using System;

namespace KeepersCompound.TMV;

public static class RectPacker
{
    public struct Rect
    {
        public int Id;
        public ushort X;
        public ushort Y;
        public ushort Width;
        public ushort Height;
    }

    enum ExpandDir
    {
        X,
        Y,
    }

    public static Rect Pack(Rect[] rectangles, ushort minWidth = 512, ushort minHeight = 512)
    {
        ArgumentNullException.ThrowIfNull(rectangles);
        ArgumentOutOfRangeException.ThrowIfZero(minWidth);
        ArgumentOutOfRangeException.ThrowIfZero(minHeight);

        var bounds = new Rect
        {
            Width = minWidth,
            Height = minHeight
        };
        if (rectangles.Length == 0)
        {
            return bounds;
        }

        Array.Sort(rectangles, (a, b) => a.Height.CompareTo(b.Height));

        // Naively try to pack into the row, wrapping when we reach the end
        // and expanding the bounds when needed
        ushort rowStartX = 0;
        ushort rowMaxH = 0;
        ushort x = 0;
        ushort y = 0;
        var expandDir = ExpandDir.Y;
        var rectCount = rectangles.Length;
        for (var i = 0; i < rectCount; i++)
        {
            var rect = rectangles[i];
            if (rect.Width == 0 || rect.Height == 0)
            {
                throw new ArgumentOutOfRangeException(nameof(rectangles), rectangles, $"{nameof(rectangles)} contains rect with width or height 0.");
            }

            // uh oh we've hit the edge, wrap to next row
            if (x + rect.Width > bounds.Width)
            {
                // we just loop to next row
                x = rowStartX;
                y += rowMaxH;
                rowMaxH = 0;
            }

            // uh oh we've hit the edge, expand
            if (y + rect.Height > bounds.Height)
            {
                if (expandDir == ExpandDir.X)
                {
                    // We can expand to the right
                    x = bounds.Width;
                    rowStartX = bounds.Width;
                    y = 0;
                    rowMaxH = 0;
                    bounds.Width *= 2;
                    expandDir = ExpandDir.Y;
                }
                else if (expandDir == ExpandDir.Y)
                {
                    rowStartX = 0;
                    bounds.Height *= 2;
                    expandDir = ExpandDir.X;
                }
            }

            rect.X = x;
            rect.Y = y;
            rectangles[i] = rect;

            x += rect.Width;
            if (rect.Height > rowMaxH)
            {
                rowMaxH = rect.Height;
            }
        }

        return bounds;
    }

    public static Rect TightBounds(Rect[] rectangles)
    {
        var bounds = new Rect();
        foreach (var rect in rectangles)
        {
            var w = rect.X + rect.Width;
            if (w > bounds.Width)
            {
                bounds.Width = (ushort)w;
            }

            var h = rect.Y + rect.Height;
            if (h > bounds.Height)
            {
                bounds.Height = (ushort)h;
            }
        }
        return bounds;
    }
}