/*
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 * 
 *  http://aws.amazon.com/apache2.0
 * 
 * or in the "license" file accompanying this file. This file is distributed
 * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

using System;
using System.Collections.Generic;
using System.Linq;

using Amazon.DynamoDBv2.Model;
using System.IO;
using Amazon.Runtime.Internal.Util;
using Amazon.Util;

namespace Amazon.DynamoDBv2.DocumentModel
{
    /// <summary>
    /// A DynamoDBEntry that represents a DynamoDB null (NULL) type.
    /// </summary>
    public class DynamoDBNull : DynamoDBEntry
    {
        /// <summary>
        /// Default Constructor.
        /// </summary>
        public DynamoDBNull() { }

        /// <summary>
        /// Constant DynamoDBNull for the Null value.
        /// </summary>
        public static readonly DynamoDBNull Null = new DynamoDBNull();

        #region Overrides

        internal override AttributeValue ConvertToAttributeValue(AttributeConversionConfig conversionConfig)
        {
            return new AttributeValue
            {
                NULL = true
            };
        }

        /// <summary>
        /// Implement the Clone method.
        /// </summary>
        /// <returns></returns>
        public override object Clone()
        {
            return new DynamoDBNull();
        }

        /// <summary>
        /// Implement the Equals method.
        /// </summary>
        /// <param name="obj"></param>
        /// <returns></returns>
        public override bool Equals(object obj)
        {
            var otherNull = obj as DynamoDBNull;
            if (otherNull == null)
                return false;

            return true;
        }

        /// <summary>
        /// Implement the GetHashCode method.
        /// </summary>
        /// <returns></returns>
        public override int GetHashCode()
        {
            return 0;
        }
        
        #endregion
    }
}