// SNMP NULL type.
// Copyright (C) 2008-2010 Malcolm Crowe, Lex Li, and other contributors.
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

/*
 * Created by SharpDevelop.
 * User: lextm
 * Date: 2008/4/30
 * Time: 20:07
 * 
 * To change this template use Tools | Options | Coding | Edit Standard Headers.
 */

using System;
using System.IO;

namespace GSF.Net.Snmp
{
    /// <summary>
    /// Null type.
    /// </summary>
    public sealed class Null : ISnmpData, IEquatable<Null>
    {
        private readonly byte[] _length;

        /// <summary>
        /// Initializes a new instance of the <see cref="Null"/> class.
        /// </summary>
        /// <param name="length">The length data.</param>
        /// <param name="stream">The stream.</param>
        public Null(Tuple<int, byte[]> length, Stream stream)
        {
            if (length == null)
            {
                throw new ArgumentNullException(nameof(length));
            }

            if (stream == null)
            {
                throw new ArgumentNullException(nameof(stream));
            }

            stream.IgnoreBytes(length.Item1);
            _length = length.Item2;
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="Null"/> class.
        /// </summary>
        public Null()
        {
        }

        /// <summary>
        /// Type code.
        /// </summary>
        public SnmpType TypeCode
        {
            get
            {
                return SnmpType.Null;
            }
        }

        /// <summary>
        /// Appends the bytes to <see cref="Stream"/>.
        /// </summary>
        /// <param name="stream">The stream.</param>
        public void AppendBytesTo(Stream stream)
        {
            if (stream == null)
            {
                throw new ArgumentNullException(nameof(stream));
            }
            
            stream.AppendBytes(TypeCode, _length, new byte[0]);
        }
        
        /// <summary>
        /// Determines whether the specified <see cref="Object"/> is equal to the current <see cref="Null"/>.
        /// </summary>
        /// <param name="obj">The <see cref="Object"/> to compare with the current <see cref="Null"/>. </param>
        /// <returns><value>true</value> if the specified <see cref="Object"/> is equal to the current <see cref="Null"/>; otherwise, <value>false</value>.
        /// </returns>
        public override bool Equals(object obj)
        {
            return Equals(this, obj as Null);
        }
        
        /// <summary>
        /// Serves as a hash function for a particular type.
        /// </summary>
        /// <returns>A hash code for the current <see cref="Null"/>.</returns>
        public override int GetHashCode()
        {
            return 0;
        }
        
        /// <summary>
        /// Indicates whether the current object is equal to another object of the same type.
        /// </summary>
        /// <param name="other">An object to compare with this object.</param>
        /// <returns><value>true</value> if the current object is equal to the <paramref name="other"/> parameter; otherwise, <value>false</value>.
        /// </returns>
        public bool Equals(Null other)
        {
            return Equals(this, other);
        }
        
        /// <summary>
        /// The equality operator.
        /// </summary>
        /// <param name="left">Left <see cref="Null"/> object</param>
        /// <param name="right">Right <see cref="Null"/> object</param>
        /// <returns>
        /// Returns <c>true</c> if the values of its operands are equal, <c>false</c> otherwise.</returns>
        public static bool operator ==(Null left, Null right)
        {
            return Equals(left, right);
        }
        
        /// <summary>
        /// The inequality operator.
        /// </summary>
        /// <param name="left">Left <see cref="Null"/> object</param>
        /// <param name="right">Right <see cref="Null"/> object</param>
        /// <returns>
        /// Returns <c>true</c> if the values of its operands are not equal, <c>false</c> otherwise.</returns>
        public static bool operator !=(Null left, Null right)
        {
            return !(left == right);
        }
        
        /// <summary>
        /// Returns a <see cref="String"/> that represents this <see cref="Null"/>.
        /// </summary>
        /// <returns></returns>
        public override string ToString()
        {
            return "Null";
        }
        
        /// <summary>
        /// The comparison.
        /// </summary>
        /// <param name="left">Left <see cref="Null"/> object</param>
        /// <param name="right">Right <see cref="Null"/> object</param>
        /// <returns>
        /// Returns <c>true</c> if the values of its operands are not equal, <c>false</c> otherwise.</returns>
        private static bool Equals(Null left, Null right)
        {
            object lo = left;
            object ro = right;
            if (lo == ro)
            {
                return true;
            }

            return lo != null && ro != null;
        }
    }
}