using Annulus;
using Azimuth;
using Blacklight.Core;
using Glass.Blacklight;
using Prism;

namespace Glass.Testbed.TestCases.Text
{
    /// <summary>
    /// Labels tinted by a rainbow texture, so each glyph takes its color from where it sits rather than one color for
    /// the whole text.
    /// </summary>
    public class RainbowTextTestCase : TestCase
    {
        // A power of two, since D3D9 hardware with only conditional non-power-of-two support can't repeat other sizes.
        private const int PixelsPerCycle = 512;

        private const int PixelsPerSecond = 128;

        private const string Paragraph = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod " +
            "tempor incididunt ut labore et dolore magna aliqua.";

        private readonly World world;

        public RainbowTextTestCase(World world)
        {
            this.world = world;
        }

        /// <summary>
        /// Returns a one pixel tall strip running once through the rainbow, for a tint texture to repeat across the
        /// screen.
        /// </summary>
        private BlacklightGlassTexture RainbowStrip()
        {
            var rgba = new byte[PixelsPerCycle * DecodedImage.BytesPerPixel];
            for (int x = 0; x < PixelsPerCycle; ++x)
            {
                Color color = new Hsv((double)x / PixelsPerCycle, 1, 1).ToColor();
                int offset = x * DecodedImage.BytesPerPixel;
                rgba[offset] = color.Red;
                rgba[offset + 1] = color.Green;
                rgba[offset + 2] = color.Blue;
                rgba[offset + 3] = 255;
            }

            var image = new DecodedImage(rgba, new System.Drawing.Size(PixelsPerCycle, 1));
            return new BlacklightGlassTexture { Texture = world.window.CreateTexture(image) };
        }

        /// <summary>
        /// Returns a label whose rainbow slides along, sized to the text and still at the origin.
        /// </summary>
        private static Label SlidingLabel(TextMaterialStyle style, string text, Constraints constraints)
        {
            var label = new Label(new ScrollingTintText(style, text, PixelsPerSecond, PixelsPerCycle));
            label.Bounds = Rect.FromPositionAndSize(Vector.Zero, label.PreferredSize(constraints));
            return label;
        }

        protected override void Populate()
        {
            AddCaption("Tinted by a rainbow texture sliding across the screen, so color follows position");

            var rainbow = new TextMaterialStyle
            {
                Font = Fonts.Philosopher64,
                TintColor = Colors.White,
                TintTexture = RainbowStrip(),
                Multiline = false,
            };

            var title = SlidingLabel(rainbow, "Rainbow text", Constraints.Unbounded);
            title.Bounds = title.Bounds.WithPosition(ContentAggregator.NewRow(title.Bounds.Height).TopLeft);
            Add(title);

            AddCaption("Wrapped, so the colors line up down the lines too");

            var paragraph = SlidingLabel(rainbow with { Font = Fonts.Philosopher32, Multiline = true }, Paragraph,
                Constraints.Loose(new Vector(PixelsPerCycle, Scalar.PositiveInfinity)));
            paragraph.Bounds =
                paragraph.Bounds.WithPosition(ContentAggregator.NewRow(paragraph.Bounds.Height).TopLeft);
            Add(paragraph);

            AddCaption("Pinned to the screen (left) or carried with the label (right), so only the right one starts " +
                "from the same color at its left edge");

            var screenSpace = rainbow with { Font = Fonts.Philosopher32 };
            var modelSpace = screenSpace with { TintSpace = Glass.TintSpace.Model };
            Rect pair = ContentAggregator.NewRow(48);
            Label[] pairLabels =
            {
                SlidingLabel(screenSpace, "Screen space", Constraints.Unbounded),
                SlidingLabel(modelSpace, "Model space", Constraints.Unbounded),
            };
            foreach (Label label in pairLabels)
            {
                label.Bounds = label.Bounds.WithPosition(pair.NewCol(label.Bounds.Width, margin: 40).TopLeft);
                Add(label);
            }
        }
    }
}