using System;
using System.Text.Json.Serialization;
using System.Text.Json;
using System.Text.RegularExpressions;

namespace Terminal.Gui {
	/// <summary>
	/// Json converter for the <see cref="Color"/> class.
	/// </summary>
	internal class ColorJsonConverter : JsonConverter<Color> {
		private static ColorJsonConverter _instance;

		/// <summary>
		/// Singleton
		/// </summary>
		public static ColorJsonConverter Instance {
			get {
				if (_instance == null) {
					_instance = new ColorJsonConverter ();
				}

				return _instance;
			}
		}

		public override Color Read (ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
		{
			// Check if the value is a string
			if (reader.TokenType == JsonTokenType.String) {
				// Get the color string
				var colorString = reader.GetString ();

				// Check if the color string is a color name
				if (Enum.TryParse (colorString, ignoreCase: true, out ColorNames color)) {
					// Return the parsed color
					return new Color(color);
				}
				if (Color.TryParse (colorString, out Color parsedColor)) {
					return parsedColor;
				}
				throw new JsonException ($"Unexpected color name: {colorString}.");
			} else {
				throw new JsonException ($"Unexpected token when parsing Color: {reader.TokenType}");
			}
		}

		public override void Write (Utf8JsonWriter writer, Color value, JsonSerializerOptions options)
		{
			writer.WriteStringValue (value.ToString());
		}
	}
}