using System.Collections.Concurrent;
using System.Diagnostics;
using System.Globalization;

namespace StellaOps.ElkSharp;

internal static partial class ElkEdgeRouterIterative
{
    private static ElkRoutedEdge[] RestoreProtectedRepeatCollectorCorridors(
        ElkRoutedEdge[] candidateEdges,
        ElkRoutedEdge[] referenceEdges,
        ElkPositionedNode[] nodes)
    {
        if (candidateEdges.Length == 0 || referenceEdges.Length == 0 || nodes.Length == 0)
        {
            return candidateEdges;
        }

        var graphMinY = nodes.Min(node => node.Y);
        var graphMaxY = nodes.Max(node => node.Y + node.Height);
        var minLineClearance = ResolveMinLineClearance(nodes);
        var obstacles = BuildObstacles(nodes, 0d);
        var nodesById = nodes.ToDictionary(node => node.Id, StringComparer.Ordinal);
        var restoredIds = new List<string>();
        var result = candidateEdges.ToArray();

        for (var i = 0; i < result.Length && i < referenceEdges.Length; i++)
        {
            var reference = referenceEdges[i];
            if (!ElkEdgePostProcessor.IsRepeatCollectorLabel(reference.Label)
                || !ElkEdgePostProcessor.HasCorridorBendPoints(reference, graphMinY, graphMaxY)
                || ElkEdgePostProcessor.HasCorridorBendPoints(result[i], graphMinY, graphMaxY)
                || EdgeCrossesNode(reference, obstacles)
                || EdgeViolatesNodeClearance(reference, nodes, minLineClearance))
            {
                continue;
            }

            var restored = reference;
            if (nodesById.TryGetValue(reference.SourceNodeId ?? string.Empty, out var sourceNode)
                && ElkShapeBoundaries.IsGatewayShape(sourceNode))
            {
                restored = AlignProtectedCollectorGatewaySourceExit(restored, sourceNode, graphMinY, graphMaxY);
            }

            result[i] = restored;
            restoredIds.Add(restored.Id);
        }

        return restoredIds.Count > 0
            ? ElkRepeatCollectorCorridors.SeparateSharedLanes(result, nodes, restoredIds)
            : result;
    }

    private static bool EdgeViolatesNodeClearance(
        ElkRoutedEdge edge,
        IReadOnlyCollection<ElkPositionedNode> nodes,
        double minLineClearance)
    {
        if (minLineClearance <= 0d)
        {
            return false;
        }

        foreach (var segment in ElkEdgeRoutingGeometry.FlattenSegments(edge))
        {
            var horizontal = Math.Abs(segment.Start.Y - segment.End.Y) <= 0.5d;
            var vertical = Math.Abs(segment.Start.X - segment.End.X) <= 0.5d;
            if (!horizontal && !vertical)
            {
                continue;
            }

            foreach (var node in nodes)
            {
                if (node.Id == edge.SourceNodeId || node.Id == edge.TargetNodeId)
                {
                    continue;
                }

                if (horizontal)
                {
                    var minX = Math.Min(segment.Start.X, segment.End.X);
                    var maxX = Math.Max(segment.Start.X, segment.End.X);
                    if (maxX <= node.X || minX >= node.X + node.Width)
                    {
                        continue;
                    }

                    var distance = Math.Min(
                        Math.Abs(segment.Start.Y - node.Y),
                        Math.Abs(segment.Start.Y - (node.Y + node.Height)));
                    if (distance > 0.5d && distance < minLineClearance)
                    {
                        return true;
                    }

                    continue;
                }

                var minY = Math.Min(segment.Start.Y, segment.End.Y);
                var maxY = Math.Max(segment.Start.Y, segment.End.Y);
                if (maxY <= node.Y || minY >= node.Y + node.Height)
                {
                    continue;
                }

                var horizontalDistance = Math.Min(
                    Math.Abs(segment.Start.X - node.X),
                    Math.Abs(segment.Start.X - (node.X + node.Width)));
                if (horizontalDistance > 0.5d && horizontalDistance < minLineClearance)
                {
                    return true;
                }
            }
        }

        return false;
    }

    private static bool EdgeCrossesNode(
        ElkRoutedEdge edge,
        (double Left, double Top, double Right, double Bottom, string Id)[] obstacles)
    {
        foreach (var segment in ElkEdgeRoutingGeometry.FlattenSegments(edge))
        {
            if (ElkEdgePostProcessor.SegmentCrossesObstacle(
                    segment.Start,
                    segment.End,
                    obstacles,
                    edge.SourceNodeId,
                    edge.TargetNodeId))
            {
                return true;
            }
        }

