using System;
using System.Xml;

namespace oodb.mapping
{
    public abstract class FlatTypeMapping
    {
        public OODB OODB { get; }
        public Type NativeType { get; }

        public FlatTypeMapping(OODB oodb, Type nativeType)
        {
            OODB = oodb;
            NativeType = nativeType;
        }

        public XmlElement CreateEmptyValueElement(XmlDocument xmlDocument)
        {
            XmlElement value = xmlDocument.CreateElement("Value");
            value.SetAttribute("Type", NativeType.FullName);
            return value;
        }

        public abstract XmlElement ToXml(XmlDocument xmlDocument, object value);
        public abstract object FromXml(XmlElement xmlValue);

        public abstract String ToText(object value);
        public abstract object FromText(string text);
    }

    public abstract class NaiveMapping : FlatTypeMapping
    {
        public NaiveMapping(OODB oodb, Type nativeType)
            :base(oodb,nativeType)
        {
        }

        public override object FromXml(XmlElement xmlValue)
        {
            if (!NativeType.FullName.Equals(xmlValue.GetAttribute("Type")))
                throw new ArgumentException("Type != NativeType", nameof(xmlValue));

            return FromText(xmlValue.InnerText);
        }

        public override XmlElement ToXml(XmlDocument xmlDocument, object value)
        {
            XmlElement valueElement = CreateEmptyValueElement(xmlDocument);
            if (value != null)
                valueElement.InnerText = ToText(value);

            return valueElement;
        }
    }

}