using System;
using NHibernate;
using NHibernate.Type;

class UtcDateTimeInterceptor : IInterceptor
{
    public bool OnLoad(object entity, object id, object[] state, string[] propertyNames, IType[] types)
    {
        ConvertDatabaseDateTimeToUtc(state, types);
        return true;
    }

    public bool OnSave(object entity, object id, object[] state, string[] propertyNames, IType[] types)
    {
        ConvertLocalDateToUtc(state, types);
        return true;
    }

    public bool OnFlushDirty(object entity, object id, object[] currentState, object[] previousState, string[] propertyNames,
        IType[] types)
    {
        ConvertLocalDateToUtc(currentState, types);
        return true;
    }

    private void ConvertLocalDateToUtc(object[] state, IType[] types)
    {
        int index = 0;
        foreach (IType type in types)
        {
            if ((type.ReturnedClass == typeof(DateTime)) && state[index] != null && (((DateTime)state[index]).Kind == DateTimeKind.Local))
            {
                state[index] = ((DateTime)state[index]).ToUniversalTime();
            }

            ++index;
        }
    }

    private void ConvertDatabaseDateTimeToUtc(object[] state, IType[] types)
    {
        int index = 0;
        foreach (IType type in types)
        {
            if ((type.ReturnedClass == typeof(DateTime)) && state[index] != null && (((DateTime)state[index]).Kind != DateTimeKind.Utc))
            {
                //Create a new date and assume the value stored in the database is Utc
                DateTime cur = (DateTime)state[index];
                DateTime result = DateTime.SpecifyKind(cur, DateTimeKind.Utc);
                state[index] = result;
            }

            ++index;
        }
    }

    public void OnDelete(object entity, object id, object[] state, string[] propertyNames, IType[] types)
    {
    }

    public int[] FindDirty(object entity, object id, object[] currentState, object[] previousState, string[] propertyNames, IType[] types)
    {
        return null;
    }

    public object Instantiate(Type type, object id)
    {
        return null;
    }

    public object IsUnsaved(object entity)
    {
        return null;
    }

    public void PreFlush(System.Collections.ICollection entities) { }
    public void PostFlush(System.Collections.ICollection entities) { }
}