using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Windows.Forms;

namespace BoxPacker3D
{
    public class Viewer3D
    {
        private Panel panel;

        public Viewer3D(Panel panel)
        {
            this.panel = panel;
            panel.Paint += Panel_Paint;
            _packedItems = new List<PackedItem>();
        }

        private List<PackedItem> _packedItems;
        private Box _box;
        private double _rotX = 30, _rotY = 30, _zoom = 1.0;
        private double _wallPad = 0, _itemPad = 0;

        public void Clear()
        {
            _packedItems = new List<PackedItem>();
            _box = null;
            panel.Invalidate();
        }

        public void Render(List<PackedItem> packedItems, Box box,
            double rotX, double rotY, double zoom = 1.0,
            double wallPad = 0, double itemPad = 0)
        {
            _packedItems = packedItems;
            _box = box;
            _rotX = rotX; _rotY = rotY;
            _zoom = Math.Max(0.1, zoom);
            _wallPad = wallPad; _itemPad = itemPad;
            panel.Invalidate();
        }

        private void Panel_Paint(object sender, PaintEventArgs e)
        {
            var g = e.Graphics;
            g.SmoothingMode = SmoothingMode.AntiAlias;
            g.Clear(Color.FromArgb(18, 18, 28));
            if (_box == null) { DrawWelcome(g); return; }
            DrawScene(g, panel.Width, panel.Height);
        }

        private void DrawWelcome(Graphics g)
        {
            int w = panel.Width, h = panel.Height;
            using (var brush = new SolidBrush(Color.FromArgb(40, 40, 60)))
                g.FillRectangle(brush, 0, 0, w, h);
            using (var pen = new Pen(Color.FromArgb(35, 35, 55), 1))
            {
                for (int x = 0; x < w; x += 40) g.DrawLine(pen, x, 0, x, h);
                for (int y = 0; y < h; y += 40) g.DrawLine(pen, 0, y, w, y);
            }
            using (var font = new Font("Segoe UI", 14f))
            using (var brush = new SolidBrush(Color.FromArgb(80, 100, 160)))
            {
                var sf = new StringFormat { Alignment = StringAlignment.Center, LineAlignment = StringAlignment.Center };
                g.DrawString("Zadajte rozmery škatule a kusy,\npotom kliknite 🚀 SPUSTIŤ BALENIE",
                    font, brush, new RectangleF(0, 0, w, h), sf);
            }
        }

        public Bitmap RenderToBitmap(List<PackedItem> packedItems, Box box,
            double rotX, double rotY, double zoom, int width, int height,
            double wallPad = 0, double itemPad = 0, bool whiteBg = false)
        {
            var bmp = new Bitmap(width, height);
            using (var g = Graphics.FromImage(bmp))
            {
                g.SmoothingMode = SmoothingMode.AntiAlias;
                g.Clear(whiteBg ? Color.White : Color.FromArgb(18, 18, 28));
                DrawSceneEx(g, width, height, packedItems, box, rotX, rotY, zoom, wallPad, itemPad, null, whiteBg);
            }
            return bmp;
        }

        public Bitmap RenderLayerToBitmap(List<PackedItem> packedItems, Box box,
            double rotX, double rotY, double zoom,
            double layerYMin, double layerYMax,
            int layerIndex, int totalLayers,
            int width, int height,
            double wallPad = 0, double itemPad = 0, bool whiteBg = false)
        {
            var bmp = new Bitmap(width, height);
            using (var g = Graphics.FromImage(bmp))
            {
                g.SmoothingMode = SmoothingMode.AntiAlias;
                g.Clear(whiteBg ? Color.White : Color.FromArgb(18, 18, 28));

                var layerItems = packedItems
                    .Where(p => p.Y < layerYMax - 0.001 && p.Y + p.RH > layerYMin + 0.001)
                    .ToList();

                DrawSceneEx(g, width, height, layerItems, box, rotX, rotY, zoom, wallPad, itemPad,
                    $"Vrstva {layerIndex + 1} / {totalLayers}  (Y: {layerYMin:F1} – {layerYMax:F1} mm)", whiteBg);
                
