//-----------------------------------------------------------------------
//-----------------------------------------------------------------------
//     file="ListSegment.cs"
//     Project: StgSharp
//     AuthorGroup: Nitload Space
//     Copyright (c) Nitload Space. All rights reserved.
//     
//     Permission is hereby granted, free of charge, to any person 
//     obtaining a copy of this software and associated documentation 
//     files (the “Software”), to deal in the Software without restriction, 
//     including without limitation the rights to use, copy, modify, merge,
//     publish, distribute, sublicense, and/or sell copies of the Software, 
//     and to permit persons to whom the Software is furnished to do so, 
//     subject to the following conditions:
//     
//     The above copyright notice and 
//     this permission notice shall be included in all copies 
//     or substantial portions of the Software.
//     
//     THE SOFTWARE IS PROVIDED “AS IS”, 
//     WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
//     INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
//     FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 
//     IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
//     DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
//     ARISING FROM, OUT OF OR IN CONNECTION WITH 
//     THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//     
//-----------------------------------------------------------------------
//-----------------------------------------------------------------------
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Xml.Serialization;

namespace StgSharp.Collections
{
    /// <summary>
    ///   Part of a collection. This contains a direct reference to _origin collection, so all
    ///   change to _origin collection will be reflected in this object.
    /// </summary>
    /// <typeparam name="T">
    ///
    /// </typeparam>
    public struct ListSegment<T> : ICollection<T>
    {

        private int _begin;
        private int _length;
        private List<T> _collection;

        public ListSegment( List<T> collection, int begin, int length )
        {
            ArgumentNullException.ThrowIfNull( collection );
            ArgumentOutOfRangeException.ThrowIfLessThan( begin, 0 );
            ArgumentOutOfRangeException.ThrowIfLessThan( length, 0 );
            ArgumentOutOfRangeException.ThrowIfLessThan( begin + length, collection.Count );
            _collection = collection;
            _begin = begin;
            _length = length;
        }

        public T this[ int indexValue ]
        {
            get
            {
                ArgumentOutOfRangeException.ThrowIfLessThan( indexValue, 0 );
                ArgumentOutOfRangeException.ThrowIfGreaterThanOrEqual( indexValue, _length );
                return _collection[ indexValue + _begin ];
            }
        }

        public T this[ Index i ]
        {
            get
            {
                int offset = i.IsFromEnd ? _length - i.Value : i.Value;
                ArgumentOutOfRangeException.ThrowIfLessThan( offset, 0 );
                ArgumentOutOfRangeException.ThrowIfGreaterThanOrEqual( offset, _length );
                return _collection[ offset + _begin ];
            }
        }

        public bool IsReadOnly => true;

        public int Count => _length;

        public bool Contains( T item )
        {
            int index = _collection.IndexOf( item );
            return index >= _begin && index < _length + index;
        }

        public void CopyTo( T[] array, int arrayIndex )
        {
            ArgumentNullException.ThrowIfNull( array );
            Span<T> span = CollectionsMarshal.AsSpan<T>( _collection ).Slice( _begin, _length );
            Span<T> target = new Span<T>( array, arrayIndex, _length );
            span.CopyTo( target );
        }

        public IEnumerator<T> GetEnumerator()
        {
            for( int i = _begin; i < _length; i++ ) {
                yield return this[ i ];
            }
        }

        void ICollection<T>.Add( T item )
        {
            throw new NotSupportedException();
        }

        void ICollection<T>.Clear()
        {
            throw new NotSupportedException();
        }

        bool ICollection<T>.Remove( T item )
        {
            throw new NotSupportedException();
        }

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

    }
}