using ProjectCruiser.Exceptions;

namespace ProjectCruiser.CollectionGenericObj;

public class ArrayGenObj<T> : ICollectionGenObj<T>
    where T : class
{
    // Массив объектов, которые храним
    private T?[] _collection;

    // Максимально допустимое число объектов в массиве
    private int _maxCount;
    public int Count => _collection.Count(s => (s != null));

    public int MaxCount
    {
        get { return _maxCount; }
        set
        {
            if (value > 0)
            {
                _maxCount = value;

                if (_collection.Length == 0) _collection = new T?[value];
                else Array.Resize(ref _collection, value);
            }
        }
    }

    public CollectionType GetCollectionType => CollectionType.Array;

    public ArrayGenObj()
    {
        _collection = Array.Empty<T?>();
    }

    // methods :
    public T? GetItem(int index)
    {
        if (index > _maxCount)
            throw new CollectionOverflowException(index);
        if (index < 0)
            throw new PositionOutOfCollectionException(index);

        if (_collection[index] == null)
            throw new ObjectNotFoundException(index);

        return _collection[index];

        // CollectionOverflowException
        // PositionOutOfCollectionException
        // ObjectNotFoundException
    }

    public int Insert(T? item)
    {
        if (item == null) throw
                new NullReferenceException("> Inserting item is null");

        // выход за границы, курируется CollectionOverflowException
        if (Count >= _maxCount) throw new CollectionOverflowException(Count);

        // any empty place -> fill immediately
        for (int i = Count; i < _maxCount; i++)
        {
            if (_collection[i] == null)
            {
                _collection[i] = item;
                return i;
            }
        }
        return Count;

        // NullReferenceException
        // CollectionOverflowException
    }

    public int Insert(T? item, int index)
    {
        if (index < 0 || index >= _maxCount) throw new PositionOutOfCollectionException(index);
        if (Count >= _maxCount) throw new CollectionOverflowException(Count);

        if (item == null) throw
                new NullReferenceException("> Inserting item (at position) is null");

        if (_collection[index] == null)
        {
            _collection[index] = item;
            return index;
        }
        else
        {
            int min_diff = 100, firstNullIndex = 100;

            for (int i = 0; i < Count; i++)
            {
                if (_collection[i] == null && min_diff > Math.Abs(index - i))
                {
                    min_diff = Math.Abs(index - i);
                    firstNullIndex = i;
                }
            }

            _collection[firstNullIndex] = item;
            return firstNullIndex;
        }

        // PositionOutOfCollectionException
        // CollectionOverflowException
        // NullReferenceException
    }

    public T? Remove(int index)
    {
        if (index >= _maxCount || index < 0)
        // on the other positions items don't exist
        {
            throw new PositionOutOfCollectionException(index);
        }

        T? item = _collection[index];
        _collection[index] = null;

        if (item == null) throw new ObjectNotFoundException(index);

        return item;

        // PositionOutOfCollectionException
        // ObjectNotFoundException
    }

    public IEnumerable<T?> GetItems()
    {
        for (int i = 0; i < MaxCount; ++i)
        { 
            yield return _collection[i];
        }
    }
}