Terminal.Gui/UnitTests/TextEffects/New/GradientFillTests.cs

using Terminal.Gui.Drawing;

namespace Terminal.Gui.TextEffects.Tests;

public class GradientFillTests
{
    private Gradient _gradient;

    public GradientFillTests ()
    {
        // Define the colors of the gradient stops
        var stops = new List<Color>
        {
            new Color(255, 0, 0),    // Red
            new Color(0, 0, 255)     // Blue
        };

        // Define the number of steps between each color
        var steps = new List<int> { 10 }; // 10 steps between Red -> Blue

        _gradient = new Gradient (stops, steps, loop: false);
    }

    [Fact]
    public void TestGradientFillCorners ()
    {
        var area = new Rectangle (0, 0, 10, 10);
        var gradientFill = new GradientFill (area, _gradient, Gradient.Direction.Diagonal);

        // Test the corners
        var topLeft = new Point (0, 0);
        var topRight = new Point (area.Width - 1, 0);
        var bottomLeft = new Point (0, area.Height - 1);
        var bottomRight = new Point (area.Width - 1, area.Height - 1);

        var topLeftColor = gradientFill.GetColor (topLeft);
        var topRightColor = gradientFill.GetColor (topRight);
        var bottomLeftColor = gradientFill.GetColor (bottomLeft);
        var bottomRightColor = gradientFill.GetColor (bottomRight);

        // Validate the colors at the corners
        Assert.NotNull (topLeftColor);
        Assert.NotNull (topRightColor);
        Assert.NotNull (bottomLeftColor);
        Assert.NotNull (bottomRightColor);

        // Expected colors
        var expectedTopLeftColor = new Terminal.Gui.Color (255, 0, 0); // Red
        var expectedBottomRightColor = new Terminal.Gui.Color (0, 0, 255); // Blue

        Assert.Equal (expectedTopLeftColor, topLeftColor);
        Assert.Equal (expectedBottomRightColor, bottomRightColor);

        // Additional checks can be added to verify the exact expected colors if known
        Console.WriteLine ($"Top-left: {topLeftColor}");
        Console.WriteLine ($"Top-right: {topRightColor}");
        Console.WriteLine ($"Bottom-left: {bottomLeftColor}");
        Console.WriteLine ($"Bottom-right: {bottomRightColor}");
    }

    [Fact]
    public void TestGradientFillColorTransition ()
    {
        var area = new Rectangle (0, 0, 10, 10);
        var gradientFill = new GradientFill (area, _gradient, Gradient.Direction.Diagonal);

        for (int row = 0; row < area.Height; row++)
        {
            int previousRed = 255;
            int previousBlue = 0;

            for (int col = 0; col < area.Width; col++)
            {
                var point = new Point (col, row);
                var color = gradientFill.GetColor (point);

                // Ensure color is not null
                Assert.NotNull (color);

                // Check if the current color is 'more blue' and 'less red' as it goes right and down
                Assert.True (color.R <= previousRed, $"Failed at ({col}, {row}): {color.R} > {previousRed}");
                Assert.True (color.B >= previousBlue, $"Failed at ({col}, {row}): {color.B} < {previousBlue}");

                // Update the previous color values for the next iteration
                previousRed = color.R;
                previousBlue = color.B;
            }
        }

        for (int col = 0; col < area.Width; col++)
        {
            int previousRed = 255;
            int previousBlue = 0;

            for (int row = 0; row < area.Height; row++)
            {
                var point = new Point (col, row);
                var color = gradientFill.GetColor (point);

                // Ensure color is not null
                Assert.NotNull (color);

                // Check if the current color is 'more blue' and 'less red' as it goes right and down
                Assert.True (color.R <= previousRed, $"Failed at ({col}, {row}): {color.R} > {previousRed}");
                Assert.True (color.B >= previousBlue, $"Failed at ({col}, {row}): {color.B} < {previousBlue}");

                // Update the previous color values for the next iteration
                previousRed = color.R;
                previousBlue = color.B;
            }
        }
    }
}