using System;
using System.Collections.Generic;
using ln.types.odb.values;
using System.Linq;
using ln.types.odb.ng.storage.bases;
using ln.types.threads;
using ln.types.odb.ng.diff;
using ln.types.collections;
namespace ln.types.odb.ng.storage.session
{
	public class SessionStorage : ChainedStorage
	{
		public SessionStorageContainer SessionContainer { get; }

        WeakKeyDictionary<Document, Document> cache = new WeakKeyDictionary<Document, Document>();

		public SessionStorage(SessionStorageContainer session, IStorage storage)
			:base(storage)
		{
			SessionContainer = session;
		}

		public override Document Load(Guid documentID)
		{
			lock (this)
			{
				if (!Storage.Contains(documentID))
					throw new KeyNotFoundException();

                Document keyDocument = new Document(documentID);

                if (cache.ContainsKey(keyDocument))
                    return cache.GetKeyInstance(keyDocument);

				Document document = Storage.Load(documentID);
                Document cacheDocument = document.Clone() as Document;

                cache.Add(document, cacheDocument);

                return document;
			}
		}

		public override void Save(Document document)
		{
			lock (this)
			{
                if (cache.ContainsKey(document))
                {
                    using (Storage.Lock())
                    {
                        Document cacheDocument = cache[document];
                        Document storageDocument = Storage.Load(document.ID);

                        DocumentDiff documentDiff = new DocumentDiff(cacheDocument, document);
                        documentDiff.Apply(storageDocument);

                        Storage.Save(storageDocument);
                        cache[document] = document.Clone() as Document;
                    }
                }
                else
                {
                    Storage.Save(document);
                    cache.Add(document, document.Clone() as Document);
                }
			}
		}

		public override void Delete(Guid documentID)
		{
			lock (this)
			{
                Document keyDocument = new Document(documentID);

                Storage.Delete(documentID);
                cache.Remove(keyDocument);
			}
		}

        public override bool IsCaching => true;

    }
}