using UnityEngine;
using UnityEngine.UIElements;

namespace Luneraria.UI
{
    /// <summary>
    /// A vector-drawn plate (port of scripts/ui/theme/forged_style.gd): chamfered corners, a
    /// vertical fill gradient, an edge line, an inset line, an optional top highlight and a soft
    /// shadow. Drawn from the element's size, so it stays crisp at every UI scale.
    /// </summary>
    public sealed class LunePlateStyle
    {
        public Color FillTop = LuneUiTheme.Hex("1b2027");
        public Color FillBottom = LuneUiTheme.Hex("12161b");
        public Color Edge = LuneUiTheme.Hex("8a6a3c");
        public float EdgeWidth = 1.5f;
        public Color Inner = new Color(1f, 1f, 1f, .05f);
        public float InnerInset = 4f;
        public float Chamfer = 7f;
        public Color Highlight = Color.clear;
        public Color Shadow = Color.clear;
        public float ShadowSize;
        /// <summary>Grows the drawing outside the element (focus rings).</summary>
        public float Grow;
        public bool DrawFill = true;
        /// <summary>Content margins (Godot content_margin_*), applied as padding.</summary>
        public float PadX = 12f;
        public float PadY = 12f;

        /// <summary>SaumwachtTheme.plate (inner .045) plus LuneUiTheme.plate (inner .035, inset 3, margins).</summary>
        public static LunePlateStyle Hud(Color top, Color bottom, Color edge, float edgeWidth = 1f, float cut = 6f, float padX = 12f, float padY = 10f)
        {
            return new LunePlateStyle { FillTop = top, FillBottom = bottom, Edge = edge, EdgeWidth = edgeWidth, Chamfer = cut, Inner = new Color(1f, 1f, 1f, .035f), InnerInset = 3f, PadX = padX, PadY = padY };
        }

        /// <summary>SaumwachtTheme.plate with margins: menu plates (inner .045, inset 4).</summary>
        public static LunePlateStyle Menu(Color top, Color bottom, Color edge, float edgeWidth = 1.5f, float cut = 7f, float padX = 12f, float padY = 12f)
        {
            return new LunePlateStyle { FillTop = top, FillBottom = bottom, Edge = edge, EdgeWidth = edgeWidth, Chamfer = cut, Inner = new Color(1f, 1f, 1f, .045f), InnerInset = 4f, PadX = padX, PadY = padY };
        }

        /// <summary>Keyboard focus ring outside the element (SaumwachtTheme.focus_ring).</summary>
        public static LunePlateStyle FocusRing(float cut = 7f)
        {
            return new LunePlateStyle { DrawFill = false, Edge = LuneUiTheme.Focus, EdgeWidth = 2.5f, Inner = LuneUiTheme.WithAlpha(LuneUiTheme.Focus, .55f), InnerInset = 4.5f,
                Chamfer = cut + 4f, Grow = 4f, Shadow = LuneUiTheme.WithAlpha(LuneUiTheme.Focus, .22f), ShadowSize = 5f, PadX = 0f, PadY = 0f };
        }

        public void ApplyPadding(VisualElement element)
        {
            element.style.paddingLeft = PadX;
            element.style.paddingRight = PadX;
            element.style.paddingTop = PadY;
            element.style.paddingBottom = PadY;
        }

        public LunePlateStyle WithShadow(Color shadow, float size)
        {
            var copy = (LunePlateStyle)MemberwiseClone();
            copy.Shadow = shadow;
            copy.ShadowSize = size;
            return copy;
        }

        public LunePlateStyle WithInner(Color inner)
        {
            var copy = (LunePlateStyle)MemberwiseClone();
            copy.Inner = inner;
            return copy;
        }
    }

    public static class LunePlates
    {
        static readonly Vector2[] Points = new Vector2[8];

        /// <summary>The eight corners of a chamfered rectangle, clockwise from the top left cut.</summary>
        public static Vector2[] PlatePoints(Rect rect, float cut, Vector2[] into = null)
        {
            Vector2[] result = into ?? new Vector2[8];
            float c = Mathf.Min(cut, Mathf.Min(rect.width, rect.height) * .5f);
            Vector2 p = rect.min;
            Vector2 e = rect.max;
            result[0] = new Vector2(p.x + c, p.y);
            result[1] = new Vector2(e.x - c, p.y);
            result[2] = new Vector2(e.x, p.y + c);
            result[3] = new Vector2(e.x, e.y - c);
            result[4] = new Vector2(e.x - c, e.y);
            result[5] = new Vector2(p.x + c, e.y);
            result[6] = new Vector2(p.x, e.y - c);
            result[7] = new Vector2(p.x, p.y + c);
            return result;
        }

