using System;
using System.Collections;
using System.Collections.Generic;

namespace AX.AudioSystem
{
    /// <summary>
    /// 构造一个暴露内部数组的 List。
    /// </summary>
    internal class BetterList<T>
    {
        private const int DefaultCapacity = 4;
        private const int MaxArrayLength = 0x7fefffff;

        private static readonly T[] emptyArray = new T[0];

        private T[] items;
        private int size;

        public BetterList()
        {
            items = emptyArray;
        }

        public BetterList(int capacity)
        {
            if (capacity < 0)
                throw new ArgumentOutOfRangeException("capacity");

            if (capacity == 0)
                items = emptyArray;
            else
                items = new T[capacity];
        }

        public int Capacity
        {
            get
            {
                return items.Length;
            }
            set
            {
                if (value < size)
                    throw new ArgumentOutOfRangeException("capacity");

                if (value != items.Length)
                {
                    if (value > 0)
                    {
                        T[] newItems = new T[value];

                        if (size > 0)
                            Array.Copy(items, 0, newItems, 0, size);

                        items = newItems;
                    }
                    else
                        items = emptyArray;
                }
            }
        }

        public int Count
        {
            get { return size; }
        }

        public T this[int index]
        {
            get
            {
                if ((uint)index >= (uint)size)
                    throw new ArgumentOutOfRangeException();

                return items[index];
            }

            set
            {
                if ((uint)index >= (uint)size)
                    throw new ArgumentOutOfRangeException();

                items[index] = value;
            }
        }

        public void Add(T item)
        {
            if (size == items.Length)
                EnsureCapacity(size + 1);

            items[size++] = item;
        }

        public void AddRange(IEnumerable<T> enumerable)
        {
            if (enumerable == null)
                throw new ArgumentNullException("enumerable");

            ICollection<T> collection = enumerable as ICollection<T>;

            if (collection != null)
            {
                int count = collection.Count;

                if (count > 0)
                {
                    EnsureCapacity(size + count);

                    collection.CopyTo(items, size);

                    size += count;
                }
            }
            else
            {
                foreach (var item in enumerable)
                    Add(item);
            }
        }

        public void AddRange(T[] data, int offset, int count)
        {
            if (data == null)
                throw new ArgumentNullException("data");

            if (offset < 0)
                throw new ArgumentOutOfRangeException("offset");

            if(count < 0)
                throw new ArgumentOutOfRangeException("count");

            if (data.Length - offset < count)
                throw new ArgumentOutOfRangeException("data, offset, count");

            if(count > 0)
            {
                EnsureCapacity(size + count);

                Array.Copy(data, offset, items, size, count);

                size += count;
            }
        }

        public void AddRange(T[] data)
        {
            AddRange(data, 0, data.Length);
        }

        public void Clear()
        {
            if (size > 0)
            {
                Array.Clear(items, 0, size);
                size = 0;
            }
        }

        public bool Contains(T item)
        {
            if ((Object)item == null)
            {
                for (int i = 0; i < size; i++)
                    if ((Object)items[i] == null)
                        return true;

                return false;
            }
            else
            {
                EqualityComparer<T> comparer = EqualityComparer<T>.Default;

                for (int i = 0; i < size; i++)
                {
                    if (comparer.Equals(items[i], item))
                        return true;
                }

                return false;
            }
        }

        public void CopyTo(T[] array)
        {
            CopyTo(array, 0);
        }

        public void CopyTo(int index, T[] array, int arrayIndex, int count)
        {
            if (size - index < count)
                throw new ArgumentException();

            Array.Copy(items, index, array, arrayIndex, count);
        }

        public void CopyTo(T[] array, int arrayIndex)
        {
            Array.Copy(items, 0, array, arrayIndex, size);
        }

        
        private void EnsureCapacity(int min)
        {
            if (items.Length < min)
            {
                int newCapacity = items.Length == 0 ? DefaultCapacity : items.Length * 2;
                
                if ((uint)newCapacity > MaxArrayLength)
                    newCapacity = MaxArrayLength;

                if (newCapacity < min)
                    newCapacity = min;

                Capacity = newCapacity;
            }
        }


        public int IndexOf(T item)
        {
            return Array.IndexOf(items, item, 0, size);
        }

        public int IndexOf(T item, int index)
        {
            if (index > size)
                throw new ArgumentOutOfRangeException("index");

            return Array.IndexOf(items, item, index, size - index);
        }

        public int IndexOf(T item, int index, int count)
        {
            if (index > size)
                throw new ArgumentOutOfRangeException("index");

            if (count < 0 || index > size - count)
                throw new ArgumentOutOfRangeException("count");

            return Array.IndexOf(items, item, index, count);
        }

        public bool Remove(T item)
        {
            int index = IndexOf(item);

            if (index >= 0)
            {
                RemoveAt(index);
                return true;
            }

            return false;
        }

        public void RemoveAt(int index)
        {
            if ((uint)index >= (uint)size)
                throw new ArgumentOutOfRangeException();

            size--;

            if (index < size)
            {
                Array.Copy(items, index + 1, items, index, size - index);
            }

            items[size] = default(T);
        }

        public void RemoveRange(int index, int count)
        {
            if (index < 0)
                throw new ArgumentOutOfRangeException("index");

            if (count < 0)
                throw new ArgumentOutOfRangeException("count");

            if (size - index < count)
                throw new ArgumentOutOfRangeException();

            if (count > 0)
            {
                size -= count;

                if (index < size)
                    Array.Copy(items, index + count, items, index, size - index);

                Array.Clear(items, size, count);
            }
        }

        public T[] ToArray()
        {
            var array = new T[size];

            CopyTo(array);

            return array;
        }

        /// <summary>
        /// 获得原始的数组。特别注意：不要对此数组进行操作。
        /// </summary>
        public T[] GetBuffer()
        {
            return items;
        }

        public void TrimExcess()
        {
            int threshold = (int)(((double)items.Length) * 0.9);

            if (size < threshold)
                Capacity = size;
        }
    }
}