using Azimuth;
using Annulus;
using Blacklight.Core;
using Glass.Blacklight;
using System;
using System.Drawing;

namespace Glass.Testbed
{
    /// <summary>
    /// A flat fill that cycles through the rainbow by age.
    /// </summary>
    public record RainbowMaterial : Material
    {
        public Scalar SecondsPerCycle { get; init; } = 4;

        private static readonly SolidColorMaterial Fill = new SolidColorMaterial();

        /// <summary>
        /// Red at zero, running through the spectrum and back.  A hue sweep at full saturation rather than three
        /// phase-shifted sines, which never fully clear a channel and so wash out to pastels.
        /// </summary>
        public static System.Drawing.Color ColorAt(TimeSpan age, Scalar secondsPerCycle)
        {
            double turns = age.TotalSeconds / secondsPerCycle;

            // Floor rather than % so a negative age wraps forwards instead of mirroring.
            double hue = 6 * (turns - Math.Floor(turns));
            int segment = Math.Min(5, (int)hue);
            int ramp = (int)Math.Round(255 * (1 - Math.Abs(hue % 2 - 1)));

            switch (segment)
            {
                case 0: return System.Drawing.Color.FromArgb(255, ramp, 0);
                case 1: return System.Drawing.Color.FromArgb(ramp, 255, 0);
                case 2: return System.Drawing.Color.FromArgb(0, 255, ramp);
                case 3: return System.Drawing.Color.FromArgb(0, ramp, 255);
                case 4: return System.Drawing.Color.FromArgb(ramp, 0, 255);
                default: return System.Drawing.Color.FromArgb(255, 0, ramp);
            }
        }

        public static void Render(Renderer<Cel> renderer, Cel context, RainbowMaterial material, Rect rect,
            DrawState drawState)
        {
            drawState.TintColor = ColorAt(drawState.Age, material.SecondsPerCycle);
            renderer.Render(context, Fill, rect, drawState);
        }
    }
}