using System;

namespace Dashboard.Drawing
{
    public interface IDrawCommand
    {
        /// <summary>
        /// Name of the command.
        /// </summary>
        string Name { get; }

        /// <summary>
        /// The draw extension that defines this command.
        /// </summary>
        IDrawExtension Extension { get; }

        /// <summary>
        /// The length of the command data segment, in bytes.
        /// </summary>
        /// <remarks>
        /// Must be 0 for simple commands. For commands that are variadic, the
        /// value must be less than 0. Any other positive value, otherwise.
        /// </remarks>
        int Length { get; }

        /// <summary>
        /// Get the parameters object for this command.
        /// </summary>
        /// <param name="param">The parameter array.</param>
        /// <returns>The parameters object.</returns>
        object? GetParams(DrawQueue queue, ReadOnlySpan<byte> param);

        int WriteParams(DrawQueue queue, object? obj, Span<byte> param);
    }

    public interface IDrawCommand<T> : IDrawCommand
    {
        /// <summary>
        /// Get the parameters object for this command.
        /// </summary>
        /// <param name="param">The parameter array.</param>
        /// <returns>The parameters object.</returns>
        new T? GetParams(DrawQueue queue, ReadOnlySpan<byte> param);

        new int WriteParams(DrawQueue queue, T? obj, Span<byte> param);
    }

    public sealed class DrawCommand : IDrawCommand
    {
        public string Name { get; }
        public IDrawExtension Extension { get; }
        public int Length { get; } = 0;

        public DrawCommand(string name, IDrawExtension extension)
        {
            Name = name;
            Extension = extension;
        }

        public object? GetParams(DrawQueue queue, ReadOnlySpan<byte> param)
        {
            return null;
        }

        public int WriteParams(DrawQueue queue, object? obj, Span<byte> param)
        {
            return 0;
        }
    }

    public sealed class DrawCommand<T> : IDrawCommand<T>
        where T : IParameterSerializer<T>, new()
    {
        public string Name { get; }
        public IDrawExtension Extension { get; }
        public int Length { get; }

        public DrawCommand(string name, IDrawExtension extension, int length)
        {
            Name = name;
            Extension = extension;
            Length = length;
        }

        public T? GetParams(DrawQueue queue, ReadOnlySpan<byte> param)
        {
            T t = new T();
            t.Deserialize(queue, param);
            return t;
        }

        public int WriteParams(DrawQueue queue, T? obj, Span<byte> param)
        {
            return obj!.Serialize(queue, param);
        }

        int IDrawCommand.WriteParams(DrawQueue queue, object? obj, Span<byte> param)
        {
            return WriteParams(queue, (T?)obj, param);
        }

        object? IDrawCommand.GetParams(DrawQueue queue, ReadOnlySpan<byte> param)
        {
            return GetParams(queue, param);
        }
    }
}