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

namespace Uber.Collections
{
    /// <summary>
    /// Implements a thread-safe list with support for multiple readers and one writer
    /// </summary>
    /// <typeparam name="T">Values</typeparam>
    ///
    public class SafeList<T> : IList<T>
    {
        private readonly List<T> _inner;

        [NonSerialized]
        private readonly ReaderWriterLockSlim _lock = new ReaderWriterLockSlim(LockRecursionPolicy.SupportsRecursion);

        public SafeList()
        {
            _inner = new List<T>();
        }

        public int Count
        {
            get
            {
                _lock.EnterReadLock();
                try
                {
                    return _inner.Count;
                }
                finally { _lock.ExitReadLock(); }
            }
        }

        public bool IsReadOnly
        {
            get { return false; }
        }

        public T this[int index]
        {
            get
            {
                _lock.EnterReadLock();
                try
                {
                    return _inner[index];
                }
                finally { _lock.ExitReadLock(); }
            }
            set
            {
                _lock.EnterWriteLock();
                try
                {
                    _inner[index] = value;
                }
                finally { _lock.ExitWriteLock(); }
            }
        }

        IEnumerator<T> IEnumerable<T>.GetEnumerator()
        {
            _lock.EnterReadLock();
            try
            {
                return new SafeEnumerator<T>(_inner.GetEnumerator(), _lock);
            }
            finally { _lock.ExitReadLock(); }
        }

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

        public void Clear()
        {
            _lock.EnterWriteLock();
            try
            {
                _inner.Clear();
            }
            finally { _lock.ExitWriteLock(); }
        }

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

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

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

        public IEnumerator GetEnumerator()
        {
            _lock.EnterReadLock();
            try
            {
                return new SafeEnumerator<T>(_inner.GetEnumerator(), _lock);
            }
            finally { _lock.ExitReadLock(); }
        }

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

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

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

        public ReadOnlyCollection<T> AsReadOnly()
        {
            _lock.EnterReadLock();
            try
            {
                return new ReadOnlyCollection<T>(this);
            }
            finally { _lock.ExitReadLock(); }
        }

        public void ForEach(Action<T> action)
        {
            _lock.EnterReadLock();
            try
            {
                foreach (var item in _inner)
                {
                    action(item);
                }
            }
            finally { _lock.ExitReadLock(); }
        }

        public bool Exists(Predicate<T> match)
        {
            _lock.EnterReadLock();
            try
            {
                foreach (var item in _inner)
                {
                    if (match(item))
                    {
                        return true;
                    }
                }
            }
            finally { _lock.ExitReadLock(); }

            return false;
        }
    }
}