using System;
using ln.objects.catalog;
namespace ln.types.odb.ng.diff
{
    public abstract class Diff
    {

        public abstract ODBEntity Apply(ODBEntity src);

        public static Diff Construct(ODBEntity src,ODBEntity dst)
        {
            if (!src.GetType().Equals(dst.GetType()))
            {
                return new SimpleDiff(dst);
            }
            else if (src is Document)
            {
                return new DocumentDiff(src as Document, dst as Document);
            } else if (src is ODBList)
            {
                return new ListDiff(src as ODBList, dst as ODBList);
            }

            return new SimpleDiff(dst);
        }

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


        class SimpleDiff : Diff
        {
            public ODBEntity DestinationValue { get; }

            public SimpleDiff(ODBEntity dst)
            {
                DestinationValue = dst;
            }

            public override ODBEntity Apply(ODBEntity src)
            {
                return DestinationValue;
            }

            public override string ToString()
            {
                return String.Format("[SimpleDiff DestinationValue={0}]",DestinationValue);
            }

            public override string ToTreeString(int indent)
            {
                return String.Format("= {0}", DestinationValue.ToTreeString(indent+2));
            }
        }

    }
}