#region
/* -----------------------------------------------------------------------
 * <copyright file="PithosDateTimeConverter.cs" company="GRNet">
 * 
 * Copyright 2011-2012 GRNET S.A. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 *   1. Redistributions of source code must retain the above
 *      copyright notice, this list of conditions and the following
 *      disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above
 *      copyright notice, this list of conditions and the following
 *      disclaimer in the documentation and/or other materials
 *      provided with the distribution.
 *
 *
 * THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * The views and conclusions contained in the software and
 * documentation are those of the authors and should not be
 * interpreted as representing official policies, either expressed
 * or implied, of GRNET S.A.
 * </copyright>
 * -----------------------------------------------------------------------
 */
#endregion
using System;
using System.Globalization;
using Newtonsoft.Json;
using Newtonsoft.Json.Converters;
using Newtonsoft.Json.Utilities;

namespace Pithos.Interfaces
{
    /// <summary>
    /// Converts a <see cref="DateTime"/> to and from a JavaScript date constructor (e.g. new Date(52231943)).
    /// </summary>
    public class PithosDateTimeConverter : DateTimeConverterBase
    {
        private DateTime _epoch = new DateTime(1970, 1, 1,0,0,0,DateTimeKind.Utc);

        /// <summary>
        /// Writes the JSON representation of the object.
        /// </summary>
        /// <param name="writer">The <see cref="JsonWriter"/> to write to.</param>
        /// <param name="value">The value.</param>
        /// <param name="serializer">The calling serializer.</param>
        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            double seconds;

            if (value is DateTime)
            {
                var dateTime = (DateTime)value;
                var utcDateTime = dateTime.ToUniversalTime();
                seconds = (utcDateTime - _epoch).TotalSeconds; ;
            }
            else if (value is DateTimeOffset)
            {
                var dateTimeOffset = (DateTimeOffset)value;
                var utcDateTimeOffset = dateTimeOffset.ToUniversalTime();
                seconds= (utcDateTimeOffset.UtcDateTime - _epoch).TotalSeconds;
            }
            else
            {
                throw new Exception("Expected date object value.");
            }

            writer.WriteValue(seconds);
        }

        /// <summary>
        /// Reads the JSON representation of the object.
        /// </summary>
        /// <param name="reader">The <see cref="JsonReader"/> to read from.</param>
        /// <param name="objectType">Type of the object.</param>
        /// <param name="existingValue">The existing property value of the JSON that is being converted.</param>
        /// <param name="serializer">The calling serializer.</param>
        /// <returns>The object value.</returns>
        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            Type t = (IsNullableType(objectType))
                         ? Nullable.GetUnderlyingType(objectType)
                         : objectType;

            if (reader.TokenType == JsonToken.Null)
            {
                if (!IsNullableType(objectType))
                    throw new Exception(String.Format("Cannot convert null value to {0}.",objectType));

                return null;
            }

            var seconds = double.Parse((string)reader.Value,CultureInfo.InvariantCulture);

            DateTime d =  _epoch.AddSeconds(seconds);


            if (t == typeof(DateTimeOffset))
                return new DateTimeOffset(d);
            return d;
        }

        public static bool IsNullableType(Type t)
        {
            if (t== null)
                throw new ArgumentNullException("t");

            return (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Nullable<>));
        }
    }
}