        static Rect Grow(Rect rect, float amount)
        {
            return new Rect(rect.x - amount, rect.y - amount, rect.width + amount * 2f, rect.height + amount * 2f);
        }

        public static void Draw(MeshGenerationContext context, Rect rect, LunePlateStyle style)
        {
            Rect r = Grow(rect, style.Grow);
            if (r.width < 2f || r.height < 2f)
                return;
            Painter2D painter = context.painter2D;
            if (style.Shadow.a > 0f && style.ShadowSize > 0f)
            {
                for (int layer = 0; layer < 3; layer++)
                {
                    float spread = style.ShadowSize * (layer + 1) / 3f;
                    var soft = new Color(style.Shadow.r, style.Shadow.g, style.Shadow.b, style.Shadow.a / 3f);
                    if (style.DrawFill)
                    {
                        Rect offset = new Rect(r.x, r.y + spread * .5f, r.width, r.height);
                        Polygon(painter, PlatePoints(Grow(offset, spread), style.Chamfer + spread, Points), soft);
                    }
                    else
                    {
                        // Rings only glow outwards; the element underneath stays untinted.
                        Outline(painter, PlatePoints(Grow(r, spread), style.Chamfer + spread, Points), soft, style.ShadowSize / 3f + 1f);
                    }
                }
            }
            if (style.DrawFill)
                Gradient(context, PlatePoints(r, style.Chamfer, Points), r, style.FillTop, style.FillBottom);
            if (style.Highlight.a > 0f)
            {
                float y = r.y + style.EdgeWidth + 1f;
                Line(painter, new Vector2(r.x + style.Chamfer, y), new Vector2(r.xMax - style.Chamfer, y), style.Highlight, 1f);
            }
            if (style.Inner.a > 0f && style.InnerInset > 0f)
                Outline(painter, PlatePoints(Grow(r, -style.InnerInset), Mathf.Max(1f, style.Chamfer - style.InnerInset * .45f), Points), style.Inner, 1f);
            if (style.Edge.a > 0f && style.EdgeWidth > 0f)
                Outline(painter, PlatePoints(Grow(r, -style.EdgeWidth * .5f), style.Chamfer, Points), style.Edge, style.EdgeWidth);
        }

        /// <summary>Convex polygon with a vertical colour gradient (Godot: polygon with per-vertex colours).</summary>
        public static void Gradient(MeshGenerationContext context, Vector2[] points, Rect bounds, Color top, Color bottom)
        {
            int count = points.Length;
            MeshWriteData mesh = context.Allocate(count + 1, count * 3);
            Vector2 center = Vector2.zero;
            foreach (Vector2 point in points)
                center += point;
            center /= count;
            mesh.SetNextVertex(new Vertex { position = new Vector3(center.x, center.y, Vertex.nearZ), tint = Color.Lerp(top, bottom, Fraction(center.y, bounds)) });
            foreach (Vector2 point in points)
                mesh.SetNextVertex(new Vertex { position = new Vector3(point.x, point.y, Vertex.nearZ), tint = Color.Lerp(top, bottom, Fraction(point.y, bounds)) });
            // Clockwise triangles in screen space (y down).
            for (int index = 0; index < count; index++)
            {
                mesh.SetNextIndex(0);
                mesh.SetNextIndex((ushort)(1 + index));
                mesh.SetNextIndex((ushort)(1 + (index + 1) % count));
            }
        }

        static float Fraction(float y, Rect bounds)
        {
            return Mathf.Clamp01((y - bounds.y) / Mathf.Max(1f, bounds.height));
        }

        public static void Polygon(Painter2D painter, Vector2[] points, Color color)
        {
            painter.fillColor = color;
            painter.BeginPath();
            painter.MoveTo(points[0]);
            for (int index = 1; index < points.Length; index++)
                painter.LineTo(points[index]);
            painter.ClosePath();
            painter.Fill();
        }

        public static void Outline(Painter2D painter, Vector2[] points, Color color, float width)
        {
            painter.strokeColor = color;
            painter.lineWidth = width;
            painter.lineJoin = LineJoin.Miter;
            painter.BeginPath();
            painter.MoveTo(points[0]);
            for (int index = 1; index < points.Length; index++)
                painter.LineTo(points[index]);
            painter.ClosePath();
            painter.Stroke();
        }

        public static void Line(Painter2D painter, Vector2 from, Vector2 to, Color color, float width)
        {
            painter.strokeColor = color;
            painter.lineWidth = width;
            painter.lineCap = LineCap.Butt;
            painter.BeginPath();
            painter.MoveTo(from);
            painter.LineTo(to);
            painter.Stroke();
        }
    }
}