                // Draw layer boundary indicators (subtle horizontal planes at YMin and YMax)
                DrawLayerBoundaries(g, width, height, box, layerYMin, layerYMax, rotX, rotY, zoom, whiteBg);
            }
            return bmp;
        }

        private void DrawLayerBoundaries(Graphics g, int w, int h, Box box, 
            double yMin, double yMax, double rotX, double rotY, double zoom, bool whiteBg)
        {
            double radX = rotX * Math.PI / 180.0;
            double radY = rotY * Math.PI / 180.0;
            double maxDim = Math.Max(Math.Max(box.W, box.H), box.D);
            double scale = Math.Min(w, h) * 0.38 / maxDim * zoom;
            double cx = w / 2.0, cy = h / 2.0;

            // Draw two horizontal planes (YMin and YMax) as subtle dotted lines
            var planeColor = whiteBg ? Color.FromArgb(80, 255, 100, 100) : Color.FromArgb(60, 255, 180, 100);
            using (var pen = new Pen(planeColor, 1f) { DashStyle = System.Drawing.Drawing2D.DashStyle.Dot })
            {
                // YMin plane
                DrawHorizontalPlane(g, pen, box, yMin, scale, cx, cy, radX, radY);
                // YMax plane  
                DrawHorizontalPlane(g, pen, box, yMax, scale, cx, cy, radX, radY);
            }
        }

        private void DrawHorizontalPlane(Graphics g, Pen pen, Box box, double y, 
            double scale, double cx, double cy, double radX, double radY)
        {
            double yRel = y - box.H / 2;  // relative to box center
            double hw = box.W / 2, hd = box.D / 2;
            
            // Four corners of the plane
            var p1 = Project(-hw, yRel, -hd, scale, cx, cy, radX, radY);
            var p2 = Project( hw, yRel, -hd, scale, cx, cy, radX, radY);
            var p3 = Project( hw, yRel,  hd, scale, cx, cy, radX, radY);
            var p4 = Project(-hw, yRel,  hd, scale, cx, cy, radX, radY);
            
            // Draw rectangle
            g.DrawLine(pen, p1, p2);
            g.DrawLine(pen, p2, p3);
            g.DrawLine(pen, p3, p4);
            g.DrawLine(pen, p4, p1);
        }

        private void DrawScene(Graphics g, int w, int h)
            => DrawSceneEx(g, w, h, _packedItems, _box, _rotX, _rotY, _zoom, _wallPad, _itemPad, null, false);

        private void DrawSceneEx(Graphics g, int w, int h,
            List<PackedItem> items, Box box,
            double rotX, double rotY, double zoom,
            double wallPad, double itemPad,
            string layerLabel, bool whiteBg)
        {
            double radX = rotX * Math.PI / 180.0;
            double radY = rotY * Math.PI / 180.0;

            double maxDim = Math.Max(Math.Max(box.W, box.H), box.D);
            double scale = Math.Min(w, h) * 0.38 / maxDim * zoom;
            double cx = w / 2.0, cy = h / 2.0;

            var sorted = items
                .Select(pi => (pi, depth: Transform(
                    pi.X + pi.RW / 2 - box.W / 2,
                    pi.Y + pi.RH / 2 - box.H / 2,
                    pi.Z + pi.RD / 2 - box.D / 2, radX, radY).Z))
                .OrderBy(t => t.depth)
                .ToList();

            DrawBoxOutline(g, scale, cx, cy, box, radX, radY, alpha: whiteBg ? 100 : 40, wallPad: wallPad, whiteBg: whiteBg);

            if (box.WallThickness > 0.001)
                DrawWallThicknessZone(g, scale, cx, cy, box, radX, radY, whiteBg);

            if (wallPad > 0.001)
                DrawPaddingZone(g, scale, cx, cy, box, radX, radY, wallPad, whiteBg);

            foreach (var (pi, _) in sorted)
                DrawCuboid(g, pi, scale, cx, cy, box, radX, radY);

            DrawBoxOutline(g, scale, cx, cy, box, radX, radY, alpha: whiteBg ? 220 : 180, wallPad: wallPad, whiteBg: whiteBg);

