using ln.collections;
using System;
using System.Collections.Generic;
using System.Text;

namespace ln.objects.storage
{
    class BinaryObjectCache
    {
        BTree<Guid, BTree<int, BinaryObject>> firstLevel = new BTree<Guid, BTree<int, BinaryObject>>();


        public BinaryObjectCache() { }

        BTree<int,BinaryObject> GetSecondLevel(Guid uid)
        {
            if (!firstLevel.TryGet(uid,out BTree<int,BinaryObject> secondLevel))
            {
                secondLevel = new BTree<int, BinaryObject>();
                firstLevel.Add(uid, secondLevel);
            }
            return secondLevel;
        }
        bool TryGetSecondLevel(Guid uid, out BTree<int, BinaryObject> secondLevel) => firstLevel.TryGet(uid, out secondLevel) && !secondLevel.Empty;

        public void Add(BinaryObject binaryObject)
        {
            BTree<int, BinaryObject> secondLevel = GetSecondLevel(binaryObject.UID);
            secondLevel.Add(binaryObject.Version, binaryObject);
        }
        public void Remove(BinaryObject binaryObject)
        {
            BTree<int, BinaryObject> secondLevel = GetSecondLevel(binaryObject.UID);
            secondLevel.Remove(binaryObject.Version);
        }

        public bool Contains(Guid uid) => GetSecondLevel(uid).ContainsKey(uid);
        public IEnumerable<Guid> UIDs => firstLevel.Keys;

        public IEnumerable<BinaryObject> GetBinaryObjects(Guid uid) => GetSecondLevel(uid).Values;
        public BinaryObject GetLatestBinaryObject(Guid uid)
        {
            BTree<int, BinaryObject> secondLevel = GetSecondLevel(uid);
            return secondLevel.LastValue();
        }
        public BinaryObject GetBinaryObject(Guid uid, int version) => GetSecondLevel(uid)[version];

        public bool TryGetBinaryObjects(Guid uid,out IEnumerable<BinaryObject> binaryObjects)
        {
            if (!TryGetSecondLevel(uid,out BTree<int,BinaryObject> secondLevel))
            {
                binaryObjects = null;
                return false;
            }

            binaryObjects = secondLevel.Values;
            return true;
        }
        public bool TryGetBinaryObject(Guid uid, int version, out BinaryObject binaryObject)
        {
            if (TryGetSecondLevel(uid, out BTree<int, BinaryObject> secondLevel))
            {
                if (version == -1)
                {
                    if (secondLevel.TryGetLastValue(out binaryObject))
                        return true;
                }
                else
                {
                    if (secondLevel.TryGet(version, out binaryObject))
                        return true;
                }
            }
            binaryObject = null;
            return false;
        }

        public bool TryGetLatestBinaryObject(Guid uid, out BinaryObject binaryObject) => GetSecondLevel(uid).TryGetLastValue(out binaryObject);
        public bool TryGetFirstBinaryObject(Guid uid, out BinaryObject binaryObject) => GetSecondLevel(uid).TryGetFirstValue(out binaryObject);

    }
}