using System;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using Umbraco.Core.Exceptions;

namespace Umbraco.Core.Serialization
{
    /// <summary>
    /// Provides a base class for custom <see cref="JsonConverter"/> implementations.
    /// </summary>
    /// <typeparam name="T">The type of the converted object.</typeparam>
    internal abstract class JsonReadConverter<T> : JsonConverter
    {
        /// <summary>
        /// Create an instance of objectType, based properties in the JSON object
        /// </summary>
        /// <param name="objectType">type of object expected</param>
        /// <param name="path">The path of the current json token.</param>
        /// <param name="jObject">contents of JSON object that will be deserialized</param>
        /// <returns></returns>
        protected abstract T Create(Type objectType, string path, JObject jObject);

        /// <inheritdoc />
        public override bool CanConvert(Type objectType)
        {
            return typeof (T).IsAssignableFrom(objectType);
        }

        /// <inheritdoc />
        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            // Load JObject from stream
            var jObject = JObject.Load(reader);

            // Create target object based on JObject
            var target = Create(objectType, reader.Path, jObject);

            Deserialize(jObject, target, serializer);

            return target;
        }

        protected virtual void Deserialize(JObject jobject, T target, JsonSerializer serializer)
        {
            // Populate the object properties
            serializer.Populate(jobject.CreateReader(), target);
        }

        /// <inheritdoc />
        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            throw new NotSupportedException("JsonReadConverter instances do not support writing.");
        }
    }
}