using System;
using ln.types.collections;
namespace ln.types.odb.ng
{
    public class IdentityCache
    {
        WeakKeyReferenceDictionary<object, Guid> reverseCache = new WeakKeyReferenceDictionary<object, Guid>();
        WeakValueDictionary<Guid, object> forwardCache = new WeakValueDictionary<Guid, object>();

        public IdentityCache()
        {
        }

        public bool TryGetValue(Guid identity,out object o)
        {
            lock (this)
            {
                return forwardCache.TryGetValue(identity, out o);
            }
        }

        public bool TryGetValue(Guid identity, out object o, Func<object> instantiator)
        {
            lock (this)
            {
                if (!TryGetValue(identity, out o))
                {
                    o = instantiator();
                    forwardCache.Add(identity, o);
                    reverseCache.Add(o, identity);
                }
                return false;
            }
        }

        public bool TryGetIdentity(object o,out Guid identity)
        {
            lock (this)
            {
                return reverseCache.TryGetValue(o, out identity);
            }
        }

        public void Ensure(Guid identity,object o)
        {
            lock (this)
            {
                if (!forwardCache.ContainsKey(identity))
                    forwardCache.Add(identity, o);
                if (!reverseCache.ContainsKey(o))
                    reverseCache.Add(o, identity);
            }
        }

    }
}