using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using OpenNest.CNC;
using OpenNest.Geometry;
using OpenNest.Math;

namespace OpenNest
{
    internal static class GraphicsHelper
    {
        public static GraphicsPath GetGraphicsPath(this Program pgm)
        {
            var figures = new List<Figure>();
            var curpos = Vector.Zero;

            AddProgram(figures, pgm, pgm.Mode, ref curpos);

            return Combine(figures, bridgeTabs: false);
        }

        public static GraphicsPath GetGraphicsPath(this Program pgm, Vector origin)
        {
            // Program coordinates are drawing-local in either mode. Translate the
            // finished path so absolute moves cannot discard the part placement.
            var path = pgm.GetGraphicsPath();
            using var translation = new Matrix();
            translation.Translate((float)origin.X, (float)origin.Y);
            path.Transform(translation);

            return path;
        }

        public static GraphicsPath GetGraphicsPath(this Shape shape)
        {
            var path = new GraphicsPath();

            AddShape(path, shape);

            return path;
        }

        public static void GetDisplayPaths(
            this Program pgm,
            Vector origin,
            out GraphicsPath cutPath,
            out GraphicsPath leadPath,
            out GraphicsPath etchPath
        ) => pgm.GetDisplayPaths(origin, out cutPath, out leadPath, out etchPath, out _);

        /// <param name="hasOpenCuts">
        /// Whether a cut contour is open, such as a cutout left attached by tabs. Filling
        /// <paramref name="cutPath"/> would close it with a chord; fill <see cref="GetFillPath"/> instead.
        /// </param>
        public static void GetDisplayPaths(
            this Program pgm,
            Vector origin,
            out GraphicsPath cutPath,
            out GraphicsPath leadPath,
            out GraphicsPath etchPath,
            out bool hasOpenCuts
        )
        {
            // A tabbed cutout's tabs are never cut, so they are filled but not drawn as cuts.
            cutPath = GetLayerPath(pgm, origin,
                layer => layer is not (LayerType.Scribe or LayerType.Leadin or LayerType.Leadout or LayerType.Tab),
                bridgeTabs: false, out hasOpenCuts);
            leadPath = GetLayerPath(pgm, origin,
                layer => layer == LayerType.Leadin || layer == LayerType.Leadout, bridgeTabs: false, out _);
            etchPath = GetLayerPath(pgm, origin, layer => layer == LayerType.Scribe, bridgeTabs: false, out _);
        }

        /// <summary>
        /// The closed material outlines to fill. Break cuts are open lines through material: a
        /// fill would close each one with a chord and leave the sliver between them unfilled.
        /// A contour cut in pieces around tabs is rejoined across its tab gaps for the same reason.
        /// </summary>
        public static GraphicsPath GetFillPath(this Program pgm, Vector origin) =>
            GetLayerPath(pgm, origin, layer => layer is not (LayerType.Scribe or LayerType.Leadin
                or LayerType.Leadout or LayerType.Break), bridgeTabs: true, out _);

        private static GraphicsPath GetLayerPath(Program pgm, Vector origin,
            System.Func<LayerType, bool> includeLayer, bool bridgeTabs, out bool hasOpenFigures)
        {
            var figures = new List<Figure>();
            var position = Vector.Zero;
            AddProgram(figures, pgm, pgm.Mode, ref position, includeLayer);
            hasOpenFigures = figures.Exists(figure => !figure.IsClosed);
            var path = Combine(figures, bridgeTabs);
            // Place the completed local path; absolute moves must not discard placement.
            using var translation = new Matrix();
            translation.Translate((float)origin.X, (float)origin.Y);
            path.Transform(translation);
            return path;
        }

        public static Image GetImage(this Program pgm, System.Drawing.Size size)
        {
            return pgm.GetImage(size, Pens.Black, null);
        }

        public static Image GetImage(this Program pgm, System.Drawing.Size size, Pen pen)
        {
            return pgm.GetImage(size, pen, null);
        }

