using System;
using System.Windows;
using System.Windows.Media;
using System.Windows.Media.Imaging;

namespace Kniip.Editor;

public enum BackgroundKind { None, Color, Gradient, Image }

public enum GradientDirection { Vertical, Horizontal, Diagonal, Radial }

/// <summary>
/// Wat er onder het knipsel ligt; alleen zichtbaar waar het knipsel transparant is.
/// De kleuren en afbeelding blijven bewaard bij het wisselen van soort.
/// </summary>
public sealed record CanvasBackground(
    BackgroundKind Kind,
    Color Color,
    Color Color2,
    GradientDirection Direction,
    BitmapSource? Image)
{
    public static readonly CanvasBackground Default = new(
        BackgroundKind.None, Colors.White, Color.FromRgb(0x00, 0x78, 0xD4), GradientDirection.Vertical, null);

    public bool IsVisible => Kind switch
    {
        BackgroundKind.None => false,
        BackgroundKind.Image => Image != null,
        _ => true
    };

    public void Render(DrawingContext dc, int width, int height)
    {
        var area = new Rect(0, 0, width, height);
        switch (Kind)
        {
            case BackgroundKind.Color:
                dc.DrawRectangle(new SolidColorBrush(Color), null, area);
                break;
            case BackgroundKind.Gradient:
                dc.DrawRectangle(CreateGradient(), null, area);
                break;
            case BackgroundKind.Image when Image != null:
                // Eigen schaalmodus: de export tekent verder met NearestNeighbor.
                var group = new DrawingGroup { ClipGeometry = new RectangleGeometry(area) };
                RenderOptions.SetBitmapScalingMode(group, BitmapScalingMode.HighQuality);
                group.Children.Add(new ImageDrawing(Image, Cover(Image.PixelWidth, Image.PixelHeight, area)));
                dc.DrawDrawing(group);
                break;
        }
    }

    private Brush CreateGradient() => Direction switch
    {
        GradientDirection.Horizontal => new LinearGradientBrush(Color, Color2, new Point(0, 0.5), new Point(1, 0.5)),
        GradientDirection.Diagonal => new LinearGradientBrush(Color, Color2, new Point(0, 0), new Point(1, 1)),
        GradientDirection.Radial => new RadialGradientBrush(Color, Color2),
        _ => new LinearGradientBrush(Color, Color2, new Point(0.5, 0), new Point(0.5, 1))
    };

    /// <summary>Afbeelding zo schalen dat ze het hele vlak vult; wat uitsteekt valt weg.</summary>
    private static Rect Cover(double imageWidth, double imageHeight, Rect area)
    {
        double scale = Math.Max(area.Width / imageWidth, area.Height / imageHeight);
        double w = imageWidth * scale, h = imageHeight * scale;
        return new Rect(area.X + (area.Width - w) / 2, area.Y + (area.Height - h) / 2, w, h);
    }
}