// This file is part of YamlDotNet - A .NET library for YAML.
// Copyright (c) Antoine Aubry
// 
// 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.

using System;
using YamlDotNet.Core;
using YamlDotNet.Core.Events;

namespace YamlDotNet.Serialization.NodeDeserializers
{
    public sealed class NullNodeDeserializer : INodeDeserializer
    {
        bool INodeDeserializer.Deserialize(IParser parser, Type expectedType, Func<IParser, Type, object> nestedObjectDeserializer, out object value)
        {
            value = null;
            var evt = parser.Peek<NodeEvent>();
            var isNull = evt != null
                && NodeIsNull(evt);

            if (isNull)
            {
                parser.SkipThisAndNestedEvents();
            }
            return isNull;
        }

        private bool NodeIsNull(NodeEvent nodeEvent)
        {
            // http://yaml.org/type/null.html

            if (nodeEvent.Tag == "tag:yaml.org,2002:null")
            {
                return true;
            }

            var scalar = nodeEvent as Scalar;
            if (scalar == null || scalar.Style != Core.ScalarStyle.Plain)
                return false;

            var value = scalar.Value;
            return value == "" || value == "~" || value == "null" || value == "Null" || value == "NULL";
        }
    }
}