        public static Image GetImage(
            this Program pgm,
            System.Drawing.Size size,
            Pen pen,
            Brush brush,
            Color? etchColor = null
        )
        {
            var img = new Bitmap(size.Width, size.Height);
            pgm.GetDisplayPaths(Vector.Zero, out var cuts, out var leads, out var etches);
            using var path = cuts;
            using var leadPath = leads;
            using var etchPath = etches;
            var bounds = path.PointCount > 0 ? path.GetBounds() : etchPath.GetBounds();
            if (path.PointCount > 0 && etchPath.PointCount > 0)
                bounds = RectangleF.Union(bounds, etchPath.GetBounds());

            var scalex = (size.Height - 10) / System.Math.Max(bounds.Height, 0.001f);
            var scaley = (size.Width - 10) / System.Math.Max(bounds.Width, 0.001f);
            var scale = scalex < scaley ? scalex : scaley;

            using var matrix = new Matrix();
            matrix.Scale(scale, -scale);

            path.Transform(matrix);
            etchPath.Transform(matrix);

            bounds = path.PointCount > 0 ? path.GetBounds() : etchPath.GetBounds();
            if (path.PointCount > 0 && etchPath.PointCount > 0)
                bounds = RectangleF.Union(bounds, etchPath.GetBounds());

            var offset = new PointF(
                (size.Width - bounds.Width) * 0.5f - bounds.X,
                (size.Height - bounds.Height) * 0.5f - bounds.Y
            );

            using var graphics = Graphics.FromImage(img);
            graphics.TranslateTransform(offset.X, offset.Y);

            if (brush != null)
            {
                using var fill = pgm.GetFillPath(Vector.Zero);
                fill.Transform(matrix);
                graphics.FillPath(brush, fill);
            }

            if (pen == null)
                pen = Pens.Black;

            using var etchPen = new Pen(etchColor ?? ColorScheme.Default.EtchColor, 1.5f);
            graphics.DrawPath(etchPen, etchPath);
            // A coincident cut must remain visible over an etch.
            graphics.DrawPath(pen, path);

            return img;
        }

        public static void GetGraphicsPaths(
            this Program pgm,
            Vector origin,
            out GraphicsPath cutPath,
            out GraphicsPath leadPath
        )
        {
            cutPath = new GraphicsPath();
            leadPath = new GraphicsPath();
            var curpos = Vector.Zero;

            AddProgramSplit(cutPath, leadPath, pgm, pgm.Mode, ref curpos);

            using var translation = new Matrix();
            translation.Translate((float)origin.X, (float)origin.Y);
            cutPath.Transform(translation);
            leadPath.Transform(translation);
        }

        private static void AddProgramSplit(
            GraphicsPath cutPath,
            GraphicsPath leadPath,
            Program pgm,
            Mode mode,
            ref Vector curpos
        )
        {
            // Capture the frame origin at entry. Sub-program Offsets are relative
            // to this fixed origin, not to the current tool position.
            var frameOrigin = curpos;
            mode = pgm.Mode;

            for (var i = 0; i < pgm.Length; ++i)
            {
                var code = pgm[i];

                switch (code.Type)
                {
                    case CodeType.ArcMove:
                        var arc = (ArcMove)code;
                        if (arc.Suppressed)
                        {
                            var endpt = arc.EndPoint;
                            if (mode == Mode.Incremental)
                                endpt += curpos;
                            curpos = endpt;
                            break;
                        }
                        var arcPath =
                            (arc.Layer == LayerType.Leadin || arc.Layer == LayerType.Leadout)
                                ? leadPath
                                : cutPath;
                        AddArc(arcPath, arc, mode, ref curpos);
                        break;

