx++;
                        }
                    }

                    _items = tempExpandedArr;
                    _count++;
                }
            }
            else
            {
                throw new ArgumentException();
            }
        }

        private bool IsInList(T[] arr, T obj)
        {
            for (int i = 0; i < arr.Length; i++)
            {
                if (object.Equals(arr[i], obj))
                {
                    return true;
                }
            }
            return false;
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return (IEnumerator)GetEnumerator();
        }

        public IEnumerator GetEnumerator()
        {
            return new GenericListEnumerator<T>(_items);
        }
    }
}