            DrawLegend(g, w, h, items, whiteBg);
            DrawInfo(g, w, h, box, items.Count, whiteBg);

            if (layerLabel != null)
            {
                using (var font = new Font("Segoe UI", 11f, FontStyle.Bold))
                using (var brush = new SolidBrush(whiteBg ? Color.FromArgb(40, 80, 160) : Color.FromArgb(220, 200, 100, 30)))
                {
                    var sf = new StringFormat { Alignment = StringAlignment.Center };
                    g.DrawString(layerLabel, font, brush, new RectangleF(0, 8, w, 28), sf);
                }
            }
        }

        private static (double X, double Y, double Z) Transform(double x, double y, double z,
            double radX, double radY)
        {
            double x1 = x * Math.Cos(radY) + z * Math.Sin(radY);
            double y1 = y;
            double z1 = -x * Math.Sin(radY) + z * Math.Cos(radY);
            double x2 = x1;
            double y2 = y1 * Math.Cos(radX) - z1 * Math.Sin(radX);
            double z2 = y1 * Math.Sin(radX) + z1 * Math.Cos(radX);
            return (x2, y2, z2);
        }

        private PointF Project(double x, double y, double z,
            double scale, double cx, double cy, double radX, double radY)
        {
            var (tx, ty, _) = Transform(x, y, z, radX, radY);
            return new PointF((float)(cx + tx * scale), (float)(cy - ty * scale));
        }

        private void DrawCuboid(Graphics g, PackedItem pi,
            double scale, double cx, double cy,
            Box box, double radX, double radY)
        {
            double x0 = pi.X - box.W / 2, y0 = pi.Y - box.H / 2, z0 = pi.Z - box.D / 2;
            double x1 = x0 + pi.RW, y1 = y0 + pi.RH, z1 = z0 + pi.RD;

            var pts = Corners8(x0, y0, z0, x1, y1, z1, scale, cx, cy, radX, radY);
            var baseColor = pi.Item.Color;

            DrawFace(g, new[] { pts[4], pts[5], pts[6], pts[7] }, Shade(baseColor, 1.00f));
            DrawFace(g, new[] { pts[5], pts[1], pts[2], pts[6] }, Shade(baseColor, 0.75f));
            DrawFace(g, new[] { pts[3], pts[2], pts[6], pts[7] }, Shade(baseColor, 0.55f));

            using (var pen = new Pen(Color.FromArgb(200, Color.Black), 0.8f))
            {
                g.DrawPolygon(pen, new[] { pts[4], pts[5], pts[6], pts[7] });
                g.DrawPolygon(pen, new[] { pts[5], pts[1], pts[2], pts[6] });
                g.DrawPolygon(pen, new[] { pts[3], pts[2], pts[6], pts[7] });
            }
        }

        private void DrawPaddingZone(Graphics g, double scale, double cx, double cy,
            Box box, double radX, double radY, double pad, bool whiteBg)
        {
            double edge = pad + box.WallThickness;
            double hw = box.W / 2 - edge, hh = box.H / 2 - edge, hd = box.D / 2 - edge;
            if (hw <= 0 || hh <= 0 || hd <= 0) return;
            var pts = new PointF[8];
            pts[0] = Project(-hw, -hh, -hd, scale, cx, cy, radX, radY);
            pts[1] = Project(hw, -hh, -hd, scale, cx, cy, radX, radY);
            pts[2] = Project(hw,  hh, -hd, scale, cx, cy, radX, radY);
            pts[3] = Project(-hw,  hh, -hd, scale, cx, cy, radX, radY);
            pts[4] = Project(-hw, -hh,  hd, scale, cx, cy, radX, radY);
            pts[5] = Project(hw, -hh,  hd, scale, cx, cy, radX, radY);
            pts[6] = Project(hw,  hh,  hd, scale, cx, cy, radX, radY);
            pts[7] = Project(-hw,  hh,  hd, scale, cx, cy, radX, radY);

            var col = whiteBg ? Color.FromArgb(150, 200, 150, 50) : Color.FromArgb(60, 255, 220, 80);
            using (var pen = new Pen(col, 1f))
            {
                pen.DashStyle = DashStyle.Dot;
                g.DrawPolygon(pen, new[] { pts[0], pts[1], pts[2], pts[3] });
                g.DrawPolygon(pen, new[] { pts[4], pts[5], pts[6], pts[7] });
                g.DrawLine(pen, pts[0], pts[4]); g.DrawLine(pen, pts[1], pts[5]);
                g.DrawLine(pen, pts[2], pts[6]); g.DrawLine(pen, pts[3], pts[7]);
            }
        }