                    case CodeType.LinearMove:
                        var line = (LinearMove)code;
                        if (line.Suppressed)
                        {
                            var endpt = line.EndPoint;
                            if (mode == Mode.Incremental)
                                endpt += curpos;
                            curpos = endpt;
                            break;
                        }
                        var linePath =
                            (line.Layer == LayerType.Leadin || line.Layer == LayerType.Leadout)
                                ? leadPath
                                : cutPath;
                        AddLine(linePath, line, mode, ref curpos);
                        break;

                    case CodeType.RapidMove:
                        {
                            var rapid = (RapidMove)code;
                            var endpt = rapid.EndPoint;
                            if (mode == Mode.Incremental)
                                endpt += curpos;
                            var dx = endpt.X - curpos.X;
                            var dy = endpt.Y - curpos.Y;
                            if (dx * dx + dy * dy > 0.001 * 0.001)
                            {
                                cutPath.StartFigure();
                                leadPath.StartFigure();
                            }
                            curpos = endpt;
                        }
                        break;

                    case CodeType.SubProgramCall:
                        var tmpmode = mode;
                        var subpgm = (SubProgramCall)code;
                        if (subpgm.Program != null)
                        {
                            cutPath.StartFigure();
                            leadPath.StartFigure();
                            curpos = new Vector(
                                frameOrigin.X + subpgm.Offset.X,
                                frameOrigin.Y + subpgm.Offset.Y
                            );
                            AddProgramSplit(cutPath, leadPath, subpgm.Program, mode, ref curpos);
                        }
                        mode = tmpmode;
                        break;
                }
            }
        }

        private static void AddArc(GraphicsPath path, ArcMove arc, Mode mode, ref Vector curpos)
        {
            var endpt = arc.EndPoint;
            var center = arc.CenterPoint;

            if (mode == Mode.Incremental)
            {
                endpt += curpos;
                center += curpos;
            }

            // start angle in degrees
            var startAngle = Angle.ToDegrees(
                System.Math.Atan2(curpos.Y - center.Y, curpos.X - center.X)
            );

            // end angle in degrees
            var endAngle = Angle.ToDegrees(
                System.Math.Atan2(endpt.Y - center.Y, endpt.X - center.X)
            );

            endAngle = Angle.NormalizeDeg(endAngle);
            startAngle = Angle.NormalizeDeg(startAngle);

            if (arc.Rotation == RotationType.CCW && endAngle < startAngle)
                endAngle += 360.0;
            else if (arc.Rotation == RotationType.CW && startAngle < endAngle)
                startAngle += 360.0;

            var dx = endpt.X - center.X;
            var dy = endpt.Y - center.Y;

            var radius = System.Math.Sqrt(dx * dx + dy * dy);

            var pt = new PointF((float)(center.X - radius), (float)(center.Y - radius));
            var size = (float)(radius * 2.0);

            if (startAngle.IsEqualTo(endAngle))
            {
                path.AddEllipse(pt.X, pt.Y, size, size);
            }
            else
            {
                var sweepAngle = (endAngle - startAngle);

                path.AddArc(pt.X, pt.Y, size, size, (float)startAngle, (float)sweepAngle);
            }

            curpos = endpt;
        }

        private static void AddLine(
            GraphicsPath path,
            LinearMove line,
            Mode mode,
            ref Vector curpos
        )
        {
            var pt = line.EndPoint;

            if (mode == Mode.Incremental)
                pt += curpos;

            var pt1 = new PointF((float)curpos.X, (float)curpos.Y);
            var pt2 = new PointF((float)pt.X, (float)pt.Y);

            path.AddLine(pt1, pt2);

            curpos = pt;
        }

        private static void AddLine(GraphicsPath path, RapidMove line, Mode mode, ref Vector curpos)
        {
            var pt = line.EndPoint;

            if (mode == Mode.Incremental)
                pt += curpos;

            curpos = pt;
        }

        /// <summary>One continuous run of drawn moves, with its program-space ends.</summary>
        private sealed record Figure(GraphicsPath Path, Vector Start, Vector End)
        {
            public bool IsClosed => Start.DistanceTo(End) <= Tolerance.Epsilon;
        }

