﻿#region License
// Copyright (c) 2007 James Newton-King
//
// 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.
#endregion

using System;
using System.Collections.Generic;
using System.Reflection;
using GodLesZ.Library.Json.Serialization;
using GodLesZ.Library.Json.Utilities;

namespace GodLesZ.Library.Json.Converters
{
  /// <summary>
  /// Converts a <see cref="KeyValuePair{TKey,TValue}"/> to and from JSON.
  /// </summary>
  public class KeyValuePairConverter : JsonConverter
  {
    private const string KeyName = "Key";
    private const string ValueName = "Value";

    /// <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)
    {
      Type t = value.GetType();
      PropertyInfo keyProperty = t.GetProperty(KeyName);
      PropertyInfo valueProperty = t.GetProperty(ValueName);

      DefaultContractResolver resolver = serializer.ContractResolver as DefaultContractResolver;

      writer.WriteStartObject();

      writer.WritePropertyName((resolver != null) ? resolver.GetResolvedPropertyName(KeyName) : KeyName);
      serializer.Serialize(writer, ReflectionUtils.GetMemberValue(keyProperty, value));
      writer.WritePropertyName((resolver != null) ? resolver.GetResolvedPropertyName(ValueName) : ValueName);
      serializer.Serialize(writer, ReflectionUtils.GetMemberValue(valueProperty, value));
      writer.WriteEndObject();
    }

    /// <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 value of object being read.</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)
    {
      bool isNullable = ReflectionUtils.IsNullableType(objectType);

      if (reader.TokenType == JsonToken.Null)
      {
        if (!isNullable)
          throw JsonSerializationException.Create(reader, "Cannot convert null value to KeyValuePair.");

        return null;
      }

      Type t = (isNullable)
       ? Nullable.GetUnderlyingType(objectType)
       : objectType;

      IList<Type> genericArguments = t.GetGenericArguments();
      Type keyType = genericArguments[0];
      Type valueType = genericArguments[1];

      object key = null;
      object value = null;

      reader.Read();

      while (reader.TokenType == JsonToken.PropertyName)
      {
        string propertyName = reader.Value.ToString();
        if (string.Equals(propertyName, KeyName, StringComparison.OrdinalIgnoreCase))
        {
          reader.Read();
          key = serializer.Deserialize(reader, keyType);
        }
        else if (string.Equals(propertyName, ValueName, StringComparison.OrdinalIgnoreCase))
        {
          reader.Read();
          value = serializer.Deserialize(reader, valueType);
        }
        else
        {
          reader.Skip();
        }

        reader.Read();
      }

      return Activator.CreateInstance(t, key, value);
    }

    /// <summary>
    /// Determines whether this instance can convert the specified object type.
    /// </summary>
    /// <param name="objectType">Type of the object.</param>
    /// <returns>
    /// 	<c>true</c> if this instance can convert the specified object type; otherwise, <c>false</c>.
    /// </returns>
    public override bool CanConvert(Type objectType)
    {
      Type t = (ReflectionUtils.IsNullableType(objectType))
        ? Nullable.GetUnderlyingType(objectType)
        : objectType;

      if (t.IsValueType() && t.IsGenericType())
        return (t.GetGenericTypeDefinition() == typeof(KeyValuePair<,>));

      return false;
    }
  }
}