// /**
//  * File: ODB.cs
//  * Author: haraldwolff
//  *
//  * This file and it's content is copyrighted by the Author and / or copyright holder.
//  * Any use wihtout proper permission is illegal and may lead to legal actions.
//  *
//  *
//  **/
using System;
using System.IO;
using System.Collections.Generic;
using Castle.DynamicProxy;
using ln.types.serialize;
using Castle.Components.DictionaryAdapter;
using System.Linq;
namespace ln.types.odb
{
    public class ODB<T> : ODB
    {
        public T Root
        {
            get => (T)RootObject;
        }

        public ODB(String basePath)
            :base(basePath, typeof(T))
        {
        }
    }

    public partial class ODB
    {
        public object RootObject { get; protected set; }

        public String BasePath { get; set; }

        private ProxyGenerator proxyGenerator = new ProxyGenerator();
        private Dictionary<Guid, WeakReference<IPersistent>> persistentObjects = new Dictionary<Guid, WeakReference<IPersistent>>();
        private Dictionary<Guid, IPersistent> persistentProxies = new Dictionary<Guid, IPersistent>();

        private Type RootType;

        public ODB(string basePath)
        {
            BasePath = Path.GetFullPath(basePath);
            if (!Directory.Exists(BasePath))
            {
                Directory.CreateDirectory(BasePath);
            }
        }

        public ODB(String basePath, Type rootType)
            : this(basePath)
        {
            RootType = rootType;

            Initialize();
        }
        public ODB(String basePath,object rootObject)
            : this(basePath)
        {
            RootType = rootObject.GetType();
            RootObject = rootObject;

            Initialize();
        }

        private void Initialize()
        {
            if (RootObject == null)
            {
                string rootHint = Path.Combine(BasePath, "root.hint");
                if (File.Exists(rootHint))
                {
                    using (ObjectReader objectReader = new ObjectReader(rootHint))
                    {
                        Guid persistenceID = objectReader.Read<Guid>();
                        RootObject = GetPersistent(persistenceID);
                    }
                }
                else
                {
                    RootObject = Activator.CreateInstance(RootType);
                }
            }
        }

        public bool Contains(Guid persistenceID)
        {
            string fn = Path.Combine(GetPersistentPath(persistenceID), String.Format("{0}.0",persistenceID));
            return File.Exists(fn);
        }

        IPersistent LoadPersistent(Guid guid)
        {
            IPersistent o = GetCachedPersistent(guid);
            if (o == null)
            {


                throw new NotImplementedException();
            }
            return o;
        }

        public void SavePersistent(IPersistent o) => SavePersistent(o, true);
        public void SavePersistent(IPersistent o,bool recurse)
        {
            SaveCollector saveCollector = new SaveCollector(this);
            saveCollector.AddPersistent(o, recurse);

            foreach (Guid persistenceID in saveCollector.GetCollectedPersistenceIDs())
            {
                SaveBytes(persistenceID, saveCollector.GetPersistentBytes(persistenceID));
            }
        }


        /* File I/O */
        private string GetPersistentPath(Guid persistenceID)
        {
            byte[] idBytes = persistenceID.ToByteArray();
            return Path.Combine(BasePath, BitConverter.ToString(idBytes, 0, 4));
        }

        private void SaveBytes(Guid persistenceID,byte[] bytes)
        {
            String p = GetPersistentPath(persistenceID);
            String fnbase = Path.Combine(p, persistenceID.ToString());

            if (!Directory.Exists(p))
                Directory.CreateDirectory(p);

            String fnn = String.Format("{0}.new", fnbase);

            using (FileStream fs = new FileStream(fnn, FileMode.CreateNew))
            {
                fs.Write(bytes,0,bytes.Length);
                fs.Close();
            }

            for (int n=5;n>0;n--)
            {
                string fn1 = String.Format("{0}.{1}",fnbase,n-1);
                string fn2 = String.Format("{0}.{1}", fnbase, n);

                if (File.Exists(fn1))
                    File.Move(fn1, fn2);
            }

            string fn = String.Format("{0}.{1}", fnbase, 0);
            File.Move(fnn, fn);
        }







        private IPersistent GetCachedPersistent(Guid persistenceID)
        {
            lock (this)
            {
                if (persistentObjects.ContainsKey(persistenceID))
                {
                    WeakReference<IPersistent> weak = persistentObjects[persistenceID];
                    IPersistent persistent = null;

                    if (weak.TryGetTarget(out persistent))
                    {
                        return persistent;
                    }
                    else
                    {
                        persistentObjects.Remove(persistenceID);
                    }
                }
            }
            return null;
        }


        /**
         * GetPersistent(..): Return Instance of an IPersistent (may be a proxy)
         * 
         **/        
        public IPersistent GetPersistent(Guid persistenceID)
        {
            if (Guid.Empty.Equals(persistenceID))
                return null;

            if (persistentObjects.ContainsKey(persistenceID))
            {
                IPersistent o = GetCachedPersistent(persistenceID);
                if (o == null)
                {
                    o = LoadPersistent(persistenceID);
                }
                return o;
            }
            return null;
        }

        class SaveCollector
        {
            public ODB ODB { get; }

            public Guid[] GetCollectedPersistenceIDs()
            {
                return persistentBytes.Keys.ToArray();
            }

            public byte[] GetPersistentBytes(Guid persistenceID)
            {
                return persistentBytes[persistenceID];
            }

            private Dictionary<Guid, byte[]> persistentBytes = new Dictionary<Guid, byte[]>();

            public SaveCollector(ODB odb)
            {
                ODB = odb;
            }

            public void AddPersistent(IPersistent persistent,bool recurse)
            {
                MemoryStream objectStream = new MemoryStream();
                ODBObjectWriter objectWriter = new ODBObjectWriter(ODB, objectStream);
                objectWriter.Write(persistent);

                persistentBytes.Add(persistent.GetPersistenceID(), objectStream.ToArray());

                if (recurse)
                {
                    foreach (IPersistent referencedPersistent in objectWriter.ReferencedPersistents)
                    {
                        AddPersistent(referencedPersistent,recurse);
                    }
                }
                else
                {
                    foreach (IPersistent referencedPersistent in objectWriter.ReferencedPersistents)
                    {
                        if (!ODB.Contains(referencedPersistent.GetPersistenceID()))
                        {
                            AddPersistent(referencedPersistent, recurse);
                        }
                    }
                }

            }
        }



        class LazyInterceptor : IInterceptor
        {
            ODB odb;
            WeakReference<IPersistent> target = null;

            public LazyInterceptor(ODB odb, Guid persistentID)
            {
                this.odb = odb;
            }

            public void Intercept(IInvocation invocation)
            {
                object t = target;
                throw new NotImplementedException();
            }
        }


    }
}