using ln.type;
using System;
using System.Collections.Generic;
using System.IO;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Text;

/**
 * typeCode list
 * 
 * 0x0000   ODBNull
 * 0x0001   ODBStringValue
 * 0x0002   ODBList
 * 0x0003   ODBGuid
 * 0x0004   ODBBool
 * 0x0005   ODBObject
 * 
 * 0x0010   ODBInteger
 * 0x0011   ODBUInteger
 * 0x0012   ODBLong
 * 0x0013   ODBULong
 * 
 * 0x0018   ODBDouble
 * 
 * 0x0020   ODBTypedMapping
 * 
 * 0x0800   ODBByteBuffer
 * 
 * 0x1000   ODBDocument
 * 0x1001   Document    (ln.types.odb.ng)
 * 
 * 
 * 
 **/



namespace ln.objects.catalog
{
    public delegate ODBEntity ODBValueFactory(object value);
    public delegate ODBEntity ODBDeserialize(byte[] storageBytes, int offset, int length);

    /// <summary>
    /// ODBEntity. The base of all ODB types.
    /// </summary>
    /// <remarks>The data model used by ODB can be described as follows:
    /// 
    /// Each piece of information to be used with ODB may be called an entity.
    /// ODB provides support for several types of entities (e.g. numbers, strings, documents, lists,...)
    /// An entity has an identity and a state.
    /// Two entities of same type having the same identity are considered to be "equal".
    /// Two entities of same type having the same identity may represent different states of the same entity. (different "Versions", e.g. an old and up to date
    /// 
    /// <c>ODBEntity</c> instances
    /// - define identity through <c>Identity</c>
    /// - may be seen as a "container" holding a certain state
    /// 
    /// <c>ODBValue</c> instances
    /// extend <c>ODBEntity</c>
    /// - implement <c>Identity</c> to return itself
    /// - implement <c>CompareTo</c> as simple "substraction"
    ///
    /// other <c>ODBEntity</c> subtypes
    /// - implement a read-only <c>Identity</c> to return a <c>ODBvalue</c> instance
    /// - implement <c>CompareTo</c> type specific without defined semantic meaning
    /// 
    /// 
    /// </remarks>
    /// 
    public abstract class ODBEntity : IComparable<ODBEntity>
    {
        int storageTypeCode;

        /// <summary>
        /// Gets the identity of this Entity.
        /// </summary>
        /// <value>The identity.</value>
        public virtual ODBValue Identity { get; }

        /// <summary>
        /// Independently clone this instance.
        /// </summary>
        /// <remarks>
        /// For immutable values this returns the instance itself.
        /// Complex ODBEntities will return a copy of themself that is completly independend of the source.
        /// </remarks>
        /// <returns>The clone.</returns>
        public abstract ODBEntity Clone();

        /// <summary>
        /// Implements the internal comparison within the same subclass of ODBEntity.
        /// </summary>
        /// <returns>The compare.</returns>
        /// <param name="other">Other.</param>
        protected abstract int compare(ODBEntity other);




        protected ODBEntity(int storageTypeCode)
        {
            this.storageTypeCode = storageTypeCode;
        }


        public int CompareTo(ODBEntity other)
        {
            if (storageTypeCode != other.storageTypeCode)
                return storageTypeCode - other.storageTypeCode;
            return compare(other);
        }

        public abstract byte[] Serialize();
        public virtual void Serialize(BinaryWriter storage)
        {
            byte[] storageBytes = Serialize();

            storage.Write(storageTypeCode);
            storage.Write(storageBytes.Length);
            storage.Write(storageBytes, 0, storageBytes.Length);
        }

        public override int GetHashCode() => Identity.GetHashCode();
        public override bool Equals(object obj)
        {
            if (Equals(GetType(), obj.GetType()) && obj is ODBEntity)
                return Equals(Identity, (obj as ODBEntity).Identity);
            return false;
        }

        public static bool operator <(ODBEntity a, ODBEntity b) => a.CompareTo(b) < 0;
        public static bool operator >(ODBEntity a, ODBEntity b) => a.CompareTo(b) > 0;
        public static bool operator <=(ODBEntity a, ODBEntity b) => a.CompareTo(b) <= 0;
        public static bool operator >=(ODBEntity a, ODBEntity b) => a.CompareTo(b) >= 0;
        public static bool operator ==(ODBEntity a, ODBEntity b) => a is null ? b is null : a.CompareTo(b) == 0;
        public static bool operator !=(ODBEntity a, ODBEntity b) => a is null ? !(b is null) : a.CompareTo(b) != 0;

        //public static implicit operator ODBEntity(ValueType v)
        //{
        //    return Mapper.Default.MapValue(v);
        //}
        //public static implicit operator ODBEntity(String v)
        //{
        //    return Mapper.Default.MapValue(v);
        //}

        //public static ODBEntity FromNative(object v)
        //{
        //    return Mapper.Default.MapValue(v);
        //}

        static Dictionary<int, ODBDeserialize> valueDeserializers = new Dictionary<int, ODBDeserialize>();
        public static void RegisterDeserializer(int storageTypeCode, ODBDeserialize deserialize)
        {
            valueDeserializers.Add(storageTypeCode, deserialize);
        }

        public static ODBEntity Deserialize(byte[] buffer, ref int offset)
        {
            int storageTypeCode = BitConverter.ToInt32(buffer, offset);
            int storageLength = BitConverter.ToInt32(buffer, offset + 4);
            if (!valueDeserializers.ContainsKey(storageTypeCode))
                throw new KeyNotFoundException(string.Format("StorageTypeCode 0x{0:x8} at offset 0x{1:x8}", storageTypeCode, offset));

            ODBEntity value = valueDeserializers[storageTypeCode](buffer, offset + 8, storageLength);
            offset += 8 + storageLength;
            return value;
        }

        public static ODBEntity Deserialize(Stream stream)
        {
            int storageTypeCode = stream.ReadInteger();
            int storageLength = stream.ReadInteger();
            byte[] b = new byte[storageLength];
            stream.Read(b, 0, storageLength);

            if (valueDeserializers.ContainsKey(storageTypeCode))
                return valueDeserializers[storageTypeCode](b, 0, storageLength);
            else
                throw new FormatException("wrong storage type code");
        }

        public override string ToString()
        {
            return string.Format("[{0} Identity={1}]", GetType().Name, Identity);
        }

        public string TreeString => ToTreeString(0);
        public abstract string ToTreeString(int indent);

        static ODBEntity()
        {
            RuntimeHelpers.RunClassConstructor(typeof(ODBNull).TypeHandle);
            RuntimeHelpers.RunClassConstructor(typeof(ODBObject).TypeHandle);
            RuntimeHelpers.RunClassConstructor(typeof(ODBList).TypeHandle);
            RuntimeHelpers.RunClassConstructor(typeof(ODBStringValue).TypeHandle);
            RuntimeHelpers.RunClassConstructor(typeof(ODBInteger).TypeHandle);
            RuntimeHelpers.RunClassConstructor(typeof(ODBUInteger).TypeHandle);
            RuntimeHelpers.RunClassConstructor(typeof(ODBLong).TypeHandle);
            RuntimeHelpers.RunClassConstructor(typeof(ODBULong).TypeHandle);
            RuntimeHelpers.RunClassConstructor(typeof(ODBDouble).TypeHandle);
            RuntimeHelpers.RunClassConstructor(typeof(ODBGuid).TypeHandle);
            RuntimeHelpers.RunClassConstructor(typeof(ODBBool).TypeHandle);
            RuntimeHelpers.RunClassConstructor(typeof(ODBByteBuffer).TypeHandle);
        }
    }
}