        /// Draws inner wire cube + corner connectors to visualise the thickness of the box walls.
        private void DrawWallThicknessZone(Graphics g, double scale, double cx, double cy,
            Box box, double radX, double radY, bool whiteBg)
        {
            double t = box.WallThickness;
            double hwO = box.W / 2, hhO = box.H / 2, hdO = box.D / 2;
            double hwI = hwO - t,    hhI = hhO - t,    hdI = hdO - t;
            if (hwI <= 0 || hhI <= 0 || hdI <= 0) return;

            // Outer 8 corners (used for connector lines)
            var outer = new PointF[8];
            outer[0] = Project(-hwO, -hhO, -hdO, scale, cx, cy, radX, radY);
            outer[1] = Project( hwO, -hhO, -hdO, scale, cx, cy, radX, radY);
            outer[2] = Project( hwO,  hhO, -hdO, scale, cx, cy, radX, radY);
            outer[3] = Project(-hwO,  hhO, -hdO, scale, cx, cy, radX, radY);
            outer[4] = Project(-hwO, -hhO,  hdO, scale, cx, cy, radX, radY);
            outer[5] = Project( hwO, -hhO,  hdO, scale, cx, cy, radX, radY);
            outer[6] = Project( hwO,  hhO,  hdO, scale, cx, cy, radX, radY);
            outer[7] = Project(-hwO,  hhO,  hdO, scale, cx, cy, radX, radY);

            // Inner 8 corners
            var inner = new PointF[8];
            inner[0] = Project(-hwI, -hhI, -hdI, scale, cx, cy, radX, radY);
            inner[1] = Project( hwI, -hhI, -hdI, scale, cx, cy, radX, radY);
            inner[2] = Project( hwI,  hhI, -hdI, scale, cx, cy, radX, radY);
            inner[3] = Project(-hwI,  hhI, -hdI, scale, cx, cy, radX, radY);
            inner[4] = Project(-hwI, -hhI,  hdI, scale, cx, cy, radX, radY);
            inner[5] = Project( hwI, -hhI,  hdI, scale, cx, cy, radX, radY);
            inner[6] = Project( hwI,  hhI,  hdI, scale, cx, cy, radX, radY);
            inner[7] = Project(-hwI,  hhI,  hdI, scale, cx, cy, radX, radY);

            // Cardboard-brown tones (slightly darker on white backgrounds for print visibility)
            var innerCol = whiteBg ? Color.FromArgb(220, 120, 80, 40)
                                   : Color.FromArgb(200, 180, 140, 90);
            var connCol  = whiteBg ? Color.FromArgb(160, 140, 95, 55)
                                   : Color.FromArgb(140, 180, 140, 90);

            // Inner wire cube (solid line)
            using (var pen = new Pen(innerCol, 1.3f))
            {
                g.DrawPolygon(pen, new[] { inner[0], inner[1], inner[2], inner[3] });
                g.DrawPolygon(pen, new[] { inner[4], inner[5], inner[6], inner[7] });
                g.DrawLine(pen, inner[0], inner[4]); g.DrawLine(pen, inner[1], inner[5]);
                g.DrawLine(pen, inner[2], inner[6]); g.DrawLine(pen, inner[3], inner[7]);
            }

