using Avalonia;
using Avalonia.Controls;
using Avalonia.Media;
using Avalonia.VisualTree;

namespace SourceGit.Views
{
    public class CommitGraph : Control
    {
        public static readonly StyledProperty<Models.CommitGraph> GraphProperty =
            AvaloniaProperty.Register<CommitGraph, Models.CommitGraph>(nameof(Graph));

        public Models.CommitGraph Graph
        {
            get => GetValue(GraphProperty);
            set => SetValue(GraphProperty, value);
        }

        public static readonly StyledProperty<IBrush> DotBrushProperty =
            AvaloniaProperty.Register<CommitGraph, IBrush>(nameof(DotBrush), Brushes.Transparent);

        public IBrush DotBrush
        {
            get => GetValue(DotBrushProperty);
            set => SetValue(DotBrushProperty, value);
        }

        public static readonly StyledProperty<bool> OnlyHighlightCurrentBranchProperty =
            AvaloniaProperty.Register<CommitGraph, bool>(nameof(OnlyHighlightCurrentBranch), true);

        public bool OnlyHighlightCurrentBranch
        {
            get => GetValue(OnlyHighlightCurrentBranchProperty);
            set => SetValue(OnlyHighlightCurrentBranchProperty, value);
        }

        static CommitGraph()
        {
            AffectsRender<CommitGraph>(GraphProperty, DotBrushProperty, OnlyHighlightCurrentBranchProperty);
        }

        public override void Render(DrawingContext context)
        {
            base.Render(context);

            var graph = Graph;
            if (graph == null)
                return;

            var histories = this.FindAncestorOfType<Histories>();
            if (histories == null)
                return;

            var list = histories.CommitListContainer;
            if (list == null)
                return;

            // Calculate drawing area.
            double width = Bounds.Width - 273 - histories.AuthorNameColumnWidth.Value;
            double height = Bounds.Height;
            double startY = list.Scroll?.Offset.Y ?? 0;
            double endY = startY + height + 28;

            // Apply scroll offset and clip.
            using (context.PushClip(new Rect(0, 0, width, height)))
            using (context.PushTransform(Matrix.CreateTranslation(0, -startY)))
            {
                // Draw contents
                DrawCurves(context, graph, startY, endY);
                DrawAnchors(context, graph, startY, endY);
            }
        }

        private void DrawCurves(DrawingContext context, Models.CommitGraph graph, double top, double bottom)
        {
            var grayedPen = new Pen(new SolidColorBrush(Colors.Gray, 0.4), Models.CommitGraph.Pens[0].Thickness);
            var onlyHighlightCurrentBranch = OnlyHighlightCurrentBranch;

            if (onlyHighlightCurrentBranch)
            {
                foreach (var link in graph.Links)
                {
                    if (link.IsMerged)
                        continue;
                    if (link.End.Y < top)
                        continue;
                    if (link.Start.Y > bottom)
                        break;

                    var geo = new StreamGeometry();
                    using (var ctx = geo.Open())
                    {
                        ctx.BeginFigure(link.Start, false);
                        ctx.QuadraticBezierTo(link.Control, link.End);
                    }

                    context.DrawGeometry(null, grayedPen, geo);
                }
            }

            foreach (var line in graph.Paths)
            {
                var last = line.Points[0];
                var size = line.Points.Count;

                if (line.Points[size - 1].Y < top)
                    continue;
                if (last.Y > bottom)
                    break;

                var geo = new StreamGeometry();
                var pen = Models.CommitGraph.Pens[line.Color];

                using (var ctx = geo.Open())
                {
                    var started = false;
                    var ended = false;
                    for (int i = 1; i < size; i++)
                    {
                        var cur = line.Points[i];
                        if (cur.Y < top)
                        {
                            last = cur;
                            continue;
                        }

                        if (!started)
                        {
                            ctx.BeginFigure(last, false);
                            started = true;
                        }

                        if (cur.Y > bottom)
                        {
                            cur = new Point(cur.X, bottom);
                            ended = true;
                        }

                        if (cur.X > last.X)
                        {
                            ctx.QuadraticBezierTo(new Point(cur.X, last.Y), cur);
                        }
                        else if (cur.X < last.X)
                        {
                            if (i < size - 1)
                            {
                                var midY = (last.Y + cur.Y) / 2;
                                ctx.CubicBezierTo(new Point(last.X, midY + 4), new Point(cur.X, midY - 4), cur);
                            }
                            else
                            {
                                ctx.QuadraticBezierTo(new Point(last.X, cur.Y), cur);
                            }
                        }
                        else
                        {
                            ctx.LineTo(cur);
                        }

                        if (ended)
                            break;
                        last = cur;
                    }
                }

                if (!line.IsMerged && onlyHighlightCurrentBranch)
                    context.DrawGeometry(null, grayedPen, geo);
                else
                    context.DrawGeometry(null, pen, geo);
            }

            foreach (var link in graph.Links)
            {
                if (onlyHighlightCurrentBranch && !link.IsMerged)
                    continue;
                if (link.End.Y < top)
                    continue;
                if (link.Start.Y > bottom)
                    break;

                var geo = new StreamGeometry();
                using (var ctx = geo.Open())
                {
                    ctx.BeginFigure(link.Start, false);
                    ctx.QuadraticBezierTo(link.Control, link.End);
                }

                context.DrawGeometry(null, Models.CommitGraph.Pens[link.Color], geo);
            }
        }

        private void DrawAnchors(DrawingContext context, Models.CommitGraph graph, double top, double bottom)
        {
            var dotFill = DotBrush;
            var dotFillPen = new Pen(dotFill, 2);
            var grayedPen = new Pen(Brushes.Gray, Models.CommitGraph.Pens[0].Thickness);
            var onlyHighlightCurrentBranch = OnlyHighlightCurrentBranch;

            foreach (var dot in graph.Dots)
            {
                if (dot.Center.Y < top)
                    continue;
                if (dot.Center.Y > bottom)
                    break;

                var pen = Models.CommitGraph.Pens[dot.Color];
                if (!dot.IsMerged && onlyHighlightCurrentBranch)
                    pen = grayedPen;

                switch (dot.Type)
                {
                    case Models.CommitGraph.DotType.Head:
                        context.DrawEllipse(dotFill, pen, dot.Center, 6, 6);
                        context.DrawEllipse(pen.Brush, null, dot.Center, 3, 3);
                        break;
                    case Models.CommitGraph.DotType.Merge:
                        context.DrawEllipse(pen.Brush, null, dot.Center, 6, 6);
                        context.DrawLine(dotFillPen, new Point(dot.Center.X, dot.Center.Y - 3), new Point(dot.Center.X, dot.Center.Y + 3));
                        context.DrawLine(dotFillPen, new Point(dot.Center.X - 3, dot.Center.Y), new Point(dot.Center.X + 3, dot.Center.Y));
                        break;
                    default:
                        context.DrawEllipse(dotFill, pen, dot.Center, 3, 3);
                        break;
                }
            }
        }
    }
}