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

//note, rewrite like ThreadSafeQueue

namespace Svelto.DataStructures
{
    /// <summary>
    ///   original code: http://devplanet.com/blogs/brianr/archive/2008/09/29/thread-safe-dictionary-update.aspx
    ///   simplified (not an IDictionary) and apdated (uses FasterList)
    /// </summary>
    /// <typeparam name = "TKey"></typeparam>
    /// <typeparam name = "TValue"></typeparam>
    [Serializable]
    public class ThreadSafeDictionary<TKey, TValue>
    {
        public ThreadSafeDictionary(int v)
        {
            dict = new Dictionary<TKey, TValue>(v);
        }

        public ThreadSafeDictionary()
        {
            dict = new Dictionary<TKey, TValue>();
        }

        // setup the lock;
        public virtual int Count
        {
            get
            {
                using (new ReadOnlyLock(dictionaryLock))
                {
                    return dict.Count;
                }
            }
        }

        public virtual bool IsReadOnly
        {
            get
            {
                using (new ReadOnlyLock(dictionaryLock))
                {
                    return dict.IsReadOnly;
                }
            }
        }

        public virtual FasterList<TKey> Keys
        {
            get
            {
                using (new ReadOnlyLock(dictionaryLock))
                {
                    return new FasterList<TKey>(dict.Keys);
                }
            }
        }

        public virtual FasterList<TValue> Values
        {
            get
            {
                using (new ReadOnlyLock(dictionaryLock))
                {
                    return new FasterList<TValue>(dict.Values);
                }
            }
        }

        public virtual TValue this[TKey key]
        {
            get
            {
                using (new ReadOnlyLock(dictionaryLock))
                {
                    return dict[key];
                }
            }

            set
            {
                using (new WriteLock(dictionaryLock))
                {
                    dict[key] = value;
                }
            }
        }

        public virtual void Add(KeyValuePair<TKey, TValue> item)
        {
            using (new WriteLock(dictionaryLock))
            {
                dict.Add(item);
            }
        }

        public virtual void Clear()
        {
            using (new WriteLock(dictionaryLock))
            {
                dict.Clear();
            }
        }

        public virtual bool Contains(KeyValuePair<TKey, TValue> item)
        {
            using (new ReadOnlyLock(dictionaryLock))
            {
                return dict.Contains(item);
            }
        }

        public virtual void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
        {
            using (new ReadOnlyLock(dictionaryLock))
            {
                dict.CopyTo(array, arrayIndex);
            }
        }

        public virtual bool Remove(KeyValuePair<TKey, TValue> item)
        {
            using (new WriteLock(dictionaryLock))
            {
                return dict.Remove(item);
            }
        }

        public virtual void Add(TKey key, TValue value)
        {
            using (new WriteLock(dictionaryLock))
            {
                dict.Add(key, value);
            }
        }

        public virtual bool ContainsKey(TKey key)
        {
            using (new ReadOnlyLock(dictionaryLock))
            {
                return dict.ContainsKey(key);
            }
        }

        public virtual bool Remove(TKey key)
        {
            using (new WriteLock(dictionaryLock))
            {
                return dict.Remove(key);
            }
        }

        public virtual bool TryGetValue(TKey key, out TValue value)
        {
            using (new ReadOnlyLock(dictionaryLock))
            {
                return dict.TryGetValue(key, out value);
            }
        }

        /// <summary>
        ///   Merge does a blind remove, and then add.  Basically a blind Upsert.
        /// </summary>
        /// <param name = "key">Key to lookup</param>
        /// <param name = "newValue">New Value</param>
        public void MergeSafe(TKey key, TValue newValue)
        {
            using (new WriteLock(dictionaryLock))
            {
                // take a writelock immediately since we will always be writing
                if (dict.ContainsKey(key))
                    dict.Remove(key);

                dict.Add(key, newValue);
            }
        }

        /// <summary>
        ///   This is a blind remove. Prevents the need to check for existence first.
        /// </summary>
        /// <param name = "key">Key to remove</param>
        public void RemoveSafe(TKey key)
        {
            using (new ReadLock(dictionaryLock))
            {
                if (dict.ContainsKey(key))
                    using (new WriteLock(dictionaryLock))
                    {
                        dict.Remove(key);
                    }
            }
        }

        // This is the internal dictionary that we are wrapping
        readonly IDictionary<TKey, TValue> dict;

        [NonSerialized] readonly ReaderWriterLockSlim dictionaryLock = Locks.GetLockInstance(LockRecursionPolicy.NoRecursion);
    }

    public static class Locks
    {
        public static ReaderWriterLockSlim GetLockInstance()
        {
            return GetLockInstance(LockRecursionPolicy.SupportsRecursion);
        }

        public static ReaderWriterLockSlim GetLockInstance(LockRecursionPolicy recursionPolicy)
        {
            return new ReaderWriterLockSlim(recursionPolicy);
        }

        public static void GetReadLock(ReaderWriterLockSlim locks)
        {
            var lockAcquired = false;
            while (!lockAcquired)
                lockAcquired = locks.TryEnterUpgradeableReadLock(1);
        }

        public static void GetReadOnlyLock(ReaderWriterLockSlim locks)
        {
            var lockAcquired = false;
            while (!lockAcquired)
                lockAcquired = locks.TryEnterReadLock(1);
        }

        public static void GetWriteLock(ReaderWriterLockSlim locks)
        {
            var lockAcquired = false;
            while (!lockAcquired)
                lockAcquired = locks.TryEnterWriteLock(1);
        }

        public static void ReleaseLock(ReaderWriterLockSlim locks)
        {
            ReleaseWriteLock(locks);
            ReleaseReadLock(locks);
            ReleaseReadOnlyLock(locks);
        }

        public static void ReleaseReadLock(ReaderWriterLockSlim locks)
        {
            if (locks.IsUpgradeableReadLockHeld)
                locks.ExitUpgradeableReadLock();
        }

        public static void ReleaseReadOnlyLock(ReaderWriterLockSlim locks)
        {
            if (locks.IsReadLockHeld)
                locks.ExitReadLock();
        }

        public static void ReleaseWriteLock(ReaderWriterLockSlim locks)
        {
            if (locks.IsWriteLockHeld)
                locks.ExitWriteLock();
        }
    }

    public abstract class BaseLock : IDisposable
    {
        protected ReaderWriterLockSlim _Locks;

        public BaseLock(ReaderWriterLockSlim locks)
        {
            _Locks = locks;
        }

        public abstract void Dispose();
    }

    public class ReadLock : BaseLock
    {
        public ReadLock(ReaderWriterLockSlim locks)
            : base(locks)
        {
            Locks.GetReadLock(_Locks);
        }

        public override void Dispose()
        {
            Locks.ReleaseReadLock(_Locks);
        }
    }

    public class ReadOnlyLock : BaseLock
    {
        public ReadOnlyLock(ReaderWriterLockSlim locks)
            : base(locks)
        {
            Locks.GetReadOnlyLock(_Locks);
        }

        public override void Dispose()
        {
            Locks.ReleaseReadOnlyLock(_Locks);
        }
    }

    public class WriteLock : BaseLock
    {
        public WriteLock(ReaderWriterLockSlim locks)
            : base(locks)
        {
            Locks.GetWriteLock(_Locks);
        }

        public override void Dispose()
        {
            Locks.ReleaseWriteLock(_Locks);
        }
    }
}