            // 8 corner connectors (outer corner → inner corner)
            using (var pen = new Pen(connCol, 0.9f))
            {
                for (int i = 0; i < 8; i++)
                    g.DrawLine(pen, outer[i], inner[i]);
            }
        }

        private void DrawBoxOutline(Graphics g, double scale, double cx, double cy,
            Box box, double radX, double radY, int alpha, double wallPad, bool whiteBg)
        {
            double hw = box.W / 2, hh = box.H / 2, hd = box.D / 2;
            var pts = new PointF[8];
            pts[0] = Project(-hw, -hh, -hd, scale, cx, cy, radX, radY);
            pts[1] = Project(hw, -hh, -hd, scale, cx, cy, radX, radY);
            pts[2] = Project(hw,  hh, -hd, scale, cx, cy, radX, radY);
            pts[3] = Project(-hw,  hh, -hd, scale, cx, cy, radX, radY);
            pts[4] = Project(-hw, -hh,  hd, scale, cx, cy, radX, radY);
            pts[5] = Project(hw, -hh,  hd, scale, cx, cy, radX, radY);
            pts[6] = Project(hw,  hh,  hd, scale, cx, cy, radX, radY);
            pts[7] = Project(-hw,  hh,  hd, scale, cx, cy, radX, radY);

            var col = whiteBg ? Color.FromArgb(alpha, 40, 80, 180) : Color.FromArgb(alpha, 100, 200, 255);
            using (var pen = new Pen(col, 1.5f))
            {
                pen.DashStyle = DashStyle.Dash;
                g.DrawPolygon(pen, new[] { pts[0], pts[1], pts[2], pts[3] });
                g.DrawPolygon(pen, new[] { pts[4], pts[5], pts[6], pts[7] });
                g.DrawLine(pen, pts[0], pts[4]); g.DrawLine(pen, pts[1], pts[5]);
                g.DrawLine(pen, pts[2], pts[6]); g.DrawLine(pen, pts[3], pts[7]);
            }

            if (alpha >= 100)
            {
                using var dimFont = new Font("Segoe UI", 11f, FontStyle.Bold);
                var colW = whiteBg ? Color.FromArgb(200, 190, 50, 50) : Color.FromArgb(220, 255, 110, 110);
                var colH = whiteBg ? Color.FromArgb(200, 50, 150, 50) : Color.FromArgb(220, 110, 230, 110);
                var colD = whiteBg ? Color.FromArgb(200, 50, 50, 190) : Color.FromArgb(220, 110, 130, 255);

                // midpoint helpers
                PointF Mid(PointF a, PointF b) => new PointF((a.X + b.X) / 2, (a.Y + b.Y) / 2);

                void DrawDimLabel(string text, PointF pos, Color dimCol)
                {
                    var sz = g.MeasureString(text, dimFont);
                    float tx = pos.X - sz.Width / 2;
                    float ty = pos.Y - sz.Height / 2;
                    // dark background rect for readability
                    var bgCol = whiteBg ? Color.FromArgb(180, 255, 255, 255) : Color.FromArgb(180, 20, 20, 30);
                    using var bgBr = new SolidBrush(bgCol);
                    g.FillRectangle(bgBr, tx - 2, ty - 1, sz.Width + 4, sz.Height + 2);
                    using var br = new SolidBrush(dimCol);
                    g.DrawString(text, dimFont, br, tx, ty);
                }

                // šírka: midpoint of bottom-front edge, offset down
                var midW = Mid(pts[0], pts[1]);
                DrawDimLabel($"šírka {box.W:F0}", new PointF(midW.X, midW.Y + 24), colW);

                // dĺžka: midpoint of bottom-right edge, offset right+down
                var midD = Mid(pts[1], pts[5]);
                DrawDimLabel($"dĺžka {box.D:F0}", new PointF(midD.X + 24, midD.Y + 10), colD);

                // výška: midpoint of right-front edge, offset right
                var midH = Mid(pts[1], pts[2]);
                DrawDimLabel($"výška {box.H:F0}", new PointF(midH.X + 30, midH.Y), colH);
            }
        }

        private PointF[] Corners8(double x0, double y0, double z0,
            double x1, double y1, double z1,
            double scale, double cx, double cy, double radX, double radY)
        {
            return new[]
            {
                Project(x0, y0, z0, scale, cx, cy, radX, radY),
                Project(x1, y0, z0, scale, cx, cy, radX, radY),
                Project(x1, y1, z0, scale, cx, cy, radX, radY),
                Project(x0, y1, z0, scale, cx, cy, radX, radY),
                Project(x0, y0, z1, scale, cx, cy, radX, radY),
                Project(x1, y0, z1, scale, cx, cy, radX, radY),
                Project(x1, y1, z1, scale, cx, cy, radX, radY),
                Project(x0, y1, z1, scale, cx, cy, radX, radY),
            };
        }