        return false;
    }

    private static ElkRoutedEdge AlignProtectedCollectorGatewaySourceExit(
        ElkRoutedEdge edge,
        ElkPositionedNode sourceNode,
        double graphMinY,
        double graphMaxY)
    {
        var path = new List<ElkPoint>();
        foreach (var section in edge.Sections)
        {
            if (path.Count == 0)
            {
                path.Add(section.StartPoint);
            }

            path.AddRange(section.BendPoints);
            path.Add(section.EndPoint);
        }

        if (path.Count < 2)
        {
            return edge;
        }

        var corridorIndex = 1;
        for (var i = 1; i < path.Count; i++)
        {
            if (path[i].Y < graphMinY - 8d || path[i].Y > graphMaxY + 8d)
            {
                corridorIndex = i;
                break;
            }
        }

        var corridorPoint = path[corridorIndex];
        var boundaryReferences = sourceNode.Kind == "Decision"
            ? new[]
            {
                (BoundaryReference: path[^1], ExitReference: path[^1]),
                (BoundaryReference: corridorPoint, ExitReference: corridorPoint),
                (BoundaryReference: corridorPoint, ExitReference: path[^1]),
            }
            : new[]
            {
                (BoundaryReference: corridorPoint, ExitReference: corridorPoint),
            };

        List<ElkPoint>? rebuilt = null;
        var bestScore = double.PositiveInfinity;
        foreach (var (boundaryReference, exitReference) in boundaryReferences)
        {
            var boundary = ElkShapeBoundaries.ProjectOntoShapeBoundary(sourceNode, boundaryReference);
            boundary = ElkShapeBoundaries.PreferGatewayEdgeInteriorBoundary(sourceNode, boundary, boundaryReference);
            var exteriorApproach = ElkShapeBoundaries.BuildPreferredGatewaySourceExteriorPoint(sourceNode, boundary, exitReference);
            var desiredExitDx = exitReference.X - boundary.X;
            var desiredExitDy = exitReference.Y - boundary.Y;
            if (Math.Abs(desiredExitDx) >= Math.Abs(desiredExitDy) * 1.15d && Math.Sign(desiredExitDx) != 0)
            {
                exteriorApproach = new ElkPoint
                {
                    X = desiredExitDx > 0d
                        ? sourceNode.X + sourceNode.Width + 8d
                        : sourceNode.X - 8d,
                    Y = boundary.Y,
                };
            }
            else if (Math.Abs(desiredExitDy) >= Math.Abs(desiredExitDx) * 1.15d && Math.Sign(desiredExitDy) != 0)
            {
                exteriorApproach = new ElkPoint
                {
                    X = boundary.X,
                    Y = desiredExitDy > 0d
                        ? sourceNode.Y + sourceNode.Height + 8d
                        : sourceNode.Y - 8d,
                };
            }

            var candidate = new List<ElkPoint> { boundary };
            if (!ElkEdgeRoutingGeometry.PointsEqual(boundary, exteriorApproach))
            {
                candidate.Add(exteriorApproach);
            }

            if (!ElkEdgeRoutingGeometry.PointsEqual(candidate[^1], corridorPoint))
            {
                var corner = BuildOrthogonalCollectorCorner(candidate[^1], corridorPoint);
                if (corner is not null && !ElkEdgeRoutingGeometry.PointsEqual(candidate[^1], corner))
                {
                    candidate.Add(corner);
                }

                if (!ElkEdgeRoutingGeometry.PointsEqual(candidate[^1], corridorPoint))
                {
                    candidate.Add(corridorPoint);
                }
            }

            for (var i = corridorIndex + 1; i < path.Count; i++)
            {
                candidate.Add(path[i]);
            }

            candidate = NormalizeProtectedCollectorTail(candidate, graphMinY, graphMaxY);
            var score = ScoreProtectedCollectorGatewaySourceExitCandidate(candidate, sourceNode, exitReference);
            if (score >= bestScore)
            {
                continue;
            }

            bestScore = score;
            rebuilt = candidate;
        }

        rebuilt ??= NormalizeProtectedCollectorTail(path, graphMinY, graphMaxY);

        return new ElkRoutedEdge
        {
            Id = edge.Id,
            SourceNodeId = edge.SourceNodeId,
            TargetNodeId = edge.TargetNodeId,
            SourcePortId = edge.SourcePortId,
            TargetPortId = edge.TargetPortId,
            Kind = edge.Kind,
            Label = edge.Label,
            Sections =
            [
                new ElkEdgeSection
                {
                    StartPoint = rebuilt[0],
                    EndPoint = rebuilt[^1],
                    BendPoints = rebuilt.Count > 2
                        ? rebuilt.Skip(1).Take(rebuilt.Count - 2).ToArray()
                        : [],
                },
            ],
        };
    }

}