using System;

using Newtonsoft.Json;

namespace LightTimetable.Models
{
    public abstract class FactoryConverter<T, TInput> : JsonConverter
    {
        /// <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)
        {
            throw new NotSupportedException("FactoryConverter should only be used while deserializing.");
        }

        /// <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)
        {
            if (reader.TokenType == JsonToken.Null)
                return null;

            T value = CreateAndPopulate(objectType, serializer.Deserialize<TInput>(reader));

            if (value == null)
                throw new JsonSerializationException("No object created.");

            return value;
        }

        /// <summary>
        /// Creates an object which will then be populated by the serializer.
        /// </summary>
        /// <param name="objectType">Type of the object.</param>
        /// <returns></returns>
        public abstract T CreateAndPopulate(Type objectType, TInput jsonFields);

        /// <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)
        {
            return typeof(T).IsAssignableFrom(objectType);
        }

        /// <summary>
        /// Gets a value indicating whether this <see cref="JsonConverter"/> can write JSON.
        /// </summary>
        /// <value>
        ///     <c>true</c> if this <see cref="JsonConverter"/> can write JSON; otherwise, <c>false</c>.
        /// </value>
        public override bool CanWrite => false;
    }
}