        /// <summary>
        /// Adds every figure to one path. With <paramref name="bridgeTabs"/>, an open figure is
        /// joined end-to-start with the open figure starting nearest its end, until its own start
        /// is nearer, so the tab-separated pieces of one contour fill as a single region.
        /// </summary>
        private static GraphicsPath Combine(List<Figure> figures, bool bridgeTabs)
        {
            var path = new GraphicsPath();
            var pending = new List<Figure>(figures);

            while (pending.Count > 0)
            {
                var figure = pending[0];
                pending.RemoveAt(0);

                if (!bridgeTabs || figure.IsClosed)
                {
                    path.AddPath(figure.Path, false);
                    figure.Path.Dispose();
                    continue;
                }

                using var chain = new GraphicsPath();
                chain.AddPath(figure.Path, false);
                figure.Path.Dispose();
                var end = figure.End;

                while (true)
                {
                    Figure next = null;
                    var nextGap = end.DistanceTo(figure.Start);

                    foreach (var candidate in pending)
                    {
                        if (candidate.IsClosed)
                            continue;
                        var gap = end.DistanceTo(candidate.Start);
                        if (gap < nextGap)
                        {
                            next = candidate;
                            nextGap = gap;
                        }
                    }

                    if (next == null)
                        break;

                    pending.Remove(next);
                    chain.AddPath(next.Path, true);
                    next.Path.Dispose();
                    end = next.End;
                }

                path.AddPath(chain, false);
            }

            return path;
        }

        private static void AddProgram(List<Figure> figures, Program pgm, Mode mode, ref Vector curpos,
            System.Func<LayerType, bool> includeLayer = null)
        {
            // Capture the frame origin at entry. Sub-program Offsets are relative
            // to this fixed origin, not to the current tool position.
            var frameOrigin = curpos;
            mode = pgm.Mode;
            GraphicsPath currentFigure = null;
            var figureStart = curpos;

            // Call before moving past a skipped code so the figure records where its cut ended.
            void Flush(Vector end)
            {
                if (currentFigure != null)
                {
                    figures.Add(new Figure(currentFigure, figureStart, end));
                    currentFigure = null;
                }
            }

            void BeginFigure(Vector start)
            {
                if (currentFigure == null)
                {
                    currentFigure = new GraphicsPath();
                    figureStart = start;
                }
            }

            for (int i = 0; i < pgm.Length; ++i)
            {
                var code = pgm[i];

                switch (code.Type)
                {
                    case CodeType.ArcMove:
                        {
                            var arc = (ArcMove)code;
                            if (includeLayer == null
                                ? arc.Layer != LayerType.Leadin && arc.Layer != LayerType.Leadout
                                : !arc.Suppressed && includeLayer(arc.Layer))
                            {
                                BeginFigure(curpos);
                                AddArc(currentFigure, arc, mode, ref curpos);
                            }
                            else
                            {
                                Flush(curpos);
                                var endpt = arc.EndPoint;
                                if (mode == Mode.Incremental)
                                    endpt += curpos;
                                curpos = endpt;
                            }
                        }
                        break;

                    case CodeType.LinearMove:
                        {
                            var line = (LinearMove)code;
                            if (includeLayer == null
                                ? line.Layer != LayerType.Leadin && line.Layer != LayerType.Leadout
                                : !line.Suppressed && includeLayer(line.Layer))
                            {
                                BeginFigure(curpos);
                                AddLine(currentFigure, line, mode, ref curpos);
                            }
                            else
                            {
                                Flush(curpos);
                                var endpt = line.EndPoint;
                                if (mode == Mode.Incremental)
                                    endpt += curpos;
                                curpos = endpt;
                            }
                        }
                        break;

                    case CodeType.RapidMove:
                        {
                            var rapid = (RapidMove)code;
                            var endpt = rapid.EndPoint;
                            if (mode == Mode.Incremental)
                                endpt += curpos;
                            var dx = endpt.X - curpos.X;
                            var dy = endpt.Y - curpos.Y;
                            if (dx * dx + dy * dy > 0.001 * 0.001)
                                Flush(curpos);
                            curpos = endpt;
                        }
                        break;

                    case CodeType.SubProgramCall:
                        {
                            Flush(curpos);
                            var tmpmode = mode;
                            var subpgm = (SubProgramCall)code;

