// /**
//  * File: ListMapping.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.Collections;
using System.Linq;
using System.Collections.Generic;
using System.Reflection;
using ln.objects.catalog;

namespace ln.types.odb.ng.mappings
{
    public class ListMapping : IODBMapping
    {
        public Type TargetType { get; }

        public ListMapping(Type targetType)
        {
            TargetType = targetType;
        }


        private Array UnmapArray(Mapper mapper, ODBList list)
        {
            Array array = Array.CreateInstance(TargetType.GetElementType(), list.Count);
            for (int n = 0; n < list.Count; n++)
                array.SetValue(mapper.UnmapValue(TargetType.GetElementType(), list[n]), n);
            return array;
        }
        private ODBList MapArray(Mapper mapper, Array array)
        {
            ODBList list = new ODBList();
            for (int n = 0; n < array.Length; n++)
            {
                list.Add(mapper.MapValue(array.GetValue(n)));
            }
            return list;
        }

        public object UnmapList(Mapper mapper, ODBList list)
        {
            IList ilist = (IList)Activator.CreateInstance(TargetType, true);
            for (int n = 0; n < list.Count; n++)
            {
                ilist.Add(mapper.UnmapValue(TargetType.GetGenericArguments()[0], list[n]));
            }
            return ilist;
        }
        public ODBList MapList(Mapper mapper, object value)
        {
            ODBList list = new ODBList();
            IList ilist = (IList)value;
            for (int n = 0; n < ilist.Count; n++)
                list.Add(mapper.MapValue(ilist[n]));
            return list;
        }

        public object UnmapSet(Mapper mapper, ODBList list)
        {
            Type entype = typeof(UnmappingEnumeration<>).MakeGenericType(TargetType.GetGenericArguments());
            object en = Activator.CreateInstance(entype, mapper, list);

            return Activator.CreateInstance(TargetType, en );
        }
        public ODBList MapSet(Mapper mapper, object value)
        {
            ODBList list = new ODBList();
            IEnumerable ienum  = (IEnumerable)value;
            foreach (object item in ienum)
                list.Add(mapper.MapValue(item));
            return list;
        }

        public object UnmapValue(Mapper mapper, ODBEntity oval)
        {
            if (TargetType.IsArray)
                return UnmapArray(mapper, (ODBList)oval);

            if (TargetType.IsGenericType)
            {
                if (typeof(List<>).Equals(TargetType.GetGenericTypeDefinition()))
                {
                    return UnmapList(mapper, (ODBList)oval);
                }
                else if (typeof(HashSet<>).Equals(TargetType.GetGenericTypeDefinition()))
                {
                    return UnmapSet(mapper, (ODBList)oval);
                }
            }

            throw new NotImplementedException();
        }

        public ODBEntity MapValue(Mapper mapper, object value)
        {
            if (TargetType.IsArray)
                return MapArray(mapper, (Array)value);

            if (TargetType.IsGenericType)
            {
                if (typeof(List<>).Equals(TargetType.GetGenericTypeDefinition()))
                {
                    return MapList(mapper, value);
                }
                else if (typeof(HashSet<>).Equals(TargetType.GetGenericTypeDefinition()))
                {
                    return MapSet(mapper, value);
                }
            }
            throw new NotImplementedException();
        }

        class UnmappingEnumeration<T> : IEnumerable<T>
        {
            Type TargetType;
            Mapper mapper;
            ODBList list;

            public UnmappingEnumeration(Mapper mapper,ODBList list)
            {
                TargetType = typeof(T);
                this.mapper = mapper;
                this.list = list;
            }

            public IEnumerator<T> GetEnumerator()
            {
                foreach (ODBEntity item in list)
                    yield return (T)mapper.UnmapValue(TargetType, item);
            }

            IEnumerator IEnumerable.GetEnumerator()
            {
                return GetEnumerator();
            }
        }


    }
}