///////////////////////////////////////////////////////////////////////////
//  Copyright (C) Wizardry and Steamworks 2017 - License: GNU GPLv3      //
//  Please see: http://www.gnu.org/licenses/gpl.html for legal details,  //
//  rights of fair usage, the disclaimer and warranty conditions.        //
///////////////////////////////////////////////////////////////////////////

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

namespace wasSharp.Collections.Specialized
{
    public static class ConcurrentListExtensions
    {
        public static ConcurrentList<T> ToConcurrentList<T>(this IEnumerable<T> enumerable)
        {
            return new ConcurrentList<T>(enumerable);
        }
    }

    public class ConcurrentList<T> : IList<T>
    {
        private readonly ReaderWriterLockSlim _lock = new ReaderWriterLockSlim(LockRecursionPolicy.SupportsRecursion);
        private readonly List<T> _list;

        public ConcurrentList(IEnumerable<T> v)
        {
            _lock.EnterWriteLock();
            try
            {
                _list = new List<T>();
                foreach (var i in v)
                {
                    _list.Add(i);
                }
            }
            finally
            {
                if (_lock.IsWriteLockHeld) _lock.ExitWriteLock();
            }
        }

        public ConcurrentList()
        {
            _lock.EnterWriteLock();
            try
            {
                _list = new List<T>();
            }
            finally
            {
                if (_lock.IsWriteLockHeld) _lock.ExitWriteLock();
            }
        }

        public bool IsReadOnly
        {
            get
            {
                _lock.EnterReadLock();
                try
                {
                    return ((IList<T>)_list).IsReadOnly;
                }
                finally
                {
                    if (_lock.IsReadLockHeld) _lock.ExitReadLock();
                }
            }
        }

        int ICollection<T>.Count
        {
            get
            {
                _lock.EnterReadLock();
                try
                {
                    return _list.Count;
                }
                finally
                {
                    if (_lock.IsReadLockHeld) _lock.ExitReadLock();
                }
            }
        }

        public T this[int index]
        {
            get
            {
                _lock.EnterReadLock();
                try
                {
                    return _list[index];
                }
                finally
                {
                    if (_lock.IsReadLockHeld) _lock.ExitReadLock();
                }
            }

            set
            {
                _lock.EnterWriteLock();
                try
                {
                    _list[index] = value;
                }
                finally
                {
                    if (_lock.IsWriteLockHeld) _lock.ExitWriteLock();
                }
            }
        }

        public int IndexOf(T item)
        {
            _lock.EnterReadLock();
            try
            {
                return _list.IndexOf(item);
            }
            finally
            {
                if (_lock.IsReadLockHeld) _lock.ExitReadLock();
            }
        }

        public void Insert(int index, T item)
        {
            _lock.EnterWriteLock();
            try
            {
                _list.Insert(index, item);
            }
            finally
            {
                if (_lock.IsWriteLockHeld) _lock.ExitWriteLock();
            }
        }

        public void RemoveAt(int index)
        {
            _lock.EnterWriteLock();
            try
            {
                _list.RemoveAt(index);
            }
            finally
            {
                if (_lock.IsWriteLockHeld) _lock.ExitWriteLock();
            }
        }

        public void Add(T item)
        {
            _lock.EnterWriteLock();
            try
            {
                _list.Add(item);
            }
            finally
            {
                if (_lock.IsWriteLockHeld) _lock.ExitWriteLock();
            }
        }

        public void Clear()
        {
            _lock.EnterWriteLock();
            try
            {
                _list.Clear();
            }
            finally
            {
                if (_lock.IsWriteLockHeld) _lock.ExitWriteLock();
            }
        }

        public bool Contains(T item)
        {
            _lock.EnterReadLock();
            try
            {
                return _list.Contains(item);
            }
            finally
            {
                if (_lock.IsReadLockHeld) _lock.ExitReadLock();
            }
        }

        public void CopyTo(T[] array, int arrayIndex)
        {
            _lock.EnterReadLock();
            try
            {
                _list.CopyTo(array, arrayIndex);
            }
            finally
            {
                if (_lock.IsReadLockHeld) _lock.ExitReadLock();
            }
        }

        public bool Remove(T item)
        {
            _lock.EnterWriteLock();
            try
            {
                return _list.Remove(item);
            }
            finally
            {
                if (_lock.IsWriteLockHeld) _lock.ExitWriteLock();
            }
        }

        public IEnumerator<T> GetEnumerator()
        {
            _lock.EnterReadLock();
            try
            {
                using (var enumerator = _list.GetEnumerator())
                {
                    while (enumerator.MoveNext())
                        yield return enumerator.Current;
                }
            }
            finally
            {
                if (_lock.IsReadLockHeld) _lock.ExitReadLock();
            }
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            _lock.EnterReadLock();
            try
            {
                using (var enumerator = _list.GetEnumerator())
                {
                    while (enumerator.MoveNext())
                        yield return enumerator.Current;
                }
            }
            finally
            {
                if (_lock.IsReadLockHeld) _lock.ExitReadLock();
            }
        }
    }
}