                            if (subpgm.Program != null)
                            {
                                curpos = new Vector(
                                    frameOrigin.X + subpgm.Offset.X,
                                    frameOrigin.Y + subpgm.Offset.Y
                                );
                                AddProgram(figures, subpgm.Program, mode, ref curpos, includeLayer);
                            }

                            mode = tmpmode;
                            break;
                        }
                }
            }

            Flush(curpos);
        }

        private static void AddArc(GraphicsPath path, Arc arc)
        {
            var diameter = arc.Diameter;

            var endAngle = Angle.NormalizeDeg(Angle.ToDegrees(arc.EndAngle));
            var startAngle = Angle.NormalizeDeg(Angle.ToDegrees(arc.StartAngle));

            if (arc.Rotation == RotationType.CCW && endAngle < startAngle)
                endAngle += 360.0;
            else if (arc.Rotation == RotationType.CW && startAngle < endAngle)
                startAngle += 360.0;

            var sweepAngle = (endAngle - startAngle);

            path.AddArc(
                (float)(arc.Center.X - arc.Radius),
                (float)(arc.Center.Y - arc.Radius),
                (float)diameter,
                (float)diameter,
                (float)(startAngle),
                (float)sweepAngle
            );
        }

        private static void AddCircle(GraphicsPath path, Circle circle)
        {
            var diameter = circle.Diameter;

            path.AddEllipse(
                (float)(circle.Center.X - circle.Radius),
                (float)(circle.Center.Y - circle.Radius),
                (float)diameter,
                (float)diameter
            );
        }

        private static void AddLine(GraphicsPath path, Line line)
        {
            path.AddLine(
                (float)line.StartPoint.X,
                (float)line.StartPoint.Y,
                (float)line.EndPoint.X,
                (float)line.EndPoint.Y
            );
        }

        private static void AddShape(GraphicsPath path, Shape shape)
        {
            foreach (var entity in shape.Entities)
            {
                if (entity.Layer != null)
                {
                    if (
                        string.Equals(
                            entity.Layer.Name,
                            SpecialLayers.Leadin.Name,
                            System.StringComparison.OrdinalIgnoreCase
                        )
                        || string.Equals(
                            entity.Layer.Name,
                            SpecialLayers.Leadout.Name,
                            System.StringComparison.OrdinalIgnoreCase
                        )
                    )
                    {
                        continue;
                    }
                }

                switch (entity.Type)
                {
                    case EntityType.Arc:
                        AddArc(path, (Arc)entity);
                        break;

                    case EntityType.Circle:
                        AddCircle(path, (Circle)entity);
                        break;

                    case EntityType.Line:
                        AddLine(path, (Line)entity);
                        break;

                    case EntityType.Polygon:
                        AddPolygon(path, (Polygon)entity);
                        break;

                    case EntityType.Shape:
                        var subpath = new GraphicsPath();
                        AddShape(subpath, (Shape)entity);
                        path.AddPath(subpath, false);
                        subpath.Dispose();
                        break;
                }
            }
        }

        private static void AddPolygon(GraphicsPath path, Polygon polygon)
        {
            var pts = new PointF[polygon.Vertices.Count];

            for (int i = 0; i < pts.Length; i++)
            {
                var pt = polygon.Vertices[i];
                pts[i] = new PointF((float)pt.X, (float)pt.Y);
            }

            path.AddPolygon(pts);
        }
    }
}