using Avalonia;
using Avalonia.Controls;

namespace LehrerApp.Desktop.Views.Groups;

/// <summary>
/// Ordnet Sitzplätze in einem Raster an und fügt zwischen ausgewählten Spalten zusätzliche
/// transparente Breite ein. Anders als ein UniformGrid kann der Abstand je Spaltengrenze variieren.
/// </summary>
public sealed class SeatingPlanPanel : Panel
{
    public static readonly StyledProperty<int> ColumnsProperty =
        AvaloniaProperty.Register<SeatingPlanPanel, int>(nameof(Columns), 1);

    public static readonly StyledProperty<IReadOnlyList<double>> ColumnGapWidthsProperty =
        AvaloniaProperty.Register<SeatingPlanPanel, IReadOnlyList<double>>(
            nameof(ColumnGapWidths), Array.Empty<double>());

    public int Columns
    {
        get => GetValue(ColumnsProperty);
        set => SetValue(ColumnsProperty, value);
    }

    public IReadOnlyList<double> ColumnGapWidths
    {
        get => GetValue(ColumnGapWidthsProperty);
        set => SetValue(ColumnGapWidthsProperty, value);
    }

    static SeatingPlanPanel() =>
        AffectsMeasure<SeatingPlanPanel>(ColumnsProperty, ColumnGapWidthsProperty);

    protected override Size MeasureOverride(Size availableSize)
    {
        foreach (var child in Children)
            child.Measure(Size.Infinity);

        if (Children.Count == 0) return default;
        var columns = Math.Max(1, Columns);
        var rows = (int)Math.Ceiling((double)Children.Count / columns);
        var cellWidth = Children.Max(child => child.DesiredSize.Width);
        var cellHeight = Children.Max(child => child.DesiredSize.Height);
        return new Size(cellWidth * columns + GapWidth(columns), cellHeight * rows);
    }

    protected override Size ArrangeOverride(Size finalSize)
    {
        if (Children.Count == 0) return finalSize;
        var columns = Math.Max(1, Columns);
        var cellWidth = Children.Max(child => child.DesiredSize.Width);
        var cellHeight = Children.Max(child => child.DesiredSize.Height);

        for (var index = 0; index < Children.Count; index++)
        {
            var column = index % columns;
            var row = index / columns;
            var child = Children[index];
            var x = column * cellWidth + GapWidthBefore(column);
            var childX = x + Math.Max(0, (cellWidth - child.DesiredSize.Width) / 2);
            var childY = row * cellHeight + Math.Max(0, (cellHeight - child.DesiredSize.Height) / 2);
            child.Arrange(new Rect(childX, childY, child.DesiredSize.Width, child.DesiredSize.Height));
        }

        return finalSize;
    }

    private double GapWidth(int columns) =>
        Enumerable.Range(0, Math.Max(0, columns - 1)).Sum(GapAt);

    private double GapWidthBefore(int column) =>
        Enumerable.Range(0, Math.Max(0, column)).Sum(GapAt);

    private double GapAt(int index) => index < ColumnGapWidths.Count
        ? Math.Clamp(ColumnGapWidths[index], 0, 300)
        : 0;
}