        private static void DrawFace(Graphics g, PointF[] corners, Color color)
        {
            using (var brush = new SolidBrush(Color.FromArgb(210, color)))
                g.FillPolygon(brush, corners);
        }

        private static Color Shade(Color c, float f) => Color.FromArgb(
            Math.Min(255, (int)(c.R * f)),
            Math.Min(255, (int)(c.G * f)),
            Math.Min(255, (int)(c.B * f)));

        private void DrawLegend(Graphics g, int w, int h, List<PackedItem> items, bool whiteBg)
        {
            if (items == null || items.Count == 0) return;
            var unique = items
                .GroupBy(p => p.Item.Name)
                .Select(grp => (grp.Key, grp.First().Item.Color, grp.Count()))
                .ToList();

            int lx = 10, ly = 10;
            var txtCol = whiteBg ? Color.Black : Color.White;
            using (var titleFont = new Font("Segoe UI", 8.5f, FontStyle.Bold))
            using (var itemFont = new Font("Segoe UI", 8f))
            {
                using (var b = new SolidBrush(txtCol))
                    g.DrawString("Legenda:", titleFont, b, lx, ly);
                ly += 18;
                foreach (var (name, color, cnt) in unique)
                {
                    using (var b = new SolidBrush(color))
                        g.FillRectangle(b, lx, ly, 12, 12);
                    using (var p = new Pen(Color.Black, 0.5f))
                        g.DrawRectangle(p, lx, ly, 12, 12);
                    using (var b = new SolidBrush(txtCol))
                        g.DrawString($"{name} (×{cnt})", itemFont, b, lx + 16, ly);
                    ly += 16;
                }
            }
        }

        private void DrawInfo(Graphics g, int w, int h, Box box, int count, bool whiteBg)
        {
            string info = $"Škatuľa: {box.W} × {box.D} × {box.H} mm  |  Kusov: {count}";
            var txtCol = whiteBg ? Color.FromArgb(60, 60, 60) : Color.FromArgb(120, 120, 140);
            using (var font = new Font("Segoe UI", 8.5f))
            using (var brush = new SolidBrush(txtCol))
            {
                var sf = new StringFormat { Alignment = StringAlignment.Center };
                g.DrawString(info, font, brush, new RectangleF(0, h - 22, w, 20), sf);
            }
        }

        public static List<(double YMin, double YMax)> GetLayers(List<PackedItem> packed)
        {
            if (packed == null || packed.Count == 0) return new List<(double, double)>();

            var yVals = new SortedSet<double>();
            yVals.Add(0);
            foreach (var p in packed)
            {
                yVals.Add(Math.Round(p.Y, 3));
                yVals.Add(Math.Round(p.Y + p.RH, 3));
            }

            var sorted = yVals.ToList();
            var layers = new List<(double, double)>();
            for (int i = 0; i < sorted.Count - 1; i++)
            {
                double yMin = sorted[i], yMax = sorted[i + 1];
                bool hasItem = packed.Any(p =>
                    p.Y < yMax - 0.001 && p.Y + p.RH > yMin + 0.001);
                if (hasItem)
                    layers.Add((yMin, yMax));
            }

            var merged = new List<(double, double)>();
            if (layers.Count == 0) return merged;
            double curMin = layers[0].Item1, curMax = layers[0].Item2;
            for (int i = 1; i < layers.Count; i++)
            {
                bool newItemStartsHere = packed.Any(p => Math.Abs(p.Y - layers[i].Item1) < 0.001);
                if (newItemStartsHere)
                {
                    merged.Add((curMin, curMax));
                    curMin = layers[i].Item1;
                }
                curMax = layers[i].Item2;
            }
            merged.Add((curMin, curMax));
            return merged;
        }
    }
}