using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.Text;
using System.Threading.Tasks;

namespace Tango.Core
{
    public static class Extensions
    {
        public static int IndexOf<T>(this IEnumerable<T> source, T item)
        {
            var entry = source.Select((x, i) => new { Value = x, Index = i })
                        .Where(x => object.Equals(x.Value, item))
                        .FirstOrDefault();
            return entry != null ? entry.Index : -1;
        }

        public static void CopyTo<T>(this IEnumerable<T> source, T[] array, int startIndex)
        {
            int lowerBound = array.GetLowerBound(0);
            int upperBound = array.GetUpperBound(0);
            if (startIndex < lowerBound)
                throw new ArgumentOutOfRangeException("startIndex", "The start index must be greater than or equal to the array lower bound");
            if (startIndex > upperBound)
                throw new ArgumentOutOfRangeException("startIndex", "The start index must be less than or equal to the array upper bound");

            int i = 0;
            foreach (var item in source)
            {
                if (startIndex + i > upperBound)
                    throw new ArgumentException("The array capacity is insufficient to copy all items from the source sequence");
                array[startIndex + i] = item;
                i++;
            }
        }
    }

    public class WeakList<T> : IList<T>
    {
        private List<WeakReference<T>> _innerList = new List<WeakReference<T>>();

        #region IList<T> Members

        public int IndexOf(T item)
        {
            return _innerList.Select(wr => wr.Target).IndexOf(item);
        }

        public void Insert(int index, T item)
        {
            _innerList.Insert(index, new WeakReference<T>(item));
        }

        public void RemoveAt(int index)
        {
            _innerList.RemoveAt(index);
        }

        public T this[int index]
        {
            get
            {
                return _innerList[index].Target;
            }
            set
            {
                _innerList[index] = new WeakReference<T>(value);
            }
        }

        #endregion

        #region ICollection<T> Members

        public void Add(T item)
        {
            _innerList.Add(new WeakReference<T>(item));
        }

        public void Clear()
        {
            _innerList.Clear();
        }

        public bool Contains(T item)
        {
            return _innerList.Any(wr => object.Equals(wr.Target, item));
        }

        public void CopyTo(T[] array, int arrayIndex)
        {
            _innerList.Select(wr => wr.Target).CopyTo(array, arrayIndex);
        }

        public int Count
        {
            get { return _innerList.Count; }
        }

        public bool IsReadOnly
        {
            get { return false; }
        }

        public bool Remove(T item)
        {
            int index = IndexOf(item);
            if (index > -1)
            {
                RemoveAt(index);
                return true;
            }
            return false;
        }

        #endregion

        #region IEnumerable<T> Members

        public IEnumerator<T> GetEnumerator()
        {
            return _innerList.Select(x => x.Target).GetEnumerator();
        }

        #endregion

        #region IEnumerable Members

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return this.GetEnumerator();
        }

        #endregion

        public void Purge()
        {
            _innerList.RemoveAll(wr => !wr.IsAlive);
        }
    }

    [Serializable]
    public class WeakReference<T> : WeakReference
    {
        public WeakReference(T target)
            : base(target)
        {
        }

        public WeakReference(T target, bool trackResurrection)
            : base(target, trackResurrection)
        {
        }

        public WeakReference(SerializationInfo info, StreamingContext context)
            : base(info, context)
        {
        }

        public new T Target
        {
            get
            {
                return (T)base.Target;
            }
        }
    }
}